THERMO INSTRUMENT SYSTEMS INC
SC TO-T, 2000-03-13
MEASURING & CONTROLLING DEVICES, NEC
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<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   SCHEDULE TO

                                 (Rule 14d-100)

            TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                                ONIX SYSTEMS INC.
                            (Name of Subject Company)

                              ONIX ACQUISITION INC.
                                    (Offeror)

                         THERMO INSTRUMENT SYSTEMS INC.
                                    (Offeror)

                           THERMO ELECTRON CORPORATION
                                    (Offeror)

                     COMMON STOCK, PAR VALUE $0.01 PER SHARE
                         (Title of Class of Securities)

                                CUSIP 67088G 10 8
                      (CUSIP Number of Class of Securities)

                             Seth H. Hoogasian, Esq.
                                 General Counsel
                           Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046
                                 (781) 622-1000
   (Name, Address and Telephone Number of Person Authorized to Receive Notices
                 and Communications on Behalf of Filing Persons)

                                 with a copy to:

                              Neil H. Aronson, Esq.
               Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                              One Financial Center
                           Boston, Massachusetts 02111
                                 (617) 542-6000


<PAGE>


                            CALCULATION OF FILING FEE

Transaction Valuation(1): $30,003,669           Amount of Filing Fee(2): $6,001

(1)   For purposes of calculating fee only. This amount is based upon (a) the
maximum number of Shares to be purchased pursuant to the Offer and (b) the price
offered per Share.

(2)   The amount of the filing fee, calculated in accordance with Regulation
240.0-11 under the Securities Exchange Act of 1934, as amended, equals 1/50 of
one percent of the Transaction Valuation.

[ ]   Check the box if any part of the fee is offset as provided by Rule
      0-11(a)(2) and identify the filing with which the offsetting fee was
      previously paid. Identify the previous filing by registration
      statement number, or the Form or Schedule and the date of its filing.

           Amount Previously Paid:                               Not applicable
           Form or Registration No.:                             Not applicable
           Filing Party:                                         Not applicable
           Date Filed:                                           Not applicable

[ ]   Check the box if the filing relates solely to preliminary
      communications made before the commencement of a tender offer.

      Check the appropriate boxes below to designate any transactions to
      which the statement relates:

      [X]        third-party tender offer subject to Rule 14d-1.

      [ ]        issuer tender offer subject to Rule 13e-4.

      [X]        going-private transaction subject to Rule 13e-3.

      [ ]        amendment to Schedule 13D under Rule 13d-2.

      Check the following box if the filing is a final amendment reporting
      the results of the tender offer: [ ]


<PAGE>



This Tender Offer Statement on Schedule TO relates to the offer by ONIX
Acquisition Inc., a Delaware corporation (the "Purchaser") and a wholly-owned
subsidiary of Thermo Instrument Systems Inc., a Delaware corporation ("Thermo
Instrument"), to purchase all outstanding shares of common stock, par value
$0.01 per share (the "Shares"), of ONIX Systems Inc., a Delaware corporation
(the "Company"), at a purchase price of $9.00 per Share net to the seller in
cash, without interest thereon, upon the terms and subject to the conditions
set forth in the Offer to Purchase dated March 13, 2000 (the "Offer to
Purchase"), a copy of which is attached hereto as Exhibit 12(a)(1), and in
the related Letter of Transmittal (which, together with the Offer to
Purchase, constitute the "Offer"), a copy of which is attached hereto as
Exhibit 12(a)(2). The information in the Offer to Purchase under the captions
"Summary", "Introduction", "The Company", "Special Factors", "The Tender
Offer", "Certain Federal Income Tax Consequences", "Price Range Of The
Shares; Dividends", "Certain Information Concerning The Company", "Certain
Information Concerning The Purchaser, Thermo Instrument And Thermo Electron",
"Source And Amount Of Funds", "The Merger; Appraisal Rights", "Fees And
Expenses" and "Miscellaneous" and Schedules I, II and III to the Offer to
Purchase are incorporated herein by reference as set forth below.

ITEM 1.   SUMMARY TERM SHEET.

See the section of the Offer to Purchase captioned "Summary".

ITEM 2.   SUBJECT COMPANY INFORMATION.

          (a) See the section of the Offer to Purchase captioned "Certain
          Information Concerning The Company".

          (b) See the section of the Offer to Purchase captioned "Introduction".

          (c) See the section of the Offer to Purchase captioned "Price Range Of
          The Shares; Dividends".

ITEM 3.   IDENTITY AND BACKGROUND OF FILING PERSON.

          (a) See the section of the Offer to Purchase captioned "Certain
          Information Concerning The Purchaser, Thermo Instrument And Thermo
          Electron" and Schedule I to the Offer to Purchase ("Members Of The
          Boards Of Directors And Executive Officers Of The Purchaser, Thermo
          Instrument And Thermo Electron").

          (b) See the section of the Offer to Purchase captioned "Certain
          Information Concerning The Purchaser, Thermo Instrument And Thermo
          Electron" and Schedule I to the Offer to Purchase ("Members Of The
          Boards Of Directors And Executive Officers Of The Purchaser, Thermo
          Instrument And Thermo Electron").

          (c) See the section of the Offer to Purchase captioned "Certain
          Information Concerning The Purchaser, Thermo Instrument And Thermo
          Electron" and Schedule I to the Offer to Purchase ("Members Of The
          Boards Of Directors And Executive Officers Of The Purchaser, Thermo
          Instrument And Thermo Electron").

ITEM 4.   TERMS OF THE TRANSACTION.

          (a) See the sections of the Offer to Purchase captioned "Summary",
          "Introduction", "Special Factors - The Merger", "Special Factors -
          Other Possible Purchases Of Shares", "Special Factors - Certain
          Effects Of The Offer And The Merger", "The Tender Offer - Terms Of
          The Offer; Expiration Date", "The Tender Offer - Acceptance For
          Payment And Payment For Shares", "The Tender Offer - Procedures For
          Accepting The Offer And Tendering Shares", "The Tender Offer -
          Withdrawal Rights" and "Certain Federal Income Tax Consequences".

ITEM 5.   PAST CONTACTS, TRANSACTIONS, NEGOTIATIONS AND AGREEMENTS.

          (a) See the sections of the Offer to Purchase captioned "Special
          Factors - Conflicts Of Interest - Executive Officers and Directors of
          the Company" and "Certain Information Concerning The Purchaser, Thermo
          Instrument And Thermo Electron - Certain Transactions" and Schedule I
          to the Offer to Purchase ("Members Of The Boards Of Directors And
          Executive Officers Of The Purchaser, Thermo Instrument And Thermo
          Electron").

          (b) See the sections of the Offer to Purchase captioned "Special
          Factors - Background To The Offer And The Merger", "Special Factors -
          Conduct Of The Company's Business After The Offer And The Merger",
          "Certain Information Concerning The Purchaser, Thermo Instrument And
          Thermo Electron - Certain Transactions" and Schedule II to the Offer
          to Purchase ("Information Concerning Transactions In The Common Stock
          Of The Company").

<PAGE>

ITEM 6.   PURPOSE OF THE TRANSACTION AND PLANS OR PROPOSALS.

          (a) and (c)(1)-(7) See the sections of the Offer to Purchase captioned
          "Introduction", "Special Factors - Background To The Offer And The
          Merger", "Special Factors - Reasons For The Offer And The Merger",
          "Special Factors - The Merger", "Special Factors - Other Possible
          Purchases Of Shares", "Special Factors - Certain Effects Of The Offer
          And The Merger", "Special Factors - Conduct Of The Company's Business
          After The Offer And The Merger", "Special Factors - Conduct Of The
          Company's Business If The Offer Is Not Completed" and "The Merger;
          Appraisal Rights".


<PAGE>




ITEM 7.   SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

          (a), (b) and (d) See the section of the Offer to Purchase captioned
          "Source And Amount Of Funds".

ITEM 8.   INTEREST IN SECURITIES OF THE SUBJECT COMPANY.

          (a) See the section of the Offer to Purchase captioned "Introduction"
          and Schedule I to the Offer to Purchase ("Members Of The Boards Of
          Directors And Executive Officers Of The Purchaser, Thermo Instrument
          And Thermo Electron").

          (b) See Schedule II to the Offer to Purchase ("Information Concerning
          Transactions In The Common Stock Of The Company").

ITEM 9.   PERSONS/ASSETS RETAINED, EMPLOYED, COMPENSATED OR USED.

          (a) See the sections of the Offer to Purchase captioned "Introduction"
          and "Fees And Expenses".

ITEM 10.  FINANCIAL STATEMENTS.

          (a) The financial statements of the Purchaser, Thermo Instrument and
          Thermo Electron Corporation, a Delaware corporation ("Thermo
          Electron"), are not material to the Offer.

          (b) The pro forma financial statements of the Purchaser, Thermo
          Instrument and Thermo Electron are not material to the Offer.

ITEM 11.  ADDITIONAL INFORMATION.

          (a)(1) None.

          (a)(2) See the sections of the Offer to Purchase captioned
          "Introduction", "The Tender Offer - Acceptance For Payment And Payment
          For Shares" and "The Tender Offer - Certain Legal Matters; Regulatory
          Approvals".

          (a)(3) See the section of the offer to Purchase captioned "The Tender
          Offer - Certain Legal Matters; Regulatory Approvals".

          (a)(4) See the section of the Offer to Purchase captioned "Special
          Factors - Certain Effects Of The Offer And The Merger".

          (a)(5) None.

          (b) The information set forth in the Offer to Purchase and the Letter
          of Transmittal is incorporated herein by reference.

ITEM 12.   EXHIBITS.

          (a)(1) Offer to Purchase dated March 13, 2000.

          (a)(2) Letter of Transmittal.

          (a)(3) Notice of Guaranteed Delivery.


<PAGE>



          (a)(4) Letter from the Dealer Managers to Brokers, Dealers, Commercial
          Banks, Trust Companies and Nominees.

          (a)(5) Letter to Clients for use by Brokers, Dealers, Commercial
          Banks, Trust Companies and Nominees.

          (a)(6) Summary Advertisement as published on March 13, 2000.

          (a)(7) Guidelines for Certification of Taxpayer Identification Number
          on Substitute Form W-9.

          (a)(8) Press Release issued by Thermo Instrument on January 31, 2000
          (incorporated herein by reference to Exhibit 99 to the Current Report
          on Form 8-K of Thermo Instrument filed with the Securities and
          Exchange Commission (the "Commission") on February 1, 2000).

          (a)(9) Press Release issued by Thermo Electron on January 31, 2000
          (incorporated herein by reference to Exhibit 99 to the Current Report
          on Form 8-K of Thermo Electron filed with the Commission on
          February 1, 2000).

          (a)(10) Press Release issued by Thermo Electron on March 6, 2000.

          (a)(11) Press Release issued by Thermo Instrument on March 13, 2000.

          (b) Loan Agreement dated as of March 1, 2000 between Thermo Electron
          and Thermo Instrument.

          (d) None.

          (g) Slide Presentation of Thermo Electron to Financial Analysts.

          (h) None.

ITEM 13. INFORMATION REQUIRED BY SCHEDULE 13E-3.

          Item 2. Subject Company Information.

               (d) See the section of the Offer to Purchase captioned "Price
               Range Of The Shares; Dividends".

               (e) See the sections of the Offer to Purchase captioned "The
               Company" and "Certain Information Concerning The Company".

               (f) See Schedule II to the Offer to Purchase ("Information
               Concerning Transactions In The Common Stock Of The Company").

          Item 4. Terms of the Transaction.

               (c) None.

               (d) See the section of the Offer to Purchase captioned "The
               Merger; Appraisal Rights" and Schedule III to the Offer to
               Purchase ("Section 262 Of The Delaware General Corporation
               Law").

               (e) See the section of the Offer to Purchase captioned "Certain
               Information Concerning The Company".

               (f) Not applicable.

          Item 5. Past Contacts, Transactions, Negotiations and Agreements.

               (c) See the sections of the Offer to Purchase captioned
               "Introduction" and "Special Factors - Background To The Offer And
               The Merger".

               (e) See the sections of the Offer to Purchase captioned "Special
               Factors - The Merger" and "Source And Amount Of Funds".

          Item 6. Purposes of the Transaction and Plans or Proposals

<PAGE>

               (b) See the section of the Offer to Purchase captioned "Special
               Factors - The Merger".

               (c)(8) See the section of the Offer to Purchase captioned
               "Special Factors - Certain Effects Of The Offer And The Merger".

          Item 7. Purposes, Alternatives, Reasons and Effects.

               (a), (b) and (c) See the sections of the Offer to Purchase
               captioned "Introduction", "Special Factors - Background To The
               Offer And The Merger", "Special Factors - Reasons For The Offer
               And The Merger" and "Special Factors - Position Of Thermo
               Instrument And Thermo Electron As To Fairness Of The Offer And
               The Merger".

               (d) See the sections of the Offer to Purchase captioned "Special
               Factors - Certain Effects Of The Offer And The Merger", "Special
               Factors - Conduct Of The Company's Business After The Offer And
               The Merger", "Special Factors - Conduct Of The Company's Business
               If The Offer Is Not Completed", "Certain Federal Income Tax
               Consequences" and "The Merger; Appraisal Rights".

          Item 8. Fairness of the Transaction.

               (a), (b), (c), (d), (e) and (f) See the sections of the Offer to
               Purchase captioned "Special Factors - Background To The Offer
               And The Merger", "Special Factors - Position Of Thermo
               Instrument And Thermo Electron As To Fairness Of The Offer
               And The Merger", "Special Factors - Summary Of The Advisors'
               Analysis And Opinion", "Special Factors - Certain Projected
               Financial Data", "Special Factors - Other Possible Purchases
               Of Shares" and "Special Factors - The Merger."

          Item 9. Reports, Opinions, Appraisals and Negotiations.

               (a), (b) and (c) See the sections of the Offer to Purchase
               captioned "Special Factors - Summary Of The Advisors' Analysis
               And Opinion" and "Special Factors - Certain Projected Financial
               Data".

          Item 10. Source and Amount of Funds or Other Consideration.

               (c) See the section of the Offer to Purchase captioned "Fees And
               Expenses".

          Item 12. The Solicitation or Recommendation.

               (d) See the section of the Offer to Purchase captioned "Special
               Factors - Conflicts Of Interest".

               (e) Except for the positions of the member of the Special
               Committee of the Board of Directors of the Company and the Boards
               of Directors of Thermo Electron and Thermo Instrument as set
               forth in the sections of the Offer to Purchase captioned
               "Special Factors - Background To The Offer And The Merger" and
               "Special Factors Position Of Thermo Instrument And Thermo
               Electron As To Fairness Of The Offer And The Merger", the
               filing persons are not aware of any officer, director or
               affiliate of the Company or any person listed on Schedule I to
               the Offer to Purchase who has made a recommendation either in
               support of or against the Offer.

          Item 13. Financial Statements.

               (a) (1) The audited consolidated financial statements of the
               Company as of and for the fiscal years ended January 2, 1999 and
               January 3, 1998 are incorporated herein by reference to the
               Consolidated Financial Statements of the Company included as
               Exhibit 13 to the Company's Annual Report on Form 10-K for the
               fiscal year ended January 2, 1999 filed with the Commission on
               March 29, 1999.

               (2) The unaudited consolidated financial statements of the
               Company for the three and nine month fiscal periods ended October
               2, 1999 are incorporated herein by reference to Item 1
               ("Financial Statements") of Part I of the Company's Quarterly
               Report on Form 10-Q for the quarter ended October 2, 1999 filed
               with the Commission on November 5, 1999.

               (3) See the section of the Offer to Purchase captioned "Certain
               Information Concerning the Company - Selected Consolidated
               Financial Information".

<PAGE>

               (b) The pro forma financial statements of the Company are not
               material to the Offer.

          Item 14. Persons/Assets Retained, Employed, Compensated or Used.

               (b) None.

          Item 16. Exhibits.

               (c) Opinion of J.P. Morgan Securities Inc. and The Beacon Group
               Capital Services, LLC dated January 29, 2000.

               (f) Statement of Appraisal Rights. See the section of the Offer
               to Purchase captioned "The Merger; Appraisal Rights" and
               Schedule III to the Offer to Purchase ("Section 262 Of The
               Delaware General Corporation Law").


<PAGE>



                                    SIGNATURE

After due inquiry and to the best of my knowledge and belief, I certify that the
information set forth in this Statement is true, complete and correct.

                                          ONIX ACQUISITION INC.

                                          BY: /s/ Earl R. Lewis
                                          --------------------------------------
                                               Name:    Earl R. Lewis
                                               Title: President

                                          THERMO INSTRUMENT SYSTEMS INC.

                                          BY: /s/ Earl R. Lewis
                                          --------------------------------------
                                               Name:    Earl R. Lewis
                                               Title: President and Chief
                                                      Executive Officer

                                          THERMO ELECTRON CORPORATION

                                          BY: /s/ Theo Melas-Kyriazi
                                          --------------------------------------
                                               Name:    Theo Melas-Kyriazi
                                               Title: Vice President and Chief
                                                         Financial Officer

Date: March 13, 2000


<PAGE>



                                  EXHIBIT INDEX

<TABLE>
<CAPTION>

EXHIBIT           DESCRIPTION

<S>               <C>
12(a)(1)          Offer to Purchase dated March 13, 2000

12(a)(2)          Letter of Transmittal

12(a)(3)          Notice of Guaranteed Delivery

12(a)(4)          Letter from the Dealer Managers to Brokers,
                  Dealers, Commercial Banks, Trust Companies and
                  Nominees

12(a)(5)          Letter to Clients for use by Brokers, Dealers,
                  Commercial Banks, Trust Companies and Nominees

12(a)(6)          Summary Advertisement as published on March 13, 2000

12(a)(7)          Guidelines for Certification of Taxpayer
                  Identification Number on Substitute Form W-9

12(a)(8)          Press Release issued by Thermo Instrument on January 31,
                  2000 (incorporated herein by reference to
                  Exhibit 99 to the Current Report on Form 8-K of
                  Thermo Instrument filed with the Commission on February 1,
                  2000)

12(a)(9)          Press Release issued by Thermo Electron on January
                  31, 2000 (incorporated herein by reference to
                  Exhibit 99 to the Current Report on Form 8-K of
                  Thermo Electron filed with the Commission on
                  February 1, 2000)

12(a)(10)         Press Release issued by Thermo Electron on March 6, 2000

12(a)(11)         Press Release issued by Thermo Instrument on March 13, 2000

12(b)             Loan Agreement dated as of March 1, 2000 between
                  Thermo Electron and Thermo Instrument

12(c)             Opinion of J.P. Morgan Securities Inc. and The
                  Beacon Group Capital Services, LLC dated January
                  29, 2000

12(d)             Not applicable

12(e)             Not applicable

12(f)             Summary of Appraisal Rights (Included in Exhibit
                  12(a)(1) in the section captioned "The Merger;
                  Appraisal Rights" and Schedule III to Exhibit 12(a)(1)
                  ("Section 262 Of The Delaware General Corporation
                  Law")

12(g)             Slide Presentation of Thermo Electron to Financial
                  Analysts

12(h)             Not applicable

</TABLE>



<PAGE>
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.
                                       AT
                              $9.00 NET PER SHARE
                                       BY
                             ONIX ACQUISITION INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
                         THERMO INSTRUMENT SYSTEMS INC.

    THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
       CITY TIME, ON FRIDAY, APRIL 7, 2000, UNLESS THE OFFER IS EXTENDED.

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES OF COMMON STOCK OF ONIX SYSTEMS INC. (THE "COMPANY") WHICH, TOGETHER WITH
SHARES OWNED BY THERMO ELECTRON CORPORATION AND ITS SUBSIDIARIES, INCLUDING
THERMO INSTRUMENT SYSTEMS INC., CONSTITUTES AT LEAST NINETY PERCENT (90%) OF THE
OUTSTANDING SHARES OF THE COMPANY ON THE EXPIRATION DATE. AS OF JANUARY 28,
2000, THERMO ELECTRON CORPORATION AND ITS SUBSIDIARIES OWNED AN AGGREGATE OF
11,819,167 SHARES OF THE COMPANY'S OUTSTANDING COMMON STOCK, WHICH CONSTITUTED
82.3% OF THE OUTSTANDING SHARES OF COMMON STOCK ON SUCH DATE. THE OFFER IS ALSO
SUBJECT TO OTHER IMPORTANT TERMS AND CONDITIONS CONTAINED IN THIS OFFER TO
PURCHASE.

                            ------------------------

    NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THIS OFFER, PASSED UPON THE FAIRNESS
OR MERITS OF THIS OFFER OR DETERMINED WHETHER THIS OFFER TO PURCHASE IS ACCURATE
OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIME.

                            ------------------------

                     THE DEALER MANAGERS FOR THE OFFER ARE:
                          J.P. MORGAN SECURITIES INC.
                                      AND
                     THE BEACON GROUP CAPITAL SERVICES, LLC

March 13, 2000
<PAGE>
                                    SUMMARY

    BEFORE YOU MAKE ANY DECISION WITH RESPECT TO THE TENDER OFFER, YOU SHOULD
READ THE FOLLOWING SUMMARY TOGETHER WITH THE MORE DETAILED INFORMATION INCLUDED
ELSEWHERE IN THIS OFFER TO PURCHASE. THIS SUMMARY AND THE REMAINDER OF THIS
OFFER TO PURCHASE INCLUDE INFORMATION REGARDING THE TENDER OFFER, THE PROPOSED
SUBSEQUENT SHORT-FORM MERGER, ONIX SYSTEMS INC. AND THE POSITION OF THERMO
INSTRUMENT SYSTEMS INC. AND THERMO ELECTRON CORPORATION REGARDING THE FAIRNESS
OF THE TERMS OF THE TENDER OFFER AND THE MERGER.

- - PRINCIPAL TERMS OF THE TENDER OFFER AND THE MERGER.

    - TENDER OFFER FOR ALL OUTSTANDING SHARES (PAGE 29).  ONIX
      Acquisition Inc., a wholly-owned subsidiary of Thermo Instrument
      Systems Inc., is offering to purchase in a tender offer all of the
      outstanding shares of common stock of ONIX Systems Inc. that Thermo
      Electron Corporation and its subsidiaries, including Thermo Instrument, do
      not currently own.

    - AFFILIATION OF ONIX SYSTEMS, ONIX ACQUISITION, THERMO INSTRUMENT AND
      THERMO ELECTRON (PAGES 7 AND 23).  ONIX Systems is a majority-owned
      subsidiary of Thermo Instrument. ONIX Acquisition is a wholly-owned
      subsidiary of Thermo Instrument. Thermo Instrument is a majority-owned
      subsidiary of Thermo Electron. Certain officers and directors of Thermo
      Instrument and Thermo Electron are also officers or directors of ONIX
      Systems. See "Certain Information Concerning The Company" and "Certain
      Information Concerning The Purchaser, Thermo Instrument And Thermo
      Electron."

    - TENDER OFFER PRICE (PAGES 7 AND 41).  The consideration being offered in
      the tender offer is $9.00 per share in cash. This price represents a
      premium of approximately 31% over $6.896, which was the average closing
      price of ONIX Systems common stock on the American Stock Exchange for the
      one-month period prior to the date the tender offer was announced. This
      price also represents a premium of approximately 3% over $8.75, which was
      the closing price of ONIX Systems common stock on the American Stock
      Exchange on January 28, 2000, the last trading day prior to the date of
      the announcement. The closing price of ONIX Systems common stock on the
      American Stock Exchange on March 9, 2000 was $8.8125 per share. For more
      information regarding the trading range of ONIX Systems common stock, see
      "Price Range Of The Shares; Dividends."

    - CONDITIONS TO THE TENDER OFFER (PAGE 34).  The tender offer is subject to
      a number of conditions, including the condition that enough shares of ONIX
      Systems common stock are tendered and not withdrawn so that on the
      expiration date of the tender offer Thermo Electron and its subsidiaries,
      including Thermo Instrument, will together own at least 90% of ONIX
      Systems' outstanding shares. Assuming that no outstanding ONIX Systems
      stock options are exercised, this 90% tender condition will be met if at
      least 1,102,605 shares of ONIX Systems common stock are validly tendered
      and not withdrawn prior to the expiration date of the tender offer. See
      "The Tender Offer--Certain Conditions Of The Offer."

    - ONIX SYSTEMS SHARES OUTSTANDING; OWNERSHIP BY THERMO ELECTRON AND ITS
      SUBSIDIARIES (PAGE 7).  As of January 28, 2000, ONIX Systems had
      14,357,524 shares of common stock outstanding. In addition, options to
      purchase 667,817 shares of ONIX Systems common stock were outstanding at
      such date. Thermo Electron and Thermo Instrument owned in the aggregate
      11,819,167 shares of ONIX Systems common stock, or approximately 82.3% of
      the outstanding shares of ONIX Systems common stock on January 28, 2000.
      Of the shares of ONIX Systems common stock owned by Thermo Electron and
      Thermo Instrument, an aggregate of 127,567 shares have been reserved for
      issuance under stock options granted by Thermo Instrument and Thermo
      Electron under their employee stock option plans.

    - EXPIRATION OF THE TENDER OFFER (PAGE 29).  The tender offer will expire at
      12:00 midnight on April 7, 2000. We can elect at any time to extend the
      tender offer. If we extend the tender offer, we will issue a press release
      announcing the extension. See "The Tender Offer--Terms Of The Offer;
      Expiration Date."

                                       2
<PAGE>
    - PROCEDURES FOR ACCEPTING THE TENDER OFFER AND TENDERING SHARES
      (PAGE 31).  In order for your shares of ONIX Systems common stock to be
      purchased in the tender offer, you must follow the procedures described in
      "The Tender Offer--Procedures For Accepting The Offer And Tendering
      Shares" and in the accompanying Letter of Transmittal prior to the
      expiration of the tender offer.

    - PAYMENT FOR TENDERED SHARES (PAGE 30).  If all of the conditions of the
      tender offer are satisfied or waived and your shares of ONIX Systems
      common stock are accepted for payment, we will pay you for your shares
      promptly after the expiration of the tender offer. See "The Tender Offer--
      Acceptance For Payment And Payment For Shares."

    - WITHDRAWAL RIGHTS (PAGE 34).  You may withdraw shares that you have
      tendered at any time on or prior to April 7, 2000, or, if the tender offer
      is extended, prior to the expiration of the tender offer. Unless accepted
      for payment on or prior to May 11, 2000, you may also withdraw shares you
      have tendered at any time after that date. In order for a withdrawal to be
      effective, American Stock Transfer & Trust Company, the depositary for the
      tender offer, must receive your notice of withdrawal prior to the
      expiration of the tender offer at one of the addresses on the back cover
      of this Offer to Purchase. For more information on your withdrawal rights,
      see "The Tender Offer--Withdrawal Rights."

    - SUBSEQUENT MERGER (PAGES 24 AND 49).  The tender offer is the first step
      in Thermo Instrument's plan to take ONIX Systems private. If the tender
      offer is completed, Thermo Electron and its subsidiaries, including Thermo
      Instrument, will together own at least 90% of ONIX Systems' outstanding
      shares. Promptly following the closing of the tender offer, Thermo
      Electron and Thermo Instrument plan to contribute their shares of ONIX
      Systems common stock to ONIX Acquisition in exchange for common stock of
      ONIX Acquisition. Thermo Electron and Thermo Instrument would then cause
      ONIX Acquisition to merge with and into ONIX Systems in a so-called
      "short-form" merger. After the merger, ONIX Systems would be owned
      exclusively by Thermo Instrument and Thermo Electron. ONIX Acquisition
      does not intend to enter into a merger agreement with ONIX Systems or to
      seek the approval of the board of directors of ONIX Systems for such
      merger. Stockholders of ONIX Systems who do not tender their shares of
      ONIX Systems common stock in the tender offer will not be entitled to vote
      their shares with respect to this merger, but will have a statutory right
      to demand a judicial appraisal of the fair value of their shares of ONIX
      Systems common stock. See "The Merger; Appraisal Rights." The
      consideration in the merger would be the same $9.00 per share in cash as
      is payable in the tender offer. See "Special Factors--The Merger."

    - OTHER POSSIBLE PURCHASES OF ONIX SYSTEMS COMMON STOCK (PAGE 24).  If,
      after the tender offer is completed but prior to consummation of the
      merger, the aggregate ownership by Thermo Electron and its subsidiaries of
      the outstanding shares of ONIX Systems common stock should fall below 90%
      due to the exercise of outstanding options or for any other reason, ONIX
      Acquisition intends to acquire additional shares of ONIX Systems common
      stock on the open market or in privately negotiated transactions to the
      extent required for the aggregate ownership of ONIX Systems common stock
      by Thermo Electron and its subsidiaries to equal or exceed 90%. These
      purchases would be made at market prices or privately negotiated prices at
      the time of purchase, which may be higher or lower than the price of $9.00
      per share in the tender offer and the merger. See "Special Factors--Other
      Possible Purchases of Shares."

    - SOURCE OF FUNDS (PAGE 48).  The total amount of funds required for ONIX
      Acquisition to purchase all of the outstanding shares of ONIX Systems
      common stock pursuant to the tender offer and merger, assuming no
      outstanding options are exercised, and to pay related expenses is
      estimated to be approximately $24.3 million. ONIX Acquisition will obtain
      the funds to purchase the ONIX Systems common stock in the tender offer
      and the merger from Thermo Instrument as a loan or a capital contribution.
      Thermo Instrument intends to use a combination of its own working capital
      and borrowings from Thermo Electron to fund this loan or capital
      contribution. Thermo Electron has committed to provide any required loan
      financing to Thermo Instrument. Because the tender

                                       3
<PAGE>
      offer and the merger are for cash and Thermo Instrument and Thermo
      Electron have access to sufficient cash to fund the tender offer and the
      merger, we do not believe that the financial condition of Thermo
      Instrument, Thermo Electron or ONIX Acquisition is relevant to your
      decision whether to tender your shares in the tender offer. See "Source
      And Amount Of Funds."

- - THERMO INSTRUMENT'S AND THERMO ELECTRON'S POSITION ON THE FAIRNESS OF THE
  OFFER AND THE MERGER (PAGE 12).

    - DETERMINATION OF THE SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF THERMO
      INSTRUMENT AND THE BOARD OF DIRECTORS OF THERMO ELECTRON.  The board of
      directors of Thermo Instrument, at a meeting held on January 20, 2000,
      appointed Richard F. Syron and Polyvios C. Vintiadis, directors of Thermo
      Instrument, to act as a special committee of the board of directors of
      Thermo Instrument, with full authority to authorize and determine the
      terms of the tender offer and merger and to determine whether the tender
      offer and merger are fair to the public stockholders of ONIX Systems. The
      board of directors of Thermo Electron and the special committee of the
      board of directors of Thermo Instrument have determined that the terms of
      the tender offer and merger are fair to the stockholders of ONIX Systems.
      In considering the fairness of the tender offer and merger from a
      financial point of view, the board of directors of Thermo Electron and the
      special committee of the board of directors of Thermo Instrument reviewed
      and relied in part upon an analysis of the ranges of potential values of
      the shares of ONIX Systems common stock that resulted from the application
      of several accepted valuation methodologies. This analysis, including the
      selection of valuation methodologies, was prepared by J.P. Morgan
      Securities Inc. and The Beacon Group Capital Services, LLC. J.P. Morgan
      and The Beacon Group are the financial advisors to the special committee
      of the board of directors of Thermo Instrument and the board of directors
      of Thermo Electron in connection with the tender offer and the merger and
      the reorganization of Thermo Electron and its subsidiaries described
      below. For a discussion of the factors that the board of directors of
      Thermo Electron and the special committee of the board of directors of
      Thermo Instrument considered in making their determinations as to the
      fairness of the tender offer and the merger and a summary of the financial
      analysis prepared by J.P. Morgan and The Beacon Group, see "Special
      Factors--Position Of Thermo Instrument And Thermo Electron As To Fairness
      Of The Offer And The Merger" and "Special Factors--Summary Of The
      Advisors' Analysis and Opinion."

    - POTENTIAL CONFLICTS OF INTEREST.  Thermo Instrument is the majority
      stockholder of ONIX Systems. Thermo Electron is the majority stockholder
      of Thermo Instrument. Some of the officers and directors of Thermo
      Instrument and Thermo Electron are also officers or directors of ONIX
      Systems and own shares of common stock of, or hold options to purchase
      shares of common stock of, Thermo Electron, Thermo Instrument and/or ONIX
      Systems. As a result, there are various potential or actual conflicts of
      interest in connection with the tender offer and the merger. See "Special
      Factors--Conflicts Of Interest."

- - CONSEQUENCES OF THE OFFER AND THE MERGER (PAGE 24).

    Completion of the tender offer and the merger would have the following
consequences:

    - Thermo Instrument and Thermo Electron would have complete control over
      ONIX Systems' business.

    - Thermo Instrument and Thermo Electron would own 100% of the equity
      interest in ONIX Systems' business and would solely have the benefit or
      detriment of any change in ONIX Systems' value.

    - The shares of ONIX Systems would no longer be listed on the American Stock
      Exchange.

    - ONIX Systems would no longer be subject to the requirements of the
      Securities Exchange Act of 1934, including requirements to file annual and
      other periodic reports or to provide the type of going-private disclosure
      contained in this offer to purchase.

                                       4
<PAGE>
    If you do not tender your shares of ONIX Systems common stock and the tender
offer is completed, your shares will remain outstanding until the subsequent
merger of ONIX Acquisition and ONIX Systems. After the merger, each of your
shares will, subject to statutory appraisal rights, be converted into the right
to receive $9.00 in cash, without interest.

- - APPRAISAL RIGHTS (PAGE 49).

    If you tender your shares of ONIX Systems common stock in the tender offer,
you will not be entitled to exercise statutory appraisal rights under the
Delaware General Corporation Law. If you do not tender your shares in the tender
offer, upon the subsequent merger of ONIX Acquisition and ONIX Systems, you will
have a statutory right to dissent and demand payment of the judicially appraised
fair value of your ONIX Systems shares plus a fair rate of interest, if any,
from the date of the merger. This value may be more or less than the $9.00 per
share cash consideration in the tender offer and the merger. See "The Merger;
Appraisal Rights."

- - PURPOSE OF THE TENDER OFFER (PAGE 10).

    On January 31, 2000, Thermo Electron announced that its board of directors
had authorized its management to proceed with a major reorganization of the
operations of Thermo Electron and its subsidiaries. As part of this
reorganization, Thermo Electron plans to acquire the public minority interests
in most of its subsidiaries that have minority investors, spin off its
separation technologies and fiber-based products business and its medical
products business, and divest a variety of non-core businesses. The primary goal
of the reorganization is for Thermo Electron and each of its spun-off
subsidiaries to focus on its core business. The purpose of this tender offer and
the proposed subsequent merger is to acquire the minority public interest in
ONIX Systems as part of Thermo Electron's overall reorganization and to provide
ONIX Systems' stockholders with $9.00 in cash for each of their shares of ONIX
Systems common stock. Following the tender offer and merger, Thermo Electron
plans to retain ONIX Systems as part of Thermo Electron's core instrument
business.

- - FOR MORE INFORMATION (PAGES 42 AND 45).

    More information regarding ONIX Systems, Thermo Instrument and Thermo
Electron is available from their public filings with the Securities and Exchange
Commission. See "Certain Information Concerning the Company" and "Certain
Information Concerning the Purchaser, Thermo Instrument and Thermo Electron."

    If you have any questions about the tender offer, please call the
information agent, D.F. King & Co., Inc. If you are a banker or broker, call
collect at (212) 269-5550. All others should call toll-free at (800) 290-6433.

                                       5
<PAGE>
                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                PAGE
                                                              --------
<S>                                                           <C>
SUMMARY.....................................................         2
INTRODUCTION................................................         7
THE COMPANY.................................................         9
SPECIAL FACTORS.............................................        10
THE TENDER OFFER............................................        29
CERTAIN FEDERAL INCOME TAX CONSEQUENCES.....................        39
PRICE RANGE OF THE SHARES; DIVIDENDS........................        40
CERTAIN INFORMATION CONCERNING THE COMPANY..................        41
CERTAIN INFORMATION CONCERNING THE PURCHASER, THERMO                44
  INSTRUMENT AND THERMO ELECTRON............................
SOURCE AND AMOUNT OF FUNDS..................................        47
THE MERGER; APPRAISAL RIGHTS................................        48
FEES AND EXPENSES...........................................        51
MISCELLANEOUS...............................................        52
</TABLE>

<TABLE>
<S>                     <C>
SCHEDULE I              MEMBERS OF THE BOARDS OF DIRECTORS AND EXECUTIVE OFFICERS OF
                        THE PURCHASER, THERMO INSTRUMENT AND THERMO ELECTRON

SCHEDULE II             INFORMATION CONCERNING TRANSACTIONS IN THE COMMON STOCK OF
                        THE COMPANY

SCHEDULE III            SECTION 262 OF THE DELAWARE GENERAL CORPORATION LAW
</TABLE>

                                   IMPORTANT

    ANY STOCKHOLDER OF THE COMPANY DESIRING TO TENDER ALL OR ANY PORTION OF SUCH
STOCKHOLDER'S SHARES (AS DEFINED HEREIN) SHOULD EITHER (1) COMPLETE AND SIGN THE
ACCOMPANYING LETTER OF TRANSMITTAL (OR A FACSIMILE THEREOF) IN ACCORDANCE WITH
THE INSTRUCTIONS IN THE LETTER OF TRANSMITTAL, HAVE SUCH STOCKHOLDER'S SIGNATURE
THEREON GUARANTEED IF REQUIRED BY THE INSTRUCTIONS IN THE LETTER OF TRANSMITTAL,
MAIL OR DELIVER THE LETTER OF TRANSMITTAL (OR A MANUALLY SIGNED FACSIMILE) OR,
IN THE CASE OF A BOOK-ENTRY TRANSFER EFFECTED PURSUANT TO THE PROCEDURES SET
FORTH IN "THE TENDER OFFER--PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING
SHARES," AN AGENT'S MESSAGE (AS DEFINED HEREIN), AND ANY OTHER REQUIRED
DOCUMENTS TO THE DEPOSITARY (AS DEFINED HEREIN), AND EITHER DELIVER THE
CERTIFICATES REPRESENTING SUCH SHARES TO THE DEPOSITARY ALONG WITH THE LETTER OF
TRANSMITTAL (OR A MANUALLY SIGNED FACSIMILE) OR DELIVER SUCH SHARES PURSUANT TO
THE PROCEDURES FOR BOOK-ENTRY TRANSFER SET FORTH IN "THE TENDER
OFFER--PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES" OR (2) REQUEST
SUCH STOCKHOLDER'S BROKER, DEALER, COMMERCIAL BANK, TRUST COMPANY OR OTHER
NOMINEE TO EFFECT THE TRANSACTION FOR SUCH STOCKHOLDER. ANY STOCKHOLDER HAVING
SHARES REGISTERED IN THE NAME OF A BROKER, DEALER, COMMERCIAL BANK, TRUST
COMPANY OR OTHER NOMINEE MUST CONTACT SUCH BROKER, DEALER, COMMERCIAL BANK,
TRUST COMPANY OR OTHER NOMINEE IF SUCH STOCKHOLDER DESIRES TO TENDER SUCH
SHARES.

    A STOCKHOLDER WHO DESIRES TO TENDER SHARES AND WHOSE CERTIFICATES
REPRESENTING SUCH SHARES ARE NOT IMMEDIATELY AVAILABLE, OR WHO CANNOT COMPLY IN
A TIMELY MANNER WITH THE PROCEDURES FOR BOOK-ENTRY TRANSFER, MAY TENDER SUCH
SHARES BY FOLLOWING THE PROCEDURES FOR GUARANTEED DELIVERY SET FORTH IN "THE
TENDER OFFER--PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES."

    QUESTIONS AND REQUESTS FOR ASSISTANCE OR FOR ADDITIONAL COPIES OF THIS OFFER
TO PURCHASE, THE LETTER OF TRANSMITTAL OR OTHER TENDER OFFER MATERIALS MAY BE
DIRECTED TO THE INFORMATION AGENT OR THE DEALER MANAGERS, AT THEIR RESPECTIVE
ADDRESSES AND TELEPHONE NUMBERS SET FORTH ON THE BACK COVER OF THIS OFFER TO
PURCHASE. STOCKHOLDERS MAY ALSO CONTACT THEIR BROKER, DEALER, COMMERCIAL BANK OR
TRUST COMPANY FOR ASSISTANCE CONCERNING THE OFFER.

                                       6
<PAGE>
TO THE HOLDERS OF COMMON STOCK OF ONIX SYSTEMS INC.:

                                  INTRODUCTION

    ONIX Acquisition Inc. (the "Purchaser"), a Delaware corporation and a
wholly-owned subsidiary of Thermo Instrument Systems Inc., a Delaware
corporation ("Thermo Instrument"), hereby offers to purchase all outstanding
shares of common stock, par value $.01 per share (the "Shares"), of ONIX
Systems Inc., a Delaware corporation (the "Company"), at a purchase price of
$9.00 per Share (the "Offer Price"), net to the seller in cash, without interest
thereon, upon the terms and subject to the conditions set forth in this Offer to
Purchase and in the related Letter of Transmittal (which, together with any
amendments or supplements hereto or thereto, collectively constitute the
"Offer"). Thermo Instrument is a majority-owned subsidiary of Thermo Electron
Corporation, a Delaware corporation ("Thermo Electron").

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES WHICH, TOGETHER WITH THE SHARES OWNED BY THERMO ELECTRON AND ITS
SUBSIDIARIES, INCLUDING THERMO INSTRUMENT, CONSTITUTES AT LEAST NINETY PERCENT
(90%) OF THE OUTSTANDING SHARES ON THE EXPIRATION DATE OF THE OFFER (THE
"MINIMUM CONDITION"). THE OFFER IS ALSO SUBJECT TO OTHER IMPORTANT TERMS AND
CONDITIONS CONTAINED IN THIS OFFER TO PURCHASE. SEE "THE TENDER OFFER--CERTAIN
CONDITIONS OF THE OFFER."

    As of January 28, 2000, there were 14,357,524 Shares outstanding and 667,817
Shares reserved for issuance pursuant to options (the "Options") outstanding as
of such date under the Company's option plans. As of such date, Thermo
Instrument owned 11,524,867 Shares, or approximately 80.3% of the outstanding
Shares (76.7% assuming all outstanding Options are exercised). Of the Shares
owned by Thermo Instrument, 49,250 Shares have been reserved for issuance under
stock options granted by Thermo Instrument under its stock option plans. As of
January 28, 2000, Thermo Electron owned 294,300 Shares, or approximately 2.0% of
the outstanding Shares (1.96% assuming all outstanding Options are exercised).
Of the Shares owned by Thermo Electron, 78,317 Shares have been reserved for
issuance under stock options granted by Thermo Electron under its stock option
plans.

    Based upon the number of outstanding Shares as of January 28, 2000 and
assuming no Options are exercised, 1,102,605 Shares must be tendered in the
Offer in order to satisfy the Minimum Condition. Assuming all outstanding
Options are exercised, 1,703,640 Shares must be tendered in the Offer in order
to satisfy the Minimum Condition.

    Tendering stockholders will not be obligated to pay brokerage fees or
commissions or, except as otherwise provided in Instruction 6 of the Letter of
Transmittal, stock transfer taxes with respect to the purchase by the Purchaser
of Shares pursuant to the Offer. The Purchaser will pay all fees and expenses of
J.P. Morgan Securities Inc. ("J.P. Morgan") and The Beacon Group Capital
Services, LLC ("The Beacon Group"), which are acting as the Dealer Managers (the
"Dealer Managers"), American Stock Transfer & Trust Company, which is acting as
the Depositary (the "Depositary"), and D.F. King & Co. Inc., which is acting as
the Information Agent (the "Information Agent"), in connection with the Offer.
See "Fees And Expenses."

    This Offer to Purchase and the documents incorporated by reference in this
Offer to Purchase include certain forward-looking statements. These statements
appear throughout this Offer to Purchase and include statements regarding the
intent, belief or current expectations of Thermo Instrument and Thermo Electron
and their Boards of Directors, including statements concerning Thermo
Instrument's and Thermo Electron's strategies following completion of the Offer
and their plans with respect to the acquisition of all of the equity interests
in the Company. Such forward-looking statements are not guarantees of future
performance and involve risks and uncertainties. Actual results may differ
materially from those described in such forward-looking statements as a result
of various factors.

                                       7
<PAGE>
    THIS OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION THAT SHOULD BE READ CAREFULLY BEFORE ANY DECISION IS MADE
WITH RESPECT TO THE OFFER.

    If the Offer is completed, Thermo Electron, Thermo Instrument and the
Purchaser together will own at least 90% of the Shares. Promptly following the
closing of the Offer, Thermo Instrument and Thermo Electron plan to contribute
their Shares to the Purchaser in exchange for common stock of the Purchaser.
Thermo Electron and Thermo Instrument would then cause the Purchaser to merge
with and into the Company in a so-called "short-form" merger between the Company
and the Purchaser (the "Merger"). After the Merger, the Company would be owned
exclusively by Thermo Instrument and Thermo Electron. Stockholders of the
Company who do not tender their Shares in the Offer would not be entitled to
vote on the Merger. The consideration per Share in the Merger would be the same
as the Offer Price.

    If, after the Offer is completed but prior to consummation of the Merger,
the aggregate ownership by Thermo Electron and its subsidiaries, including
Thermo Instrument, of the outstanding Shares should fall below 90% due to the
exercise of outstanding Options or for any other reason, the Purchaser intends
to acquire additional Shares on the open market or in privately negotiated
transactions to the extent required for such ownership to equal or exceed 90%.
Any such purchases would be made at market prices or privately negotiated prices
at the time of purchase, which may be higher or lower than the Offer Price. For
a discussion of other actions Thermo Instrument and Thermo Electron may take if
the Offer is not completed, see "Special Factors--Conduct Of The Company's
Business If the Offer Is Not Completed."

    The Purchaser, Thermo Instrument and Thermo Electron have filed with the
Securities and Exchange Commission (the "Commission") a Tender Offer Statement
on Schedule TO (including the information required by Schedule 13E-3) (the
"Schedule TO") under the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), relating to the Offer, the Merger and other potential purchases
of Shares.

                                       8
<PAGE>
                                  THE COMPANY

    The Company designs, develops, markets and services sophisticated field
measurement instruments and on-line sensors for the process control industry.
The Company operates in two segments: Measurement Instruments and
Industry-Specific Systems. The Company's products are sold primarily to
participants in process industries, including oil and gas producers, refiners,
pipelines, distributors, and chemical and petrochemical companies, as well as
water and wastewater, iron and steel, semiconductor, minerals and mining, and
pulp and paper companies.

    The Company's Measurement Instruments segment manufactures field measurement
instruments and on-line sensors in four general product areas: flow, level and
density, composition analysis, and data acquisition and display. Flow
measurement instruments include gas flow computers, noncontacting ultrasonic
flow meters, turbine flow meters and air flow measurement systems. Level and
density measurement instruments include intelligent point-level and
continuous-level measurement instruments. Composition analysis measurement
instruments include sulfur analyzers, infrared and ultraviolet spectrometers,
gas chromatographs, portable elemental analysis instruments and on-line mass
spectrometers. Data acquisition and display instruments include strip chart
recorders, paperless recorders, AC harmonic analyzers, and data acquisition and
analysis systems.

    The Industry-Specific Systems segment offers sophisticated sensor systems
that are used to provide real-time measurement, data collection, recording,
analysis and local control of process functions. These special purpose
instruments and sensors include rod pump controllers, remote terminal units,
gas-injection systems and wellhead safety systems.

    The Company was incorporated in August 1997. In connection with the
Company's incorporation, Thermo Instrument transferred to the Company all of the
stock of CAC Inc., CAC Limited, Flow Automation Inc., Flow Automation U.K.
Limited, VG Gas Analysis Systems Inc., Westronics Inc., Houston Atlas Inc., TN
Technologies Inc. and Kay-Ray/Sensall Inc. in exchange for 10,666,667 Shares.
The Company acquired the Peek Measurement Business from Thermo Power Corporation
effective November 1997, and both the Rustrak Ranger Logger product line from a
subsidiary of Danaher Corporation and the business of Fluid Data, Inc. from
Elsag-Bailey, Inc. in December 1997. In July 1998, the Company acquired certain
businesses of the Mid-South Companies. The Company completed its initial public
offering in March 1998. In the initial public offering, the Company sold
3,300,000 Shares to the public at a price of $14.50 per Share (for net proceeds
of $43.7 million).

                                       9
<PAGE>
                                SPECIAL FACTORS

BACKGROUND TO THE OFFER AND THE MERGER

    THE THERMO ELECTRON REORGANIZATION.  On January 31, 2000, Thermo Electron
announced that its Board of Directors had authorized its management to proceed
with a major reorganization of the operations of Thermo Electron and its
subsidiaries. As part of this reorganization, Thermo Electron plans to acquire
the public minority interest in most of its subsidiaries that have minority
investors, spin off its separation technologies and fiber-based products
business and its medical products business, and divest a variety of non-core
businesses. The primary goal of the reorganization is for Thermo Electron and
each of its spun-off subsidiaries to focus on their respective core businesses.
The purpose of the Offer and the Merger is to acquire the minority public
interest in the Company as part of Thermo Electron's overall reorganization and
to provide the stockholders of the Company other than Thermo Electron and Thermo
Instrument (the "Public Stockholders") with $9.00 per Share in cash. Following
the Offer and the Merger, Thermo Electron plans to retain the Company as part of
Thermo Electron's core instrument business.

    Previously, on August 12, 1998, Thermo Electron announced that its Board of
Directors had authorized a proposed corporate reorganization to reduce the
complexity of Thermo Electron's corporate structure; consolidate and
strategically realign certain businesses so as to enhance their competitive
market positions and improve management coordination; and, increase the
liquidity in the public markets for the stock of Thermo Electron's publicly
traded subsidiaries. Under the proposal, two public Thermo Instrument
subsidiaries--Metrika Systems Corporation and the Company--and an indirect
public Thermo Electron subsidiary, Thermo Sentron Inc., would have been merged
to form one combined majority-owned public subsidiary of Thermo Instrument.
Under the proposal, stockholders of each of the three companies would have
received shares of common stock of the combined entity in exchange for their
shares in the subsidiaries. On December 10, 1998, however, Thermo Electron
announced that its Board of Directors had determined that Metrika Systems
Corporation and the Company would remain individual public subsidiaries of
Thermo Instrument and not be combined with Thermo Sentron Inc. as had been
previously announced.

    ACTIONS OF THE SPECIAL COMMITTEE OF THERMO INSTRUMENT'S BOARD OF
DIRECTORS.  The Board of Directors of Thermo Instrument, at a meeting held on
January 20, 2000, appointed Richard F. Syron and Polyvios C. Vintiadis,
directors of Thermo Instrument, to act as a special committee of the board of
directors of Thermo Instrument (the "Instrument Special Committee") with full
authority to authorize and determine the terms of the Offer and the Merger and
to determine whether the Offer and the Merger are fair to the Public
Stockholders. Neither Dr. Syron nor Mr. Vintiadis is an officer or director of
the Company or owns Shares or options to purchase Shares. Dr. Syron is the Chief
Executive Officer and a director of Thermo Electron. On January 22, 2000 and
January 29, 2000, the Instrument Special Committee held meetings at which the
proposed plan to acquire the minority stockholder interest in the Company
through the Offer and the Merger was presented and discussed. Effective
March 7, 2000, Dr. Syron resigned from the Board of Directors of Thermo
Instrument.

    ACTIONS OF THERMO ELECTRON'S BOARD OF DIRECTORS.  On January 18, 2000 and
January 28, 2000, the Board of Directors of Thermo Electron held special
meetings at which Thermo Electron's management presented the proposal for Thermo
Instrument to acquire all of the Shares that Thermo Electron and its
subsidiaries, including Thermo Instrument, did not already own as a part of the
proposed corporate reorganization of Thermo Electron and certain of its
subsidiaries. Messrs. George N. Hatsopoulos, John N. Hatsopoulos and Frank
Jungers, members of Thermo Electron's Board of Directors, initially took part in
each of the meetings, but were excused from discussions of the terms of the
Offer and the Merger and from taking action with respect to the Offer because
they hold Shares or options to purchase Shares. The Board of Directors of Thermo
Electron considered all of the factors relating to the Offer and the Merger
referred to below under "--Reasons For The Offer And The Merger" that were
considered by the Instrument Special Committee. The Board of Directors of Thermo
Electron also discussed the fact that the acquisition by Thermo Instrument of
the minority stockholder interest in the Company would advance the goal of
Thermo Electron's proposed corporate reorganization. After consideration of
these factors, the members

                                       10
<PAGE>
of the Board of Directors of Thermo Electron, other than those members indicated
above who did not participate in the voting, unanimously resolved that Thermo
Electron would not object if Thermo Instrument determined to take the Company
private through Thermo Instrument's acquisition for cash through the Offer and
Merger of all of the Shares held by the Public Stockholders at a purchase price
of $9.00 per Share.

REASONS FOR THE OFFER AND THE MERGER

    BENEFITS AND DETRIMENTS TO THE COMPANY OF THE OFFER AND THE MERGER.  In
determining whether to make the Offer and thereafter effect the Merger, the
Board of Directors of Thermo Electron and the Instrument Special Committee
considered several factors, including the financial performance and
profitability of the Company and the potential benefits to the Company's
business if the Company were to become part of a larger business unit. Thermo
Electron's Board of Directors and the Instrument Special Committee also
considered the following factors:

    - the prospect of achieving greater marketing, operating and administrative
      efficiency as a result of the Company's operations being conducted in a
      more coordinated manner with Thermo Electron's other instruments
      subsidiaries;

    - the reduction in the amount of public information available to competitors
      about the Company's businesses that would result from the termination of
      the Company's obligations under the reporting requirements of the
      Commission;

    - the elimination of additional burdens on management associated with public
      reporting and other tasks resulting from the Company's public company
      status, including, for example, the dedication of time by and resources of
      the Company's management and Board of Directors to stockholder and analyst
      inquiries and investor and public relations;

    - the decrease in costs, particularly those associated with being a public
      company (for example, as a privately-held entity, the Company would no
      longer be required to file quarterly, annual or other periodic reports
      with the Commission or publish and distribute to its stockholders annual
      reports and proxy statements), that the Board of Directors of Thermo
      Electron and the Instrument Special Committee anticipate could result in
      savings of approximately $450,000 per year, including fees for an audit by
      an independent accounting firm and legal fees;

    - the greater flexibility that the Company's management would have to focus
      on long-term business goals, as opposed to quarterly earnings, as a
      non-reporting company, particularly in light of the potential volatility
      in the Company's quarterly earnings; and

    - recent public capital market trends affecting small-cap companies,
      including perceived lack of interest by institutional investors in
      companies with a limited public float.

    The Board of Directors of Thermo Electron and the Instrument Special
Committee also considered the advantages and disadvantages of certain
alternatives to acquiring the minority stockholder interest in the Company,
including:

    - a sale of their equity interests in the Company; and

    - leaving the Company as a majority-owned, public subsidiary.

    The first alternative, selling Thermo Electron's and Thermo Instrument's
equity interests in the Company, was briefly considered. It was not an
alternative that was pursued at length, given that Thermo Electron and Thermo
Instrument did not want to sell their equity interests in the Company, but
rather intended to retain the Company as a part of Thermo Electron's core
instruments business.

    In the view of the Board of Directors of Thermo Electron and the Instrument
Special Committee, the principal advantage of leaving the Company as a
majority-owned, public subsidiary of Thermo Instrument was the ability of Thermo
Instrument to invest the cash that would be required to buy the minority
stockholder interest in the Company for other purposes. The disadvantages of
leaving the Company as a

                                       11
<PAGE>
majority-owned, public subsidiary that were considered by the Board of Directors
of Thermo Electron and the Instrument Special Committee included the inability
to achieve many of the benefits of taking the Company private discussed above.
The Board of Directors of Thermo Electron and the Instrument Special Committee
concluded that the advantages of leaving the Company as a majority-owned, public
subsidiary of Thermo Instrument were significantly outweighed by the
disadvantages of doing so, and accordingly that alternative was rejected.

    The Instrument Special Committee and Thermo Electron's Board of Directors
have determined to make the Offer and effect the Merger at this time as part of
a larger reorganization of Thermo Electron and its subsidiaries. The Company's
stock price was not a significant factor in the timing of the Instrument Special
Committee's decision to acquire the minority stockholder interest in the
Company.

    CONSIDERATION OF LIQUIDITY AND SHARE PRICE; TIMING.  The Board of Directors
of Thermo Electron and the Instrument Special Committee also considered the
relatively low volume of trading in the Shares and considered that the Offer and
the Merger would result in immediate, enhanced liquidity for the Public
Stockholders. The Board of Directors of Thermo Electron and the Instrument
Special Committee considered trends in the price of the Shares in the past
twelve months and during the period between the Company's initial public
offering and the announcement of the intention of Thermo Electron and Thermo
Instrument to take the Company private.

    ALTERNATIVE STRUCTURE CONSIDERED.  The Board of Directors of Thermo Electron
and the Instrument Special Committee also considered whether to structure the
transaction as a tender offer followed by a short-form merger or as a long-form
merger. In determining to structure the transaction as a tender offer followed
by a short-form merger, the Board of Directors of Thermo Electron and the
Instrument Special Committee considered the following:

    - Unless at least 90% of the outstanding Shares are owned by the Purchaser,
      it could not effect a short-form merger. Unlike a long-form merger, the
      approval of the Company's Board of Directors is not required to complete a
      short-form merger.

    - A tender offer followed by a short-form merger would permit Thermo
      Instrument and Thermo Electron to acquire the minority interest in the
      Company on an expeditious basis and provide the Public Stockholders with a
      prompt opportunity to receive the Offer Price of $9.00 per Share.

    - In the Offer, each Public Stockholder would individually determine whether
      to accept the Offer Price of $9.00 per Share.

    - Public Stockholders who do not tender their Shares in the Offer could
      preserve their appraisal rights in the Merger under state law.

    After discussing the advantages and disadvantages of acquiring the minority
stockholder interest in the Company, including the alternative method of
acquiring such interests through a long-form merger, the Board of Directors of
Thermo Electron and the Instrument Special Committee authorized taking the
Company private through a tender offer for all of the Shares of the Company that
Thermo Electron and its subsidiaries, including Thermo Instrument, did not
already own, at a price per Share of $9.00 in cash, to be followed by a
short-form merger at the same price.

POSITION OF THERMO INSTRUMENT AND THERMO ELECTRON AS TO FAIRNESS OF THE OFFER
  AND THE MERGER

    Because Thermo Instrument and Thermo Electron together currently own a
majority of the Shares, Thermo Electron, Thermo Instrument and the Purchaser are
deemed "affiliates" of the Company under Rule 12b-2 of the Exchange Act.
Accordingly, in compliance with Rule 13e-3 under the Exchange Act, the Board of
Directors of Thermo Electron and the Instrument Special Committee have
considered the fairness of the Offer and the Merger to the Public Stockholders.

    DETERMINATIONS OF THE BOARD OF DIRECTORS OF THERMO ELECTRON AND THE
INSTRUMENT SPECIAL COMMITTEE.  In authorizing the Offer and the Merger, the
Board of Directors of Thermo Electron and the Instrument

                                       12
<PAGE>
Special Committee determined that the Offer and the Merger are fair to the
Public Stockholders. In reaching their determinations that the terms of the
Offer and the Merger are fair to the Public Stockholders, the Board of Directors
of Thermo Electron and the Instrument Special Committee considered the factors
set forth under this section captioned "Position Of Thermo Instrument And Thermo
Electron As To Fairness Of The Offer And The Merger," which constitute all of
the material factors considered by the Board of Directors of Thermo Electron and
the Instrument Special Committee in making their determinations. The Board of
Directors of Thermo Electron and the Instrument Special Committee determined
that each of the following factors supported their belief that the Offer and the
Merger are fair to the Public Stockholders:

    - FINANCIAL ANALYSIS.  In considering the fairness of the Offer and the
      Merger from a financial point of view to the Company's stockholders,
      including the Public Stockholders, the Board of Directors of Thermo
      Electron and the Instrument Special Committee reviewed and relied in part
      upon an analysis of the ranges of potential values of the Shares that
      resulted from the application of several accepted valuation methodologies.
      This financial analysis, including the selection of valuation
      methodologies, was prepared by J.P. Morgan Securities Inc. ("J.P. Morgan")
      and The Beacon Group Capital Services, LLC ("The Beacon Group", and
      together with J.P. Morgan, the "Advisors") to assist the Board of
      Directors of Thermo Electron and the Instrument Special Committee with
      their evaluation of the Offer and the Merger. Thermo Electron retained
      J.P. Morgan and The Beacon Group as its financial advisors for the purpose
      of advising Thermo Electron in connection with its strategic alternatives,
      including advising the Board of Directors of Thermo Electron and the
      Instrument Special Committee in connection with the acquisition of the
      minority interest in the Company. The financial analyses undertaken by the
      Advisors included an analysis based upon public trading multiples,
      comparable buy-out transactions and discounted cash flows. The analysis of
      trading multiples of companies engaged in businesses which the Advisors
      judged to be analogous to the Company's business indicated an estimated
      range of equity values for the Shares of approximately $8.50 to $9.50 per
      Share. The analysis of other buyout transactions indicated an estimated
      range of equity values for the Shares of between $7.75 and $9.50 per
      Share. The analysis based upon discounted cash flows indicated an
      estimated range of equity values for the Shares of between $7.50 and $8.25
      per Share. See "--Summary of The Advisors' Analysis and Opinion."

    - INFORMATION CONCERNING THE FINANCIAL PERFORMANCE, CONDITION, BUSINESS
      OPERATIONS AND PROSPECTS OF THE COMPANY.  The Board of Directors of Thermo
      Electron and the Instrument Special Committee believed the Offer Price to
      be attractive in light of the Company's current financial performance,
      profitability and growth prospects. In addition, the Offer and the Merger
      would shift the risk of the future financial performance of the Company
      from the Public Stockholders, who do not have the power to control
      decisions made as to the Company's business, entirely to Thermo Electron
      and Thermo Instrument, who do have the power to control the Company's
      business and who have the resources to manage and bear the risks inherent
      in the business over the long term. See "--Certain Projected Financial
      Data."

    - THE PREMIUM REFLECTED IN THE OFFER PRICE OF $9.00 PER SHARE.  The Board of
      Directors of Thermo Electron and the Instrument Special Committee
      considered the current and historical trading prices of the Shares. The
      market price of the Shares had declined from $14.50 on March 25, 1998, the
      date of the Company's initial public offering, to $8.75 on January 28,
      2000, the last trading day immediately prior to the announcement by Thermo
      Instrument and Thermo Electron of their intention to take the Company
      private. The Offer Price represents a premium of approximately 31% over
      the average closing price of $6.896 for the one-month period prior to the
      announcement. The Offer Price also represents a premium of approximately
      3% over the closing price of $8.75 on January 28, 2000. The purchase by
      Thermo Instrument would eliminate the exposure of the Public Stockholders
      to any future or continued declines in the price of the Shares. See
      "--Certain Effects Of The Offer And The Merger."

    - TERMS OF THE OFFER.  The Board of Directors of Thermo Electron and the
      Instrument Special Committee considered the terms of the Offer and the
      Merger, including (1) the amount and form

                                       13
<PAGE>
      of the consideration, (2) the limited number of conditions to the
      obligations of the Purchaser, including the absence of a financing
      condition, (3) the tender offer structure, which would provide an
      expeditious means for the Public Stockholders to receive the Offer Price
      and (4) the Minimum Condition.

    - THE MARKET PRICE AND RELATIVE LACK OF LIQUIDITY FOR THE SHARES AND THE
      LIQUIDITY THAT WOULD BE REALIZED BY THE PUBLIC STOCKHOLDERS FROM THE
      ALL-CASH OFFER.  The Board of Directors of Thermo Electron and the
      Instrument Special Committee believed that the liquidity that would result
      from the Offer and the Merger would be beneficial to the Public
      Stockholders because Thermo Instrument's and Thermo Electron's combined
      significant ownership of Shares (1) results in a relatively small public
      float that necessarily limits the amount of trading in the Shares and
      (2) decreases the likelihood that a proposal to acquire the Shares would
      be made by an independent entity without the consent of Thermo Instrument
      and Thermo Electron.

    - THERMO ELECTRON'S AND THERMO INSTRUMENT'S DETERMINATION TO RETAIN THEIR
      MAJORITY OWNERSHIP OF THE COMPANY AND NOT TO SEEK A THIRD PARTY BUYER FOR
      THE COMPANY.  Thermo Instrument and Thermo Electron stated their current
      intention to retain their majority holdings in the Company, which
      foreclosed the opportunity to consider an alternative transaction with a
      third party purchaser of the Company or otherwise provide liquidity to the
      Public Stockholders. Accordingly, it is unlikely that finding a third
      party buyer for the Company was a realistic option for the Public
      Stockholders.

    With the exception of the letter from and discussions with a financial
institution set forth below, neither Thermo Instrument nor Thermo Electron
received an offer for the Company from a third party in the prior two years.
Neither Thermo Instrument nor Thermo Electron solicited an offer for the Company
from a third party in the prior two years.

    In October 1999, the management of Thermo Electron received a one page
letter from a financial institution expressing interest in "exploring the
possibility of acquiring" the Company. The letter indicated that its preliminary
analysis of public information regarding the Company would support a valuation
in the $10 to $12 per Share range. The potential buyer indicated a desire to
perform sufficient due diligence to firm up an offer, with appropriate access to
be given to the Company and management. Subsequent to this letter, management of
Thermo Electron and the Company engaged in limited discussions with the
potential buyer. Following these discussions, the potential buyer orally reduced
its offer to $10 per Share and expressed concern regarding various issues in the
Company's operations and future results. The potential buyer expressed the need
to conduct further due diligence and secure financing in order to firm up any
offer it might make for the Company. Management of Thermo Electron expressed its
concern with these conditions to the potential buyer, and to date, the Company
has not received a firm offer or any further correspondence from this potential
buyer. There have also been no further discussions between the parties regarding
the possible acquisition of the Company.

    PROCEDURAL FAIRNESS.  The Board of Directors of Thermo Electron and the
Instrument Special Committee also determined that the Offer and the Merger are
procedurally fair to the Public Stockholders. In making such determination, the
Board of Directors of Thermo Electron and the Instrument Special Committee
considered the following factors:

    - Each Public Stockholder can individually determine whether to tender
      Shares in the Offer.

    - The Offer provides the opportunity for the Public Stockholders to sell
      their Shares without incurring brokerage and other costs typically
      associated with market sales.

    - In determining the Offer Price, the Board of Directors of Thermo Electron
      and the Instrument Special Committee relied in part upon an analysis
      prepared by the Advisors of the ranges of potential values of the Shares
      that resulted from the application of several accepted valuation
      methodologies. See "--Summary Of The Advisors' Analysis and Opinion."

    - Public Stockholders who believe that the terms of the Offer and the Merger
      are not fair can pursue appraisal rights in the Merger under state law.

                                       14
<PAGE>
    CERTAIN NEGATIVE CONSIDERATIONS.  The Board of Directors of Thermo Electron
and the Instrument Special Committee also considered the following factors, each
of which they considered to be negative, in their deliberations concerning the
fairness of the terms of the Offer and the Merger:

    - TERMINATION OF PARTICIPATION IN FUTURE GROWTH OF THE COMPANY.  Following
      the successful completion of the Offer and the Merger, the Public
      Stockholders would cease to participate in the future earnings or growth,
      if any, of the Company or benefit from increases, if any, in the value of
      their holdings in the Company.

    - CONFLICTS OF INTEREST.  The financial interests of Thermo Electron and
      Thermo Instrument are adverse, as to the Offer Price, to the financial
      interests of the Public Stockholders. In addition, some of the officers
      and directors of the Company, Thermo Instrument and Thermo Electron have
      actual or potential conflicts of interest in connection with the Offer and
      the Merger. See "--Conflicts Of Interest."

    - NO PUBLIC STOCKHOLDER APPROVAL.  The Offer and the Merger do not provide
      the Public Stockholders with an opportunity to vote on the proposed
      transaction.

    - NO UNAFFILIATED REPRESENTATIVE OR INDEPENDENT DIRECTOR APPROVAL.  The
      members of the Board of Directors of the Company who are not employees of
      the Company or directors or executive officers of Thermo Instrument or
      Thermo Electron have not retained an unaffiliated representative to act
      solely on behalf of the Public Stockholders for purposes of negotiating
      the terms of the Offer and the Merger or preparing a report concerning the
      fairness of the Offer and the Merger. The Board of Directors of the
      Company has delegated to a special committee of an independent director
      (the "Special Committee") the authority to make a recommendation to the
      Public Stockholders with respect to the Offer and to prepare a
      Solicitation/Recommendation Statement on Schedule 14D-9, as required by
      the rules of the Commission. The Special Committee retained Tucker Anthony
      Cleary Gull to act as financial advisor to the Special Committee.

    OTHER FACTORS.  The Board of Directors of Thermo Electron and the Instrument
Special Committee did not consider the net book value of the Company as a
relevant factor in assessing the Company's value and, accordingly, did not
evaluate the fairness of the Offer Price in relation to the Company's net book
value. The Board of Directors of Thermo Electron and the Instrument Special
Committee relied in part upon valuation methodologies selected by the Advisors
for the purpose of their financial analysis, and the Board of Directors of
Thermo Electron and the Instrument Special Committee noted that the Advisors did
not employ net book value in their financial analysis. Moreover, the Board of
Directors of Thermo Electron and the Instrument Special Committee did not
believe that an analysis based upon net book value was appropriate for an
instruments business, as this valuation methodology more typically is used in
the banking, utilities, real estate and financial services industries.

    The Board of Directors of Thermo Electron and the Instrument Special
Committee also did not consider "shopping" the Company to prospective
purchasers. Shopping the Company would not only entail substantial time delays
and allocation of management's time and energy, but would also disrupt and
discourage the Company's employees and create uncertainty among the Company's
customers and suppliers. Furthermore, Thermo Instrument and Thermo Electron do
not intend to sell the Company, but rather intend to continue to operate the
Company as part of Thermo Electron's core instruments business.

    The Board of Directors of Thermo Electron and the Instrument Special
Committee did not consider the Offer Price as compared to any implied
liquidation value because it was not contemplated that the Company be
liquidated, whether or not the Offer and the Merger were completed. See
"--Conduct Of The Company's Business After The Offer And The Merger."

    RECENT PURCHASES OF SHARES BY THERMO ELECTRON AND THERMO INSTRUMENT.  See
Schedule II to this Offer to Purchase for information on purchases of Shares by
Thermo Electron and Thermo Instrument (as well as by the Company) during the
past two years.

                                       15
<PAGE>
    CONCLUSIONS OF THE BOARD OF DIRECTORS OF THERMO ELECTRON AND THE INSTRUMENT
SPECIAL COMMITTEE.  The Board of Directors of Thermo Electron and the Instrument
Special Committee concluded that, given the performance of the Shares between
the Company's initial public offering and the announcement of the intention of
Thermo Electron and Thermo Instrument to take the Company private, the
uncertainties surrounding the Company's future growth prospects and the limited
trading market for the Shares, the Offer and Merger would result in a fair
treatment of the Public Stockholders. In determining that the Offer and the
Merger are fair to the Public Stockholders, the Board of Directors of Thermo
Electron and the Instrument Special Committee considered the above factors as a
whole and did not assign specific or relative weights to them, other than that
the Offer Price of $9.00 per Share in cash was considered the most important
factor.

    In making the determination as to fairness, the Instrument Special Committee
and the Board of Directors of Thermo Electron also had access to the financial
projections for the fourth quarter of fiscal 1999 and for fiscal 1999 and 2000,
which were prepared by the Company as part of its normal operations (the "2000
Projections"). See "--Certain Projected Financial Data."

SUMMARY OF THE ADVISORS' ANALYSIS AND OPINION

    Thermo Electron retained J.P. Morgan and The Beacon Group as its exclusive
financial advisors for the purpose of advising Thermo Electron in connection
with its strategic alternatives, including advising the Board of Directors of
Thermo Electron and the Instrument Special Committee in connection with the
acquisition of the minority interest in the Company. On a number of occasions on
or about January 14, 2000, the Advisors discussed with the management of Thermo
Electron the preliminary results of their analysis of the ranges of potential
values of the Shares that resulted from the application of several accepted
valuation methodologies. The Advisors subsequently presented the results of
their Analysis to the Board of Directors of Thermo Electron on January 18, 2000
and January 28, 2000 and to the Instrument Special Committee on January 22, 2000
and January 29, 2000. This financial analysis, including the selection of
valuation methodologies, was prepared by the Advisors to assist the Board of
Directors of Thermo Electron and the Instrument Special Committee with their
evaluation of the Offer and the Merger. At the January 28, 2000 and January 29,
2000 meetings of the Board of Directors of Thermo Electron and the Instrument
Special Committee, respectively, the Advisors also orally delivered their
opinion (the "Opinion"), subsequently confirmed in a written opinion dated
January 29, 2000, that, as of such date and based upon and subject to the
various factors, assumptions and limitations set forth in their Opinion, the
consideration of $9.00 net per Share in cash to be paid pursuant to the Offer
and the Merger was fair from a financial point of view to Thermo Instrument and
Thermo Electron.

    THE ADVISORS' FINANCIAL ANALYSIS AND RELATED OPINION WAS PROVIDED TO THE
BOARD OF DIRECTORS OF THERMO ELECTRON AND THE INSTRUMENT SPECIAL COMMITTEE. THE
OPINION IS DIRECTED ONLY TO THE FAIRNESS OF THE CONSIDERATION FROM A FINANCIAL
POINT OF VIEW TO THERMO INSTRUMENT AND THERMO ELECTRON (AND NOT TO THE PUBLIC
STOCKHOLDERS) AND DOES NOT CONSTITUTE A RECOMMENDATION AS TO WHETHER OR NOT THE
PUBLIC STOCKHOLDERS SHOULD TENDER THEIR SHARES IN THE OFFER.

                                       16
<PAGE>
    In conducting their financial analysis and rendering their Opinion, the
Advisors reviewed, among other things:

    - the audited financial statements of the Company, Thermo Instrument and
      Thermo Electron for the fiscal year ended January 2, 1999;

    - the unaudited financial statements of the Company, Thermo Instrument and
      Thermo Electron for the period ended October 2, 1999;

    - current and historical market prices of the Shares;

    - certain publicly available information concerning the business of the
      Company and of certain other companies engaged in businesses deemed by the
      Advisors to be comparable to those of the Company;

    - the reported market prices for securities of certain other companies
      deemed by the Advisors to be comparable to the Company;

    - publicly available terms of certain transactions involving companies
      deemed by the Advisors to be comparable to the Company and the
      consideration paid for such companies;

    - the terms of other business combinations deemed relevant by the Advisors;

    - the 2000 Projections; and

    - certain agreements with respect to outstanding indebtedness or obligations
      of the Company, Thermo Instrument and Thermo Electron.

    The Advisors also held discussions with certain members of the management of
the Company, Thermo Instrument and Thermo Electron with respect to certain
aspects of the Offer and the Merger. In addition, the Advisors held discussions
with certain members of management of the Company, Thermo Instrument and Thermo
Electron with respect to the past and current business operations of the
Company, the financial condition and future prospects and operations of the
Company and certain other matters believed necessary or appropriate to the
Advisors' inquiry. In addition, the Advisors reviewed such other financial
studies and analyses and considered such other information as the Advisors
deemed appropriate for the purposes of their financial analysis and Opinion. No
limitation was placed upon the scope of the Advisors' investigation or valuation
methodologies by Thermo Instrument or Thermo Electron.

    The Advisors relied upon and assumed, without independent verification, the
accuracy and completeness of all information that was publicly available or that
was furnished to, or discussed with, the Advisors by Thermo Instrument, Thermo
Electron and the Company or otherwise reviewed by the Advisors, and the Advisors
have not assumed any responsibility or liability therefor. The Advisors also
assumed that there have been no material changes in the Company's condition,
results of operations, business or prospects since the date of the most recent
financial statements made available to the Advisors. The Advisors have not
conducted, and did not assume any responsibility for conducting, any valuation,
appraisal or physical inspection of any of the Company's assets or liabilities
(contingent or otherwise), nor have any valuations or appraisals been provided
to the Advisors. In relying on the financial analyses, projections and estimates
provided to, or discussed with, the Advisors, the Advisors have assumed that
they have been reasonably prepared based on assumptions reflecting the best
currently available estimates and judgments by management as to the expected
future financial performance of the Company.

    The 2000 Projections used by the Advisors were prepared by management of the
Company. None of the Company, Thermo Instrument or Thermo Electron publicly
discloses internal management projections of the type used by the Advisors in
connection with the Advisors' analysis of the Offer and the Merger, and such
projections were not prepared with a view toward public disclosure. The 2000
Projections and the additional projections prepared by the Advisors were based
on numerous variables and assumptions that are inherently uncertain and may be
beyond the control of the management of the Company, Thermo Electron and Thermo
Instrument, including, without limitation, factors related to general economic
and

                                       17
<PAGE>
competitive conditions and prevailing interest rates. Accordingly, actual
results could vary significantly from those set forth in such projections. See
"--Certain Projected Financial Data."

    The Advisors' financial analysis and Opinion are necessarily based on
economic, market and other conditions as in effect on, and the information made
available to the Advisors as of, the date of their Opinion. Subsequent
developments may affect the financial analysis and the conclusions in the
Opinion, and the Advisors do not have any obligation to update, revise or
reaffirm their financial analysis or Opinion.

    In accordance with customary investment banking practice, the Advisors
employed generally accepted valuation methods in conducting their financial
analysis and reaching their Opinion. The following is a summary of the material
financial analyses undertaken by the Advisors with respect to the Company and
presented to the Board of Directors of Thermo Electron and the Instrument
Special Committee:

    PUBLIC TRADING MULTIPLES. Using publicly available information, the
    Advisors compared selected financial data of the Company with similar
    data for selected publicly traded companies engaged in businesses which
    the Advisors judged to be analogous to the Company's business. The
    companies selected by the Advisors were Roxbury Group plc.,
    Milltronics Ltd. and Moore Products Co. These companies were selected,
    among other reasons, because they compete in similar industries with
    fairly similar competitive dynamics and growth potential. For each
    comparable company, publicly available financial performance through the
    most recent last twelve months was measured. In addition, the Advisors
    derived estimates of sales, EBITDA, EBIT and net income for the year
    ended December 31, 2000 for each comparable company from the
    Institutional Brokers Estimates System.

    The Advisors applied a range of multiples derived from such analysis to
    the Company's estimated (based upon the 2000 Projections) sales, EBITDA,
    EBIT and net income for fiscal years 1999 and 2000, and arrived at an
    estimated range of equity values for the Shares of approximately $8.50
    to $9.50 per Share.

    SELECTED TRANSACTION ANALYSIS. Using publicly available information, the
    Advisors examined 21 selected transactions in which companies engaged in
    businesses which the Advisors judged to be analogous to the Company's
    were acquired within the last four years. Specifically, the Advisors
    reviewed the following transactions (indicated as target/acquiror): Met
    One Inc./ Pacific Scientific Co., Semiconductor Systems Inc./FSI
    International Inc., Span Instruments Inc./ Tylan General Inc., Measurex
    Corporation/Honeywell Inc., John Chatillon & Sons, Lloyd/ AMETEK Inc.,
    Petrotech Inc./Roper Industries Inc., Numar Corporation/Halliburton Co.,
    Milltronics Ltd./Siemens AG, Moore Products Co./Siemens Energy &
    Automation (subsidiary of Siemens AG), BIE
    Technologies Inc./Shareholders, Gems Sensors, Inc./Danaher Corporation,
    Computational Systems Inc./Emerson Electric Co., Phase Shift
    Technology Inc./ADE Corporation, Granville-Phillips Co./Helix Technology
    Corporation, Data Measurement Corporation/Metrika Systems Corporation,
    Unit Instruments Inc./United States Filter Corporation,
    Inframetrics Inc./FLIR Systems, Inc., Environmental Systems
    Corporation/TSI Inc., TSI Inc./Investor Group, Drexelbrook Engineering
    Co./AMETEK Inc. and The Mobrey Group plc/The Roxboro Group plc. The
    Advisors applied a range of multiples derived from such analysis to the
    Company's estimated (based upon the 2000 Projections) sales, EBITDA,
    EBIT and net income for fiscal year 1999, and arrived at an estimated
    range of equity values for the Shares of between $7.75 and $9.50 per
    Share

    No company or transaction used in the comparable public trading multiple
    analysis or the selected transaction analysis is identical to the
    Company or the Offer and the Merger. Accordingly, an analysis of the
    results of the foregoing necessarily involves complex considerations and
    judgments concerning differences in financial and operating
    characteristics of the Company and other factors that could affect the
    public trading value of the companies to which they are being compared.
    In evaluating the comparable companies, the Advisors made judgments and
    assumptions with regard to industry performance, general business,
    economic,

                                       18
<PAGE>
    market and financial conditions and other matters, many of which are
    beyond the control of the Company.

    DISCOUNTED CASH FLOW ANALYSIS. The Advisors conducted a discounted cash
    flow analysis for the purpose of determining the fully diluted equity
    value per Share. The Advisors calculated the unlevered free cash flows
    that the Company is expected to generate during fiscal years 2000
    through 2004 based upon financial projections prepared by the Advisors
    after discussions with the management of the Company, Thermo Instrument
    and Thermo Electron. The Advisors also calculated a range of terminal
    asset values of the Company at the end of the 5-year period ending 2004
    by applying a perpetual growth rate ranging from 1.0% to 2.0% to the
    unlevered free cash flow of the Company during the final year of the
    5-year period. The unlevered free cash flows and the range of terminal
    asset values were then discounted to present values using a range of
    discount rates from 11.0% to 12.0%, which were chosen by the Advisors
    based upon an analysis of the Company's weighted average cost of
    capital. The present value of the unlevered free cash flows and the
    range of terminal asset values were then adjusted for the Company's
    estimated 1999 fiscal year-end excess cash, option exercise proceeds and
    total debt. Based on this analysis, the Advisors calculated an estimated
    range of equity values of between $7.50 and $8.25 per Share.

    HISTORICAL COMMON STOCK PERFORMANCE. The Advisors conducted a historical
    analysis of the closing price of the Shares over the 52-week period
    prior to the date of their Opinion and also reviewed the closing price
    of the Shares as of the date two weeks prior to the date of their
    Opinion. During the 52-week period, based on closing prices on the
    American Stock Exchange, the Company's Shares achieved a high closing
    price of $8.75 on January 28, 2000 and a low closing price of $4.50 on
    October 18, 1999. On January 14, 2000, the closing price of the Shares
    was $7.50.

    The summary set forth above does not purport to be, and is not, a complete
description of the financial analyses or data undertaken or presented by the
Advisors. The summary of the Advisors' Opinion set forth in this Offer to
Purchase is qualified in its entirety by reference to the full text of the
written Opinion. The full text of the Advisors' written Opinion, which sets
forth among other things the assumptions made, procedures followed, matters
considered and limitations on the scope of the review undertaken by J.P. Morgan
and The Beacon Group in conducting their financial analysis and in rendering
their Opinion, is attached as Exhibit 12(c) to the Schedule TO. The written
Opinion should be read carefully and in its entirety. A copy of the Advisors'
written Opinion will be made available for inspection and copying at the
principal office of Thermo Electron during its regular business hours upon
request from any record holder of the Shares or a representative of such person
designated as such in writing or may be obtained from the Schedule TO filed with
the Commission. Requests to have the Opinion made available should be directed
to the Corporate Secretary of Thermo Electron at the address set forth under
"Certain Information Concerning The Purchaser, Thermo Instrument And Thermo
Electron."

    The preparation of the financial analysis and the related fairness Opinion
is a complex process and is not necessarily susceptible to partial analysis or
summary description. In arriving at their Opinion, the Advisors considered the
results of all of their analyses as a whole and did not attribute any particular
weight to any analysis or factor considered by them. The Advisors believe that
the summary set forth above and their analyses must be considered as a whole and
that selecting portions thereof, without considering all of their analyses,
could create an incomplete view of the processes underlying their analyses and
Opinion. In addition, the Advisors may have given various analyses and factors
more or less weight than other analyses and factors, and may have deemed various
assumptions more or less probable than other assumptions so that the ranges of
valuation resulting from any particular financial analysis described should not
be taken as the Advisors' view of the actual value of the Company. The Advisors
based their analyses on assumptions that they deemed reasonable, including
assumptions concerning general business and economic conditions and
industry-specific factors. The other principal assumptions upon which the
Advisors based their analyses are set forth above under the description of each
such analysis. The Advisors' analyses are not necessarily indicative of actual
values or actual future results that might be achieved, which values may be
higher or lower than those indicated. Moreover, the Advisors' analyses are not
and do

                                       19
<PAGE>
not purport to be appraisals or otherwise reflective of the prices at which
businesses actually could be bought or sold.

    As described above, the Advisors' financial analysis and Opinion was only
one of many factors considered by the Board of Directors of Thermo Electron and
the Instrument Special Committee in their determination that the terms of the
Offer and the Merger are fair to the Public Stockholders and should not be
viewed as determinative of the views of the Board of Directors of Thermo
Electron and the Instrument Special Committee with respect to the value of the
Company.

    The Advisors advised the Board of Directors of Thermo Electron and the
Instrument Special Committee in connection with the Offer and the Merger in part
because the Advisors had been retained to advise Thermo Electron in connection
with the overall reorganization of Thermo Electron and its subsidiaries. The
Board of Directors of Thermo Electron and the Instrument Special Committee also
considered J.P. Morgan's and The Beacon Group's experience and expertise. J.P.
Morgan is an international corporate and investment bank and The Beacon Group is
a nationally recognized private investment banking firm. As part of their
investment banking businesses, J.P. Morgan and The Beacon Group are regularly
engaged in the valuation of businesses and securities in connection with mergers
and acquisitions, investments for passive and control purposes, negotiated
underwritings, competitive biddings, secondary distributions of listed and
unlisted securities, private placements and valuations for estate, corporate and
other purposes.

    J.P. Morgan has advised the Board of Directors of Thermo Electron and the
Instrument Special Committee that, in the ordinary course of its business, it or
its affiliates may actively trade the debt and/or equity securities of the
Company, Thermo Instrument, Thermo Electron and their affiliates for their own
account and for the accounts of customers and, accordingly, may at any time hold
a long or short term position in such securities.

    In October 1999, Thermo Electron engaged The Beacon Group as its financial
advisor in connection with Thermo Electron's proposed acquisition of the
outstanding shares held by public stockholders in certain subsidiaries. Thermo
Electron paid The Beacon Group $500,000 in fees for services rendered pursuant
to that engagement in connection with the acquisition of the outstanding
publicly-held shares of common stock of ThermoTrex Corporation and ThermoLase
Corporation.

    As noted above, J.P. Morgan and The Beacon Group have acted as financial
advisors to Thermo Electron for the purpose of advising Thermo Electron in
connection with its strategic alternatives, including the proposed
reorganization of Thermo Electron and its subsidiaries. As part of the proposed
reorganization, it is contemplated that Thermo Electron will acquire the
publicly-held minority interest in Thermo Instrument and that J.P. Morgan and
The Beacon Group will act as financial advisors to Thermo Electron in connection
with such acquisition.

    Pursuant to a letter agreement among Thermo Electron and J.P. Morgan and The
Beacon Group, dated January 17, 2000, Thermo Electron has agreed to pay each of
J.P. Morgan and The Beacon Group a fee of $500,000 for its services in
connection with the Offer and the Merger. In addition, J.P. Morgan and The
Beacon Group will be reimbursed for expenses incurred in connection with these
transactions. The letter agreement also relates to the overall proposed
reorganization of Thermo Electron and provides for separate fees for services
with respect to other elements of Thermo Electron's reorganization. These other
fees include a minimum retainer for each of J.P. Morgan and The Beacon Group of
$1.25 million, and the engagement letter provides for substantial additional
compensation if some or all of the other elements of Thermo Electron's
reorganization are completed. Thermo Electron has agreed to indemnify J.P.
Morgan and The Beacon Group and their affiliates against certain liabilities,
including liabilities under the federal securities laws in connection with their
engagement

CERTAIN PROJECTED FINANCIAL DATA

    The Company does not, as a matter of course, make public forecasts or
projections as to future sales, earnings or other income statement data, cash
flows or balance sheet and financial position information.

                                       20
<PAGE>
However, the Instrument Special Committee and the Board of Directors of Thermo
Electron had access to the 2000 Projections and made the 2000 Projections
available to the Advisors. The 2000 Projections were prepared by the Company's
management in the regular course of its financial planning.

    The following summaries of the 2000 Projections are included in this Offer
to Purchase because the 2000 Projections were made available to the Board of
Directors of Thermo Electron, the Instrument Special Committee and the Advisors.
The 2000 Projections do not reflect any of the effects of the Offer, the Merger
or other changes that may in the future be deemed appropriate concerning the
Company and its assets, business, operations, properties, policies, corporate
structure, capitalization and management in light of the circumstances then
existing. Thermo Instrument and Thermo Electron believe that the assumptions
upon which the 2000 Projections are based were reasonable at the time the 2000
Projections were prepared, given the information known by management of the
Company at such time.

    The 2000 Projections were not prepared with a view toward public disclosure
or compliance with published guidelines of the Commission or the American
Institute of Certified Public Accountants regarding forward-looking information
or generally accepted accounting principles. Neither the Company's independent
auditors, nor any other independent accountants, have compiled, examined or
performed any procedures with respect to the prospective financial information
contained in the 2000 Projections nor have they expressed any opinion or given
any form of assurance on such information or its achievability, and they assume
no responsibility for, and disclaim any association with, such prospective
financial information. Furthermore, the 2000 Projections necessarily make
numerous assumptions, many of which are beyond the control of Thermo Instrument
and Thermo Electron and may prove not to have been, or may no longer be,
accurate. Additionally, this information, except as otherwise indicated, does
not reflect revised prospects for the Company's businesses, changes in general
business and economic conditions, or any other transaction or event that has
occurred or that may occur and that was not anticipated at the time such
information was prepared. Accordingly, such information is not necessarily
indicative of current values or future performance, which may be significantly
more favorable or less favorable than as set forth below, and should not be
regarded as a representation that they will be achieved.

    THE 2000 PROJECTIONS ARE NOT GUARANTEES OF PERFORMANCE. THEY INVOLVE RISKS,
UNCERTAINTIES AND ASSUMPTIONS. THE FUTURE FINANCIAL RESULTS AND STOCKHOLDER
VALUE OF THE COMPANY MAY MATERIALLY DIFFER FROM THOSE EXPRESSED IN THE 2000
PROJECTIONS. MANY OF THE FACTORS THAT WILL DETERMINE THESE RESULTS AND VALUES
ARE BEYOND THE COMPANY'S ABILITY TO CONTROL OR PREDICT. STOCKHOLDERS ARE
CAUTIONED NOT TO PLACE UNDUE RELIANCE ON THE 2000 PROJECTIONS. THERE CAN BE NO
ASSURANCE THAT THE 2000 PROJECTIONS WILL BE REALIZED OR THAT THE COMPANY'S
FUTURE FINANCIAL RESULTS WILL NOT MATERIALLY VARY FROM THE 2000 PROJECTIONS. THE
COMPANY DOES NOT INTEND TO UPDATE OR REVISE THE 2000 PROJECTIONS.

                                       21
<PAGE>
    The following are the 2000 Projections:

                                2000 PROJECTIONS
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                              PROJECTED Q4   PROJECTED   PROJECTED
                                                                  1999         1999        2000
                                                              ------------   ---------   ---------
<S>                                                           <C>            <C>         <C>
SELECTED INCOME STATEMENT DATA:
Revenues....................................................     $35,094     $138,613    $138,732
                                                                 -------     --------    --------
Costs and Operating Expenses:
  Cost of revenues..........................................      21,380       86,715      84,452
  Selling, general, and administrative expenses.............       9,334       36,442      34,878
  Research and development expenses.........................       2,553        9,844       9,942
  Restructuring costs.......................................          85          319          --
                                                                 -------     --------    --------
                                                                  33,352      133,320     129,272
                                                                 -------     --------    --------
Operating Income............................................       1,742        5,293       9,460
Interest Income.............................................         430        1,675       1,860
Interest Expense............................................         (49)        (172)       (113)
                                                                 -------     --------    --------
Income Before Provision for Income Taxes....................       2,123        6,796      11,207
Provision for Income Taxes..................................         852        2,581       4,144
                                                                 -------     --------    --------
Net Income..................................................     $ 1,271     $  4,215    $  7,063
                                                                 =======     ========    ========
SELECTED BALANCE SHEET DATA:
Accounts Receivable, Net....................................     $33,000     $ 33,000    $ 31,374
Inventories.................................................      25,093       25,093      24,092
Prepaid Income Taxes and Other Current Assets...............       5,968        5,968       5,756
                                                                 -------     --------    --------
Total Current Assets Excluding Cash and Investments.........      64,061       64,061      61,222
Property, Plant, and Equipment:
  Balance, beginning of period..............................      11,518       10,136      11,401
  Additions.................................................         906        4,383       2,188
  Depreciation expense......................................        (554)      (2,366)     (2,781)
  Sales.....................................................        (469)        (752)         --
                                                                 -------     --------    --------
  Balance, end of period....................................      11,401       11,401      10,808
Cost in Excess of Net Assets of Acquired Companies..........      62,127       62,127      60,278
</TABLE>

                                       22
<PAGE>
CONFLICTS OF INTEREST

    THERMO ELECTRON AND THERMO INSTRUMENT.  The financial interest of Thermo
Electron and Thermo Instrument are adverse as to the Offer Price to the
financial interests of the Public Stockholders.

    DIRECTORS OF THERMO ELECTRON AND THERMO INSTRUMENT.  The members of the
Board of Directors of Thermo Electron and the Instrument Special Committee own
common stock of, or hold options to purchase the common stock of, Thermo
Electron, Thermo Instrument and/or the Company. In addition, a member of the
Board of Directors of Thermo Electron is also a director of the Company. These
positions and equity interests present these directors with actual or potential
conflicts of interest in determining the fairness of the Offer and the Merger to
the Public Stockholders. See Schedule I to this Offer to Purchase for a listing
of the positions that the members of the Boards of Directors of Thermo Electron
and Thermo Instrument hold with Thermo Electron, Thermo Instrument and the
Company and their ownership of the common stock of Thermo Electron, Thermo
Instrument and the Company. To the knowledge of each of the Purchaser, Thermo
Instrument and Thermo Electron, all of the directors and executive officers of
Thermo Electron and Thermo Instrument who own Shares have advised Thermo
Instrument that they intend to tender their Shares in the Offer.

    EXECUTIVE OFFICERS AND DIRECTORS OF THE COMPANY.  In considering any
position that the Board of Directors of the Company may take with respect to the
Offer, the Public Stockholders should be aware that the executive officers and
certain directors of the Company have interests in connection with the Offer and
the Merger that present them with actual or potential conflicts of interest, as
summarized below.

    Following consummation of the Offer and the Merger, Thermo Instrument
anticipates that the Board of Directors of the Company, as the corporation
surviving the Merger (the "Surviving Corporation"), will be comprised solely of
members of the Company's and Thermo Instrument's management. Officers and
directors of the Company who own Shares will receive the Offer Price in the
Offer or the Merger on the same terms as the Public Stockholders.

    As of January 28, 2000, the members of the Board of Directors and executive
officers of the Company owned in the aggregate 21,800 Shares and will receive a
payment for their Shares in the aggregate amount of $196,200, assuming that they
tender all of their Shares in the Offer or their Shares are acquired in the
Merger. To the knowledge of each of the Purchaser, Thermo Instrument and Thermo
Electron, all of the directors and executive officers of the Company, other than
the member of the Company's Special Committee, who own Shares have advised
Thermo Instrument that they intend to tender their Shares in the Offer. The
member of the Special Committee will make his intentions, as to whether he plans
to tender, hold or sell any Shares that he owns, known in the Special
Committee's Solicitation/ Recommendation Statement on Schedule 14D-9.

    In addition, as of January 28, 2000, such Board members and executive
officers of the Company held options to acquire an aggregate of 307,332 Shares,
with exercise prices ranging from $6.93 to $14.25. Unvested Options held by such
persons will be assumed by Thermo Electron in the Merger and converted into
options to acquire shares of Thermo Electron's common stock on the same terms as
are applicable to all the other holders of Options. In the case of vested
Options held by such persons, the holders will be given the opportunity to elect
in the Merger either to convert the Options into vested options for Thermo
Electron common stock or to receive cash for their Options at the Offer Price
less the applicable exercise price on the same terms as are applicable to all
the other holders of Options. See "--Certain Effects Of The Offer And The
Merger--Assumption of Options by Thermo Electron."

    Certain members of the Board of Directors of the Company and certain
executive officers of the Company are directors or officers of Thermo Electron
and/or Thermo Instrument. All of such directors and executive officers in the
Company hold equity interests in Thermo Instrument and Thermo Electron.
Mr. Earl R. Lewis, a director and the chairman of the Board of Directors of the
Company, is also the chief operating officer, measurement and detection, of
Thermo Electron, and the president and chief executive officer, and a director,
of Thermo Instrument. Mr. Melas-Kyriazi, the chief financial officer of the
Company, is also a vice president of Thermo Electron and the chief financial
officer of Thermo Electron

                                       23
<PAGE>
and Thermo Instrument. Mr. Paul Kelleher, the chief accounting officer of the
Company is also the chief accounting officer of Thermo Electron and Thermo
Instrument. Consequently, these directors and officers receive or have received
compensation not only from the Company but also from Thermo Electron, Thermo
Instrument and/or their affiliates.

    INDEMNIFICATION AGREEMENTS.  Thermo Electron has entered into separate
indemnification agreements with each of the Company's officers and directors
providing for indemnification of and advancement of expenses to such persons
directly by Thermo Electron in the event that such person, by reason of his or
her status as a director or officer of the Company (or service as a director,
officer or fiduciary of another enterprise at the request of Thermo Electron),
is made or threatened to be made a party to any threatened, pending, or
completed action, suit or other proceeding, whether civil, criminal,
administrative or investigative, if the indemnitee acted in good faith and in a
manner the indemnitee reasonably believed to be in or not opposed to the best
interests of Thermo Electron, and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his or her conduct was unlawful.
In the case of any threatened, pending or completed action, suit or proceeding
by or in the right of Thermo Electron, indemnification shall be made to the
maximum extent permitted under Delaware law.

OTHER POSSIBLE PURCHASES OF SHARES

    If the Offer is successfully completed, Thermo Electron and its
subsidiaries, including Thermo Instrument, will collectively own at least 90% of
the outstanding Shares. If, after the Offer is completed but prior to the
effective date of the Merger, as a result of the exercise of Options or for any
other reason, Thermo Electron and its subsidiaries collectively own less than
90% of the outstanding Shares, the Purchaser intends to acquire additional
Shares in the open market or in privately negotiated transactions to the extent
required for Thermo Electron and its subsidiaries' collective ownership of
Shares to equal or exceed 90%. If the Offer is not completed, the Purchaser may
make open market or privately negotiated purchases of Shares to the extent
necessary in order for Thermo Electron and its subsidiaries collectively to own
at least 90% of the outstanding Shares. Such open market or privately negotiated
purchases would be made at market prices or privately negotiated prices at the
time of purchase, which may be higher or lower than the Offer Price.

THE MERGER

    If the Offer is successfully completed, Thermo Instrument and Thermo
Electron plan to contribute the Shares they own to the Purchaser in exchange for
capital stock of the Purchaser and to cause the Purchaser to merge into the
Company in a short-form merger. The short-form merger would occur as soon as
possible after completion of the Offer. After the short-form merger, the Company
would be owned exclusively by Thermo Electron and Thermo Instrument. Under the
Delaware General Corporation Law (the "DGCL"), if the Purchaser owns at least
90% of the outstanding Shares, the Purchaser would have the power to approve,
adopt and consummate the Merger without a vote of the Company's stockholders
(other than the Purchaser) or Board of Directors.

    On the effective date of the Merger, each outstanding Share (other than
Shares held by stockholders, if any, who are entitled to and perfect their
appraisal rights under Section 262 of the DGCL) would be cancelled and converted
into the right to receive the Offer Price in cash, without interest. After the
Merger, Thermo Instrument and Thermo Electron will, directly or indirectly, own
100% of the equity interest in the Surviving Corporation.

CERTAIN EFFECTS OF THE OFFER AND THE MERGER

    GENERAL.  Upon completion of the Offer and the Merger, Thermo Instrument and
Thermo Electron would have complete control over the conduct of the Company's
business and together would have a 100% interest in the net book value and net
earnings of the Company. In addition, Thermo Instrument and Thermo Electron
would receive the benefit of complete control over any future increases in the
value of the Company and would bear the complete risk of any losses incurred in
the operation of the Company

                                       24
<PAGE>
and any decrease in the value of the Company. Thermo Electron's and its
subsidiaries' aggregate ownership of the Company prior to the transactions
contemplated by the Offer and the Merger was approximately 82.3%. Upon
completion of the Offer and the Merger, Thermo Electron's and its subsidiaries'
aggregate interest in the Company's net book value of approximately
$147.9 million on January 1, 2000 and net earnings of $2.3 million for the year
ended January 1, 2000 would increase from approximately 82.3% of such amounts to
100% of such amounts.

    BENEFITS AND DETRIMENTS TO THE PUBLIC STOCKHOLDERS.  Upon completion of the
Offer and the Merger, the Public Stockholders would no longer have any interest
in, and would not be stockholders of, the Company and therefore would not
participate in the Company's future earnings and potential growth and would no
longer bear the risk of any decreases in the value of the Company. In addition,
the Public Stockholders would not share in any distribution of proceeds after
any sales of businesses of the Company, whether contemplated at the time of the
Offer or thereafter. See "--Conduct Of The Company's Business After The Offer
And The Merger." All of the Public Stockholders' other incidents of stock
ownership, such as the rights to vote on certain corporate decisions, to elect
directors, to receive distributions upon the liquidation of the Company and to
receive appraisal rights upon certain mergers or consolidations of the Company
(unless such appraisal rights are perfected in connection with the Merger), as
well as the benefit of potential increases in the value of their holdings in the
Company based on any improvements in the Company's future performance, would be
extinguished upon acceptance of Shares tendered in the Offer or, if not
tendered, upon completion of the Merger.

    Upon completion of the Offer and the Merger, the Public Stockholders would
also not bear the risks of potential decreases in the value of their holdings in
the Company based on any downturns in the Company's future performance. Instead,
the Public Stockholders would have immediate liquidity in the form of the Offer
Price in place of an ongoing equity interest in the Company in the form of the
Shares. In summary, if the Offer and the Merger are completed, the Public
Stockholders would have no ongoing rights as stockholders of the Company (other
than statutory appraisal rights in the case of Public Stockholders who are
entitled to and perfect such rights under Delaware law).

    POSSIBLE EFFECT OF THE OFFER AND OPEN MARKET PURCHASES ON THE MARKET FOR
SHARES.  Following the completion of the Offer and prior to the effective date
of the Merger, the purchase of Shares by the Purchaser pursuant to the Offer or
any subsequent open market or privately negotiated purchases would reduce the
number of Shares that might otherwise trade publicly and may reduce the number
of holders of Shares. This could adversely affect the liquidity and market value
of the remaining Shares held by the public.

    AMERICAN STOCK EXCHANGE LISTING.  If the Offer and Merger are consummated,
the Shares would not meet the requirements for continued listing on the American
Stock Exchange and would be delisted. Assuming that the Merger occurs shortly
after the completion of the Offer, Thermo Electron and Thermo Instrument do not
expect the American Stock Exchange to delist the Shares until after the
effective date of the Merger.

    Following the closing of the Offer and prior to the effective date of the
Merger, depending upon the aggregate market value and the number of Shares not
purchased pursuant to the Offer or any subsequent open market or privately
negotiated purchases, as well as the number of Public Stockholders who are not
affiliated with Thermo Instrument or Thermo Electron, the Shares may no longer
meet the quantitative requirements for continued listing on the American Stock
Exchange. The listing requirements of the American Stock Exchange require that
an issuer have at least 200,000 publicly held shares, held by at least 300
stockholders, with a market value of at least $1,000,000 and have stockholders'
equity of at least $2,000,000 or $4,000,000 (depending on profitability levels
during the issuer's four most recent fiscal years).

    In the event that the Shares no longer meet the requirements for listing on
the American Stock Exchange, it is possible that the Shares would continue to
trade in the over-the-counter market prior to the effective date of the Merger
and that price or other quotations might still be available from other sources.

                                       25
<PAGE>
The extent of the public market for the Shares and the availability of such
quotations would, however, depend upon such factors as the number of holders
and/or the aggregate market value of such Shares remaining at such time, the
interest in maintaining a market in such Shares on the part of securities firms,
the possible termination of registration of such Shares under the Exchange Act,
as described below, and other factors. The Purchaser cannot predict whether a
reduction in the number of Shares that might otherwise trade publicly would have
an adverse or beneficial effect on the market price for or marketability of the
Shares or whether it would cause future market prices to be greater or less than
the price paid in the Offer and the Merger.

    EXCHANGE ACT REGISTRATION.  The Shares are currently registered under the
Exchange Act. If the Offer and the Merger are completed, however, the Company's
reporting obligations under the Exchange Act would terminate.

    Prior to the effective date of the Merger, the purchase of Shares pursuant
to the Offer or open market or privately negotiated purchases following
consummation of the Offer may result in the Shares becoming eligible for
deregistration under the Exchange Act. Registration of the Shares may be
terminated upon application by the Company to the Commission if the Shares are
not listed on a national securities exchange (see "--American Stock Exchange
Listing") and there are fewer than 300 record holders of the Shares. Thermo
Instrument presently intends to seek to cause the Company to terminate the
registration of the Shares under the Exchange Act as soon after the consummation
of the Offer or the Merger as the requirements for termination of registration
are met.

    The termination of the registration of the Shares under the Exchange Act
would substantially reduce the information required to be furnished by the
Company to holders of the Shares and would make certain provisions of the
Exchange Act, such as the short-swing profit recovery provisions of
Section 16(b), the requirement of furnishing a proxy statement in connection
with stockholders' meetings pursuant to Section 14(a) and the requirements of
Rule 13e-3 under the Exchange Act with respect to "going private" transactions,
no longer applicable to the Shares. Furthermore, "affiliates" of the Company and
persons holding "restricted securities" of the Company may be deprived of the
ability to dispose of the securities pursuant to Rule 144 under the Securities
Act. If registration of the Shares under the Exchange Act were terminated, the
Shares would no longer be "margin securities" or eligible for listing on the
American Stock Exchange.

    MARGIN REGULATIONS.  The Shares are currently "margin securities" under the
rules of the Board of Governors of the Federal Reserve System (the "Federal
Reserve Board"), which has the effect, among other things, of allowing brokers
to extend credit on the collateral of such Shares for the purpose of buying,
carrying or trading in securities ("purpose loans"). If the Offer and the Merger
are completed, the Shares would no longer be "margin securities." Following the
purchase of Shares pursuant to the Offer or any subsequent open market or
privately negotiated purchases and prior to the effective date of the Merger,
depending upon factors such as the number of record holders of the Shares and
the number and market value of publicly held Shares, the Shares might no longer
constitute "margin securities" for purposes of the Federal Reserve Board's
margin regulations and therefore could no longer be used as collateral for
purpose loans made by brokers. In addition, if registration of the Shares under
the Exchange Act were terminated, the Shares would no longer constitute "margin
securities."

    TREATMENT OF ONIX SYSTEMS OPTIONS.  The Company has, from time to time,
issued Options to acquire Shares pursuant to the Company's Equity Incentive Plan
(the "Plan"). On the effective date of the Merger, each outstanding unvested
Option under the Company's Plan will be assumed by Thermo Electron and converted
into options to acquire shares of Thermo Electron common stock as provided
below. In the case of vested Options, the holders will be given the opportunity
to elect in the Merger either to convert the Options into vested options for
Thermo Electron common stock or to receive cash from Thermo Instrument in an
amount equal to the number of Shares that have vested under such Option
multiplied by the difference between the Offer Price and the exercise price per
Share of such Option. Each Option assumed by Thermo Electron will continue to
have, and be subject to, the same terms and conditions,

                                       26
<PAGE>
including the vesting of shares issuable upon the exercise thereof, as were
applicable to the Option immediately prior to the effective date of the Merger,
except that:

    - each Option will be exercisable (or will become exercisable in accordance
      with its terms) for that number of whole shares of Thermo Electron common
      stock equal to the product of the number of Shares that were issuable upon
      exercise of such Option immediately prior to the effective date of the
      Merger multiplied by the Exchange Ratio (as defined below), rounded down
      to the nearest whole number of shares of Thermo Electron common stock, and

    - the per share exercise price for the shares of Thermo Electron common
      stock issuable upon exercise of such assumed Option will be equal to the
      quotient determined by dividing the exercise price per Share at which such
      Option was exercisable immediately prior to the effective date of the
      Merger by the Exchange Ratio, rounded up to the nearest whole cent.

    The "Exchange Ratio" is a fraction, the numerator of which is the Offer
Price and the denominator of which is the closing price of the Thermo Electron
common stock on the day immediately preceding the effective date of the Merger
as reported on the consolidated transactions tape.

    DEFERRED COMPENSATION PLAN FOR DIRECTORS.  On the effective date of the
Merger, the Company's deferred compensation plan for directors (the "Deferred
Compensation Plan") will terminate. None of the Company's directors currently
participate in the Deferred Compensation Plan.

    ACCOUNTING TREATMENT.  The Offer and the Merger would be accounted for as
the acquisition of a minority interest by Thermo Instrument, using the purchase
method of accounting.

    TAX CONSEQUENCES.  For federal income tax purposes, the receipt of the cash
consideration by holders of the Shares pursuant to the Offer or the Merger will
be a taxable sale of the holder's Shares. See "Certain Federal Income Tax
Consequences."

CONDUCT OF THE COMPANY'S BUSINESS AFTER THE OFFER AND THE MERGER

    Following Thermo Electron's reorganization, Thermo Electron plans to retain
the Company as part of Thermo Electron's core measurement and detection
instruments business. In connection with the reorganization of Thermo Electron
and its subsidiaries, Thermo Electron intends to evaluate ways in which its
instruments businesses, including the Company's business, can be more
efficiently integrated and operated. Thermo Instrument and Thermo Electron may
consider the sale of certain of the Company's businesses, but they do not
currently have, and are not currently negotiating, any commitment or agreement
for any such sale. Additionally, Thermo Electron and Thermo Instrument do not
currently contemplate any material change in the composition of the Company's
current management, except that Thermo Instrument intends to appoint a Board of
Directors of the Company comprised solely of members of the Company's and Thermo
Instrument's management after the Merger.

    In connection with its reorganization, Thermo Electron currently intends to
acquire all of the outstanding common stock of Thermo Instrument that it does
not currently own. If such transaction is completed, the Company will become a
wholly-owned subsidiary of Thermo Electron.

    Except as otherwise described in this Offer to Purchase, the Purchaser,
Thermo Instrument and Thermo Electron do not have, as of the date of this Offer
to Purchase, any specific plans or proposals for:

    - any extraordinary corporate transaction involving the Company after the
      completion of the Offer and the Merger;

    - any sale or transfer of a material amount of assets currently held by the
      Company after the completion of the Offer and the Merger;

    - any change in the Board of Directors or management of the Company;

    - any material change in the Company's dividend rate or policy; or

    - any other material change in the Company's corporate structure or
      business.

                                       27
<PAGE>
CONDUCT OF THE COMPANY'S BUSINESS IF THE OFFER IS NOT COMPLETED

    If the Offer is not completed because the Minimum Condition or another
condition is not satisfied or waived, Thermo Electron and Thermo Instrument
expect that the Company's current management will continue to operate the
Company's business substantially as presently operated. See "--Conduct Of The
Company's Business After The Offer And The Merger." However, Thermo Instrument
and Thermo Electron anticipate that if the Offer is not completed, Thermo
Instrument and Thermo Electron will re-evaluate the role of the Company within
the overall reorganization strategy being pursued by Thermo Electron. In
particular, Thermo Instrument and Thermo Electron may consider:

    - engaging in open market or privately negotiated purchases of Shares to
      increase Thermo Electron's and its subsidiaries' aggregate ownership of
      Shares to at least 90% of the outstanding Shares and then effecting a
      short-form merger;

    - proposing that the Purchaser and the Company enter into a long-form merger
      agreement, which would require the approval of the Company's Board of
      Directors and the vote of Thermo Electron's, Thermo Instrument's and the
      Purchaser's Shares in favor of such merger;

    - keeping outstanding the public minority interest in the Company, in which
      case the Public Stockholders would receive no cash for their Shares and
      would bear the risk that the trading price per Share could decline to a
      price that is less than the Offer Price; or

    - selling their interests in the Company or pursuing a sale of the entire
      Company to a third party.

    If Thermo Instrument and Thermo Electron were to pursue any of these
alternatives, it may take considerably longer for the Public Stockholders to
receive any consideration for their Shares (other than through sales in the open
market) than if they had tendered their Shares in the Offer. Any such
transaction may result in proceeds per Share to the Public Stockholders that are
more or less than the Offer Price.

                                       28
<PAGE>
                                THE TENDER OFFER

TERMS OF THE OFFER; EXPIRATION DATE

    Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), the Purchaser will accept for payment and pay for all Shares validly
tendered prior to the Expiration Date (as defined below) and not properly
withdrawn as provided in "--Withdrawal Rights." The term "Expiration Date" means
12:00 midnight, New York City time, on Friday, April 7, 2000, unless and until
the Purchaser, in its sole discretion, shall have extended the period during
which the Offer is open, in which event the term "Expiration Date" shall mean
the latest time and date at which the Offer, as so extended by the Purchaser,
shall expire.

    Subject to the applicable rules and regulations of the Commission, the
Purchaser expressly reserves the right, in its sole discretion, at any time and
from time to time, to extend the period during which the Offer is open for any
reason, including the failure to satisfy any of the conditions specified in
"--Certain Conditions Of The Offer," and thereby delay acceptance for payment
of, and payment for, any Shares, by giving oral or written notice of such
extension to the Depositary. There can be no assurance that the Purchaser will
exercise its right to extend the Offer. During any such extension, all Shares
previously tendered and not properly withdrawn will remain subject to the Offer,
subject to the rights of a tendering stockholder to withdraw such stockholder's
Shares. See "--Withdrawal Rights."

    Subject to the applicable rules and regulations of the Commission, the
Purchaser also expressly reserves the right, in its sole discretion, at any time
and from time to time, to (1) terminate the Offer and not accept for payment (or
pay for) any Shares if any of the conditions referred to in "--Certain
Conditions Of The Offer" has not been satisfied or upon the occurrence and
during the continuance of any of the events specified in "--Certain Conditions
Of The Offer," and (2) waive any condition or amend the Offer in any respect, in
each case by giving oral or written notice of termination, waiver or amendment
to the Depositary and by making a public announcement thereof. The Purchaser
acknowledges (a) that Rule 14e-1(c) under the Exchange Act requires the
Purchaser to pay the consideration offered or return the Shares tendered
promptly after the termination or withdrawal of the Offer and (b) that the
Purchaser may not delay acceptance for payment of, or payment for, any Shares
upon the occurrence of any of the conditions specified in "--Certain Conditions
Of The Offer" without extending the period during which the Offer is open.

    If the Minimum Condition or any other condition specified in "--Certain
Conditions Of The Offer" is not fulfilled by the Expiration Date, the Purchaser
reserves the right (but shall not be obligated) to (1) decline to purchase any
of the Shares tendered, return all tendered Shares to tendering stockholders and
terminate the Offer, (2) extend the Offer and retain all tendered Shares until
the expiration of the Offer, as extended, subject to the terms and conditions of
the Offer (including any rights of stockholders to withdraw their Shares), or
(3) waive or reduce the condition and, subject to complying with applicable
rules and regulations of the Commission, accept for payment and purchase all
Shares validly tendered.

    Any extension, termination or amendment will be followed as promptly as
practicable by a public announcement thereof, such announcement, in the case of
an extension, to be made no later than 9:00 a.m., New York City time, on the
next business day after the previously scheduled Expiration Date. Without
limiting the manner in which the Purchaser may choose to make any public
announcement, except as provided by applicable law (including Rules 14d-4(c),
14d-6(d) and 14e-1 under the Exchange Act, which require that material changes
be promptly disseminated to holders of Shares), the Purchaser will have no
obligation to publish, advertise or otherwise communicate any such public
announcement other than by issuing a release to the Dow Jones News Service.

    If the Purchaser makes a material change in the terms of the Offer or the
information concerning the Offer, or waives a material condition of the Offer,
the Purchaser will disseminate additional tender offer materials (including by
public announcement as set forth above) and extend the Offer to the extent
required by Rules 14d-4(d), 14d-6(d) and 14e-1 under the Exchange Act. The
minimum period during

                                       29
<PAGE>
which the Offer must remain open following material changes in the terms of the
Offer or information concerning the Offer, other than a change in price, a
change in percentage of securities sought or a change in any dealer's soliciting
fee, will depend upon the facts and circumstances, including the relative
materiality of the changes. With respect to a change in price or, subject to
certain limitations, a change in the percentage of securities sought or a change
in any dealer's soliciting fee, a minimum ten business day period from the date
of such change is generally required to allow for adequate dissemination of such
change to stockholders. Accordingly, if, prior to the Expiration Date, the
Purchaser decreases the number of Shares being sought, increases the
consideration offered pursuant to the Offer or adds a dealer's soliciting fee,
and if the Offer is scheduled to expire at any time earlier than the period
ending on the tenth business day from the date that notice of such increase,
decrease or addition is first published, sent or given to stockholders, the
Offer will be extended at least until the expiration of such ten business day
period. For purposes of the Offer, a "business day" means any day other than a
Saturday, Sunday or a federal holiday and consists of the time period from
12:01 a.m. through 12:00 midnight, New York City time.

    The Company has provided the Purchaser with the Company's stockholder list
and security position listings for the purpose of disseminating the Offer to
holders of Shares. This Offer to Purchase and the related Letter of Transmittal
and, if required, other relevant material will be mailed to record holders of
Shares and will be furnished to brokers, dealers, commercial banks, trust
companies and similar persons whose names, or the names of whose nominees,
appear on the Company's stockholder list or, if applicable, who are listed as
participants in a clearing agency's security position listing for subsequent
transmittal to beneficial owners of Shares.

ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES

    Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), the Purchaser will purchase by accepting for payment, and will pay
for, all Shares validly tendered prior to the Expiration Date and not properly
withdrawn (including Shares validly tendered and not withdrawn during any
extension of the Offer, if the Offer is extended, subject to the terms and
conditions of such extension), promptly after the Expiration Date. In addition,
subject to complying with Rule 14e-1 under the Exchange Act, the Purchaser
expressly reserves the right, in its sole discretion, to delay the acceptance
for payment of, or payment for, Shares in order to comply, in whole or in part,
with any applicable law.

    In all cases, payment for Shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by the Depositary of:

    - certificates evidencing Shares ("Share Certificates") or timely
      confirmation of a book-entry transfer of such Shares ("Book-Entry
      Confirmation") into the Depositary's account at The Depository Trust
      Company (the "Book-Entry Transfer Facility") pursuant to the procedures
      set forth in "--Procedures For Accepting The Offer And Tendering Shares";

    - the Letter of Transmittal (or a facsimile thereof), properly completed and
      duly executed, with any required signature guarantees, or an Agent's
      Message (as defined below) in connection with a book-entry transfer; and

    - any other documents required by the Letter of Transmittal.

    Accordingly, payment may be made to tendering stockholders at different
times if delivery of the Shares and other required documents occurs at different
times.

    The term "Agent's Message" means a message transmitted by the Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of a
Book-Entry Confirmation, which states that the Book-Entry Transfer Facility has
received an express acknowledgment from the participant in the Book-Entry
Transfer Facility tendering the Shares which are the subject of such Book-Entry
Confirmation, that such participant has received and agrees to be bound by the
terms of the Letter of Transmittal and that the Purchaser may enforce such
agreement against such participant.

                                       30
<PAGE>
    For purposes of the Offer, the Purchaser will be deemed to have accepted for
payment, and thereby purchased, Shares validly tendered and not properly
withdrawn if, as and when the Purchaser gives oral or written notice to the
Depositary of the Purchaser's acceptance for payment of such Shares pursuant to
the Offer. Upon the terms and subject to the conditions of the Offer, payment
for Shares so accepted for payment pursuant to the Offer will be made by deposit
of the aggregate purchase price therefor with the Depositary, which will act as
agent for tendering stockholders for the purpose of receiving payment from the
Purchaser and transmitting such payment to stockholders whose Shares have been
accepted for payment. UNDER NO CIRCUMSTANCES WILL INTEREST ON THE PURCHASE PRICE
FOR SHARES BE PAID, REGARDLESS OF ANY EXTENSION OF THE OFFER OR DELAY IN MAKING
SUCH PAYMENT. Upon the deposit of funds with the Depositary for the purpose of
making payment to validly tendering stockholders, the Purchaser's obligation to
make such payment shall be satisfied and such tendering stockholders must
thereafter look solely to the Depositary for payment of the amounts owed to them
by reason of the acceptance for payment of Shares pursuant to the Offer.

    If any tendered Shares are not accepted for payment pursuant to the terms
and conditions of the Offer for any reason, or if Share Certificates are
submitted for more Shares than are tendered, Share Certificates representing
Shares not purchased or not tendered will be returned, without expense, to the
tendering stockholder (or, in the case of Shares tendered by book-entry transfer
of such Shares into the Depositary's account at the Book-Entry Transfer Facility
pursuant to the procedures for book-entry transfer set forth in "--Procedures
For Accepting The Offer And Tendering Shares," such Shares will be credited to
an account maintained at the Book-Entry Transfer Facility), as soon as
practicable following expiration or termination of the Offer.

    If, prior to the Expiration Date, the Purchaser increases the consideration
to be paid per Share, the Purchaser will pay such increased consideration for
all Shares purchased pursuant to the Offer, whether or not such Shares have been
tendered or purchased prior to such increase in consideration.

    The Purchaser reserves the right to transfer or assign, in whole or in part
from time to time, to one or more of its affiliates, the right to purchase the
Shares tendered pursuant to the Offer, but any such transfer or assignment will
not relieve the Purchaser of its obligations under the Offer, nor will any such
transfer or assignment in any way prejudice the rights of tendering stockholders
to receive payment for Shares validly tendered and accepted for payment pursuant
to the Offer.

PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES

    GENERAL.  Except as set forth below, in order for Shares to be validly
tendered pursuant to the Offer, the Letter of Transmittal (or a facsimile
thereof), properly completed and duly executed, together with any required
signature guarantees, or an Agent's Message in connection with a book-entry
delivery of Shares, and any other documents required by the Letter of
Transmittal, must be received by the Depositary at one of its addresses set
forth on the back cover of this Offer to Purchase prior to the Expiration Date,
and either (l) Share Certificates evidencing tendered Shares must be received by
the Depositary at such address or such Shares must be tendered pursuant to the
procedures for book-entry transfer set forth below (and a Book-Entry
Confirmation must be received by the Depositary), in each case prior to the
Expiration Date, or (2) the guaranteed delivery procedures set forth below must
be complied with.

    No alternative, conditional or contingent tenders will be accepted and no
fractional Shares will be purchased. All tendering stockholders, by execution of
the Letter of Transmittal (or a facsimile thereof), waive any right to receive
any notice of the acceptance of their Shares for payment.

    THE METHOD OF DELIVERY OF SHARE CERTIFICATES, THE LETTER OF TRANSMITTAL AND
ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER
FACILITY, IS AT THE SOLE OPTION AND RISK OF EACH TENDERING STOCKHOLDER AND,
EXCEPT AS OTHERWISE PROVIDED UNDER THIS HEADING "--PROCEDURES FOR ACCEPTING THE
OFFER AND TENDERING SHARES," THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY
RECEIVED BY THE DEPOSITARY. IF DELIVERY IS MADE BY MAIL, REGISTERED MAIL WITH
RETURN RECEIPT REQUESTED, PROPERLY

                                       31
<PAGE>
INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO
ENSURE TIMELY DELIVERY.

    BOOK-ENTRY TRANSFER.  The Depositary will make a request to establish
accounts with respect to the Shares at the Book-Entry Transfer Facility for
purposes of the Offer within two business days after the date of this Offer to
Purchase. Any financial institution that is a participant in the system of the
Book-Entry Transfer Facility may make book-entry delivery of Shares by causing
the Book-Entry Transfer Facility to transfer such Shares into the Depositary's
account at the Book-Entry Transfer Facility in accordance with the Book-Entry
Transfer Facility's procedures for such transfer. Although delivery of Shares
may be effected through book-entry transfer into the Depositary's account at the
Book-Entry Transfer Facility, the Letter of Transmittal (or a facsimile
thereof), properly completed and duly executed, together with any required
signature guarantees, or an Agent's Message, and any other documents required by
the Letter of Transmittal, must, in any case, be received by the Depositary at
one of its addresses set forth on the back cover of this Offer to Purchase prior
to the Expiration Date in order for such Shares to be validly tendered pursuant
to the Offer, or the tendering stockholder must comply with the guaranteed
delivery procedures described below.

    DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN ACCORDANCE WITH
THE BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO
THE DEPOSITARY.

    SIGNATURE GUARANTEES.  Signatures on all Letters of Transmittal must be
guaranteed by a firm that is a bank, broker, dealer, credit union, savings
association or other entity which is a member in good standing of the Securities
Transfer Agents Medallion Program, the Stock Exchanges' Medallion Program or the
New York Stock Exchange, Inc. Medallion Signature Program (an "Eligible
Institution"), unless Shares tendered thereby are tendered (1) by a registered
holder of Shares who has not completed either the box entitled "Special Delivery
Instructions" or the box entitled "Special Payment Instructions" on the Letter
of Transmittal or (2) for the account of an Eligible Institution. See
Instruction 1 of the Letter of Transmittal.

    If the Share Certificates are registered in the name of a person other than
the signer of the Letter of Transmittal, or if payment is to be made, or Share
Certificates for unpurchased Shares are to be returned, to a person other than
the registered holder(s), then the tendered Share Certificates must be endorsed
or accompanied by appropriate stock powers signed exactly as the name(s) of the
registered holder(s) appear(s) on the Share Certificates with the signature(s)
on such Share Certificates or stock powers guaranteed by an Eligible Institution
as provided above and in the Letter of Transmittal. See Instructions 1 and 5 of
the Letter of Transmittal.

    GUARANTEED DELIVERY.  If a stockholder desires to tender Shares pursuant to
the Offer and such stockholder's Share Certificates are not immediately
available or time will not permit all of the required documents to reach the
Depositary prior to the Expiration Date, or the procedure for book-entry
transfer cannot be completed on a timely basis, such Shares may nevertheless be
tendered, provided that all of the following conditions are satisfied:

    - such tender is made by or through an Eligible Institution;

    - a properly completed and duly executed Notice of Guaranteed Delivery,
      substantially in the form provided by the Purchaser with the Letter of
      Transmittal, is received by the Depositary, in accordance with the
      procedure set forth as provided below, prior to the Expiration Date; and

    - the Share Certificates (or a Book-Entry Confirmation) for all tendered
      Shares, in proper form for transfer, in each case together with the Letter
      of Transmittal (or a facsimile thereof), properly completed and duly
      executed, with any required signature guarantees or, in the case of a
      book-entry transfer, an Agent's Message and any other documents required
      by the Letter of Transmittal, are received by the Depositary within three
      American Stock Exchange trading days after the date of execution of such
      Notice of Guaranteed Delivery.

                                       32
<PAGE>
    The Notice of Guaranteed Delivery may be delivered by hand or transmitted by
telegram, facsimile transmission or mail to the Depositary and must include a
guarantee by an Eligible Institution in the form set forth in the Notice of
Guaranteed Delivery.

    Notwithstanding any other provision of this Offer, payment for Shares
accepted for payment pursuant to the Offer will in all cases be made only after
timely receipt by the Depositary of Share Certificates therefor (or Book-Entry
Confirmation of the transfer of such Shares into the Depositary's account at the
Book-Entry Transfer Facility), a properly completed and duly executed Letter of
Transmittal (or a facsimile thereof), together with any required signature
guarantees or, in the case of a book-entry transfer, an Agent's Message, and any
other documents required by the Letter of Transmittal. Accordingly, payment may
not be made to all tendering stockholders at the same time and will depend upon
when Share Certificates or Book-Entry Confirmations of such Shares are received
by the Depositary.

    BACKUP FEDERAL INCOME TAX WITHHOLDING.  Under the U.S. federal income tax
laws, the Depositary may, under certain circumstances, be required to withhold
31% of the amount of any payments made to certain stockholders pursuant to the
Offer. To prevent such backup federal income tax withholding with respect to
payments made to certain stockholders of the purchase price of Shares purchased
pursuant to the Offer, each such stockholder must provide the Depositary with
such stockholder's correct taxpayer identification number and certify that such
stockholder is not subject to backup federal income tax withholding by
completing the Substitute Form W-9 included in the Letter of Transmittal. See
Instruction 9 of the Letter of Transmittal.

    APPOINTMENT AS PROXY.  By executing the Letter of Transmittal, a tendering
stockholder irrevocably appoints designees of the Purchaser as such
stockholder's attorneys-in-fact and proxies in the manner set forth in the
Letter of Transmittal, each with full power of substitution with respect to any
Shares tendered thereby (and with respect to any and all other Shares or other
securities issued or issuable in respect of such Shares on or after January 31,
2000). All such powers of attorney and proxies shall be considered irrevocable
and coupled with an interest in the tendered Shares. Such appointment will be
effective when, and only to the extent that, the Purchaser accepts the tendered
Shares for payment and deposits the purchase price therefor with the Depositary.
Upon such deposit, all prior powers of attorney and proxies given by such
stockholder at any time with respect to such Shares (and other Shares and
securities issued or issuable in respect of the tendered Shares on or after
January 31, 2000) will, without further action, be revoked, and no subsequent
powers of attorney or proxies may be given nor any subsequent written consents
be executed by such stockholder (and, if given or executed, will not be deemed
effective). Upon such deposit by the Purchaser, the designees of the Purchaser
will, with respect to such Shares and other securities, be empowered to exercise
all voting and other rights of such stockholder as they in their sole discretion
may deem proper at any annual or special meeting of the Company's stockholders,
or any adjournment or postponement thereof, or by written consent in lieu of any
such meeting or otherwise. The Purchaser reserves the right to require that, in
order for Shares to be deemed validly tendered, immediately upon the Purchaser's
payment for such Shares, the Purchaser must be able to exercise full voting and
other rights of a record and beneficial holder, including, without limitation,
voting at any meeting of stockholders or by written consent in lieu of any such
meeting.

    DETERMINATION OF VALIDITY.  All questions as to the validity, form,
eligibility (including the time of receipt) and acceptance for payment of any
tendered Shares pursuant to any of the procedures described above will be
determined by the Purchaser, in its sole discretion, which determination will be
final and binding on all parties. The Purchaser reserves the absolute right to
reject any and all tenders of any particular Shares determined by it not to be
in appropriate form or for which the acceptance of or payment may, in the
opinion of its counsel, be unlawful. The Purchaser also reserves the absolute
right to waive any of the conditions of the Offer or any defect or
irregularities in the tender of any particular Shares, whether or not similar
defects or irregularities are waived in the case of any other Shares. The
Purchaser's interpretations of the terms and conditions of the Offer (including
the Letter of Transmittal and Instructions thereto) will be final and binding.
No tender of Shares will be deemed to have been validly made until all defects
and irregularities have been cured or waived. None of the Purchaser, any of its
affiliates or assigns, the Dealer

                                       33
<PAGE>
Managers, the Information Agent, the Depositary or any other person will be
under any duty to give notification of any defects or irregularities in tenders
or incur any liability for failure to give any such notification.

    THE PURCHASER'S ACCEPTANCE FOR PAYMENT OF SHARES TENDERED PURSUANT TO THE
OFFER WILL CONSTITUTE A BINDING AGREEMENT BETWEEN THE TENDERING STOCKHOLDER AND
THE PURCHASER UPON THE TERMS AND SUBJECT TO THE CONDITIONS OF THE OFFER.

WITHDRAWAL RIGHTS

    Except as otherwise provided in this Section, tenders of Shares made
pursuant to the Offer are irrevocable. Shares tendered pursuant to the Offer may
be withdrawn at any time prior to the Expiration Date and, unless previously
accepted for payment as provided herein, may also be withdrawn at any time after
May 11, 2000.

    If the Purchaser extends the Offer, is delayed in, or delays, its acceptance
for payment or payment for Shares or is unable to accept for payment or pay for
Shares for any reason, then, without prejudice to the Purchaser's other rights
under the Offer, tendered Shares may nevertheless be retained by the Depositary,
on behalf of the Purchaser, and may not be withdrawn except to the extent
tendering stockholders are entitled to and duly exercise withdrawal rights as
described in this Section. Any such extension or delay will be accompanied by an
extension of the Offer to the extent required by law.

    In order for a withdrawal to be effective, a written, telegraphic or
facsimile transmission notice of withdrawal must be timely received by the
Depositary at one of its addresses set forth on the back cover of this Offer to
Purchase. Any such notice of withdrawal must specify the name of the person who
tendered the Shares to be withdrawn, the number of Shares to be withdrawn and
the name of the registered holder of the Shares to be withdrawn, if different
from that of the person who tendered such Shares. If Share Certificates to be
withdrawn have been delivered or otherwise identified to the Depositary, then,
prior to the physical release of such Share Certificates, the tendering
stockholder must also submit the serial numbers shown on such Share Certificates
to the Depositary and the signatures on the notice of withdrawal must be
guaranteed by an Eligible Institution, unless such Shares have been tendered for
the account of an Eligible Institution. If Shares have been tendered pursuant to
the procedures for book-entry transfer, as set forth in "--Procedures For
Accepting The Offer And Tendering Shares," any notice of withdrawal must specify
the name and number of the account at the Book-Entry Transfer Facility to be
credited with the withdrawn Shares and must otherwise comply with the procedures
of the Book-Entry Transfer Facility.

    Withdrawals may not be revoked and any Shares properly withdrawn will
thereafter be deemed not to have been validly tendered for purposes of the
Offer. However, withdrawn Shares may be re-tendered at any time prior to the
Expiration Date by following the procedures described in "--Procedures For
Accepting The Offer And Tendering Shares."

    All questions as to the form and validity (including the time of receipt) of
any notice of withdrawal will be determined by the Purchaser, in its sole
discretion, which determination will be final and binding on all parties. None
of the Purchaser, its affiliates or assigns, the Dealer Managers, the
Information Agent, the Depositary or any other person will be under any duty to
give notification of any defects or irregularities in any notice of withdrawal
or incur any liability for failure to give any such notification.

CERTAIN CONDITIONS OF THE OFFER

    Notwithstanding any other provisions of the Offer, and in addition to (and
not in limitation of) the Purchaser's rights to extend and amend the Offer at
any time in its sole discretion, the Purchaser shall not be required to accept
for payment or, subject to any applicable rules and regulations of the
Commission, including Rule 14e-1(c) under the Exchange Act (relating to the
Purchaser's obligation to pay for or return tendered Shares promptly after
termination or withdrawal of the Offer), pay for, and may delay the acceptance
for payment of or, subject to the restriction referred to above, the payment
for, any tendered

                                       34
<PAGE>
Shares, and may amend or terminate the Offer if (1) the Minimum Condition has
not been satisfied or (2) at any time on or after March 13, 2000 and before the
time of acceptance of the Shares for payment pursuant to the Offer, any of the
following events shall occur:

        (a) any change shall have occurred in the business, properties, assets,
    liabilities, capitalization, stockholders' equity, financial condition, cash
    flows, operations, licenses, franchises or results of operations of the
    Company or its subsidiaries which has a material adverse effect on the
    Company and its subsidiaries taken as a whole; or

        (b) any government or governmental authority or agency, whether
    domestic, foreign or supranational (a "Governmental Entity"), shall have
    instituted or threatened any action, proceeding, application, claim or
    counterclaim, sought or obtained any judgment, order or injunction, or taken
    any other action, which (i) challenges the acquisition by Thermo Electron,
    Thermo Instrument or the Purchaser (or any other affiliate of Thermo
    Electron) of any Shares pursuant to the Offer or the Merger, restrains,
    prohibits or materially delays the making or consummation of the Offer or
    the Merger, prohibits the performance of any of the contracts or other
    arrangements entered into by Thermo Electron, Thermo Instrument or the
    Purchaser (or any other affiliate of Thermo Electron) in connection with the
    acquisition of the Shares or the Company, seeks to obtain any material
    amount of damages, or otherwise directly or indirectly adversely affects the
    Offer or the Merger, (ii) seeks to prohibit or limit materially the
    ownership or operation by the Company, Thermo Electron, Thermo Instrument or
    the Purchaser (or any other affiliate of Thermo Electron) of all or any
    material portion of the business or assets of the Company or of Thermo
    Electron and its affiliates, or to compel the Company, Thermo Electron,
    Thermo Instrument or the Purchaser (or any other affiliate of Thermo
    Electron) to dispose of or to hold separate all or any material portion of
    the business or assets of Thermo Electron or any of its affiliates or of the
    Company or any of its subsidiaries as a result of the transactions
    contemplated by the Offer or the Merger, (iii) seeks to impose any material
    limitation on the ability of the Company, Thermo Electron, Thermo Instrument
    or the Purchaser (or any other affiliate of Thermo Electron) to conduct the
    Company's or any subsidiary's business or own such assets, (iv) seeks to
    impose or confirm any material limitation on the ability of Thermo Electron,
    Thermo Instrument or the Purchaser (or any other affiliate of Thermo
    Electron) to acquire or hold, or to exercise full rights of ownership of,
    any Shares, including the right to vote such Shares on all matters properly
    presented to the stockholders of the Company, (v) seeks to require
    divestiture by Thermo Electron, Thermo Instrument or the Purchaser or any of
    their affiliates of all or any of the Shares or (vi) otherwise has resulted
    in or has a reasonable likelihood of resulting in, a material adverse effect
    on the business, financial condition, results of operation or prospects of
    the Company, Thermo Electron or Thermo Instrument (a "Material Adverse
    Effect"); or

        (c) there shall have been entered or issued any preliminary or permanent
    judgment, order, decree, ruling or injunction or any other action taken by
    any Governmental Entity or court, whether on its own initiative or the
    initiative of any other person, which (i) restrains, prohibits or materially
    delays the making or consummation of the Offer or the Merger, prohibits the
    performance of any of the contracts or other arrangements entered into by
    Thermo Electron, Thermo Instrument or the Purchaser (or any other affiliate
    of Thermo Electron) in connection with the acquisition of the Shares or the
    Company or otherwise directly or indirectly materially adversely affects the
    Offer or the Merger, (ii) prohibits or limits materially the ownership or
    operation by the Company, Thermo Electron, Thermo Instrument or the
    Purchaser (or any other affiliate of Thermo Electron) of all or any material
    portion of the business or assets of the Company and its subsidiaries taken
    as a whole or of Thermo Electron, Thermo Instrument or the Purchaser (or any
    other affiliate of Thermo Electron), or compels the Company, Thermo
    Electron, Thermo Instrument or the Purchaser (or any other affiliate of
    Thermo Electron) to dispose of or to hold separate all or any material
    portion of the business or assets of Thermo Electron or any of its
    affiliates or of the Company or any of its subsidiaries as a result of the
    transactions contemplated by the Offer or the Merger, (iii) imposes any
    material limitation on the ability of the Company, Thermo Electron, Thermo
    Instrument or the Purchaser (or any other affiliate of Thermo Electron) to
    conduct the Company's or any subsidiary's

                                       35
<PAGE>
    business or own such assets, (iv) imposes or confirms any material
    limitation on the ability of Thermo Electron, Thermo Instrument or the
    Purchaser (or any other affiliate of Thermo Electron) to acquire or hold, or
    to exercise full rights of ownership of, any Shares, including the right to
    vote such Shares on all matters properly presented to the stockholders of
    the Company, (v) requires divestiture by Thermo Electron, Thermo Instrument
    or the Purchaser of any of their affiliates of all or any of the Shares or
    (vi) otherwise has resulted in, or has a reasonable likelihood of resulting
    in, a Material Adverse Effect; or

        (d) there shall have been instituted or be pending before any
    Governmental Entity or court any action, proceeding, application, claim or
    counterclaim or any judgment, order or injunction sought or any other action
    taken by any person or entity (other than a Governmental Entity) which
    (i) challenges the acquisition by Thermo Electron, Thermo Instrument or the
    Purchaser (or any other affiliate of Thermo Electron) of any Shares pursuant
    to the Offer or the Merger, restrains, prohibits or materially delays the
    making or consummation of the Offer or the Merger, prohibits the performance
    of any of the contracts or other arrangements entered into by Thermo
    Electron, Thermo Instrument or the Purchaser (or any other affiliate of
    Thermo Electron) in connection with the acquisition of the Shares of the
    Company, seeks to obtain any material amount of damages, or otherwise
    directly or indirectly adversely affects the Offer or the Merger,
    (ii) seeks to prohibit or limit materially the ownership or operation by the
    Company, Thermo Electron, Thermo Instrument or the Purchaser (or any other
    affiliate of Thermo Electron) of all or any material portion of the business
    or assets of the Company or of Thermo Electron and its affiliates, or to
    compel the Company, Thermo Electron, Thermo Instrument or the Purchaser (or
    any other affiliate of Thermo Electron) to dispose of or to hold separate
    all or any material portion of the business or assets of Thermo Electron or
    any of its affiliates or of the Company or any of its subsidiaries as a
    result of the transactions contemplated by the Offer or the Merger,
    (iii) seeks to impose any material limitation on the ability of the Company,
    Thermo Electron, Thermo Instrument or the Purchaser (or any other affiliate
    of Thermo Electron) to conduct the Company's or any subsidiary's business or
    own such assets, (iv) seeks to impose or confirm any material limitation on
    the ability of Thermo Electron, Thermo Instrument or the Purchaser (or any
    other affiliate of Thermo Electron) to acquire or hold, or to exercise full
    rights of ownership of, any Shares, including the right to vote such Shares
    on all matters properly presented to the stockholders of the Company,
    (v) seeks to require divestiture by Thermo Electron, Thermo Instrument or
    the Purchaser (or any other affiliate of Thermo Electron) of all or any of
    the Shares or (vi) otherwise has resulted in or, in the Purchaser's
    reasonable discretion, has a reasonable likelihood of resulting in a
    Material Adverse Effect; and which in the case of clause (i), (ii), (iii),
    (iv) or (v) is successful or the Purchaser determines, in its reasonable
    discretion, has a reasonable likelihood of being successful; or

        (e) there shall be any statute, rule or regulation enacted, promulgated,
    entered, enforced or deemed applicable to the Offer or the Merger, or any
    other action shall have been taken by any Governmental Entity or court that
    results in, directly or indirectly, any of the consequences referred to in
    clauses (i) through (vi) of paragraph (b) above; or

        (f) there shall have occurred any general suspension of trading in, or
    limitation on prices for, securities on the New York Stock Exchange,
    American Stock Exchange or in the over-the-counter market (other than any
    temporary suspension pursuant to a circuit breaker procedure then in effect
    and lasting for not more than three trading hours), any declaration of a
    banking moratorium by federal or New York authorities or general suspension
    of payments in respect of lenders that regularly participate in the U.S.
    market in loans, any material limitation by any federal, state or local
    government or any court, administrative or regulatory agency or commission
    or other governmental authority or agency in the United States that
    materially affects the extension of credit generally by lenders that
    regularly participate in the United States market in loans, any commencement
    of a war involving the United States or any commencement of armed
    hostilities or other national or international circumstance involving the
    United States that has a material adverse effect on bank syndication or
    financial markets in the United States or, in the case of any of the
    foregoing

                                       36
<PAGE>
    occurrences existing on or at the time of the commencement of the Offer, a
    material acceleration or worsening thereof; which in the reasonable judgment
    of the Purchaser, in any such case, and regardless of the circumstances
    giving rise to such condition, makes it inadvisable to proceed with the
    Offer, the Merger and/or with such acceptance for payment or payments.

    The foregoing conditions are for the sole benefit of the Purchaser and its
affiliates and may be asserted by the Purchaser regardless of any circumstances
giving rise to any condition and may be waived by the Purchaser, in whole or in
part, at any time and from time to time in the reasonable discretion of the
Purchaser. The failure by the Purchaser (or any affiliate of the Purchaser) at
any time to exercise any of the foregoing rights will not be deemed a waiver of
any right, and each right will be deemed an ongoing right which may be asserted
at any time and from time to time.

CERTAIN LEGAL MATTERS; REGULATORY APPROVALS

    GENERAL.  Except as described below, none of Thermo Electron, Thermo
Instrument or the Purchaser is aware of any license or regulatory permit that
appears to be material to the business of the Company and its subsidiaries that
might be adversely affected by the Purchaser's acquisition of Shares as
contemplated herein.

    Except as described in this section, none of Thermo Electron, Thermo
Instrument or the Purchaser is aware of any other material filing, approval or
other action by any federal or state governmental or administrative authority
that would be required for the acquisition of Shares by the Purchaser as
contemplated herein. Should any such other approval or action be required, it is
currently contemplated that such approval or other action would be sought. There
is, however, no present intention to delay the purchase of Shares tendered
pursuant to the Offer or the Merger pending the outcome of any such other
approval or action. There can be no assurance that any such other approval or
action, if needed, would be obtained without substantial conditions or that
adverse consequences might not result to the Purchaser's, Thermo Instrument's,
Thermo Electron's or the Company's business in the event that such other
approvals were not obtained or such other actions were not taken. The
Purchaser's obligation under the Offer to accept for payment and pay for Shares
is subject to certain conditions, including conditions relating to the legal
matters discussed in this section. See "--Certain Conditions Of The Offer."

    ANTITRUST.  The Purchaser believes that the Offer and the Merger are exempt
from the reporting requirements contained in the Hart-Scott-Rodino Antitrust
Improvements Act of 1976. Nevertheless, there can be no assurance that a
challenge to the Offer and the Merger on antitrust grounds will not be made, or,
if such challenge is made, what the result will be.

    FOREIGN APPROVALS.  The Company conducts business in a number of foreign
countries and jurisdictions. In connection with the acquisition of the Shares
pursuant to the Offer or the Merger, the laws of certain of those foreign
countries and jurisdictions may require the filing of information with, or the
obtaining of the approval or consent of, governmental authorities in such
countries and jurisdictions. The governments in such countries and jurisdictions
might attempt to impose additional conditions on the Company's operations
conducted in such countries and jurisdictions as a result of the acquisition of
the Shares pursuant to the Offer or the Merger. If such approvals or consents
are found to be required, the Purchaser intends to make the appropriate filings
and applications. In the event such a filing or application is made for the
requisite foreign approvals or consents, there can be no assurance that such
approvals or consents will be granted and, if such approvals or consents are
received, there can be no assurance as to the date of such approvals or
consents. In addition, there can be no assurance that the Purchaser will be able
to cause the Company or its subsidiaries to satisfy or comply with such laws or
that compliance or noncompliance will not have adverse consequences for the
Company or any subsidiary after purchase of the Shares pursuant to the Offer or
the Merger.

    STATE ANTI-TAKEOVER STATUTES.  Section 203 of the DGCL prohibits business
combination transactions involving a Delaware corporation (such as the Company)
and an "interested stockholder" (defined generally as any person that directly
or indirectly beneficially owns 15% or more of the outstanding voting

                                       37
<PAGE>
stock of the subject corporation) for three years following the time such person
became an interested stockholder, unless special requirements are met or certain
exceptions apply, including that prior to such time the board of directors of
the subject corporation approved either the business combination or the
transaction which resulted in such person being an interested stockholder. The
Purchaser believes that neither the Offer nor the Merger is prohibited by
Section 203 of the DGCL.

    A number of other states have adopted laws and regulations applicable to
attempts to acquire securities of corporations which are incorporated, or have
substantial assets, stockholders, principal executive offices or principal
places of business, or whose business operations otherwise have substantial
economic effects, in such states. In 1982, in EDGAR v. MITE CORP., the Supreme
Court of the United States invalidated on constitutional grounds the Illinois
Business Takeover Statute, which, as a matter of state securities law, made
takeovers of corporations meeting certain requirements more difficult. However,
in 1987 in CTS CORP. v. DYNAMICS CORP. OF AMERICA, the Supreme Court held that
the State of Indiana may, as a matter of corporate law, and, in particular, with
respect to those aspects of corporate law concerning corporate governance,
constitutionally disqualify a potential acquiror from voting on the affairs of a
target corporation without the prior approval of the remaining stockholders. The
state law before the Supreme Court was by its terms applicable only to
corporations that had a substantial number of stockholders in that state and
were incorporated there.

    The Company, directly or through subsidiaries, conducts business in a number
of states throughout the United States, some of which have enacted takeover
laws. None of Thermo Electron, Thermo Instrument or the Purchaser knows whether
any of these laws will, by their terms, apply to the Offer or the Merger, and
the Purchaser has not necessarily complied with any such laws. Should any person
seek to apply any state takeover law, the Purchaser will take such action as
then appears desirable, which may include challenging the validity or
applicability of any such statute in appropriate court proceedings. In the event
it is asserted that one or more state takeover laws is applicable to the Offer
or the Merger, and an appropriate court does not determine that it is
inapplicable or invalid as applied to the Offer or the Merger, the Purchaser
might be required to file certain information with, or receive approvals from,
the relevant state authorities. In addition, if enjoined, the Purchaser might be
unable to accept for payment any Shares tendered pursuant to the Offer or be
delayed in continuing or consummating the Offer. In such case, the Purchaser may
not be obligated to accept for payment any Shares tendered. See "--Certain
Conditions Of The Offer."

DIVIDENDS AND DISTRIBUTIONS

    If, on or after January 31, 2000, the Company should declare or pay any
dividend or other distribution (including, without limitation, the issuance of
additional Shares pursuant to a stock dividend or stock split or the issuance of
rights for the purchase of any securities) with respect to the Shares that is
payable or distributable to stockholders of record on a date occurring prior to
the transfer to the name of the Purchaser or its nominees or transferees on the
Company's stock transfer records of the Shares purchased pursuant to the Offer,
then, without prejudice to the Purchaser's rights described in "--Certain
Conditions Of The Offer," (1) the purchase price per Share payable by the
Purchaser pursuant to the Offer will be reduced in the amount of any such cash
dividend or distribution, and (2) the whole of any non-cash dividend or
distribution (including, without limitation, additional Shares or rights as
aforesaid) will be required to be remitted promptly and transferred by each
tendering stockholder to the Depositary for the account of the Purchaser
accompanied by appropriate documentation of transfer. Pending such remittance or
appropriate assurance thereof, the Purchaser will be entitled to all rights and
privileges as owner of any such non-cash dividend, distribution or right, and
may withhold the entire purchase price or deduct from the purchase price the
amount of value of such non-cash dividend, distribution or right, as determined
by the Purchaser in its sole discretion.

    If, on or after January 31, 2000, the Company should split the Shares or
combine or otherwise change the Shares or its capitalization, then, without
prejudice to the Purchaser's rights described under the heading "--Certain
Conditions Of The Offer," appropriate adjustments to reflect such split,
combination or change may be made by the Purchaser in the purchase price and
other terms of the Offer, including, without limitation, the number or type of
securities offered to be purchased.

                                       38
<PAGE>
                    CERTAIN FEDERAL INCOME TAX CONSEQUENCES

    The following is a general summary of the material U.S. federal income tax
consequences of the Offer and the Merger to the beneficial owners of Shares.
This summary is based upon the provisions of the Internal Revenue Code of 1986,
as amended (the "Code"), applicable treasury regulations thereunder, judicial
decisions and current administrative rulings as in effect on the date of this
Offer to Purchase. The discussion does not address all aspects of U.S. federal
income taxation that may be relevant to particular taxpayers in light of their
personal circumstances or to taxpayers subject to special treatment under the
Code (for example, life insurance companies, foreign corporations, foreign
partnerships, foreign estates or trusts, or individuals who are not citizens or
residents of the United States and beneficial owners whose Shares were acquired
pursuant to the exercise of warrants, employee stock options or otherwise as
compensation) and does not address any aspect of state, local, foreign or other
taxation.

    The receipt of cash for Shares pursuant to the Offer or the Merger will be a
taxable transaction for federal income tax purposes under the Code, and may also
be a taxable transaction under applicable state, local or foreign income or
other tax laws. Generally, for federal income tax purposes, a beneficial owner
of Shares that tenders Shares pursuant to the Offer or surrenders Shares
pursuant to the Merger will recognize gain or loss equal to the difference
between the amount of cash received by the beneficial owner and the aggregate
tax basis in the Shares sold pursuant to the Offer or canceled and converted to
cash pursuant to the Merger. Gain or loss will be calculated separately for each
block of Shares purchased pursuant to the Offer or canceled and converted to
cash pursuant to the Merger.

    Gain or loss on the disposition of Shares will be capital gain or loss,
assuming that the Shares are held as capital assets. Capital gains of
individuals, estates and trusts generally are subject to a maximum federal
income tax rate of (i) 20% if, at the time the tendered Shares are accepted for
payment (in the case of the Offer) or the Effective Time of the Merger (in the
case of the Merger), the beneficial owner held the Shares for more than one year
or (ii) 39.6% if, at the time the tendered Shares are accepted for payment (in
the case of the Offer) or the Effective Time of the Merger (in the case of the
Merger), the beneficial owner held the Shares for not more than one year.
Capital gains of corporations generally are taxed at the federal income tax
rates applicable to corporate ordinary income. In addition, the ability of both
corporate and non-corporate beneficial owners to use capital losses to offset
ordinary income is limited.

    In general, cash received by Public Stockholders who exercise statutory
appraisal rights ("Dissenting Stockholders") in respect of such appraisal rights
will result in the recognition of gain or loss to the Dissenting Stockholders.
Any such Dissenting Stockholder should consult with its tax advisor for a full
understanding of the tax consequences of the receipt of cash in respect of
appraisal rights pursuant to the Merger.

    A beneficial owner may be subject to backup federal income tax withholding
at a rate of 31% with respect to the amount of cash received pursuant to the
Offer or the Merger unless the owner provides its tax identification number
("TIN") and certifies that such number is correct or properly certifies that it
is awaiting a TIN, or unless an exemption applies. A beneficial owner that does
not furnish its TIN may be subject to a penalty imposed by the Internal Revenue
Service. See "The Tender Offer--Procedures For Accepting The Offer And Tendering
Shares--Backup Federal Income Tax Withholding."

    If backup withholding applies to a beneficial owner, the Depositary is
required to withhold 31% from payments to such owner. Backup withholding is not
an additional tax. Rather, the amount of the backup withholding can be credited
against the federal income tax liability of the person subject to the backup
withholding, provided that the required information is given to the Internal
Revenue Service. If backup withholding results in an overpayment of tax, a
refund can be obtained by the beneficial owner upon filing an income tax return.

    EACH BENEFICIAL OWNER OF SHARES IS URGED TO CONSULT SUCH BENEFICIAL OWNER'S
TAX ADVISOR AS TO THE SPECIFIC TAX CONSEQUENCES TO SUCH BENEFICIAL OWNER OF THE
OFFER AND THE MERGER, INCLUDING THE APPLICATION OF STATE, LOCAL, FOREIGN AND
OTHER TAX LAWS.

                                       39
<PAGE>
                      PRICE RANGE OF THE SHARES; DIVIDENDS

    PRICE RANGE OF SHARES.  The Shares are listed on the American Stock Exchange
under the symbol "ONX". The following table sets forth the high and low sales
prices per Share on the American Stock Exchange, as reported in publicly
available sources for each of the periods indicated.

<TABLE>
<CAPTION>
                                                                  HIGH           LOW
                                                              ------------   ------------
<S>                                                           <C>            <C>
Fiscal Year Ended January 2, 1999:
  First Quarter (beginning March 25, 1998)..................  $15 3/4        $14 1/2
  Second Quarter............................................  16             12 5/16
  Third Quarter.............................................  12 5/8         6
  Fourth Quarter............................................  8 3/16         5 1/8

Fiscal Year Ended January 1, 2000:
  First Quarter.............................................  7 7/8          5 3/8
  Second Quarter............................................  7 1/8          5 1/8
  Third Quarter.............................................  7              5 1/2
  Fourth Quarter............................................  6 3/8          4 1/2

Fiscal Year Ending December 30, 2000:
  First Quarter (through March 9, 2000).....................  $ 9            $ 6 1/4
</TABLE>

    As of January 28, 2000, there were 66 holders of record of the Shares and
approximately 400 beneficial owners of the Shares.

    On January 28, 2000, the last full trading day prior to the public
announcement of Thermo Electron's and Thermo Instrument's intention to commence
the Offer, the closing sale price per Share, as reported on the American Stock
Exchange, was $8.75. On March 9, 2000, the closing price per Share, as reported
on the American Stock Exchange, was $8.8125.

STOCKHOLDERS ARE URGED TO OBTAIN CURRENT MARKET QUOTATIONS FOR THE SHARES.

    DIVIDENDS.  The Company has never declared or paid any cash dividends in
respect of the Shares.

                                       40
<PAGE>
                   CERTAIN INFORMATION CONCERNING THE COMPANY

    Stockholders are urged to review the publicly available information
concerning the Company before acting on the Offer.

    GENERAL.  The Company designs, develops, markets and services sophisticated
field measurement instruments and on-line sensors for the process control
industry. The Company operates in two segments: Measurement Instruments and
Industry-Specific Systems. The Company's products are sold primarily to
participants in process industries, including oil and gas producers, refiners,
pipelines, distributors, and chemical and petrochemical companies, as well as
water and wastewater, iron and steel, semiconductor, minerals and mining, and
pulp and paper companies.

    The Company's Measurement Instruments segment manufactures field measurement
instruments and on-line sensors in four general product areas: flow, level and
density, composition analysis, and data acquisition and display. Flow
measurement instruments include gas flow computers, noncontacting ultrasonic
flow meters, turbine flow meters and air flow measurement systems. Level and
density measurement instruments include intelligent point-level and
continuous-level measurement instruments. Composition analysis measurement
instruments include sulfur analyzers, infrared and ultraviolet spectrometers,
gas chromatographs, portable elemental analysis instruments and on-line mass
spectrometers. Data acquisition and display instruments include strip chart
recorders, paperless recorders, AC harmonic analyzers, and data acquisition and
analysis systems.

    The Industry-Specific Systems segment offers sophisticated sensor systems
that are used to provide real-time measurement, data collection, recording,
analysis and local control of process functions. These special purpose
instruments and sensors include rod pump controllers, remote terminal units,
gas-injection systems and wellhead safety systems.

    The principal executive offices of the Company are located at 22001 North
Park Drive, Kingwood, Texas 77339-3804, and its telephone number is
(781) 622-1000.

    The Company is subject to the disclosure requirements of the Exchange Act
and in accordance therewith is required to file reports, proxy statements and
other information with the Commission relating to its business, financial
condition and other matters. In addition, the Company is required to file within
10 business days of the commencement of this Offer, and to distribute to the
Company's Stockholders, a statement on Schedule 14D-9 regarding its
recommendation to the Company's stockholders with respect to the Offer. Such
reports, proxy statements, Schedule 14D-9 and other information are available
for inspection at the Commission's public reference facilities at 450 Fifth
Street, N.W., Washington, D.C. 20549 and should also be available for inspection
at the regional offices of the Commission located at 7 World Trade Center, Suite
1300, New York, New York 10048 and Citicorp Center, 500 West Madison Street,
Suite 1400, Chicago, Illinois 60661. Copies may be obtained at prescribed rates
from the Commission's principal office at 450 Fifth Street, N.W., Washington,
D.C. 20549. The Commission also maintains a web site that contains reports,
proxy and information statements and other information regarding registrants
that file electronically with the Commission at http://www.sec.gov. In addition,
certain material filed by the Company may also be available for inspection at
the offices of the American Stock Exchange, 86 Trinity Place, New York, NY
10006-1881.

    None of Thermo Electron, Thermo Instrument or the Purchaser intends to grant
unaffiliated stockholders special access to the Company's records in connection
with the Offer. None of Thermo Electron, Thermo Instrument or the Purchaser
intends to obtain counsel or appraisal services for unaffiliated stockholders of
the Company.

                                       41
<PAGE>
    FINANCIAL INFORMATION.  Set forth below is certain selected consolidated
financial information with respect to the Company and its subsidiaries excerpted
or derived from the audited consolidated financial statements contained in the
Company's Annual Report on Form 10-K for its fiscal year ended January 2, 1999
and the unaudited financial statements contained in the Company's Quarterly
Reports on Form 10-Q for the quarters ended October 2, 1999 and October 3, 1998
(collectively, the "Company Reports"). More comprehensive financial information
is included in the Company Reports and in other documents filed by the Company
with the Commission (which may be inspected or obtained in the manner set forth
above), and the following financial information is qualified in its entirety by
reference to the Company Reports and other documents and all of the financial
information (including any related notes) contained therein or incorporated
therein by reference.

    The selected financial information presented below as of and for the fiscal
years ended January 2, 1999, January 3, 1998, December 28, 1996 and
December 30, 1995, has been derived from the Company's Consolidated Financial
Statements, which have been audited by Arthur Andersen LLP. The selected
financial information as of and for the fiscal year ended December 31, 1994 and
the nine months ended October 2, 1999 and October 3, 1998 has not been audited.
The results of operations for the nine months ended October 2, 1999 are not
necessarily indicative of results for the entire year.

                  SELECTED CONSOLIDATED FINANCIAL INFORMATION

<TABLE>
<CAPTION>
                                     NINE MONTHS ENDED
                                    -------------------
                                    OCT. 2,    OCT. 3,
                                      1999     1998(A)    1998(A)    1997(B)    1996(C)    1995(D)      1994
                                    --------   --------   --------   --------   --------   --------   --------
                                                           (IN THOUSANDS EXCEPT PER SHARE AMOUNTS)
<S>                                 <C>        <C>        <C>        <C>        <C>        <C>        <C>
STATEMENT OF INCOME DATA:
Revenues..........................  $103,519   $115,434   $153,653   $121,525   $95,316    $72,105    $62,059
Net Income........................     2,944      6,534      8,000      8,799     4,858      3,627      1,264
Basic and Diluted Earnings per
  Share...........................       .21        .45        .55        .79       .46        .34        .12
Weighted Average Shares:
  Basic...........................    14,357     14,564     14,515     11,083    10,667     10,667     10,667
  Diluted.........................    14,357     14,570     14,520     11,083    10,667     10,667     10,667
BALANCED SHEET DATA (AT END OF
  PERIOD):
Working Capital...................  $ 77,815   $ 74,326   $ 74,843   $ 41,947   $29,873    $26,199    $13,327
Total Assets......................   181,192    190,467    180,578    159,709    97,010     76,221     71,710
Shareholders' Investment..........   149,044    150,161    146,547    104,938    73,110     59,791     50,795
OTHER DATA:
Book Value per Share..............  $  10.38   $  10.00   $  10.21   $   8.53
Cash Dividends....................        --         --         --         --        --         --         --
Ratio of Earnings to Fixed
  Charges (e).....................     6.63x     12.67x     11.28x     18.19x
</TABLE>

- ------------------------

(a) Reflects the July 1998 acquisition of the Mid-South Companies and the
    March 1998 initial public offering of Company common stock.

(b) Reflects the acquisition of the Peek Measurement Business effective in
    November 1997, the December 1997 acquisition of Fluid Data, Inc. and the
    September and October 1997 private placements of Company common stock.

(c) Reflects the October 1996 acquisition of Kay-Ray/Sensall and the March 1996
    acquisition of VG Gas Analysis.

(d) Reflects the July 1995 acquisition of Flow Automation.

(e) For purposes of computing the ratios of earnings to fixed charges,
    "earnings" represent income before taxes, plus fixed charges. "Fixed
    charges" consist of interest on indebtedness and one-third of rental
    expense, which is deemed to be the interest component of such rental
    expense.

                                       42
<PAGE>
    RECENTLY RELEASED FINANCIAL DATA.  The selected financial information of the
Company presented below for the three and twelve month periods ended January 1,
2000 and January 2, 1999 was publicly released by the Company on February 22,
2000. With the exception of the financial information for the twelve months
ended January 2, 1999, this financial information is not audited and full
financial statements reflecting such information have not yet been filed with
the Commission.

                      CONSOLIDATED STATEMENT OF OPERATIONS

<TABLE>
<CAPTION>
                                                         THREE MONTHS ENDED         TWELVE MONTHS ENDED
                                                       ----------------------      ----------------------
                                                       JAN. 1,       JAN. 2,       JAN. 1,       JAN. 2,
                                                         2000          1999          2000          1999
                                                       --------      --------      --------      --------
                                                            (IN THOUSANDS EXCEPT PER SHARE AMOUNTS)
<S>                                                    <C>           <C>           <C>           <C>
Revenues.........................................      $36,450       $38,219       $139,969      $153,653
                                                       -------       -------       --------      --------
Costs and Operating Expenses:
  Cost of revenues...............................       26,018        24,504         91,353        93,082
  Selling, general, and administrative
    expenses.....................................        9,069         9,684         36,177        38,870
  Research and development expenses..............        2,485         2,294          9,776         9,232
  Restructuring costs, net.......................           --          (256)           234           905
  Loss on sale of property.......................          135            --            135            --
                                                       -------       -------       --------      --------
                                                        37,707        36,226        137,675       142,089
                                                       -------       -------       --------      --------
Operating Income (Loss)..........................       (1,257)        1,993          2,294        11,564
Interest Income..................................          538           426          1,783         1,990
Interest Expense.................................          (60)          (55)          (183)         (332)
                                                       -------       -------       --------      --------
Income (Loss) Before Income Taxes................         (779)        2,364          3,894        13,222
Income Tax Benefit (Provision)...................          154          (898)        (1,575)       (5,222)
                                                       -------       -------       --------      --------
Net Income (Loss)................................      $  (625)      $ 1,466       $  2,319      $  8,000
                                                       =======       =======       ========      ========
Basic and Diluted Earnings (Loss) per Share......      $  (.04)      $   .10       $    .16      $    .55
                                                       =======       =======       ========      ========
Weighted Average Shares:
  Basic..........................................       14,358        14,369         14,357        14,515
                                                       =======       =======       ========      ========
  Diluted........................................       14,358        14,370         14,357        14,520
                                                       =======       =======       ========      ========
</TABLE>

                                       43
<PAGE>
                 CERTAIN INFORMATION CONCERNING THE PURCHASER,
                     THERMO INSTRUMENT AND THERMO ELECTRON

THE PURCHASER

    The Purchaser is a newly organized, wholly-owned subsidiary of Thermo
Instrument formed for the purpose of making the Offer. The Purchaser is
organized under the laws of the State of Delaware. The Purchaser's principal
executive offices are located at 81 Wyman Street, P.O. Box 9046, Waltham,
Massachusetts 02454-9046, and its telephone number is (781) 622-1000.

    The name, business address, principal occupation, employment history and
citizenship of each of the executive officers and directors of the Purchaser are
set forth on Schedule I hereto.

    During the past five years, the Purchaser has not been convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors) or
been a party to any judicial or administrative proceeding (except for any
matters that were dismissed without sanction or settlement) that resulted in a
judgment, decree or final order enjoining the Purchaser from future violations
of, or prohibiting activities subject to, federal or state securities laws, or a
finding of any violation of federal or state securities laws.

THERMO INSTRUMENT

    Thermo Instrument, a Delaware corporation, develops, manufactures and
markets measurement instruments used to monitor, collect and analyze
information. These systems are used for multiple applications in a range of
industries, including industrial processing, food and beverage production, life
sciences research and medical diagnostics. Thermo Instrument's businesses
operate in the following instrumentation segments: Analytical, Life Sciences,
Process Control and Industrial.

       ANALYTICAL SEGMENT. In the Analytical segment, ThermoQuest Corporation
       manufactures mass spectrometers, liquid chromatographs and gas
       chromatographs for the pharmaceutical, environmental and industrial
       marketplaces. Thermo Optek Corporation supplies scientific equipment for
       the preparation and preservation of chemical samples, and consumables for
       the chromatography industry.

       LIFE SCIENCES SEGMENT. In the Life Sciences segment, Thermo BioAnalysis
       Corporation develops, manufactures and markets instruments, consumables
       and information-management systems used in pharmaceutical research and
       production, and in clinical diagnostics.

       PROCESS CONTROL SEGMENT. In the Process Control segment, the Company
       designs, develops, markets and services sophisticated field-measurement
       instruments and on-line sensors for process-control industries, such as
       the oil and gas industries. Metrika Systems Corporation manufactures
       on-line process optimization systems that provide real-time,
       nondestructive analysis of the composition of raw materials in
       basic-materials production processes, including coal, cement and
       minerals, and manufactures advanced systems used principally by producers
       of finished flat metals.

       INDUSTRIAL SEGMENT. In the Industrial segment, ThermoSpectra Corporation
       develops, manufactures and markets precision imaging and inspection,
       temperature-control, and test and measurement instruments. Thermo Vision
       Corporation designs, manufactures and markets a diverse array of
       photonics products (light-based technologies), including optical
       components, imaging sensors and systems, lasers, optically based
       instruments, opto-electronics and fiber optics.

    Thermo Instrument's common stock is listed on the American Stock Exchange
under the symbol "THI". The principal executive offices of Thermo Instrument are
located at 81 Wyman Street, Waltham, Massachusetts 02454-9046, and its telephone
number is (781) 622-1000.

    Thermo Instrument is subject to the disclosure requirements of the Exchange
Act and in accordance therewith is required to file reports, proxy statements
and other information with the Commission relating to its business, financial
condition and other matters. Such reports, proxy statements and other
information

                                       44
<PAGE>
are available for inspection and copying at prescribed rates at the offices of
the Commission and the American Stock Exchange as set forth under "Certain
Information Concerning The Company."

    The name, business address, principal occupation, five-year employment
history and citizenship of each of the directors and executive officers of
Thermo Instrument are set forth in Schedule I hereto.

    During the past five years, Thermo Instrument has not been convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors) or
been a party to any judicial or administrative proceeding (except for any
matters that were dismissed without sanction or settlement) that resulted in a
judgment, decree or final order enjoining Thermo Instrument from future
violations of, or prohibiting activities subject to, federal or state securities
laws, or a finding of any violation of federal or state securities laws.

THERMO ELECTRON

    Thermo Electron, a Delaware corporation, and its subsidiaries develop and
manufacture a broad range of products that are sold worldwide. Thermo Electron
is a world leader in monitoring, analytical and biomedical instrumentation;
biomedical products including heart-assist devices, respiratory-care equipment
and mammography systems; and paper recycling and papermaking equipment. Thermo
Electron also develops alternative-energy systems and clean fuels, provides a
range of services including industrial outsourcing and environmental-liability
management and conducts research and development in advanced imaging, laser and
electronic information-management technologies. Thermo Electron performs its
business through wholly-owned subsidiaries and divisions, as well as
majority-owned subsidiaries that are partially owned by public or private
investors.

    On January 31, 2000, Thermo Electron announced that its Board of Directors
had authorized its management to proceed with a major reorganization of the
operations of Thermo Electron and its subsidiaries. As part of this
reorganization, Thermo Electron plans to acquire the public minority interest in
most of its subsidiaries that have minority investors, spin off its separation
technologies and fiber-based products business and its medical products
business, and divest a variety of non-core businesses. The primary goal of this
reorganization is for Thermo Electron and each of its spun-off subsidiaries to
focus on its respective core business. The purpose of the Offer and the Merger
is to acquire the minority public interest in the Company as part of Thermo
Electron's overall reorganization and to provide the Public Stockholders with
$9.00 per Share in cash. Following the Offer and the Merger, Thermo Electron
plans to retain the Company as part of Thermo Electron's core instrument
business.

    Thermo Electron's common stock is listed on the New York Stock Exchange
under the symbol "TMO". The principal executive offices of Thermo Electron are
located at 81 Wyman Street, P.O. Box 9046, Waltham, Massachusetts 02454-9046,
and its telephone number is (781) 622-1000.

    Thermo Electron is subject to the disclosure requirements of the Exchange
Act and in accordance therewith is required to file reports, proxy statements
and other information with the Commission relating to its business, financial
condition and other matters. Such reports, proxy statements and other
information are available for inspection and copying at prescribed rates at the
offices of the Commission as set forth under "Certain Information Concerning The
Company." In addition, certain material filed by Thermo Electron may also be
available for inspection at the offices of the New York Stock Exchange, 20 Broad
Street, New York, New York 10005.

    The name, business address, principal occupation, five-year employment
history and citizenship of each of the directors and executive officers of
Thermo Electron are set forth in Schedule I hereto.

    During the past five years, Thermo Electron has not been convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors) or
been a party to any judicial or administrative proceeding (except for any
matters that were dismissed without sanction or settlement) that resulted in a
judgment, decree or final order enjoining Thermo Electron from future violations
of, or prohibiting activities subject to, federal or state securities laws, or a
finding of any violation of federal or state securities laws.

                                       45
<PAGE>
CERTAIN TRANSACTIONS

    Except as otherwise set forth in this Offer to Purchase, none of the
Purchaser, Thermo Instrument or Thermo Electron or, to the best knowledge of the
Purchaser, Thermo Instrument and Thermo Electron, any of the persons listed on
Schedule I hereto, has any contract, arrangement, understanding or relationship
with any other person with respect to any Shares or other securities of the
Company, including, but not limited to, any contract, arrangement, understanding
or relationship concerning the transfer or voting of any such Shares or other
securities, joint ventures, loan or option arrangements, puts or calls,
guaranties of loans, guaranties against loss or the giving or withholding of
proxies.

    PRIOR CONTACTS.  Except as set forth in this Offer to Purchase (particularly
the section entitled "Special Factors--Background To The Offer And The Merger"),
since January 1, 1998, there have been no contacts, negotiations or transactions
between the Purchaser, Thermo Instrument, Thermo Electron, any subsidiary of the
Purchaser, Thermo Instrument or Thermo Electron or, to the best knowledge of the
Purchaser, Thermo Instrument and Thermo Electron, any of the persons listed on
Schedule I hereto, on the one hand, and the Company or any of its officers,
directors or affiliates, on the other hand, concerning a merger, consolidation
or acquisition, a tender offer or other acquisition of securities, an election
of directors or a sale or other transfer of a material amount of assets, other
than votes cast by Thermo Electron or Thermo Instrument for the election of
directors of the Company in the normal course.

    PRIOR BUSINESS RELATIONSHIPS.  Except as set forth in this Offer to
Purchase, none of the Purchaser, Thermo Instrument or Thermo Electron or, to the
best knowledge of the Purchaser, Thermo Instrument or Thermo Electron, any of
the persons listed on Schedule I hereto has, since January 1, 1998, had any
business relationships or transactions with the Company or any of its executive
officers, directors or affiliates that would require disclosure herein under the
rules and regulations of the Commission applicable to the Offer or the Merger.

    TRANSACTIONS BETWEEN THE COMPANY AND THERMO INSTRUMENT OR THERMO
ELECTRON.  In January 1998, the Company acquired certain businesses comprising
the Peek Measurement Business of Peek plc from Thermo Power Corporation ("Thermo
Power"), a subsidiary of Thermo Electron, for approximately $19.1 million,
effective November 1997. The purchase price represents the sum of (i) the net
tangible book value of the Peek Measurement Business as of the date of the
acquisition by Thermo Power of Peek plc in November 1997, plus (ii) the total
goodwill associated with Thermo Power's acquisition of Peek plc equal to the
total fiscal 1997 revenue of the Peek Measurement Business relative to the total
revenues of Peek plc for such period, plus (iii) $1.0 million, which represents
an estimate of the amount of tax incurred by Thermo Power as a result of the
transfer of the Peek Measurement Business to the Company. In addition, the
Company paid $256,000 in interest, representing interest on the purchase price,
from November 6, 1997 through January 29, 1998 at an interest rate equal to the
90-day Commercial Paper Composite Rate plus 25 basis points, set at the
beginning of each quarter.

    In January 1998, the Company borrowed $12.0 million from Thermo Instrument
to partially fund the Company's acquisition of the Peek Measurement Business
from Thermo Power. This loan, which had an interest rate equal to the 90-day
Commercial Paper Composite Rate plus 25 basis points, set at the beginning of
each quarter, was repaid in April 1998.

    FINANCIAL INFORMATION.  Because the Offer Price will be paid in cash, the
Purchaser, Thermo Instrument and Thermo Electron do not believe that financial
information with respect to the Purchaser, Thermo Instrument, Thermo Electron
and their subsidiaries would be material to a stockholder's evaluation of the
Offer and the Merger. Financial information concerning Thermo Instrument, Thermo
Electron and their subsidiaries is filed by Thermo Instrument and Thermo
Electron with the Commission (which may be inspected and copies thereof obtained
at the offices of the Commission as set forth in "Certain Information Concerning
The Company").

                                       46
<PAGE>
                           SOURCE AND AMOUNT OF FUNDS

    The total amount of funds required by the Purchaser to purchase all of the
outstanding Shares pursuant to the Offer and the Merger, and to pay related fees
and expenses, is estimated to be approximately $24.3 million. The Purchaser will
obtain the funds to purchase the Shares in the Offer and the Merger from Thermo
Instrument as a loan or capital contribution. Thermo Instrument will use a
combination of its own working capital and borrowings from Thermo Electron to
fund this loan or capital contribution. Thermo Electron has committed to provide
any required financing to Thermo Instrument. Any loan by Thermo Electron to
Thermo Instrument will be evidenced by unsecured note due September 1, 2000 that
will bear interest at a floating rate equal to the 30-day Dealer Commercial
Paper Rate (the "DCP Rate") plus 150 basis points, adjusted at the beginning of
each fiscal month of Thermo Instrument. The interest rate of the note will be
reduced to the DCP Rate plus 50 basis points to the extent of any funds invested
by Thermo Instrument's majority-owned subsidiaries in Thermo Electron's cash
management arrangement.

                                       47
<PAGE>
                          THE MERGER; APPRAISAL RIGHTS

THE MERGER

    Following the consummation of the Offer, subject to the terms and conditions
and in accordance with the DGCL, Thermo Instrument plans to cause the Purchaser
to merge with and into the Company. Upon the effective date of the Merger:

    - each Share issued and outstanding immediately prior to the effective date
      of the Merger (other than Shares owned by Public Stockholders, if any, who
      are entitled to and who properly exercise their dissenters' rights (See
      "--Appraisal Rights" below) under the DGCL) will be cancelled and
      extinguished and be converted into and become a right to receive the Offer
      Price per Share; and

    - each outstanding share of the Purchaser's capital stock issued and
      outstanding immediately prior to the effective date of the Merger will be
      converted into one validly issued, fully paid and nonassessable share of
      the same class of common stock of the Surviving Corporation. As a result
      of the Merger, Thermo Instrument and Thermo Electron will own all of the
      outstanding equity interests in the Company.

    Under the DGCL, if the Purchaser holds at least 90% of the outstanding
Shares, the Purchaser would have the power to effect the Merger, without a vote
of the Company's Board of Directors or other stockholders. The Purchaser intends
to take all necessary and appropriate action to cause the Merger to become
effective as soon as reasonably practicable after the consummation of the Offer
and without a meeting of the Company's stockholders.

APPRAISAL RIGHTS

    Stockholders who tender their Shares in the Offer are not entitled to
appraisal rights under the DGCL. If the Purchaser effects the Merger, then
Company stockholders who do not tender their Shares to the Purchaser pursuant to
the Offer would have the right to demand an appraisal of the fair value of their
Shares in accordance with the provisions of Section 262 of the DGCL
("Section 262"), which sets forth the rights and obligations of Company
stockholders demanding an appraisal and the procedures to be followed.

    Under the DGCL, record holders of the Shares who follow the procedures set
forth in Section 262 will be entitled to have their Shares appraised by the
Court of Chancery of the State of Delaware and to receive payment of the fair
value of such shares together with a fair rate of interest, if any, as
determined by such court. The fair value as determined by the Delaware court is
exclusive of any element of value arising from the accomplishment or expectation
of the Merger. The following is a summary of certain of the provisions of
Section 262 of the DGCL and is qualified in its entirety by reference to the
full text of Section 262, a copy of which is attached to this Offer to Purchase
as Schedule III.

    The Surviving Corporation would notify the Public Stockholders of record as
of the effective date of the Merger, and of the approval and consummation of the
Merger and the availability of appraisal rights under Section 262 within ten
days of the effective date of the Merger (the "Merger Notice"). Any Public
Stockholder entitled to appraisal rights would have the right, within 20 days
after the date of mailing of the Merger Notice, to demand in writing from the
Surviving Corporation an appraisal of his Shares. Such demand will be sufficient
if it reasonably informs the Surviving Corporation of the identity of the
stockholder and that the stockholder intends to demand an appraisal of the fair
value of his Shares. Failure to make such a timely demand would foreclose a
Public Stockholder's right to appraisal.

    Only a holder of record of Shares at the time of the Merger is entitled to
assert appraisal rights for the Shares registered in that holder's name. A
demand for appraisal should be executed by or on behalf of the holder of record
fully and correctly, as the holder's name appears on the holder's Share
Certificates. Holders of Shares who hold their shares in brokerage accounts or
other nominee forms and wish to exercise appraisal rights should consult with
their brokers to determine the appropriate procedures for the making of a demand
for appraisal by such nominee. All written demands for appraisal of the Shares
should

                                       48
<PAGE>
be sent or delivered to Sandra L. Lambert, Secretary, ONIX Systems Inc., c/o
Thermo Electron Corporation, 81 Wyman Street, P.O. Box 9046, Waltham,
Massachusetts 02454-9046, so as to be received within the 20 days after the
mailing of the Merger Notice.

    If the Shares are owned of record in a fiduciary capacity, such as by a
trustee, guardian or custodian, execution of the demand should be made in that
capacity, and if the Shares are owned of record by more than one person, as in a
joint tenancy or tenancy in common, the demand should be executed by or on
behalf of all joint owners. An authorized agent, including one or more joint
owners, may execute a demand for appraisal on behalf of a holder of record;
however, the agent must identify the record owner or owners and expressly
disclose the fact that, in executing the demand, the agent is agent for such
owner or owners.

    A record holder such as a broker holding Shares as nominee for several
beneficial owners may exercise appraisal rights with respect to the Shares held
for one or more beneficial owners while not exercising such rights with respect
to the Shares held for other beneficial owners; in such case, the written demand
should set forth the number of shares as to which appraisal is sought and where
no number of shares is expressly mentioned the demand will be presumed to cover
all Shares held in the name of the record owner.

    Within 10 calendar days after the effective date of the Merger, the
Surviving Corporation must send a notice as to the effectiveness of the Merger.
Within 120 calendar days after the effective date of the Merger, the Surviving
Corporation, or any stockholder entitled to appraisal rights under Section 262
and who has complied with the foregoing procedures, may file a petition in the
Delaware Court of Chancery demanding a determination of the fair value of the
Shares of all such stockholders. The Surviving Corporation is not under any
obligation, and has no present intention, to file a petition with respect to the
appraisal of the fair value of the Shares. Accordingly, it is the obligation of
the stockholders to initiate all necessary action to perfect their appraisal
rights within the time prescribed in Section 262.

    Within 120 calendar days after the effective date of the Merger, any
stockholder of record who has complied with the requirements for exercise of
appraisal rights will be entitled, upon written request, to receive from the
Surviving Corporation a statement setting forth the aggregate number of Shares
with respect to which demands for appraisal have been received and the aggregate
number of holders of such Shares. Such statement must be mailed within 10
calendar days after a written request therefor has been received by the
Surviving Corporation or within 10 calendar days after the expiration of the
period for the delivery of demands for appraisal, whichever is later.

    If a petition for an appraisal is timely filed, after a hearing on such
petition, the Delaware Court of Chancery will determine the stockholders
entitled to appraisal rights and will appraise the fair value of the Shares,
exclusive of any element of value arising from the accomplishment or expectation
of the Merger, together with a fair rate of interest, if any, to be paid upon
the amount determined to be the fair value. Holders considering seeking
appraisal should be aware that the fair value of their Shares as determined
under Section 262 could be more than, the same as or less than the amount per
share that they would otherwise receive if they did not seek appraisal of their
Shares. The Delaware Supreme Court has stated that "proof of value by any
techniques or methods that are generally considered acceptable in the financial
community and otherwise admissible in court" should be considered in the
appraisal proceedings. In addition, Delaware courts have decided that the
statutory appraisal remedy, depending on factual circumstances, may or may not
be a dissenter's exclusive remedy. The Court will also determine the amount of
interest, if any, to be paid upon the amounts to be received by persons whose
Shares have been appraised. The costs of the action may be determined by the
Court and taxed upon the parties as the Court deems equitable. The Court may
also order that all or a portion of the expenses incurred by any holder of
Shares in connection with an appraisal, including, without limitation,
reasonable attorneys' fees and the fees and expenses of experts used in the
appraisal proceeding, be charged pro rata against the value of all the Shares
entitled to appraisal.

    The Court may require stockholders who have demanded an appraisal and who
hold Shares represented by certificates to submit their certificates for Shares
to the Court for notation thereon of the

                                       49
<PAGE>
pendency of the appraisal proceedings. If any stockholder fails to comply with
such direction, the Court may dismiss the proceedings as to such stockholder.

    Any stockholder who has duly demanded an appraisal in compliance with
Section 262 will not, after the effective date of the Merger, be entitled to
vote the Shares subject to such demand for any purpose or be entitled to the
payment of dividends or other distributions on those shares (except dividends or
other distributions payable to holders of record of Shares as of a date prior to
the effective date of the Merger).

    If any stockholder who demands appraisal of shares under Section 262 fails
to perfect, or effectively withdraws or loses, the right to appraisal, as
provided in the DGCL, the Shares of such holder will be converted into the right
to receive the Offer Price, without interest. A stockholder will fail to
perfect, or effectively lose, the right to appraisal if no petition is filed
within 120 calendar days after the effective date of the Merger. A stockholder
may withdraw a demand for appraisal by delivering to the Surviving Corporation a
written withdrawal of the demand for appraisal and acceptance of the Merger,
except that any such attempt to withdraw made more than 60 calendar days after
the effective date of the Merger will require the written approval of the
Surviving Corporation. Once a petition for appraisal has been filed, such
appraisal proceeding may not be dismissed as to any stockholder without the
approval of the Court.

    For federal income tax purposes, stockholders who receive cash for their
Shares upon exercise of Dissenters' Rights will realize taxable gain or loss.
See "Federal Income Tax Consequences."

    THE FOREGOING SUMMARY DOES NOT PURPORT TO BE A COMPLETE STATEMENT OF THE
PROCEDURES TO BE FOLLOWED BY STOCKHOLDERS DESIRING TO EXERCISE THEIR DISSENTING
APPRAISAL RIGHTS AND IS QUALIFIED IN ITS ENTIRETY BY EXPRESS REFERENCE TO THE
DELAWARE APPRAISAL STATUTE, THE FULL TEXT OF WHICH IS ATTACHED HERETO AS
SCHEDULE III. STOCKHOLDERS ARE URGED TO READ SCHEDULE III IN ITS ENTIRETY SINCE
FAILURE TO COMPLY WITH THE PROCEDURES SET FORTH THEREIN WILL RESULT IN THE LOSS
OF APPRAISAL RIGHTS.

                                       50
<PAGE>
                               FEES AND EXPENSES

    The Advisors are acting as financial advisors to Thermo Instrument and
Thermo Electron in connection with the Offer and the Merger. The Advisors are
also acting as Dealer Managers in connection with the Offer. For a discussion of
the fees to be paid to the Advisors in connection with Offer and the Merger, see
"Special Factors--Summary Of The Advisors' Analysis and Opinion."

    The Purchaser has retained D.F. King & Co., Inc. to act as the Information
Agent and American Stock Transfer & Trust Company to act as the Depositary in
connection with the Offer. The Information Agent may contact holders of Shares
by mail, telephone, telex, telecopy, telegraph and personal interview and may
request brokers, dealers, commercial banks, trust companies and other nominees
to forward the Offer material to beneficial owners. Each of the Information
Agent and the Depositary will receive reasonable and customary compensation for
its services and will be reimbursed for certain reasonable out-of-pocket
expenses and will be indemnified against certain liabilities and expenses in
connection with the Offer, including certain liabilities under U.S. federal
securities laws.

    The Purchaser will not pay any fees or commissions to any broker or dealer
or any other person for soliciting tenders of Shares pursuant to the Offer
(other than to the Dealer Managers and the Information Agent). Brokers, dealers,
commercial banks and trust companies will, upon request, be reimbursed by the
Purchaser for customary mailing and handling expenses incurred by them in
forwarding materials to their customers.

    The following is an estimate of fees and expenses to be incurred by the
Purchaser in connection with the Offer:

<TABLE>
<S>                                                           <C>
Financial Advisors..........................................  $1,000,000
Legal.......................................................     250,000
Printing....................................................     100,000
Advertising.................................................      25,000
Filing......................................................       6,001
Depositary..................................................       7,500
Information Agent (including mailing).......................      12,000
Miscellaneous...............................................      99,499
                                                              ----------
                                                              $1,500,000
                                                              ==========
</TABLE>

    The Company will not pay any of the fees and expenses to be incurred by the
Purchaser in connection with the Offer.

                                       51
<PAGE>
                                 MISCELLANEOUS

    The Offer is being made solely by this Offer to Purchase and the related
Letter of Transmittal and is being made to all holders of Shares. The Offer is
not being made to (nor will tenders be accepted from or on behalf of) holders of
Shares in any jurisdiction in which the making of the Offer or the acceptance
thereof would not be in compliance with the laws of such jurisdiction. In any
jurisdiction where the securities, blue sky or other laws require the Offer to
be made by a licensed broker or dealer, the Offer shall be deemed to be made on
behalf of the Purchaser by the Dealer Managers or one or more registered brokers
or dealers licensed under the laws of such jurisdiction.

    Thermo Electron, Thermo Instrument and the Purchaser have filed with the
Commission a Schedule TO together with exhibits, pursuant to Rule 14d-3 and
Rule 13e-3 promulgated by the Commission under the Exchange Act, furnishing
certain additional information with respect to the Offer. Such statement and any
amendments thereto, including exhibits, may be examined and copies may be
obtained at the same places and in the same manner as set forth with respect to
information about the Company in "Certain Information Concerning The Company"
(except that such statement and amendments may not be available in the regional
offices of the Commission).

    NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR MAKE ANY
REPRESENTATION ON BEHALF OF THE PURCHASER NOT CONTAINED HEREIN OR IN THE LETTER
OF TRANSMITTAL AND, IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATION MUST
NOT BE RELIED ON AS HAVING BEEN AUTHORIZED.

March 13, 2000

                                       52
<PAGE>
                                   SCHEDULE I
                     MEMBERS OF THE BOARDS OF DIRECTORS AND
   EXECUTIVE OFFICERS OF THE PURCHASER, THERMO INSTRUMENT AND THERMO ELECTRON

DIRECTOR AND EXECUTIVE OFFICER OF THE PURCHASER

    Earl R. Lewis is the sole director and president of the Purchaser.
Biographical and other information with respect to Mr. Lewis is set forth below
under "--Directors and Executive Officers of Thermo Instrument" and "--Directors
and Executive Officers of Thermo Electron."

DIRECTORS AND EXECUTIVE OFFICERS OF THERMO INSTRUMENT

    The name, business address, position with Thermo Instrument, present
principal occupation or employment and five-year employment history of each of
the directors and executive officers of Thermo Instrument, together with the
names, principal businesses and addresses of any corporations or other
organizations in which such principal occupations are conducted, are set forth
below. Unless otherwise indicated, each occupation set forth refers to Thermo
Instrument, each individual is a United States citizen and each individual's
business address is 81 Wyman Street, Waltham, Massachusetts 02454. Unless
otherwise indicated, to the knowledge of each of the Purchaser, Thermo
Instrument, and Thermo Electron no director or executive officer of Thermo
Instrument beneficially owns any Shares (or rights to acquire Shares). Unless
otherwise indicated, to the knowledge of each of the Purchaser, Thermo
Instrument, and Thermo Electron no director or executive officer of Thermo
Instrument has been convicted in a criminal proceeding during the last five
years (excluding traffic violations or similar misdemeanors) and no director or
executive officer of Thermo Instrument was a party to any judicial or
administrative proceeding during the last five years (except for any matters
that were dismissed without sanction or settlement) that resulted in a
judgement, decree or final order enjoining the person from future violations of,
or prohibiting activities subject to, federal or state securities laws, or a
finding of any violation of federal or state securities laws. Richard F. Syron
resigned from the Board of Directors of Thermo Instrument effective March 7,
2000. John N. Hatsopoulos resigned from the Board of Directors of Thermo
Instrument effective February 20, 2000. Arvin H. Smith resigned from the Board
of Directors of Thermo Instrument effective February 15, 2000.

<TABLE>
<S>                                    <C>
GEORGE N. HATSOPOULOS                  Dr. Hatsopoulos, 73, has been a director of Thermo
                                       Instrument since 1986. He served as president, chief
                                       executive officer and chairman of the board of Thermo
                                       Electron from 1956 until January 1997, June 1999 and January
                                       2000, respectively. Dr. Hatsopoulos is also a director of
                                       Photoelectron Corporation, Thermedics Inc., Thermo Ecotek
                                       Corporation, Thermo Electron, Thermo Fibertek Inc. and
                                       ThermoTrex Corporation.

EARL R. LEWIS                          Mr. Lewis, 56, has been a director and the chief executive
                                       officer of Thermo Instrument since January 1998, and has
                                       been president of Thermo Instrument since March 1997. He was
                                       chief operating officer of Thermo Instrument from January
                                       1996 to January 1998. Prior to that time, he was executive
                                       vice president of Thermo Instrument from January 1996 to
                                       March 1997 and senior vice president from January 1994 to
                                       January 1996. Mr. Lewis has been the chief operating
                                       officer, measurement and detection, of Thermo Electron since
                                       September 1998. Prior to his appointment as chief operating
                                       officer, Mr. Lewis served as senior vice president of
                                       Thermo Electron from June 1998 to September 1998 and vice
                                       president from September 1996 to June 1998. Mr. Lewis served
                                       as chief executive officer of Thermo Optek Corporation, a
                                       majority-owned subsidiary of Thermo Instrument that
                                       manufactures analytical instruments that measure energy and
                                       light for
</TABLE>

                                      I-1
<PAGE>
<TABLE>
<S>                                    <C>
                                       purposes of materials analysis, characterization and
                                       preparation, from its inception in August 1995 to January
                                       1998. Mr. Lewis is a director of FLIR Systems Inc., Metrika
                                       Systems Corporation, ONIX Systems, SpectRx Inc.,
                                       Spectra-Physics Lasers, Inc., Thermedics Detection Inc.,
                                       Thermo BioAnalysis Corporation, Thermo Optek Corporation and
                                       ThermoQuest Corporation.

POLYVIOS C. VINTIADIS                  Mr. Vintiadis, 64, has been a director of Thermo Instrument
                                       since July 1993. Mr. Vintiadis has been the chairman and
                                       chief executive officer of Towermarc Corporation, a real
                                       estate development company located at Two Sound View Drive,
                                       Greenwich, CT 06830, since 1984. Mr. Vintiadis is also a
                                       director of Spectra-Physics Lasers, Inc. and Thermo
                                       TerraTech Inc.

RICHARD W. K. CHAPMAN                  Dr. Chapman, 54, has been senior vice president of Thermo
                                       Instrument since July 1998 and was a vice president of
                                       Thermo Instrument from 1992 until July 1998. He has been the
                                       chief executive officer, president and a director of
                                       ThermoQuest Corporation, a majority-owned subsidiary of
                                       Thermo Instrument since its inception in June 1995.
                                       ThermoQuest Corporation develops and distributes mass
                                       spectrometers, liquid chromatographs, gas chromatographs and
                                       multi-instrument combinations of these products for the
                                       pharmaceutical, environmental and industrial marketplaces,
                                       and is located at 2215 Grand Avenue Parkway, Austin, TX
                                       78728-3812.

DENIS A. HELM                          Mr. Helm, 61, has been executive vice president of Thermo
                                       Instrument since January 1999, and was a senior vice
                                       president from 1994 to 1998. From 1981 to 1998, Mr. Helm
                                       also served as president of Thermo Instrument's Thermo
                                       Environmental Instruments Inc. subsidiary, a manufacturer of
                                       instruments and systems for detecting and monitoring
                                       environmental pollutants. Mr. Helm also served as chief
                                       executive officer of Metrika Systems Corporation, a
                                       majority-owned subsidiary of Thermo Instrument from November
                                       1996 until February 1998. Mr. Helm's business address is 8
                                       East Forge Parkway, Franklin, MA 02038. Mr. Helm is also a
                                       director of Metrika Systems Corporation.

BARRY S. HOWE                          Mr. Howe, 44, has been a vice president of Thermo Instrument
                                       since 1994. He has been president and chief executive
                                       officer of ThermoSpectra Corporation, a subsidiary of Thermo
                                       Instrument, that develops, manufactures and markets
                                       precision imaging, inspection, temperature control and test
                                       and measurement instruments since March 1998 and was
                                       appointed president, chief executive officer and a director
                                       of Thermo Optek Corporation, a majority-owned subsidiary of
                                       Thermo Instrument in October 1999. Thermo Optek is a
                                       manufacturer of analytical instruments that measure energy
                                       and light for purposes of materials analysis,
                                       characterization and preparation. Mr. Howe also served as
                                       president and chief executive officer of Thermo BioAnalysis
                                       Corporation, a majority-owned subsidiary of Thermo
                                       Instrument, from February 1995 to March 1998. Mr. Howe's
                                       business address is 8 East Forge Parkway, Franklin, MA
                                       02038.

PAUL F. KELLEHER                       Mr. Kelleher, 57, has been the chief accounting officer of
                                       Thermo Instrument since 1986. He has been the senior vice
                                       president, finance and administration, of Thermo Electron
                                       since June 1997, and served
</TABLE>

                                      I-2
<PAGE>
<TABLE>
<S>                                    <C>
                                       as its vice president, finance from 1987 until 1997.
                                       Mr. Kelleher served as Thermo Electron's controller from
                                       1982 until January 1996. Mr. Kelleher is a director of
                                       ThermoLase Corporation.

THEO MELAS-KYRIAZI                     Mr. Melas-Kyriazi, 40, has been the chief financial officer
                                       of Thermo Instrument since January 1999. He has been a vice
                                       president of Thermo Electron since March 1998 and its chief
                                       financial officer since January 1999. Prior to his
                                       appointment as a vice president of Thermo Electron,
                                       Mr. Melas-Kyriazi served as president and chief executive
                                       officer of ThermoSpectra Corporation, a subsidiary of Thermo
                                       Instrument that develops, manufactures and markets precision
                                       imaging, inspection, temperature control, and test and
                                       measurement instruments, from its inception in August 1994
                                       until March 1998. He is a director of ThermoRetec
                                       Corporation. Mr. Melas-Kyriazi is a citizen of Greece.
</TABLE>

    STOCK OWNERSHIP.  The following table sets forth the beneficial ownership of
common stock of the Company, as well as the common stock of Thermo Instrument
and Thermo Electron, as of January 31, 2000, with respect to each director and
executive officer of Thermo Instrument. No director or executive officer of
Thermo Instrument beneficially owns any shares of capital stock of the
Purchaser. While certain directors and executive officers of Thermo Instrument
are also directors and executive officers of Thermo Electron or its subsidiaries
other than the Purchaser, all such persons disclaim beneficial ownership of the
shares of common stock beneficially owned by Thermo Electron.

<TABLE>
<CAPTION>
                                                          THERMO            THERMO
                                                        INSTRUMENT         ELECTRON             ONIX
NAME(1)                                              SYSTEMS INC. (2)   CORPORATION (3)   SYSTEMS INC. (4)
- -------                                              ----------------   ---------------   ----------------
<S>                                                  <C>                <C>               <C>
Richard W. K. Chapman..............................        225,530            79,801             7,500
George N. Hatsopoulos..............................        203,207         3,909,357            20,000
Denis A. Helm......................................        278,638           167,163             7,500
Barry S. Howe......................................        303,290            71,655             7,500
Paul F. Kelleher...................................         31,730           213,530             3,333
Earl R. Lewis......................................        436,499           215,477            35,333
Theo Melas-Kyriazi.................................        182,715           458,532            30,000
Polyvios C. Vintiadis..............................         17,597             2,500                 0
All directors and current executive officers as a
  group (8 persons)................................      1,679,206         5,118,015           111,166
</TABLE>

- --------------

(1) Except as reflected in the footnotes to this table, shares of the common
    stock beneficially owned consist of shares owned by the indicated person or
    by that person for the benefit of minor children, and all share ownership
    includes sole voting and investment power.

(2) Shares of the common stock of Thermo Instrument beneficially owned by
    Dr. Chapman, Dr. Hatsopoulos, Mr. Helm, Mr. Howe, Mr. Kelleher, Mr. Lewis,
    Mr. Melas-Kyriazi, Mr. Vintiadis and all directors and current executive
    officers as a group include 196,249, 24,066, 216,250, 273,156, 27,116,
    409,081, 163,687, 11,745 and 1,321,350 shares, respectively, that such
    person or group had the right to acquire within 60 days of January 31, 2000,
    through the exercise of stock options. Shares beneficially owned by
    Dr. Hatsopoulos, Mr. Kelleher, Mr. Melas-Kyriazi and all directors and
    current executive officers as a group include 598, 495, 468 and 1,561
    shares, respectively, allocated through January 31, 2000, to their
    respective accounts maintained pursuant to Thermo Electron's employee stock
    ownership plan, of which the trustees, who have investment power over its
    assets, are executive officers of Thermo Electron (the "ESOP"). Shares
    beneficially owned by Mr. Vintiadis and all directors and current executive
    officers as a group include 5,590 shares, allocated through January 1, 2000,
    to Mr. Vintiadis' account maintained under Thermo Instrument's deferred
    compensation plan for directors. Shares beneficially owned by
    Dr. Hatsopoulos include 26,773 shares held by his spouse

                                      I-3
<PAGE>
    and 117,187 shares that a family limited partnership indirectly controlled
    by Dr. Hatsopoulos has the right to acquire within 60 days of January 31,
    2000 through the exercise of stock options. Dr. Hatsopoulos disclaims
    beneficial interest in the shares owned by the family limited partnership
    except to the extent of his pecuniary interest therein. Shares beneficially
    owned by Mr. Helm include a total of 5,264 shares held in custodial accounts
    for the benefit of four minor children. Shares beneficially owned by
    Mr. Howe include 374 shares held in custodial accounts for the benefit of
    his minor children. Shares beneficially owned by Mr. Lewis include 2,987
    shares held by his spouse. No director or current executive officer
    beneficially owned more than 1% of the common stock outstanding as of
    January 31, 2000; all directors and current executive officers as a group
    beneficially owned 1.41% of the common stock outstanding as of such date.

(3) Shares of the common stock of Thermo Electron beneficially owned by
    Dr. Chapman, Dr. Hatsopoulos, Mr. Helm, Mr. Howe, Mr. Kelleher, Mr. Lewis,
    Mr. Melas-Kyriazi and all directors and current executive officers as a
    group include 76,248, 25,448, 99,816, 64,141, 179,359, 212,278, 384,361 and
    1,091,831 shares, respectively, that such person or group had the right to
    acquire within 60 days of January 31, 2000, through the exercise of stock
    options. Shares beneficially owned by Dr. Hatsopoulos, Mr. Kelleher,
    Mr. Melas-Kyriazi and all directors and current executive officers as a
    group include 2,266, 1,426, 1,071 and 4,763 shares, respectively, allocated
    through January 31, 2000, to their respective accounts maintained pursuant
    to the ESOP. Shares beneficially owned by Dr. Hatsopoulos include 144,437
    shares held by his spouse, 311,708 shares held by a family trust of which
    his spouse is the trustee and 566,262 shares held by a family limited
    partnership indirectly controlled by Dr. Hatsopoulos. Shares beneficially
    owned by Dr. Hatsopoulos also include 50,000 shares that a family trust, of
    which Dr. Hatsopoulos' spouse is the trustee, has the right to acquire
    within 60 days of January 31, 2000 and 2,149,500 shares that a family
    limited partnership indirectly controlled by Dr. Hatsopoulos has the right
    to acquire within 60 days of January 31, 2000 through the exercise of stock
    options. Dr. Hatsopoulos disclaims beneficial interest in the shares owned
    by the family limited partnership except to the extent of his pecuniary
    interest therein. Shares beneficially owned by Mr. Helm include 8,100 shares
    held in custodial accounts for the benefit of his minor children. Shares
    beneficially owned by Mr. Howe include 200 shares held in custodial accounts
    for the benefit of his minor children. Except for Dr. Hatsopoulos, who
    beneficially owned 2.46% of the Thermo Electron common stock outstanding as
    of January 31, 2000, no director or current executive officer beneficially
    owned more than 1% of such common stock outstanding as of January 31, 2000;
    all directors and current executive officers as a group beneficially owned
    3.23% of the Thermo Electron common stock outstanding as of such date.

(4) Shares of the common stock of ONIX Systems beneficially owned by
    Dr. Chapman, Dr. Hatsopoulos, Mr. Helm, Mr. Howe, Mr. Kelleher, Mr. Lewis,
    Mr. Melas-Kyriazi and all directors and executive officers as a group
    include 7,500, 20,000, 7,500, 7,500, 3,333, 33,333, 30,000 and 119,166
    shares, respectively, that each person or group had the right to acquire
    within 60 days of January 31, 2000, through the exercise of stock options.
    No director or current executive officer owned more than 1% of the common
    stock of ONIX Systems outstanding as of January 31, 2000; all directors and
    current executive officers as a group beneficially owned less than 1% of
    such common stock outstanding as of such date.

DIRECTORS AND EXECUTIVE OFFICERS OF THERMO ELECTRON

    The name, business address, position with Thermo Electron, present principal
occupation or employment and five-year employment history of each of the
directors and executive officers of Thermo Electron, together with the names,
principal businesses and addresses of any corporations or other organizations in
which such principal occupations are conducted, are set forth below. Unless
otherwise indicated, each occupation set forth refers to Thermo Electron, each
individual is a United States citizen and each individual's business address is
81 Wyman Street, Waltham, Massachusetts 02454. Unless otherwise indicated, to
the knowledge of each of the Purchaser, Thermo Instrument and Thermo Electron,
no director or executive officer of Thermo Electron beneficially owns any Shares
(or rights to acquire Shares). Unless otherwise indicated, to the knowledge of
each of the Purchaser, Thermo Instrument and Thermo

                                      I-4
<PAGE>
Electron, no director or executive officer of Thermo Electron has been convicted
in a criminal proceeding during the last five years (excluding traffic
violations or similar misdemeanors) and no director or executive officer of
Thermo Electron was a party to any judicial or administrative proceeding during
the last five years (except for any matters that were dismissed without sanction
or settlement) that resulted in a judgement, decree or final order enjoining the
person from future violations of, or prohibiting activities subject to, federal
or state securities laws, or a finding of any violation of federal or state
securities laws. John N. Hatsopoulos resigned from the Board of Directors of
Thermo Electron effective February 21, 2000.

<TABLE>
<S>                                    <C>
SAMUEL W. BODMAN                       Mr. Bodman, 61, has been a director of Thermo Electron since
                                       May 1999. Since 1988, Mr. Bodman has served as the chairman
                                       and chief executive officer of Cabot Corporation, a
                                       manufacturer of specialty chemicals and materials located at
                                       75 State Street, Boston, MA 02109. Mr. Bodman is also a
                                       director of Cabot Corporation, John Hancock Financial
                                       Services, Inc., Security Capital Group Incorporated and
                                       Westvaco Corporation.

PETER O. CRISP                         Mr. Crisp, 67, has been a director of Thermo Electron since
                                       1974. Mr. Crisp was a general partner of Venrock Associates,
                                       a venture capital investment firm located at 30 Rockefeller
                                       Plaza, New York, NY 10112, for more than five years until
                                       his retirement in September 1997. He has been the vice
                                       chairman of Rockefeller Financial Services, Inc. since
                                       December 1997. Mr. Crisp is also a director of American
                                       Superconductor Corporation, Evans & Sutherland Computer
                                       Corporation, NovaCare Inc., Thermedics Inc., ThermoTrex Cor-
                                       poration and United States Trust Corporation.

ELIAS P. GYFTOPOULOS                   Dr. Gyftopoulos, 72, has been a director of Thermo Electron
                                       since 1976. Dr. Gyftopoulos is Professor Emeritus of the
                                       Massachusetts Institute of Technology, where he was the Ford
                                       Professor of Mechanical Engineering and of Nuclear
                                       Engineering for more than 20 years until his retirement in
                                       1996. Dr. Gyftopoulos is also a director of Thermo
                                       BioAnalysis Corporation, Thermo Cardiosystems Inc.,
                                       ThermoLase Corporation, ThermoRetec Corporation and Trex
                                       Medical Corporation.

GEORGE N. HATSOPOULOS                  Dr. Hatsopoulos, 73, has been a director of Thermo Electron
                                       since he founded Thermo Electron in 1956. He served as
                                       president, chief executive officer and chairman of the board
                                       of Thermo Electron from 1956 until January 1997, June 1999
                                       and January 2000, respectively. Dr. Hatsopoulos is also a
                                       director of Photoelectron Corporation, Thermedics Inc.,
                                       Thermo Ecotek Corporation, Thermo Fibertek Inc., Thermo
                                       Instrument and ThermoTrex Corporation.

FRANK JUNGERS                          Mr. Jungers, 73, has been a director of Thermo Electron
                                       since 1978. Mr. Jungers has been a consultant on business
                                       and energy matters since 1977. His business address is 822
                                       N.W. Murray Boulevard, Suite 242, Portland, OR 97229.
                                       Mr. Jungers is also a director of The AES Corporation,
                                       Donaldson, Lufkin & Jenrette, Inc., Georgia-Pacific
                                       Corporation, ONIX Systems, Statia Terminals Group N.V.,
                                       Thermo Ecotek Corporation and ThermoQuest Corporation.

ROBERT A. MCCABE                       Mr. McCabe, 65, has been a director of Thermo Electron since
                                       1962. He has been the chairman of Pilot Capital Corporation
                                       located at 444 Madison Avenue, Suite 2103, New York, NY
                                       10022, which is engaged in private investments, since 1998.
                                       Mr. McCabe was the president of
</TABLE>

                                      I-5
<PAGE>
<TABLE>
<S>                                    <C>
                                       Pilot Capital Corporation from 1987 to 1998. Mr. McCabe is
                                       also a director of Atlantic Bank & Trust Company, Burns
                                       International Services Corporation, Church & Dwight Company
                                       and Thermo Optek Corporation.

HUTHAM S. OLAYAN                       Ms. Olayan, 46, has been a director of Thermo Electron since
                                       1987. She has served since 1995 as president and a director
                                       of Olayan America Corporation, a member of the Olayan Group,
                                       and as president and a director of Competrol Real Estate
                                       Limited, another member of the Olayan Group, from 1986 until
                                       its merger into Olayan America Corporation in 1997. The
                                       surviving company which is located at 505 Park Avenue, Suite
                                       1100, New York, NY 10022, is engaged in private investments,
                                       including real estate, and advisory services. Ms. Olayan is
                                       also a director of Trex Medical Corporation. Ms. Olayan is
                                       a citizen of Saudi Arabia.

ROBERT W. O'LEARY                      Mr. O'Leary, 56, has been a director of Thermo Electron
                                       since June 1998. He has been the president and chairman of
                                       Premier, Inc., a strategic alliance of not-for-profit health
                                       care and hospital systems located at 12225 El Camino Real,
                                       San Diego, CA 92130, since 1995. Mr. O'Leary is also a
                                       director of Eco Soil Systems, Inc.

RICHARD F. SYRON                       Dr. Syron, 56, has been a director of Thermo Electron since
                                       September 1997, its president and chief executive officer
                                       since June 1999 and chairman of the board since January
                                       2000. From April 1994 until May 1999, Dr. Syron was the
                                       chairman and chief executive officer of the American Stock
                                       Exchange, Inc. located at 86 Trinity Place, New York, NY
                                       10006-1881. Dr. Syron is also a director of Dreyfus
                                       Corporation, John Hancock Financial Services, Inc. and
                                       Thermo Fibertek Inc.

ROGER D. WELLINGTON                    Mr. Wellington, 73, has been a director of Thermo Electron
                                       since 1986. Mr. Wellington serves as the president and chief
                                       executive officer of Wellington Consultants, Inc. and
                                       Wellington Associates Inc., international business
                                       consulting firms he founded in 1994 and 1989, respectively,
                                       each of which is located at P.O. Box 8186, 5555 Gulf of
                                       Mexico Drive, Unit 302, Longboat Key, FL 34228.
                                       Mr. Wellington is also a director of Photoelectron
                                       Corporation and Thermo Fibergen Inc.

BRIAN D. HOLT                          Mr. Holt, 51, became the chief operating officer, energy and
                                       environment, of Thermo Electron in September 1998. Mr. Holt
                                       has been the president and chief executive officer of Thermo
                                       Ecotek Corporation, a majority-owned subsidiary of Thermo
                                       Electron located at 245 Winter Street, Waltham, MA 02451,
                                       which is involved in clean-power resources, clean fuels and
                                       naturally derived products for protecting crops, since
                                       February 1994. From March 1996 to September 1998, he was a
                                       vice president of Thermo Electron. Mr. Holt is also a
                                       director of The Randers Killam Group, Inc., Thermo Ecotek
                                       Corporation, ThermoRetec Corporation and Thermo TerraTech
                                       Inc.

JOHN T. KEISER                         Mr. Keiser, 64, became chief operating officer, biomedical,
                                       of Thermo Electron in September 1998 and was a vice
                                       president from April 1997 until his promotion. Mr. Keiser
                                       has been the president and chief executive officer of
                                       Thermedics Inc., a manufacturer of biomedical products,
                                       product quality-assurance systems and security devices,
                                       since March 1998 and December 1998, respectively, and served
                                       as a
</TABLE>

                                      I-6
<PAGE>
<TABLE>
<S>                                    <C>
                                       senior vice president of Thermedics Inc. from 1994 until his
                                       promotion to president. He has also been the president of
                                       Thermo Electron's wholly-owned biomedical group, a
                                       manufacturer of medical equipment and instruments, since
                                       1994. Mr. Keiser is a director of Metrika Systems
                                       Corporation, Thermedics Inc., Thermedics Detection Inc.,
                                       Thermo Cardiosystems Inc., ThermoLase Corporation, Thermo
                                       Sentron Inc., ThermoTrex Corporation and Trex Medical
                                       Corporation.

PAUL F. KELLEHER                       Mr. Kelleher, 57, has been the senior vice president,
                                       finance and administration, of Thermo Electron since June
                                       1997, and served as its vice president, finance from 1987
                                       until 1997. Mr. Kelleher served as Thermo Electron's
                                       controller from 1982 until January 1996. Mr. Kelleher is a
                                       director of ThermoLase Corporation.

EARL R. LEWIS                          Mr. Lewis, 56, became chief operating officer, measurement
                                       and detection, of Thermo Electron in September 1998, and
                                       served as senior vice president of Thermo Electron from June
                                       1998 to September 1998 and vice president from September
                                       1996 to June 1998. Mr. Lewis has been president and chief
                                       executive officer of Thermo Instrument since March 1997 and
                                       January 1998, respectively, and was chief operating officer
                                       from January 1996 to January 1998. Prior to that time, he
                                       was executive vice president of Thermo Instrument from
                                       January 1996 to March 1997 and senior vice president from
                                       January 1994 to January 1996. Mr. Lewis served as chief
                                       executive officer of Thermo Optek Corporation, a
                                       majority-owned subsidiary of Thermo Instrument and a
                                       manufacturer of analytical instruments that measure energy
                                       and light for purposes of materials analysis,
                                       characterization and preparation, from its inception in
                                       August 1995 to January 1998. Mr. Lewis is a director of FLIR
                                       Systems Inc., Metrika Systems Corporation, ONIX Systems,
                                       SpectRx Inc., Spectra-Physics Lasers, Inc., Thermedics
                                       Detection Inc., Thermo BioAnalysis Corporation, Thermo
                                       Instrument, Thermo Optek Corporation and ThermoQuest
                                       Corporation.

THEO MELAS-KYRIAZI                     Mr. Melas-Kyriazi, 40, has been a vice president of Thermo
                                       Electron since March 1998 and its chief financial officer
                                       since January 1999. Prior to his appointment as a vice
                                       president of Thermo Electron, Mr. Melas-Kyriazi served as
                                       president and chief executive officer of ThermoSpectra
                                       Corporation, a subsidiary of Thermo Instrument that
                                       develops, manufactures and markets precision imaging,
                                       inspection, temperature control, and test and measurement
                                       instruments, from its inception in August 1994 until March
                                       1998. He is a director of ThermoRetec Corporation.
                                       Mr. Melas-Kyriazi is a citizen of Greece.

WILLIAM A. RAINVILLE                   Mr. Rainville, 58, became chief operating officer, recycling
                                       and resource recovery, of Thermo Electron in September 1998.
                                       Mr. Rainville was a senior vice president of Thermo Electron
                                       from March 1993 to September 1998, and a vice president of
                                       Thermo Electron from 1986 to 1993. He has been president and
                                       chief executive officer of Thermo Fibertek Inc., a
                                       majority-owned subsidiary of Thermo Electron located at 245
                                       Winter Street, Waltham, MA 02451 that develops and
                                       manufactures equipment and products for the papermaking and
                                       paper-recycling industries, since its inception in 1991.
                                       Mr. Rainville is also a director of Thermo Ecotek
                                       Corporation,
</TABLE>

                                      I-7
<PAGE>
<TABLE>
<S>                                    <C>
                                       Thermo Fibergen Inc., Thermo Fibertek Inc., ThermoRetec
                                       Corporation and Thermo TerraTech Inc.
</TABLE>

    STOCK OWNERSHIP.  The following table sets forth the beneficial ownership of
common stock of the Company, as well as the common stock of Thermo Instrument
and Thermo Electron, as of January 31, 2000, with respect to each director and
executive officer of Thermo Electron. No director or executive officer of Thermo
Electron beneficially owns any shares of capital stock of the Purchaser. The
directors and executive officers of Thermo Electron disclaim beneficial
ownership of the shares of common stock beneficially owned by Thermo Electron.

<TABLE>
<CAPTION>
                                                          THERMO           THERMO
                                                         ELECTRON        INSTRUMENT           ONIX
NAME (1)                                              CORPORATION(2)   SYSTEMS INC.(3)   SYSTEMS INC.(4)
- --------                                              --------------   ---------------   ---------------
<S>                                                   <C>              <C>               <C>
Samuel W. Bodman....................................       27,599                 0                0
Peter O. Crisp......................................      121,767             3,009                0
Elias P. Gyftopoulos................................       91,399            88,842                0
George N. Hatsopoulos...............................    3,909,357           203,207           20,000
Brian D. Holt.......................................      322,941               999            2,000
Frank Jungers.......................................      171,021            26,412           40,000
John T. Keiser......................................      331,636           155,211            2,000
Paul F. Kelleher....................................      213,530            31,730            3,333
Earl R. Lewis.......................................      215,477           436,499           35,666
Robert A. McCabe....................................       66,326            46,846                0
Theo Melas-Kyriazi..................................      458,532           182,715           30,000
Hutham S. Olayan....................................       49,568             3,009                0
Robert W. O'Leary...................................       43,830               666                0
William A. Rainville................................      361,499            19,065           10,000
Richard F. Syron....................................    1,074,006                 0                0
Roger D. Wellington.................................       55,795             6,759                0
All directors and current executive officers as a
  group (16 persons)................................    7,514,283         1,204,969          142,666
</TABLE>

- --------------

(1) Except as reflected in the footnotes to this table, shares beneficially
    owned consist of shares owned by the indicated person or by that person for
    the benefit of minor children, and all share ownership includes sole voting
    and investment power.

(2) Shares of the common stock of Thermo Electron beneficially owned by
    Mr. Bodman, Mr. Crisp, Dr. Gyftopoulos, Dr. Hatsopoulos, Mr. Holt,
    Mr. Jungers, Mr. Keiser, Mr. Kelleher, Mr. Lewis, Mr. McCabe,
    Mr. Melas-Kyriazi, Ms. Olayan, Mr. O'Leary, Mr. Rainville, Dr. Syron,
    Mr. Wellington and all directors and current executive officers as a group
    include 26,000, 25,596, 27,442, 25,448, 284,948, 24,673, 263,230, 179,359,
    212,278, 27,442, 384,361, 27,442, 27,000, 294,630, 1,011,000, 24,673 and
    2,865,522 shares, respectively, that such person or members of the group
    have the right to acquire within 60 days of January 31, 2000, through the
    exercise of stock options. Shares beneficially owned by Dr. Hatsopoulos,
    Mr. Kelleher, Mr. Melas-Kyriazi and all directors and current executive
    officers as a group include 2,266, 1,426, 1,071 and 4,763 shares,
    respectively, allocated to their respective accounts maintained pursuant to
    Thermo Electron's employee stock ownership plan (the "ESOP"), of which the
    trustees, who have investment power over its assets, are executive officers
    of Thermo Electron. Shares beneficially owned by Mr. Bodman, Mr. Crisp,
    Dr. Gyftopoulos, Mr. Jungers, Mr. McCabe, Ms. Olayan, Mr. O'Leary,
    Dr. Syron, Mr. Wellington and all directors and current executive officers
    as a group include 1,599, 49,277, 1,378, 80,427, 34,725, 19,876, 3,830,
    2,506, 26,342 and 219,960 shares, respectively, allocated to accounts
    maintained pursuant to Thermo Electron's deferred compensation plan for
    directors. Shares beneficially owned by Dr. Hatsopoulos include 144,437
    shares held by his spouse, 311,708 shares held by a family trust of which
    his spouse is the trustee and 566,262 shares held by a family limited
    partnership indirectly controlled by Dr. Hatsopoulos. Shares beneficially
    owned by Dr. Hatsopoulos also include 50,000 shares that a family trust, of
    which Dr. Hatsopoulos' spouse is the

                                      I-8
<PAGE>
    trustee, has the right to acquire within 60 days of January 31, 2000 and
    2,149,500 shares that a family limited partnership indirectly controlled by
    Dr. Hatsopoulos has the right to acquire within 60 days of January 31, 2000
    through the exercise of stock options. Dr. Hatsopoulos disclaims beneficial
    interest in the shares owned by the family limited partnership except to the
    extent of his pecuniary interest therein. Shares beneficially owned by
    Ms. Olayan do not include 6,150,000 shares owned by Crescent Holding GmbH, a
    member of the Olayan Group. Crescent Holding GmbH is indirectly controlled
    by Suliman S. Olayan, Ms. Olayan's father. Ms. Olayan disclaims beneficial
    ownership of the shares owned by Crescent Holding GmbH. Except for
    Dr. Hatsopoulos, who beneficially owned 2.44% of the Thermo Electron common
    stock outstanding as of January 31, 2000, no director or current executive
    officer beneficially owned more than 1% of the Thermo Electron common stock
    outstanding as of such date; all directors and current executive officers as
    a group beneficially owned 4.71% of the Thermo Electron common stock
    outstanding as of January 31, 2000.

(3) Shares of the common stock of Thermo Instrument beneficially owned by
    Mr. Crisp, Dr. Gyftopoulos, Dr. Hatsopoulos, Mr. Holt, Mr. Jungers,
    Mr. Keiser, Mr. Kelleher, Mr. Lewis, Mr. McCabe, Mr. Melas-Kyriazi,
    Ms. Olayan, Mr. O'Leary, Mr. Rainville, Mr. Wellington and all directors and
    current executive officers as a group include 3,009, 40,586, 24,066, 999,
    11,443, 71,311, 27,116, 409,081, 7,925, 163,687, 3,009, 666, 19,065, 3,009
    and 902,159 shares, respectively, that such person or members of the group
    have the right to acquire within 60 days of January 31, 2000, through the
    exercise of stock options. Shares beneficially owned by Dr. Hatsopoulos,
    Mr. Kelleher, Mr. Melas-Kyriazi and all directors and current executive
    officers as a group include 598, 495, 468 and 1,561 shares, respectively,
    allocated to accounts maintained pursuant to the ESOP. Shares beneficially
    owned by Mr. Jungers, Mr. McCabe and all directors and current executive
    officers as a group include 13,563, 8,908 and 22,471 shares, respectively,
    allocated to their respective accounts maintained pursuant to Thermo
    Instrument's deferred compensation plan for directors. Shares beneficially
    owned by Dr. Hatsopoulos include 26,773 shares held by his spouse and
    117,187 shares that a family limited partnership indirectly controlled by
    Dr. Hatsopoulos has the right to acquire within 60 days of January 31, 2000
    through the exercise of stock options. Dr. Hatsopoulos disclaims beneficial
    interest in the shares owned by the family limited partnership except to the
    extent of his pecuniary interest therein. Shares beneficially owned by
    Mr. Lewis include 2,987 shares held by his spouse. No director or current
    executive officer beneficially owned more than 1% of the Thermo Instrument
    common stock outstanding as of January 31, 2000; all directors and current
    executive officers as a group beneficially owned 1.02% of the Thermo
    Instrument common stock outstanding as of January 31, 2000.

(4) Shares of the common stock of the Company beneficially owned by
    Dr. Hatsopoulos, Mr. Holt, Mr. Jungers, Mr. Keiser, Mr. Kelleher,
    Mr. Lewis, Mr. Melas-Kyriazi, Mr. Rainville and all directors and current
    executive officers as a group include 20,000, 2,000, 30,000, 2,000, 3,333,
    33,333, 30,000, 10,000 and 130,666 shares, respectively, that such person or
    members of the group have the right to acquire within 60 days of
    January 31, 2000 through the exercise of stock options. Shares of the
    Company beneficially owned by Ms. Olayan do not include 16,666 shares owned
    by Crescent International Holdings Ltd., a member of the Olayan Group which
    is indirectly controlled by Suliman S. Olayan, Ms. Olayan's father.
    Ms. Olayan disclaims beneficial ownership of the shares owned by Crescent
    International Holdings Ltd. No director or current executive officer
    beneficially owned more than 1% of the Company common stock outstanding as
    of January 31, 2000; all directors and current executive officers as a group
    beneficially owned less than 1% of the common stock of the Company
    outstanding as of January 31, 2000.

                                      I-9
<PAGE>
                                  SCHEDULE II
                      INFORMATION CONCERNING TRANSACTIONS
                       IN THE COMMON STOCK OF THE COMPANY

    The following table sets forth information with respect to purchases of the
Company's common stock by the Company, Thermo Instrument, the Purchaser and
Thermo Electron since January 4, 1998 (the commencement of the Company's second
full fiscal year preceding the date of this Offer to Purchase).

<TABLE>
<CAPTION>
                                            NUMBER OF          RANGE OF PRICES
                                              SHARES            PAID PER SHARE             AVERAGE PURCHASE
                                            PURCHASED           DURING QUARTER             PRICE PER SHARE
QUARTER/YEAR               PURCHASER      DURING QUARTER            ($)(1)            PAID DURING QUARTER ($)(1)
- ------------           -----------------  --------------   ------------------------   --------------------------
<S>                    <C>                <C>              <C>                        <C>
3(rd) Quarter 1998...  ONIX Systems           591,183                    8.25 - 9.0              8.7387
3(rd) Quarter 1998...  Thermo Instrument      217,200                 6.125 - 8.625              6.2627
3(rd) Quarter 1998...  Thermo Electron          8,600                8.6875 - 9.125              8.9469
4(th) Quarter 1998...  ONIX Systems           684,600                  6.5 - 8.1875              7.1378
4(th) Quarter 1998...  Thermo Instrument      641,000                   5.875 - 6.5              6.1471
4(th) Quarter 1998...  Thermo Electron         76,100                 5.625 - 6.375              5.8094
1(st) Quarter 1999...  Thermo Electron        189,600                    6.75 - 7.5              6.9278
</TABLE>

- ------------

(1) Prices per share of the Company's common stock are net of commissions paid
    by the respective purchasers.

    There were no transactions in the Company's common stock effected during the
60 days preceding the date of this Offer to Purchase by Thermo Instrument, the
Purchaser, Thermo Electron or, to the best knowledge of the Purchaser, Thermo
Instrument and Thermo Electron, the Company, the directors and executive
officers of any of the Company, Thermo Instrument, the Purchaser or Thermo
Electron.

                                      II-1
<PAGE>
                                  SCHEDULE III
              SECTION 262 OF THE DELAWARE GENERAL CORPORATION LAW

262. APPRAISAL RIGHTS.

    (a) Any stockholder of a corporation of this State who holds shares of stock
on the date of the making of a demand pursuant to subsection (d) of this section
with respect to such shares, who continuously holds such shares through the
effective date of the merger or consolidation, who has otherwise complied with
subsection (d) of this section and who has neither voted in favor of the merger
or consolidation nor consented thereto in writing pursuant to Section228 of this
title shall be entitled to an appraisal by the Court of Chancery of the fair
value of the stockholder's shares of stock under the circumstances described in
subsections (b) and (c) of this section. As used in this section, the word
"stockholder" means a holder of record of stock in a stock corporation and also
a member of record of a nonstock corporation; the words "stock" and "share" mean
and include what is ordinarily meant by those words and also membership or
membership interest of a member of a nonstock corporation; and the words
"depository receipt" mean a receipt or other instrument issued by a depository
representing an interest in one or more shares, or fractions thereof, solely of
stock of a corporation, which stock is deposited with the depository.

    (b) Appraisal rights shall be available for the shares of any class or
series of stock of a constituent corporation in a merger or consolidation to be
effected pursuant to Section251 (other than a merger effected pursuant to
Section251 (g) of this title), Section252, Section254, Section257, Section258,
Section263 or Section264 of this title:

        (1) Provided, however, that no appraisal rights under this section shall
    be available for the shares of any class or series of stock, which stock, or
    depository receipts in respect thereof, at the record date fixed to
    determine the stockholders entitled to receive notice of and to vote at the
    meeting of stockholders to act upon the agreement of merger or
    consolidation, were either (i) listed on a national securities exchange or
    designated as a national market system security on an interdealer quotation
    system by the National Association of Securities Dealers, Inc. or (ii) held
    of record by more than 2,000 holders; and further provided that no appraisal
    rights shall be available for any shares of stock of the constituent
    corporation surviving a merger if the merger did not require for its
    approval the vote of the stockholders of the surviving corporation as
    provided in subsection (f) of Section251 of this title.

        (2) Notwithstanding paragraph (1) of this subsection, appraisal rights
    under this section shall be available for the shares of any class or series
    of stock of a constituent corporation if the holders thereof are required by
    the terms of an agreement of merger or consolidation pursuant to
    SectionSection251, 252, 254, 257, 258, 263 and 264 of this title to accept
    for such stock anything except:

           a.  Shares of stock of the corporation surviving or resulting from
               such merger or consolidation, or depository receipts in respect
               thereof;

           b.  Shares of stock of any other corporation, or depository receipts
               in respect thereof, which shares of stock (or depository receipts
               in respect thereof) or depository receipts at the effective date
               of the merger or consolidation will be either listed on a
               national securities exchange or designated as a national market
               system security on an interdealer quotation system by the
               National Association of Securities Dealers, Inc. or held of
               record by more than 2,000 holders;

           c.  Cash in lieu of fractional shares or fractional depository
               receipts described in the foregoing subparagraphs a. and b. of
               this paragraph; or

           d.  Any combination of the shares of stock, depository receipts and
               cash in lieu of fractional shares or fractional depository
               receipts described in the foregoing subparagraphs a., b. and c.
               of this paragraph.

        (3) In the event all of the stock of a subsidiary Delaware corporation
    party to a merger effected under Section253 of this title is not owned by
    the parent corporation immediately prior to the merger, appraisal rights
    shall be available for the shares of the subsidiary Delaware corporation.

                                     III-1
<PAGE>
    (c) Any corporation may provide in its certificate of incorporation that
appraisal rights under this section shall be available for the shares of any
class or series of its stock as a result of an amendment to its certificate of
incorporation, any merger or consolidation in which the corporation is a
constituent corporation or the sale of all or substantially all of the assets of
the corporation. If the certificate of incorporation contains such a provision,
the procedures of this section, including those set forth in subsections
(d) and (e) of this section, shall apply as nearly as is practicable.

    (d) Appraisal rights shall be perfected as follows:

        (1) If a proposed merger or consolidation for which appraisal rights are
    provided under this section is to be submitted for approval at a meeting of
    stockholders, the corporation, not less than 20 days prior to the meeting,
    shall notify each of its stockholders who was such on the record date for
    such meeting with respect to shares for which appraisal rights are available
    pursuant to subsections (b) or (c) hereof that appraisal rights are
    available for any or all of the shares of the constituent corporations, and
    shall include in such notice a copy of this section. Each stockholder
    electing to demand the appraisal of such stockholder's shares shall deliver
    to the corporation, before the taking of the vote on the merger or
    consolidation, a written demand for appraisal of such stockholder's shares.
    Such demand will be sufficient if it reasonably informs the corporation of
    the identity of the stockholder and that the stockholder intends thereby to
    demand the appraisal of such stockholder's shares. A proxy or vote against
    the merger or consolidation shall not constitute such a demand. A
    stockholder electing to take such action must do so by a separate written
    demand as herein provided. Within 10 days after the effective date of such
    merger or consolidation, the surviving or resulting corporation shall notify
    each stockholder of each constituent corporation who has complied with this
    subsection and has not voted in favor of or consented to the merger or
    consolidation of the date that the merger or consolidation has become
    effective; or

        (2) If the merger or consolidation was approved pursuant to Section228
    or Section253 of this title, each constituent corporation, either before the
    effective date of the merger or consolidation or within ten days thereafter,
    shall notify each of the holders of any class or series of stock of such
    constituent corporation who are entitled to appraisal rights of the approval
    of the merger or consolidation and that appraisal rights are available for
    any or all shares of such class or series of stock of such constituent
    corporation, and shall include in such notice a copy of this section;
    provided that, if the notice is given on or after the effective date of the
    merger or consolidation, such notice shall be given by the surviving or
    resulting corporation to all such holders of any class or series of stock of
    a constituent corporation that are entitled to appraisal rights. Such notice
    may, and, if given on or after the effective date of the merger or
    consolidation, shall, also notify such stockholders of the effective date of
    the merger or consolidation. Any stockholder entitled to appraisal rights
    may, within 20 days after the date of mailing of such notice, demand in
    writing from the surviving or resulting corporation the appraisal of such
    holder's shares. Such demand will be sufficient if it reasonably informs the
    corporation of the identity of the stockholder and that the stockholder
    intends thereby to demand the appraisal of such holder's shares. If such
    notice did not notify stockholders of the effective date of the merger or
    consolidation, either (i) each such constituent corporation shall send a
    second notice before the effective date of the merger or consolidation
    notifying each of the holders of any class or series of stock of such
    constituent corporation that are entitled to appraisal rights of the
    effective date of the merger or consolidation or (ii) the surviving or
    resulting corporation shall send such a second notice to all such holders on
    or within 10 days after such effective date; provided, however, that if such
    second notice is sent more than 20 days following the sending of the first
    notice, such second notice need only be sent to each stockholder who is
    entitled to appraisal rights and who has demanded appraisal of such holder's
    shares in accordance with this subsection. An affidavit of the secretary or
    assistant secretary or of the transfer agent of the corporation that is
    required to give either notice that such notice has been given shall, in the
    absence of fraud, be prima facie evidence of the facts stated therein. For
    purposes of determining the stockholders entitled to receive either notice,
    each constituent corporation may fix, in advance, a record date that shall
    be not more than 10 days prior to the date the notice is given, provided,
    that if the notice is given on or after the effective date of the

                                     III-2
<PAGE>
    merger or consolidation, the record date shall be such effective date. If no
    record date is fixed and the notice is given prior to the effective date,
    the record date shall be the close of business on the day next preceding the
    day on which the notice is given.

    (e) Within 120 days after the effective date of the merger or consolidation,
the surviving or resulting corporation or any stockholder who has complied with
subsections (a) and (d) hereof and who is otherwise entitled to appraisal
rights, may file a petition in the Court of Chancery demanding a determination
of the value of the stock of all such stockholders. Notwithstanding the
foregoing, at any time within 60 days after the effective date of the merger or
consolidation, any stockholder shall have the right to withdraw such
stockholder's demand for appraisal and to accept the terms offered upon the
merger or consolidation. Within 120 days after the effective date of the merger
or consolidation, any stockholder who has complied with the requirements of
subsections (a) and (d) hereof, upon written request, shall be entitled to
receive from the corporation surviving the merger or resulting from the
consolidation a statement setting forth the aggregate number of shares not voted
in favor of the merger "or consolidation and with respect to which demands for
appraisal have been received and the aggregate number of holders of such shares.
Such written statement shall be mailed to the stockholder within 10 days after
such stockholder's written request for such a statement is received by the
surviving or resulting corporation or within 10 days after expiration of the
period for delivery of demands for appraisal under subsection (d) hereof,
whichever is later.

    (f) Upon the filing of any such petition by a stockholder, service of a copy
thereof shall be made upon the surviving or resulting corporation, which shall
within 20 days after such service file in the office of the Register in Chancery
in which the petition was filed a duly verified list containing the names and
addresses of all stockholders who have demanded payment for their shares and
with whom agreements as to the value of their shares have not been reached by
the surviving or resulting corporation. If the petition shall be filed, by the
surviving or resulting corporation, the petition shall be accompanied by such a
duly verified list. The Register in Chancery, if so ordered by the Court, shall
give notice of the time and place fixed for the hearing of such petition by
registered or certified mail to the surviving or resulting corporation and to
the stockholders shown on the list at the addresses therein stated. Such notice
shall also be given by or more publications at least week before the day of the
hearing, in a newspaper of general circulation published in the City of
Wilmington, Delaware or such publication as the Court deems advisable. The forms
of the notices by mail and by publication shall be approved by the Court, and
the costs thereof shall be borne by the surviving or resulting corporation.

    (g) At the hearing on such petition, the Court shall determine the
stockholders who have complied with this section and who have become entitled to
appraisal rights. The Court may require the stockholders who have demanded an
appraisal for their shares and who hold stock represented by certificates to
submit their certificates of stock to the Register in Chancery for notation
thereon of the pendency of the appraisal proceedings; and if any stockholder
fails to comply with such direction, the Court may dismiss the proceedings as to
such stockholder.

    (h) After determining the stockholders entitled to an appraisal, the Court
shall appraise the shares, determining their fair value exclusive of any element
of value arising from the accomplishment or expectation of the merger or
consolidation, together with a fair rate of interest, if any, to be paid upon
the amount determined to be the fair value. In determining such fair value, the
Court shall take into account all relevant factors. In determining the fair rate
of interest, the Court may consider all relevant factors, including the rate of
interest which the surviving or resulting corporation would have had to pay to
borrow money during the pendency of the proceeding. Upon application by the
surviving or resulting corporation or by any stockholder entitled to participate
in the appraisal proceeding, the Court may, in its discretion, permit discovery
or other pretrial proceedings and may proceed to trial upon the appraisal prior
to the final determination of the stockholder entitled to an appraisal. Any
stockholder whose name appears on the list filed by the surviving or resulting
corporation pursuant to subsection (f) of this section and who has submitted
such stockholder's certificates of stock to the Register in Chancery, if such is
required, may participate fully in all proceedings until it is finally
determined that such stockholder is not entitled to appraisal rights under this
section

                                     III-3
<PAGE>
    (i) The Court shall direct the payment of the fair value of the shares,
together with interest, if any, by the surviving or resulting corporation to the
stockholders entitled thereto. Interest may be simple or compound, as the Court
may direct. Payment shall be so made to each such stockholder, in the case of
holders of uncertificated stock forthwith, and the case of holders of shares
represented by certificates upon the surrender to the corporation of the
certificates representing such stock. The Court's decree may be enforced as
other decrees in the Court of Chancery may be enforced, whether such surviving
or resulting corporation be a corporation of this State or of any state.

    (j) The costs of the proceeding may be determined by the Court and taxed
upon the parties as the Court deems equitable in the circumstances. Upon
application of a stockholder, the Court may order all or a portion of the
expenses incurred by any stockholder in connection with the appraisal
proceeding, including, without limitation, reasonable attorney's fees and the
fees and expenses of experts, to be charged pro rata against the value of all
the shares entitled to an appraisal.

    (k) From and after the effective date of the merger or consolidation, no
stockholder who has demanded appraisal rights as provided in subsection (d) of
this section shall be entitled to vote such stock for any purpose or to receive
payment of dividends or other distributions on the stock (except dividends or
other distributions payable to stockholders of record at a date which is prior
to the effective date of the merger or consolidation); provided, however, that
if no petition for an appraisal shall be filed within the time provided in
subsection (e) of this section, or if such stockholder shall deliver to the
surviving or resulting corporation a written withdrawal of such stockholder's
demand for an appraisal and an acceptance of the merger or consolidation, either
within 60 days after the effective date of the merger or consolidation as
provided in subsection (e) of this section or thereafter with the written
approval of the corporation, then the right of such stockholder to an appraisal
shall cease. Notwithstanding the foregoing, no appraisal proceeding in the Court
of Chancery shall be dismissed as to any stockholder without the approval of the
Court, and such approval may be conditioned upon such terms as the Court deems
just.

    (l) The shares of the surviving or resulting corporation to which the shares
of such objecting stockholders would have been converted had they assented to
the merger or consolidation shall have the status of authorized and unissued
shares of the surviving or resulting corporation. (Last amended by Ch. 339, L.
"98, eff. 7-1-98.)

                                     III-4
<PAGE>
    Manually signed facsimile copies of the Letter of Transmittal will be
accepted. The Letter of Transmittal and certificates evidencing Shares and any
other required documents should be sent or delivered by each stockholder or his
or her broker, dealer, commercial bank, trust company or other nominee to the
Depositary at one of its addresses set forth below:

                        THE DEPOSITARY FOR THE OFFER IS:

                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                              <C>
           BY MAIL:               BY HAND OR OVERNIGHT COURIER:

        40 Wall Street                   40 Wall Street
          46th Floor                       46th Floor
   New York, New York 10005         New York, New York 10005
Attn: Reorganization Department  Attn: Reorganization Department
</TABLE>

                           BY FACSIMILE TRANSMISSION:
                                 (718) 234-5001
                             Confirm by Telephone:
                                 (718) 921-8200

    Questions and requests for assistance or for additional copies of this Offer
to Purchase, the Letter of Transmittal or other tender offer materials may be
directed to the Information Agent or the Dealer Managers at their respective
addresses and telephone numbers set forth below. Stockholders may also contact
their broker, dealer, bank or trust company for assistance concerning the Offer.

                    THE INFORMATION AGENT FOR THE OFFER IS:

                             D.F. KING & CO., INC.
                          77 Water Street, 20th Floor
                               New York, NY 10005
                Bankers and Brokers call collect (212) 269-5550
                    All Others Call Toll-Free (800) 290-6433

                     THE DEALER MANAGERS FOR THE OFFER ARE:

                          J.P. MORGAN SECURITIES INC.
                                 60 Wall Street
                               New York, NY 10260
                                 (877) 869-0656

                     THE BEACON GROUP CAPITAL SERVICES, LLC
                                399 Park Avenue
                               New York, NY 10022
                                 (212) 339-9100

<PAGE>
                             LETTER OF TRANSMITTAL
                        TO TENDER SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.
                       PURSUANT TO THE OFFER TO PURCHASE
                              DATED MARCH 13, 2000
                                       BY
                             ONIX ACQUISITION INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
                         THERMO INSTRUMENT SYSTEMS INC.

    THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
                                      CITY
         TIME, ON FRIDAY, APRIL 7, 2000, UNLESS THE OFFER IS EXTENDED.

                        THE DEPOSITARY FOR THE OFFER IS:

                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                 <C>
             BY MAIL:                 BY HAND OR OVERNIGHT COURIER:

          40 Wall Street                      40 Wall Street
            46th Floor                          46th Floor
        New York, NY 10005                  New York, NY 10005
 Attn: Reorganization Department     Attn: Reorganization Department
</TABLE>

                           BY FACSIMILE TRANSMISSION:
                                 (718) 234-5001

                             CONFIRM BY TELEPHONE:
                                 (718) 921-8200

    DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH
ABOVE, OR TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER THAN AS SET
FORTH ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY. YOU MUST SIGN THIS LETTER OF
TRANSMITTAL IN THE APPROPRIATE SPACE PROVIDED THEREFOR AND COMPLETE THE
SUBSTITUTE FORM W-9 SET FORTH BELOW.

    THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

    This Letter of Transmittal is to be completed by holders of Shares (as
defined below) either if certificates evidencing Shares ("Share Certificates")
are to be forwarded herewith or, unless an Agent's Message (as defined in the
section of the Offer to Purchase dated March 13, 2000 (the "Offer to Purchase")
captioned "The Tender Offer--Acceptance For Payment And Payment For Shares") is
utilized, if delivery of Shares is to be made by book-entry transfer into the
account of American Stock Transfer & Trust Company, as Depositary (the
"Depositary"), at The Depository Trust Company ("DTC") pursuant to the
procedures set forth in the section of the Offer to Purchase captioned "The
Tender Offer--Procedures For Accepting The Offer And Tendering Shares."
Stockholders who tender Shares by book-entry transfer are referred to herein as
"Book-Entry Stockholders."

    Stockholders whose Share Certificates are not immediately available or who
cannot deliver their Share Certificates and all other documents required hereby
to the Depositary prior to the Expiration Date (as defined in the section of the
Offer to Purchase captioned "The Tender Offer--Terms Of The Offer; Expiration
Date"), or who cannot complete the procedures for delivery by book-entry
transfer on a timely basis, may tender their Shares according to the guaranteed
delivery procedures set forth in the section of the Offer to Purchase captioned
"The Tender Offer--Procedures For Accepting The Offer And Tendering Shares." See
Instruction 2.  DELIVERY OF DOCUMENTS TO DTC IN ACCORDANCE WITH DTC'S PROCEDURES
DOES NOT CONSTITUTE DELIVERY TO THE DEPOSITARY.
<PAGE>

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------
<S>                                                           <C>               <C>               <C>
                                          DESCRIPTION OF SHARES TENDERED
- ------------------------------------------------------------------------------------------------------------------
      NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)              SHARE CERTIFICATE(S) AND SHARE(S) TENDERED
 (PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S) APPEAR(S) ON      (ATTACH ADDITIONAL SIGNED LIST, IF NECESSARY)
                   SHARE CERTIFICATE(S))                                       SEE INSTRUCTION 3.
- ------------------------------------------------------------------------------------------------------------------
                                                                                  TOTAL NUMBER
                                                                                   OF SHARES
                                                                   SHARE          REPRESENTED          NUMBER
                                                                CERTIFICATE         BY SHARE         OF SHARES
                                                                 NUMBER(S)*     CERTIFICATE(S)*      TENDERED**
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
                                                              TOTAL SHARES
- ------------------------------------------------------------------------------------------------------------------
 *   Need not be completed by Book-Entry Stockholders.
 **  Unless otherwise indicated, all Shares represented by Share Certificates delivered to the Depositary will be
     deemed to have been tendered. See Instruction 4.
 IF ANY SHARE CERTIFICATES HAVE BEEN LOST OR DESTROYED, SEE INSTRUCTION 11.
- ------------------------------------------------------------------------------------------------------------------
</TABLE>

/ / CHECK HERE IF SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE TO AN
    ACCOUNT MAINTAINED BY THE DEPOSITARY WITH DTC AND COMPLETE THE FOLLOWING
    (ONLY PARTICIPANTS IN DTC MAY DELIVER SHARES BY BOOK-ENTRY TRANSFER):

Name of Tendering Institution: _________________________________________________

DTC Account Number: ____________________________________________________________

DTC Transaction Code Number: ___________________________________________________

/ / CHECK HERE IF SHARES ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED
    DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING
    (PLEASE ENCLOSE A PHOTOCOPY OF SUCH NOTICE OF GUARANTEED DELIVERY):

Name(s) of Registered Holder(s): _______________________________________________

Window Ticket Number (if any): _________________________________________________

Date of Execution of Notice of Guaranteed Delivery: ____________________________

Name of Institution that Guaranteed Delivery: __________________________________

If delivered by Book-Entry Transfer:

DTC Account Number: ____________________________________________________________

DTC Transaction Code Number: ___________________________________________________

                    NOTE: SIGNATURES MUST BE PROVIDED BELOW.
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY.

Ladies and Gentlemen:

    The undersigned hereby tenders to ONIX Acquisition Inc. (the "Purchaser"), a
Delaware corporation and a wholly-owned subsidiary of Thermo Instrument
Systems Inc., a Delaware corporation ("Thermo Instrument"), the above-described
shares of common stock, par value $0.01 per share (the "Shares"), of ONIX
Systems Inc., a Delaware corporation (the "Company"), pursuant to the
Purchaser's offer to purchase all of the outstanding Shares at a price of $9.00
per Share, net to the seller in cash, without interest thereon, upon the terms
and subject to the conditions set forth in the Offer to Purchase and in this
Letter of Transmittal (which, together with any amendments or supplements
thereto or hereto, collectively constitute the "Offer"), receipt of each of
which is hereby acknowledged. The undersigned understands that the Purchaser
reserves the right to transfer or assign, in whole or from time to time in part,
to one or more of its affiliates, the right to purchase all or any portion of
the Shares tendered pursuant to the Offer.

                                       2
<PAGE>
    Subject to, and effective upon, acceptance for payment of the Shares
tendered herewith in accordance with the terms and subject to the conditions of
the Offer, including, if the Offer is extended or amended, the terms and
conditions of any such extension or amendment, the undersigned hereby sells,
assigns and transfers to, or upon the order of, the Purchaser all right, title
and interest in and to all of the Shares that are being tendered hereby and any
and all dividends and distributions, including, without limitation,
distributions of additional Shares or rights declared, paid or issued with
respect to the tendered Shares on or after January 31, 2000 (collectively,
"Distributions"), and irrevocably constitutes and appoints the Depositary the
true and lawful agent and attorney-in-fact of the undersigned with respect to
such Shares and any Distributions with full power of substitution (such power of
attorney being deemed to be an irrevocable power coupled with an interest) to
(a) deliver such Share Certificates and any Distributions, or transfer ownership
of such Shares and any Distributions on the account books maintained by DTC,
together in either case with appropriate evidences of transfer and authenticity,
to, or upon the order of, the Purchaser, upon receipt by the Depositary, as the
undersigned's agent, of the purchase price, (b) present such Shares and any
Distributions for transfer on the books of the Company, and (c) receive all
benefits and otherwise exercise all rights of record and beneficial ownership of
such Shares and any Distributions, all in accordance with the terms and subject
to the conditions of the Offer.

    The undersigned hereby irrevocably appoints Earl R. Lewis, Kenneth J.
Apicerno, Sandra L. Lambert and Seth H. Hoogasian in their respective capacities
as officers of the Purchaser or one of its affiliates, and any individuals who
shall hereafter succeed to any such office of the Purchaser or one of its
affiliates, and each of them or any other designees of the Purchaser, as
attorneys-in-fact and proxies of the undersigned, each with full power of
substitution, to the full extent of the undersigned's rights with respect to the
Shares tendered by the undersigned and accepted for payment and paid for by the
Purchaser and any Distributions. This power of attorney and proxy shall be
considered irrevocable and coupled with an interest in the tendered Shares. Such
appointment will be effective when, and only to the extent that, the Purchaser
accepts such Shares for payment and deposits the purchase price therefor with
the Depositary. Upon such deposit, all prior powers of attorney and proxies
given by the undersigned at any time with respect to such Shares and any
Distributions will, without further action, be revoked, and no subsequent powers
of attorney or proxies may be given nor any subsequent written consents executed
by the undersigned (and, if given or executed, will not be deemed effective).
Upon such deposit by the Purchaser, the designees of the Purchaser will, with
respect to such Shares and any Distributions, be empowered to exercise all
voting and other rights of the undersigned as they in their sole discretion may
deem proper at any annual or special meeting of the Company's stockholders, or
any adjournment or postponement thereof, by written consent in lieu of any such
meeting or otherwise. The Purchaser reserves the right to require that, in order
for Shares to be deemed validly tendered, immediately upon the Purchaser's
payment for such Shares, the Purchaser must be able to exercise full voting
rights and other rights of a record and beneficial owner with respect to such
Shares and any Distributions, including, without limitation, voting at any
meeting of stockholders or by written consent in lieu of any such meeting.

    The undersigned hereby represents and warrants that (a) the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby and any Distributions and (b) when the Shares are accepted for
payment by the Purchaser, the Purchaser will acquire good, marketable and
unencumbered title to the Shares and any Distributions, free and clear of all
liens, restrictions, charges and encumbrances, and the same will not be subject
to any adverse claim. The undersigned, upon request, shall execute and deliver
any additional documents deemed by the Depositary or the Purchaser to be
necessary or desirable to complete the sale, assignment and transfer of the
Shares tendered hereby and any Distributions. In addition, the undersigned shall
promptly remit and transfer to the Depositary for the account of the Purchaser
any Distribution in respect of the Shares tendered hereby, accompanied by
appropriate documentation of transfer, and, pending such remittance or
appropriate assurance thereof, the Purchaser shall be, subject to applicable
law, entitled to all rights and privileges as record and beneficial owner of any
such Distribution and may withhold the entire purchase price of Shares tendered
hereby or deduct from the purchase price the amount or value of any such
Distribution, as determined by the Purchaser in its sole discretion.

    No authority herein conferred or agreed to be conferred shall be affected
by, and all authority herein conferred or agreed to be conferred shall survive,
the death or incapacity of the undersigned and any obligation of the undersigned
hereunder shall be binding upon the heirs, personal representatives, successors
and assigns of the undersigned.

    Except as otherwise provided in the Offer to Purchase, tenders of Shares
made pursuant to the Offer are irrevocable. Shares tendered pursuant to the
Offer may be withdrawn at any time prior to the Expiration Date (as defined in
the section of the Offer to Purchase captioned "The Tender Offer--Terms of The
Offer; Expiration Date")

                                       3
<PAGE>
and, unless theretofore accepted for payment by the Purchaser pursuant to the
Offer, may also be withdrawn at any time after May 11, 2000. See the section of
the Offer to Purchase captioned "The Tender Offer--Withdrawal Rights."

    The undersigned understands that tenders of Shares pursuant to any of the
procedures described in the section of the Offer to Purchase captioned "The
Tender Offer--Procedures For Accepting The Offer And Tendering Shares" and in
the Instructions hereto will constitute the undersigned's acceptance of the
terms and conditions of the Offer. The Purchaser's acceptance of such Shares for
payment will constitute a binding agreement between the undersigned and the
Purchaser upon the terms and subject to the conditions set forth in the Offer.

    The undersigned understands that the Offer is conditioned upon, among other
things set forth in the Offer to Purchase, there being validly tendered and not
withdrawn prior to the expiration of the Offer that number of Shares which,
together with the Shares held by Thermo Electron Corporation and its
subsidiaries, including Thermo Instrument, constitutes at least ninety percent
(90%) of the Shares outstanding on the Expiration Date.

    The undersigned understands that, under certain circumstances set forth in
the Offer to Purchase, the Purchaser may terminate or amend the Offer or may not
be required to accept for payment any of the Shares tendered herewith.

    Unless otherwise indicated herein under "Special Payment Instructions,"
please issue the check for the purchase price of all Shares accepted for payment
and issue or return any Share Certificate(s) for Shares not tendered or not
purchased in the name(s) of the registered holder(s) appearing under
"Description of Shares Tendered." Similarly, unless otherwise indicated herein
under "Special Delivery Instructions," please mail the check for the purchase
price of all Shares accepted for payment and return any Share Certificate(s) for
Shares not tendered or not purchased (and accompanying documents, as
appropriate) to the address of the registered holder(s) appearing under
"Description of Shares Tendered." In the event that both the "Special Delivery
Instructions" and the "Special Payment Instructions" boxes are completed, please
issue the check for the purchase price of all Shares accepted for payment and
return any Share Certificate(s) for Shares not tendered or not purchased in the
name(s) of, and deliver such check and return such Share Certificate(s) to, the
person(s) so indicated. Please credit any Shares tendered herewith by book-entry
transfer that are not purchased by crediting the DTC account designated above.
The undersigned recognizes that the Purchaser has no obligation pursuant to the
"Special Payment Instructions" to transfer any Shares from the name(s) of the
registered holder(s) thereof if the Purchaser does not accept for payment any of
the Shares tendered hereby.

- ------------------------------------------------

                          SPECIAL PAYMENT INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

      To be completed ONLY if Share Certificate(s) evidencing Shares not
  tendered or not purchased or the check for the purchase price of Shares
  accepted for payment are to be issued in the name of someone other than the
  undersigned.

  Issue:  / / check      / / certificates to:

  Name: ______________________________________________________________________
                                 (PLEASE PRINT)

  Address: ___________________________________________________________________
  ____________________________________________________________________________
                               (INCLUDE ZIP CODE)

   __________________________________________________________________________
                  (TAX IDENTIFICATION OR SOCIAL SECURITY NO.)
                        (SEE SUBSTITUTE FORM W-9 BELOW)

- -----------------------------------------------------
- ------------------------------------------------------------

                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

      To be completed ONLY if Share Certificate(s) evidencing Shares not
  tendered or not purchased or the check for the purchase price of Shares
  accepted for payment are to be sent to someone other than the undersigned or
  to the undersigned at an address other than that shown above.

  Mail:  / / check       / / certificates to:

  Name: ______________________________________________________________________

                                 (PLEASE PRINT)

  Address: ___________________________________________________________________

  ____________________________________________________________________________

                               (INCLUDE ZIP CODE)

- ------------------------------------------------------------

                                       4
<PAGE>

<TABLE>
    <S>        <C>                                                                                                 <C>
               ---------------------------------------------------------------------------------
                                                           IMPORTANT
    SIGN                                SIGN HERE AND COMPLETE SUBSTITUTE FORM W-9 BELOW                           SIGN
    HERE                                                                                                           HERE
            K  X                                                                                                   J
            K  X                                                                                                   J
                                                   SIGNATURE(S) OF HOLDER(S)

               Dated: , 2000
               (Must be signed by the registered holder(s) exactly as name(s) appear(s) on Share Certificate(s)
               or on a security position listing or by person(s) authorized to become registered holder(s) by
               certificates and documents transmitted herewith. If signature is by a trustee, executor,
               administrator, guardian, attorney-in-fact, officer of a corporation or other acting in a fiduciary
               or representative capacity, please provide the following information. See Instruction 5.)

               Name(s)
                                                         (PLEASE PRINT)

               Capacity (Full Title)
               Address:
                                                       (INCLUDE ZIP CODE)

               Area Code and Telephone Number:
               Tax Identification or Social Security No.:

               Dated: , 2000

                                                   GUARANTEE OF SIGNATURE(S)
                                                   (SEE INSTRUCTIONS 1 AND 5)

               Authorized Signature:
               Name:
                                                         (PLEASE PRINT)

               Title:
               Name of Firm:
                                                         (PLEASE PRINT)

               Address:
                                                       (INCLUDE ZIP CODE)

               Area Code and Telephone Number:

               Dated: , 2000
               ---------------------------------------------------------------------------------
</TABLE>

                                       5
<PAGE>
                                  INSTRUCTIONS
             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER

    1.  GUARANTEE OF SIGNATURES.  No signature guarantee is required on this
Letter of Transmittal (a) if this Letter of Transmittal is signed by the
registered holder(s) of Shares (which term, for purposes of this document, shall
include any DTC participant whose name appears on a security position listing as
the owner of Share(s)) tendered herewith, unless such holder(s) has (have)
completed either the box entitled "Special Payment Instructions" or the box
entitled "Special Delivery Instructions," or (b) if such Share(s) are tendered
for the account of a firm that is a commercial bank, broker, dealer, credit
union, savings association or other entity that is a member in good standing of
the Securities Transfer Agents Medallion Program, the Stock Exchanges' Medallion
Program or the New York Stock Exchange, Inc. Medallion Signature Program (each
of the foregoing being referred to as an "Eligible Institution"). In all other
cases, all signatures on this Letter of Transmittal must be guaranteed by an
Eligible Institution. See Instruction 5.

    2.  DELIVERY OF LETTER OF TRANSMITTAL AND CERTIFICATES.  This Letter of
Transmittal is to be completed by stockholders either if Share Certificates are
to be forwarded herewith or, unless an Agent's Message is utilized, if delivery
of Shares is to be made by book-entry transfer pursuant to the procedures set
forth in the section of the Offer to Purchase captioned "The Tender
Offer--Procedures For Accepting The Offer And Tendering Shares." In order for
Shares to be validly tendered pursuant to the Offer, this Letter of Transmittal
(or a facsimile hereof), properly completed and duly executed, together with any
required signature guarantees, or an Agent's Message in connection with a
book-entry delivery of Shares, and any other documents required by this Letter
of Transmittal, must be received by the Depositary at one of its addresses set
forth on the front cover hereof prior to the Expiration Date and either
(i) Share Certificates evidencing tendered Shares must be received by the
Depositary at such address or such Shares must be tendered by book-entry
transfer and a timely confirmation of such book-entry transfer (a "Book-Entry
Confirmation") must be received by the Depositary, in each case prior to the
Expiration Date or (ii) the guaranteed delivery procedures described in the
following sentence must be complied with. Stockholders whose Share Certificates
are not immediately available or who cannot deliver their Share Certificates and
all other required documents to reach the Depositary prior to the Expiration
Date or who cannot complete the procedure for delivery by book-entry transfer on
a timely basis may tender their Shares by properly completing and duly executing
a Notice of Guaranteed Delivery pursuant to the guaranteed delivery procedures
set forth in the section of the Offer to Purchase captioned "The Tender
Offer--Procedures For Accepting The Offer And Tendering Shares." Pursuant to
such procedures: (i) such tender must be made by or through an Eligible
Institution; (ii) a properly completed and duly executed Notice of Guaranteed
Delivery, substantially in the form made available by the Purchaser, must be
received by the Depositary prior to the Expiration Date; and (iii) the Share
Certificates (or a Book-Entry Confirmation) evidencing all tendered Shares, in
proper form for transfer, together with this Letter of Transmittal (or a
facsimile hereof), properly completed and duly executed, with any required
signature guarantees (or, in the case of a book-entry delivery, an Agent's
Message) and any other documents required by this Letter of Transmittal, must be
received by the Depositary within three American Stock Exchange trading days
after the date of execution of such Notice of Guaranteed Delivery.

    THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, SHARE CERTIFICATE(S)
AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH DTC, IS AT THE SOLE
OPTION AND RISK OF THE TENDERING STOCKHOLDER AND THE DELIVERY WILL BE DEEMED
MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF DELIVERY IS BY MAIL,
REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED.
IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

    No alternative, conditional or contingent tenders will be accepted. All
tendering stockholders, by execution of this Letter of Transmittal (or a
facsimile hereof), waive any right to receive any notice of the acceptance of
their Shares for payment.

    If Share Certificates are forwarded to the Depositary in multiple
deliveries, a properly completed and duly executed Letter of Transmittal must
accompany each such delivery.

    3.  INADEQUATE SPACE.  If the space provided herein is inadequate, the Share
Certificate number(s), the number of Shares and any other required information
should be listed on a separate signed schedule attached hereto and referenced in
the box entitled "Description of Shares Tendered."

                                       6
<PAGE>
    4.  PARTIAL TENDERS.  (NOT APPLICABLE TO BOOK-ENTRY STOCKHOLDERS.)  If fewer
than all the Shares evidenced by any Share Certificate submitted to the
Depositary herewith are to be tendered, fill in the number of Shares that are to
be tendered in the box entitled "Number of Shares Tendered." In such cases, new
Share Certificate(s) evidencing the Shares that were evidenced by the Share
Certificate(s) delivered to the Depositary herewith, but that were not tendered
hereby, will be sent to the registered holder(s) shown above, unless otherwise
provided in the box entitled "Special Delivery Instructions," as soon as
practicable after the expiration or termination of the Offer. All Shares
represented by Share Certificates delivered to the Depositary will be deemed to
have been tendered unless otherwise indicated.

    5.  SIGNATURES ON LETTER OF TRANSMITTAL, STOCK POWERS AND ENDORSEMENTS.  If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
tendered hereby, the signature(s) must correspond with the name(s) as written on
the face of the Share Certificate(s) without alteration, enlargement or any
change whatsoever.

    If any of the Shares tendered hereby are owned of record by two or more
persons, all such persons must sign this Letter of Transmittal.

    If any of the tendered Shares are registered in the names of different
holders, it will be necessary to complete, sign and submit as many separate
Letters of Transmittal as there are different registrations of Share
Certificates.

    If this Letter of Transmittal or any Share Certificate or stock power is
signed by a trustee, executor, administrator, guardian, attorney-in-fact,
officer of a corporation or other person acting in a fiduciary or representative
capacity, such person should so indicate when signing, and proper evidence
satisfactory to the Purchaser of such person's authority so to act must be
submitted.

    If this Letter of Transmittal is signed by the registered holder(s) of the
Shares listed and tendered hereby, no endorsements of Share Certificates or
separate stock powers are required, unless payment is to be made to, or Share
Certificates evidencing Shares not tendered or not purchased are to be issued in
the name of, a person other than the registered holder(s), in which case, the
Share Certificate(s) evidencing the Shares tendered hereby must be endorsed or
accompanied by appropriate stock powers signed exactly as the name(s) of the
registered holder(s) appear(s) on such Share Certificate(s). Signatures on such
Share Certificate(s) or stock powers must be guaranteed by an Eligible
Institution.

    If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Share Certificate(s) listed and tendered hereby, the
Share Certificate(s) must be endorsed or accompanied by appropriate stock
powers, in either case signed exactly as the name(s) of the registered holder(s)
appear on such Share Certificate(s). Signature(s) on such Share Certificate(s)
and stock powers must be guaranteed by an Eligible Institution.

    6.  STOCK TRANSFER TAXES.  Except as set forth in this Instruction 6, the
Purchaser will pay or cause to be paid any stock transfer taxes with respect to
the transfer and sale of Shares to it or its order pursuant to the Offer. If,
however, payment of the purchase price of Shares accepted for payment is to be
made to, or if Share Certificate(s) evidencing Shares not tendered or not
purchased are to be issued in the name of, any person other than the registered
holder(s), or if tendered Share Certificates are registered in the name of any
person other than the person(s) signing this Letter of Transmittal, then the
amount of any stock transfer taxes (whether imposed on the registered holder(s)
or such person or otherwise) payable on account of the transfer to such other
person will be deducted from the purchase price unless satisfactory evidence of
the payment of such taxes, or an exemption therefrom, is submitted.

    EXCEPT AS SET FORTH IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE SHARE CERTIFICATE(S) TENDERED HEREBY.

    7.  SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS.  If a check for the purchase
price of Shares accepted for payment is to be issued in the name of, or Share
Certificate(s) evidencing Shares not tendered or not purchased are to be issued
or returned to, a person other than the signer of this Letter of Transmittal or
if a check or such Share Certificate(s) are to be returned to a person other
than the signer of this Letter of Transmittal or to an address of the signer
other than that shown in this Letter of Transmittal, the appropriate boxes on
this Letter of Transmittal must be completed.

    8.  WAIVER OF CONDITIONS.  The conditions of the Offer may be waived by the
Purchaser, in whole or in part, at any time and from time to time in its sole
discretion.

                                       7
<PAGE>
    9.  SUBSTITUTE FORM W-9.  Under U.S. federal income tax law, a stockholder
whose tendered Shares are purchased is required to provide the Depositary with
such stockholder's correct taxpayer identification number ("TIN") (e.g., social
security number or employer identification number) on Substitute Form W-9 below
and to certify whether such stockholder is subject to backup withholding of
federal income tax. If a tendering stockholder has been notified by the Internal
Revenue Service (the "IRS") that such stockholder is subject to backup
withholding, such stockholder must cross out item 2 of the Certification box
(Part 2) of the Substitute Form W-9, unless such stockholder has since been
notified by the IRS that such stockholder is no longer subject to backup
withholding. Failure to provide the information on the Substitute Form W-9 may
subject the tendering stockholder to federal income tax withholding at the rate
of 31% on the payment of the purchase price of all Shares purchased from the
stockholder. If the Depositary is not provided with the correct TIN, the IRS may
subject the stockholder or other payee to a $50 penalty.

    Certain stockholders are not subject to these backup withholding and
reporting requirements. Exempt recipients, such as corporations, are also
requested to provide their TIN and check the "Exempt" box in Part 3. Foreign
individuals or entities must submit a Form W-8 or W-8BEN, signed under penalties
of perjury, attesting to their foreign status. A Form W-8 or W8-BEN can be
obtained from the Depositary. See the enclosed "Guidelines for Certification of
Taxpayer Identification Number on Substitute Form W-9" for more instructions.

    IF BACKUP WITHHOLDING APPLIES, THE DEPOSITARY IS REQUIRED TO WITHHOLD 31% OF
ANY PAYMENTS MADE TO THE STOCKHOLDER OR OTHER PAYEE. BACKUP WITHHOLDING IS NOT
AN ADDITIONAL TAX. RATHER, THE TAX LIABILITY OF PERSONS SUBJECT TO BACKUP
WITHHOLDING WILL BE REDUCED BY THE AMOUNT OF TAX WITHHELD. IF WITHHOLDING
RESULTS IN AN OVERPAYMENT OF TAXES, A REFUND MAY BE OBTAINED FROM THE IRS.

    The "Awaiting TIN" box in Part 3 of the Substitute Form W-9 may be checked
if the tendering stockholder has not been issued a TIN and has applied for a TIN
or intends to apply for a TIN in the near future. If the "Awaiting TIN" box in
Part 3 is checked, the stockholder or other payee must also complete the
Certificate of Awaiting Taxpayer Identification Number below in order to avoid
backup withholding. If the "Awaiting TIN" box in Part 3 is checked and the
Certificate of Awaiting Taxpayer Identification Number is completed, the
Depositary will withhold 31% of all payments made unless a properly certified
TIN is provided to the Depositary within 60 days.

    The stockholder is required to give the Depositary the TIN of the record
owner of the Shares or of the last transferee appearing on the transfers
attached to, or endorsed on, the Shares. If the Shares are in more than one name
or are not in the name of the actual owner, consult the enclosed "Guidelines for
Certification of Taxpayer Identification Number on Substitute Form W-9" for
additional guidance on which number to report.

    10.  QUESTIONS AND REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES.  Questions
and requests for assistance may be directed to the Dealer Managers or the
Information Agent at their respective addresses and telephone numbers set forth
below. Additional copies of the Offer to Purchase, this Letter of Transmittal
and all other tender offer materials may be obtained from the Information Agent
or from brokers, dealers, commercial banks or trust companies at the Purchaser's
expense.

    11.  LOST, DESTROYED OR STOLEN CERTIFICATES.  If any Share Certificate has
been lost, destroyed or stolen, the stockholder should promptly notify the
Depositary. The stockholder will then be instructed as to the steps that must be
taken in order to replace such Share Certificate. This Letter of Transmittal and
related documents cannot be processed until the procedures for replacing lost,
destroyed or stolen Share Certificates have been followed.

    IMPORTANT: THIS LETTER OF TRANSMITTAL (OR A FACSIMILE HEREOF), PROPERLY
COMPLETED AND DULY EXECUTED, OR, IF APPROPRIATE, AN AGENT'S MESSAGE, TOGETHER
WITH SHARE CERTIFICATES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL OTHER
REQUIRED DOCUMENTS, OR A PROPERLY COMPLETED AND DULY EXECUTED NOTICE OF
GUARANTEED DELIVERY, MUST BE RECEIVED BY THE DEPOSITARY PRIOR TO THE EXPIRATION
DATE.

                                       8
<PAGE>

<TABLE>
<C>                               <S>                                                    <C>
 -----------------------------------------------------------------------------------------------------------------------
                                 PAYER'S NAME: AMERICAN STOCK TRANSFER & TRUST COMPANY
 -----------------------------------------------------------------------------------------------------------------------
 SUBSTITUTE                       PART 1 -- PLEASE PROVIDE YOUR TIN IN THE BOX AT THE
 FORM W-9                         RIGHT AND CERTIFY BY SIGNING AND DATING BELOW:             Social security number
 DEPARTMENT OF THE TREASURY,                                                                           or
 INTERNAL REVENUE SERVICE
 PAYER'S REQUEST FOR TAXPAYER                                                                Employer identification
 IDENTIFICATION NUMBER ("TIN")                                                                       number
                                                                                             (If Awaiting TIN, write
                                                                                                 "Applied For")
                                  ----------------------------------------------------------------------------------
                                  PART 2 -- CERTIFICATION -- Under penalties of          PART 3 --
                                  perjury, I certify that:                               / / Awaiting TIN
                                                                                         / / Exempt
                                  (1) The number shown on this form is my correct
                                  Taxpayer Identification Number (or I am waiting for
                                      a number to be issued to me), and

                                  (2) I am not subject to backup withholding because:
                                  (a) I am exempt from backup withholding, or
                                  (b) I have not been notified by the Internal Revenue
                                      Service (the "IRS") that I am subject to backup
                                      withholding as a result of a failure to report
                                      all interest or dividends, or
                                  (c) the IRS has notified me that I am no longer
                                  subject to backup withholding.
                                  ----------------------------------------------------------------------------------
                                  CERTIFICATION INSTRUCTIONS -- You must cross out Item (2) above if you have been
                                  notified by the IRS that you are currently subject to backup withholding because of
                                  underreporting interest or dividends on your tax return. However, if after being
                                  notified by the IRS that you are subject to backup withholding you received another
                                  notification from the IRS that you are no longer subject to backup withholding, do not
                                  cross out such Item (2).
 -----------------------------------------------------------------------------------------------------------------------

         SIGN HERE  K             SIGNATURE  DATE , 2000
 -----------------------------------------------------------------------------------------------------------------------
</TABLE>

NOTE: FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING
      OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE OFFER. PLEASE REVIEW
      THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
      NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.

                                       9
<PAGE>
               YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU
        CHECKED THE "AWAITING TIN" BOX IN PART 3 OF SUBSTITUTE FORM W-9.

- --------------------------------------------------------------------------------

             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

      I certify under penalties of perjury that a Taxpayer Identification
  Number has not been issued to me, and either (1) I have mailed or delivered
  an application to receive a Taxpayer Identification Number to the
  appropriate Internal Revenue Service Center or Social Security
  Administration Office, or (2) I intend to mail or deliver an application in
  the near future. I understand that if I do not provide a Taxpayer
  Identification Number, 31% of all reportable payments made to me may be
  withheld until I provide a Taxpayer Identification Number with required
  certifications, which should be provided within 60 days.

  Signature: __________________                 Dated: _________________, 2000
- --------------------------------------------------------------------------------

                                       10
<PAGE>
                    THE INFORMATION AGENT FOR THE OFFER IS:
                             D.F. KING & CO., INC.
                          77 Water Street, 20th Floor
                               New York, NY 10005
                Bankers and Brokers call collect (212) 269-5550
                    All Others Call Toll-Free (800) 290-6433

                     THE DEALER MANAGERS FOR THE OFFER ARE:
                          J.P. MORGAN SECURITIES INC.
                                 60 Wall Street
                               New York, NY 10260
                                 (877) 869-0656
                     THE BEACON GROUP CAPITAL SERVICES, LLC
                                399 Park Avenue
                               New York, NY 10022
                                 (212) 339-9100

<PAGE>
                         NOTICE OF GUARANTEED DELIVERY
                                      FOR
                        TENDER OF SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.

    As set forth in the section captioned "The Tender Offer--Procedures For
Accepting The Offer And Tendering Shares" in the Offer to Purchase described
below, this Notice of Guaranteed Delivery or one substantially in the form
hereof must be used to tender shares of common stock, par value $0.01 per share
(the "Shares"), of ONIX Systems Inc., a Delaware corporation (the "Company"),
pursuant to the Offer (as defined below) if certificates evidencing Shares are
not immediately available or the certificates evidencing Shares and all other
required documents cannot be delivered to American Stock Transfer & Trust
Company (the "Depositary") prior to the Expiration Date (as defined in the Offer
of Purchase), or if the procedures for delivery by book-entry transfer cannot be
completed on a timely basis. This instrument may be delivered by hand or
transmitted by facsimile transmission, overnight courier or mail to the
Depositary.

                        THE DEPOSITARY FOR THE OFFER IS:

                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                 <C>
             BY MAIL:                 BY HAND OR OVERNIGHT COURIER:
          40 Wall Street                      40 Wall Street
            46th Floor                          46th Floor
     New York, New York 10005            New York, New York 10005
 Attn: Reorganization Department     Attn: Reorganization Department
</TABLE>

                           BY FACSIMILE TRANSMISSION:
                                 (718) 234-5001

                             CONFIRM BY TELEPHONE:
                                 (718) 921-8200

    DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE, OR TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER
THAN AS SET FORTH ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY.

    This Notice of Guaranteed Delivery is not to be used to guarantee
signatures. If a signature on a Letter of Transmittal is required to be
guaranteed by an Eligible Institution (as defined in the Offer to Purchase)
under the instructions thereto, such signature guarantee must appear in the
applicable space provided in the signature box in the Letter of Transmittal.

              THE GUARANTEE ON THE REVERSE SIDE MUST BE COMPLETED.
<PAGE>
Ladies and Gentlemen:

    The undersigned hereby tenders to ONIX Acquisition Inc., a Delaware
corporation and a wholly-owned subsidiary of Thermo Instrument Systems Inc., a
Delaware corporation, upon the terms and subject to the conditions set forth in
the Offer to Purchase dated March 13, 2000 (the "Offer to Purchase") and in the
related Letter of Transmittal (which, together with any amendments or
supplements thereto, collectively constitute the "Offer"), receipt of each of
which is hereby acknowledged, the number of Shares indicated below pursuant to
the guaranteed delivery procedures set forth in the section of the Offer to
Purchase captioned "The Tender Offer--Procedures For Accepting The Offer And
Tendering Shares."

<TABLE>
<S>                                                    <C>
Signature(s):                                          Address:
Name(s) of Record Holder(s):
                                                                                               Zip Code
                                                       Area Code and Tel. No.(s):
              Please Type or Print

Number of Shares:                                      Check box if Shares will be tendered by
Share Certificate No(s). (if available):               book-entry transfer: / /
                                                       DTC Account Number:
Dated: , 2000
</TABLE>

                                   GUARANTEE
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)

     The undersigned, a firm that is a commercial bank, broker, dealer, credit
 union, savings association or other entity that is a member in good standing
 of the Securities Transfer Agents Medallion Program, the Stock Exchanges'
 Medallion Program or the New York Stock Exchange, Inc. Medallion Signature
 Program, hereby guarantees to either deliver to the Depositary certificates
 evidencing all the Shares tendered hereby, in proper form for transfer, or to
 deliver such Shares pursuant to the procedure for book-entry transfer into the
 Depositary's account at The Depository Trust Company, in either case together
 with the Letter of Transmittal (or a facsimile thereof), properly completed
 and duly executed, with any required signature guarantees or an Agent's
 Message (as defined in the Offer to Purchase) in the case of a book-entry
 transfer, and any other required documents, all within three American Stock
 Exchange trading days after the date hereof.

 Name of Firm: ________________________________________________________________

 Address: _____________________________________________________________________

 ______________________________________________________________________________
                                                                       Zip Code

 Area Code and Tel. No.: ______________________________________________________

 Authorized Signature: ________________________________________________________

 Name _________________________________________________________________________

 Title:________________________________________________________________________

 Dated: _________________________________________________________________, 2000

     NOTE: DO NOT SEND CERTIFICATES WITH THIS NOTICE OF GUARANTEED DELIVERY.
         CERTIFICATES SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.

                                       2

<PAGE>

<TABLE>
<S>                                                         <C>
          J.P. MORGAN SECURITIES INC.                            THE BEACON GROUP CAPITAL SERVICES, LLC
                 60 WALL STREET                                       399 PARK AVENUE, 17TH FLOOR
               NEW YORK, NY 10260                                          NEW YORK, NY 10022
                 (877) 869-0656                                              (212) 339-9100
</TABLE>

                           OFFER TO PURCHASE FOR CASH

                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.
                                       AT
                              $9.00 NET PER SHARE
                                       BY
                             ONIX ACQUISITION INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
                         THERMO INSTRUMENT SYSTEMS INC.

  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
         TIME, ON FRIDAY, APRIL 7, 2000, UNLESS THE OFFER IS EXTENDED.

                                                                  March 13, 2000

To Brokers, Dealers, Commercial Banks,
    Trust Companies and Other Nominees:

    We have been appointed by ONIX Acquisition Inc., a Delaware corporation (the
"Purchaser") and a wholly-owned subsidiary of Thermo Instrument Systems Inc., a
Delaware corporation ("Thermo Instrument"), to act as Dealer Managers in
connection with the Purchaser's offer to purchase all outstanding shares of
common stock, par value $0.01 per share (the "Shares"), of ONIX Systems Inc., a
Delaware corporation (the "Company"), at a purchase price of $9.00 per Share,
net to the seller in cash, without interest thereon, upon the terms and subject
to the conditions set forth in the Offer to Purchase dated March 13, 2000 (the
"Offer to Purchase") and in the related Letter of Transmittal (which, together
with any amendments or supplements thereto, collectively constitute the "Offer")
enclosed herewith.

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS DESCRIBED IN THE OFFER TO
PURCHASE, THERE BEING VALIDLY TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION
OF THE OFFER THAT NUMBER OF SHARES WHICH, TOGETHER WITH SHARES OWNED BY THERMO
ELECTRON CORPORATION AND ITS SUBSIDIARIES, INCLUDING THERMO INSTRUMENT,
CONSTITUTES AT LEAST NINETY PERCENT (90%) OF THE OUTSTANDING SHARES ON THE
EXPIRATION DATE (AS DEFINED IN THE SECTION OF THE OFFER TO PURCHASE CAPTIONED
"THE TENDER OFFER--TERMS OF THE OFFER; EXPIRATION DATE"). THE OFFER IS ALSO
SUBJECT TO OTHER IMPORTANT TERMS AND CONDITIONS CONTAINED IN THE OFFER TO
PURCHASE.

    Enclosed for your information and for forwarding to your clients for whose
accounts you hold Shares registered in your name or in the name of your nominees
are copies of the following documents:

    1.  The Offer to Purchase dated March 13, 2000.

    2.  The Letter of Transmittal to tender Shares (for your use and for the
       information of your clients).

    3.  The Notice of Guaranteed Delivery for Shares (to be used to accept the
       Offer if certificates evidencing Shares ("Share Certificates") are not
       immediately available or if such Share Certificates and all other
       required documents cannot be delivered to American Stock Transfer & Trust
       Company (the "Depositary") prior to the Expiration Date or if the
       procedures for book-entry transfer cannot be completed on a timely
       basis).

    4.  A printed form of letter that may be sent to your clients for whose
       accounts you hold Shares registered in your name or in the name of your
       nominees, with space provided for obtaining such clients' instructions
       with regard to the Offer.

    5.  Guidelines for Certification of Taxpayer Identification Number on
       Substitute Form W-9.

    6.  A return envelope addressed to the Depositary.

    YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, APRIL 7, 2000, UNLESS
THE OFFER IS EXTENDED.
<PAGE>
    In all cases, payment for Shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by the Depositary of
(i) certificates evidencing Shares ("Share Certificates") or timely confirmation
of a book-entry transfer of such Shares into the Depositary's account at the
Book-Entry Transfer Facility (as defined in the section of the Offer to Purchase
captioned "The Tender Offer--Acceptance For Payment And Payment For Shares")
pursuant to the procedures set forth in the section of the Offer to Purchase
captioned "The Tender Offer--Procedures For Accepting The Offer And Tendering
Shares," (ii) the Letter of Transmittal (or a facsimile thereof), properly
completed and duly executed, with any required signature guarantees, or an
Agent's Message (as defined in the section of the Offer to Purchase captioned
"The Tender Offer--Acceptance For Payment And Payment For Shares") in connection
with a book-entry transfer, and (iii) any other documents required by the Letter
of Transmittal.

    If a stockholder desires to tender Shares pursuant to the Offer and such
stockholder's Share Certificates are not immediately available or such
stockholder cannot deliver the Share Certificates and all other required
documents to reach the Depositary prior to the Expiration Date, or such
stockholder cannot complete the procedure for delivery by book-entry transfer on
a timely basis, such Shares may nevertheless be tendered by following the
guaranteed delivery procedures specified in the section of the Offer to Purchase
captioned "The Tender Offer--Procedures For Accepting The Offer And Tendering
Shares."

    No fees or commissions will be paid to brokers, dealers or any other persons
(other than to the Dealer Managers and D.F. King & Co., Inc. (the "Information
Agent"), as described in the Offer to Purchase) for soliciting tenders of Shares
pursuant to the Offer. The Purchaser will, however, upon request, reimburse you
for customary mailing and handling expenses incurred by you in forwarding any of
the enclosed materials to your clients.

    The Purchaser will pay or cause to be paid any transfer taxes payable on the
purchase of Shares by the Purchaser pursuant to the Offer, except as otherwise
provided in Instruction 6 of the Letter of Transmittal.

    Questions and requests for assistance or for additional copies of the
enclosed materials may be directed to the Dealer Managers or the Information
Agent, at their respective addresses and telephone numbers set forth on the back
cover of the Offer to Purchase.

                                         Very truly yours,
                                         J.P. Morgan Securities Inc.
                                         The Beacon Group Capital Services, LLC

    NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
OR ANY OTHER PERSON THE AGENT OF THERMO ELECTRON CORPORATION OR ANY OF ITS
SUBSIDIARIES (INCLUDING WITHOUT LIMITATION THERMO INSTRUMENT AND THE PURCHASER),
THE COMPANY, THE DEALER MANAGERS, THE DEPOSITARY OR THE INFORMATION AGENT, OR
ANY AFFILIATE OF ANY OF THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY
STATEMENT OR USE ANY DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE
OFFER OTHER THAN THE ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.

<PAGE>
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.
                                       AT
                              $9.00 NET PER SHARE
                                       BY
                             ONIX ACQUISITION INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
                         THERMO INSTRUMENT SYSTEMS INC.

    THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
                                      CITY
         TIME, ON FRIDAY, APRIL 7, 2000, UNLESS THE OFFER IS EXTENDED.

To Our Clients:

    Enclosed for your consideration is an Offer to Purchase dated March 13, 2000
(the "Offer to Purchase") and the related Letter of Transmittal (which, together
with any amendments or supplements thereto, collectively constitute the "Offer")
relating to an offer by ONIX Acquisition Inc., a Delaware corporation (the
"Purchaser") and a wholly-owned subsidiary of Thermo Instrument Systems Inc., a
Delaware corporation ("Thermo Instrument"), to purchase all outstanding shares
of common stock, par value $0.01 per share (the "Shares"), of ONIX
Systems Inc., a Delaware corporation (the "Company"), at a purchase price of
$9.00 per Share, net to the seller in cash, without interest thereon, upon the
terms and subject to the conditions set forth in the Offer.

    We are the holder of record of Shares held by us for your account. A TENDER
OF SUCH SHARES CAN BE MADE ONLY BY US AS THE HOLDER OF RECORD AND PURSUANT TO
YOUR INSTRUCTIONS. THE LETTER OF TRANSMITTAL IS FURNISHED TO YOU FOR YOUR
INFORMATION ONLY AND CANNOT BE USED BY YOU TO TENDER SHARES HELD BY US FOR YOUR
ACCOUNT.

    We request instructions as to whether you wish to have us tender on your
behalf any or all of the Shares held by us for your account, pursuant to the
terms and subject to the conditions set forth in the Offer.

    Your attention is directed to the following:

    - The tender price is $9.00 per Share, net to the seller in cash, without
      interest thereon.

    - The Offer and withdrawal rights will expire at 12:00 midnight, New York
      City time, on Friday, April 7, 2000, unless the Offer is extended.

    - The Offer is made for all of the outstanding Shares.

    - The Offer is conditioned upon, among other things described in the Offer
      to Purchase, there being validly tendered and not withdrawn prior to the
      expiration of the Offer that number of Shares which, together with Shares
      owned by Thermo Electron Corporation and its subsidiaries, including
      Thermo Instrument, constitutes at least ninety percent (90%) of the
      outstanding Shares on the Expiration Date (as defined in the section of
      the Offer to Purchase captioned "The Tender Offer--Terms Of The Offer;
      Expiration Date"). The Offer is also subject to other important terms and
      conditions contained in the Offer to Purchase.

    - Tendering stockholders will not be obligated to pay brokerage fees or
      commissions or, except as set forth in Instruction 6 of the Letter of
      Transmittal, transfer taxes on the purchase of Shares by the Purchaser
      pursuant to the Offer.

    - In all cases, payment for Shares tendered and accepted for payment
      pursuant to the Offer will be made only after timely receipt by American
      Stock Transfer & Trust Company (the "Depositary") of (i) certificates
      evidencing Shares or timely confirmation of a book-entry transfer of such
      Shares into the Depositary's account
<PAGE>
      at the Book Entry Transfer Facility (as defined in the section of the
      Offer to Purchase captioned "The Tender Offer--Acceptance For Payment And
      Payment For Shares") pursuant to the procedures set forth in the section
      of the Offer to Purchase captioned "The Tender Offer--Procedures For
      Accepting The Offer And Tendering Shares," (ii) the Letter of Transmittal
      (or a facsimile thereof), properly completed and duly executed, with any
      required signature guarantees, or an Agent's Message (as defined in the
      section of the Offer to Purchase captioned "The Tender Offer--Acceptance
      For Payment And Payment For Shares") in connection with a book-entry
      transfer and (iii) any other documents required by the Letter of
      Transmittal.

    The Offer is being made solely by the Offer to Purchase and the related
Letter of Transmittal and is being made to all holders of Shares. The Offer is
not being made to (nor will tenders be accepted from or on behalf of) holders of
Shares in any jurisdiction in which the making of the Offer or the acceptance
thereof would not be in compliance with the laws of such jurisdiction. In any
jurisdiction where the securities, blue sky or other laws require the Offer to
be made by a licensed broker or dealer, the Offer shall be deemed to be made on
behalf of the Purchaser by J.P. Morgan Securities Inc., The Beacon Group Capital
Services, LLC or one or more registered brokers or dealers licensed under the
laws of such jurisdiction.

    If you wish to have us tender any or all of the Shares held by us for your
account, please instruct us by completing, executing and returning to us the
instruction form contained in this letter. If you authorize a tender of your
Shares, all such Shares will be tendered unless otherwise specified in such
instruction form. YOUR INSTRUCTIONS SHOULD BE FORWARDED TO US IN AMPLE TIME TO
PERMIT US TO SUBMIT A TENDER ON YOUR BEHALF PRIOR TO THE EXPIRATION OF THE
OFFER.

                                       2
<PAGE>
                        INSTRUCTIONS WITH RESPECT TO THE
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.

    The undersigned acknowledge(s) receipt of your letter enclosing the Offer to
Purchase dated March 13, 2000 (the "Offer to Purchase") and the related Letter
of Transmittal (which, together with any amendments or supplements thereto,
collectively constitute the "Offer") pursuant to an offer by ONIX
Acquisition Inc., a Delaware corporation and a wholly-owned subsidiary of Thermo
Instrument Systems Inc., a Delaware corporation, to purchase all of the
outstanding shares of common stock, par value $0.01 per share (the "Shares"), of
ONIX Systems Inc., a Delaware corporation.

    This will instruct you to tender the number of Shares indicated below (or,
if no number is indicated below, all Shares) that are held by you for the
account of the undersigned, upon the terms and subject to the conditions set
forth in the Offer.

- --------------------------------------------------------------------------------

<TABLE>
<S>                                                    <C>

  ----------------------------------------------
  Number of Shares to be
  Tendered(1):
  ----------------------------------------------

  Dated: , 2000

                                    SIGN HERE  K       X
                                                       Signature(s):

                                                       Please type or print name(s):

                                                       Address:

                                                       Area Code and Telephone Number:

                                                       Tax Identification or Social Security Number:
</TABLE>

- --------------------------------------------------------------------------------

(1) Unless otherwise indicated, it will be assumed that all of the Shares held
    by us for your account are to be tendered.

                                       3

<PAGE>
    THIS ANNOUNCEMENT IS NEITHER AN OFFER TO PURCHASE NOR A SOLICITATION OF AN
OFFER TO SELL SHARES. THE OFFER IS BEING MADE SOLELY BY THE OFFER TO PURCHASE
DATED MARCH 13, 2000 AND THE RELATED LETTER OF TRANSMITTAL AND IS BEING MADE TO
ALL HOLDERS OF SHARES. THE OFFER IS NOT BEING MADE TO (NOR WILL TENDERS BE
ACCEPTED FROM OR ON BEHALF OF) HOLDERS OF SHARES IN ANY JURISDICTION IN WHICH
THE MAKING OF THE OFFER OR THE ACCEPTANCE THEREOF WOULD NOT BE IN COMPLIANCE
WITH THE LAWS OF SUCH JURISDICTION. IN ANY JURISDICTION WHERE THE SECURITIES,
BLUE SKY OR OTHER LAWS REQUIRE THE OFFER TO BE MADE BY A LICENSED BROKER OR
DEALER, THE OFFER SHALL BE DEEMED TO BE MADE ON BEHALF OF THE PURCHASER BY J.P.
MORGAN SECURITIES INC., THE BEACON GROUP CAPITAL SERVICES, LLC OR ONE OR MORE
REGISTERED BROKERS OR DEALERS LICENSED UNDER THE LAWS OF SUCH JURISDICTION.

                      NOTICE OF OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                               ONIX SYSTEMS INC.
                                       AT
                              $9.00 NET PER SHARE
                                       BY
                             ONIX ACQUISITION INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
                         THERMO INSTRUMENT SYSTEMS INC.

    ONIX Acquisition Inc., a Delaware corporation (the "Purchaser") and a
wholly-owned subsidiary of Thermo Instrument Systems Inc., a Delaware
corporation ("Thermo Instrument"), is offering to purchase all outstanding
shares of common stock, par value $0.01 per share (the "Shares"), of ONIX
Systems Inc., a Delaware corporation (the "Company"), at a purchase price of
$9.00 per Share, net to the seller in cash, without interest thereon, upon
the terms and subject to the conditions set forth in the Offer to Purchase
dated March 13, 2000 (the "Offer to Purchase") and in the related Letter of
Transmittal (which, together with any amendments or supplements thereto,
collectively constitute the "Offer"). Thermo Electron Corporation, a Delaware
corporation ("Thermo Electron"), owns a majority of the outstanding shares of
common stock of Thermo Instrument.

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
   NEW YORK CITY TIME, ON FRIDAY APRIL 7, 2000, UNLESS THE OFFER IS EXTENDED.

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER
OF SHARES WHICH, TOGETHER WITH SHARES OWNED BY THERMO ELECTRON AND ITS
SUBSIDIARIES, INCLUDING THERMO INSTRUMENT, CONSTITUTES AT LEAST NINETY
PERCENT (90%) OF THE OUTSTANDING SHARES OF THE COMPANY ON THE EXPIRATION
DATE. THE OFFER IS ALSO SUBJECT TO CERTAIN OTHER IMPORTANT TERMS AND
CONDITIONS CONTAINED IN THE OFFER TO PURCHASE.

    The Offer is the first step in Thermo Instrument's plan to take the Company
private. The purpose of the Offer is to acquire the minority interest in the
Company as part of an overall reorganization of Thermo Electron. If the Offer is
completed, Thermo Electron, Thermo Instrument and the Purchaser together will
own at least 90% of the Shares. Promptly following the closing of the Offer,
Thermo Instrument and Thermo Electron plan to contribute their Shares to the
Purchaser and cause the Purchaser to merge with and into the Company in a
so-called "short-form" merger between the Company and the Purchaser (the


<PAGE>

"Merger"). Stockholders of the Company who do not tender their Shares in the
Offer will not be entitled to vote on the Merger. The consideration per Share
in the Merger (other than with respect to Shares held by stockholders, if
any, who are entitled to and perfect their appraisal rights under Delaware
Law) would be the same as the Offer price of $9.00.

    For purposes of the Offer, the Purchaser will be deemed to have accepted for
payment, and thereby purchased, Shares validly tendered and not properly
withdrawn if, as and when the Purchaser gives oral or written notice to American
Stock Transfer & Trust Company (the "Depositary") of the Purchaser's acceptance
for payment of such Shares pursuant to the Offer. Upon the terms and subject to
the conditions of the Offer, payment for Shares so accepted for payment pursuant
to the Offer will be made by deposit of the aggregate purchase price therefor
with the Depositary, which will act as agent for tendering stockholders for the
purpose of receiving payment from the Purchaser and transmitting such payment to
stockholders whose Shares have been accepted for payment. UNDER NO CIRCUMSTANCES
WILL INTEREST ON THE PURCHASE PRICE FOR SHARES BE PAID, REGARDLESS OF ANY
EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH PAYMENT. In all cases,
payment for Shares tendered and accepted for payment pursuant to the Offer will
be made only after timely receipt by the Depositary of (i) certificates
evidencing Shares ("Share Certificates") or timely confirmation of a book-entry
transfer of such Shares into the Depositary's account at the Book-Entry Transfer
Facility (as defined in the section of the Offer to Purchase captioned "The
Tender Offer--Acceptance For Payment And Payment For Shares") pursuant to the
procedures set forth in the section of the Offer to Purchase captioned "The
Tender Offer--Acceptance For Payment And Payment For Shares," (ii) the Letter of
Transmittal (or a facsimile thereof), properly completed and duly executed, with
any required signature guarantees, or an Agent's Message (as defined in the
section of the Offer to Purchase captioned "The Tender Offer--Acceptance For
Payment And Payment For Shares") in connection with a book-entry transfer and
(iii) any other documents required by the Letter of Transmittal.

    The term "Expiration Date" means 12:00 midnight, New York City time, on
Friday, April 7, 2000, unless and until the Purchaser, in its sole discretion,
shall have extended the period during which the Offer is open, in which event
the term "Expiration Date" shall mean the latest time and date at which the
Offer, as so extended by the Purchaser, shall expire.

    Subject to the applicable rules and regulations of the Securities and
Exchange Commission, the Purchaser expressly reserves the right, in its sole
discretion, at any time and from time to time, to extend the period during
which the Offer is open for any reason, including the failure to satisfy any
of the conditions specified in the section of the Offer to Purchase captioned
"The Tender Offer-Certain Conditions Of The Offer," and thereby delay
acceptance for payment of, or payment for, any Shares, by giving oral or
written notice of such extension to the Depositary. Any such extension will
be followed as promptly as practicable by a public announcement thereof, such
announcement to be made no later than 9:00 a.m., New York City time, on the
next business day after the previously scheduled Expiration Date. During any
such extension, all Shares previously tendered and not properly withdrawn
will remain subject to the Offer, subject to the rights of a tendering
stockholder to withdraw such stockholder's Shares.

    Except as otherwise provided in the section of the Offer to Purchase
captioned "The Tender Offer--Withdrawal Rights," tenders of Shares made pursuant
to the Offer are irrevocable. Shares tendered pursuant to the Offer may be
withdrawn at any time prior to the Expiration Date and, unless theretofore
accepted for payment by the Purchaser pursuant to the Offer, may also be
withdrawn at any time after May 11, 2000. In order for a withdrawal to be
effective, a written, telegraphic or facsimile transmission notice of withdrawal
must be timely received by the Depositary at one of its addresses set forth on
the back cover of the Offer to Purchase. Any such notice of withdrawal must
specify the name of the person who tendered the Shares to be withdrawn, the
number of Shares to be withdrawn and the name of the registered holder of the
Shares to be withdrawn, if different from that of the person who tendered such
Shares. If Share Certificates to be withdrawn have been delivered or otherwise
identified to the Depositary, then, prior to the physical release of such Share
Certificates, the tendering stockholder must also submit the serial numbers
shown on such Share Certificates to the Depositary and the signatures on the

                                       2
<PAGE>
notice of withdrawal must be guaranteed by an Eligible Institution (as defined
in the section of the Offer to Purchase captioned "The Tender Offer--Procedures
For Accepting The Offer And Tendering Shares"), unless such Shares have been
tendered for the account of an Eligible Institution. If Shares have been
tendered pursuant to the procedures for book-entry transfer, as set forth in the
section of the Offer to Purchase captioned "The Tender Offer--Procedures For
Accepting The Offer And Tendering Shares," any notice of withdrawal must specify
the name and number of the account at the Book-Entry Transfer Facility to be
credited with the withdrawn Shares and must otherwise comply with the procedures
of the Book-Entry Transfer Facility. Withdrawals may not be revoked and any
Shares properly withdrawn will thereafter be deemed not to have been validly
tendered for purposes of the Offer. However, withdrawn Shares may be retendered
at any time prior to the Expiration Date by following one of the procedures
described in the section of the Offer to Purchase captioned "The Tender
Offer--Procedures For Accepting The Offer And Tendering Shares." All questions
as to the form and validity (including the time of receipt) of any notice of
withdrawal will be determined by the Purchaser, in its sole discretion, whose
determination will be final and binding.

    The information required to be disclosed by Rule 14d-6(d)(1) and
13e-3(e)(1) of the General Rules and Regulations under the Securities
Exchange Act of 1934, as amended, is contained in the Offer to Purchase and
is incorporated herein by reference.

    The Company has provided the Purchaser with the Company's stockholders list
and security position listings for the purpose of disseminating the Offer to
holders of Shares. The Offer to Purchase and the related Letter of Transmittal
and, if required, other relevant material will be mailed to record holders of
Shares whose names appear on the Company's stockholders list and will be
furnished to brokers, dealers, commercial banks, trust companies and similar
persons whose names, or the names of whose nominees, appear on the Company's
stockholders list or, if applicable, who are listed as participants in a
clearing agency's security position listing for subsequent transmittal to
beneficial owners of Shares.

    The receipt of cash for Shares pursuant to the Offer will be a taxable
transaction for U.S. federal income tax purposes.

    THE OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION THAT SHOULD BE READ CAREFULLY BEFORE ANY DECISION IS MADE
WITH RESPECT TO THE OFFER.

    Tendering stockholders of record who tender shares directly will not be
obligated to pay brokerage fees or commissions or, except as set forth in
Instruction 6 of the Letter of Transmittal, stock transfer taxes on the purchase
of Shares by the Purchaser pursuant to the Offer. Stockholders who hold their
Shares through a bank or a broker should check with such institution as to
whether it charges any service fees. The Purchaser will pay the expenses of the
Depositary, D.F. King & Co., Inc., who is acting as the information agent (the
"Information Agent"), and J.P. Morgan Securities Inc. and The Beacon Group
Capital Services, LLC, who are acting as dealer managers (collectively, the
"Dealer Managers") in connection with the Offer.

    Questions and requests for assistance or for additional copies of the Offer
to Purchase, the Letter of Transmittal and all other tender offer materials may
be directed to the Information Agent or the Dealer Managers as set forth below,
and copies will be furnished promptly at the Purchaser's expense. No fees or
commissions will be paid to brokers, dealers or any other persons (other than
the Dealer Managers and the Information Agent) for soliciting tenders of Shares
pursuant to the Offer.

                                       3

<PAGE>
                    THE INFORMATION AGENT FOR THE OFFER IS:

                             D.F. KING & CO., INC.
                          77 Water Street, 20th Floor
                               New York, NY 10005
                Bankers and Brokers call collect: (212) 269-5550
                   All Others Call Toll Free: (800) 290-6433

                     THE DEALER MANAGERS FOR THE OFFER ARE:

                          J.P. MORGAN SECURITIES INC.
                                 60 Wall Street
                               New York, NY 10260
                                 (877) 869-0656

                     THE BEACON GROUP CAPITAL SERVICES, LLC
                                399 Park Avenue
                               New York, NY 10022
                                 (212) 339-9100

March 13, 2000


<PAGE>
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYER.--Social Security numbers have nine digits separated by two hyphens: I.E.,
000-00-0000. Employer identification numbers have nine digits separated by only
one hyphen: I.E., 00-0000000. The table below will help determine the number to
give the Payer.

<TABLE>
- -----------------------------------------------------------
                                   GIVE THE
                                   SOCIAL SECURITY
FOR THIS TYPE OF ACCOUNT:          NUMBER OF--
- -----------------------------------------------------------
<S>                                <C>
 1. An individual's account        The individual
 2. Two or more individuals        The actual owner of the
   (joint account)                 account or, if combined
                                   funds, the first
                                   individual on the
                                   account(1)
 3. Husband and wife (joint        The actual owner of the
    account)                       account or, if joint
                                   funds, the first
                                   individual on the
                                   account(1)
 4. Custodian account of a minor   The minor(2)
    (Uniform Gift to Minors Act)
 5. Adult and minor (joint         The adult, or, if the
    account)                       minor is the only
                                   contributor, the
                                   minor(1)
 6. Account in the name of         The ward, minor, or
    guardian or committee for a    incompetent person(3)
    designated ward, minor or
    incompetent person
 7. a. The usual revocable         The grantor-trustee(1)
       savings trust account
       (grantor is also trustee)
   b. So-called trust account      The actual owner(1)
      that is not a legal or
      valid trust under State
      law
 8. Sole proprietorship account    The owner(4)
- -----------------------------------------------------------
                                   GIVE THE EMPLOYER
                                   IDENTIFICATION
FOR THIS TYPE OF ACCOUNT:          NUMBER OF--
<S>                                <C>
- -----------------------------------------------------------

 9. A valid trust, estate, or      The legal entity (Do not
    pension trust                  furnish the identifying
                                   number of the personal
                                   representative or
                                   trustee unless the legal
                                   entity itself is not
                                   designated in the
                                   account title.)(5)

10. Corporate account              The corporation

11. Religious, charitable, or      The organization
    educational organization
    account

12. Partnership account held in    The partnership
    the name of the business

13. Association, club or other     The organization
    tax-exempt organization

14. A broker or registered         The broker or nominee
    nominee

15. Account with the Department    The public entity
    of Agriculture in the name
    of a public entity (such as
    a State or local government,
    school district, or prison)
    that receives agricultural
    program payments
</TABLE>

(1) List first and circle the name of the person whose number you furnish.

(2) Circle the minor's name and furnish the minor's social security number.

(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.

(4) Show the name of the owner.

(5) List first and circle the name of the legal trust, estate, or pension trust.

NOTE: If no name is circled when there is more than one name, the number will be
      considered to be that of the first name listed.
<PAGE>
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
                                     PAGE 2

OBTAINING A NUMBER

If you don't have a taxpayer identification number or you don't know your
number, obtain Form SS-5, Application for a Social Security Number Card (for
individuals), or Form SS-4, Application for Employer Identification Number (for
businesses and all other entities), at the local office of the Social Security
Administration or the Internal Revenue Service and apply for a number.

PAYEES AND PAYMENTS EXEMPT FROM BACKUP WITHHOLDING

Payees specifically exempted from backup withholding on ALL payments include the
following (Section references are to the Internal Revenue Code):
    - A corporation.
    - A financial institution.
    - An organization exempt from tax under section 501(a), or an individual
      retirement plan, or a custodial account under section 403(b)(7).
    - The United States or any agency or instrumentality thereof.
    - A State, the District of Columbia, a possession of the United States, or
      any subdivision or instrumentality thereof.
    - A foreign government, a political subdivision of a foreign government, or
      any agency or instrumentality thereof.
    - An international organization or any agency, or instrumentality thereof.
    - A registered dealer in securities or commodities registered in the U.S. or
      possession of the U.S.
    - A real estate investment trust.
    - A common trust fund operated by a bank under section 584(a).
    - An exempt charitable remainder trust, or a non-exempt trust described in
      section 4947(a)(1).
    - An entity registered at all times under the Investment Company Act of
      1940.
    - A foreign central bank of issue.

Payments of dividends and patronage dividends not generally subject to backup
withholding include the following:
    - Payments to nonresident aliens subject to withholding under section 1441.
    - Payments to partnerships not engaged in a trade or business in the U.S.
      and which have at least one nonresident partner.
    - Payments of patronage dividends where the amount received is not paid in
      money.
    - Payments made by certain foreign organizations.
    - Payments made to a nominee.

Payments of interest not generally subject to backup withholding include the
following:
    - Payments of interest on obligations issued by individuals.

NOTE: You may be subject to backup withholding if this interest is $600 or more
and is paid in the course of the payer's trade or business and you have not
provided your correct taxpayer identification number to the payer.
    - Payments of tax-exempt interest (including exempt-interest dividends under
      section 852).
    - Payments described in section 6049(b)(5) to nonresident aliens.
    - Payments on tax-free government bonds under section 1451.
    - Payments made by certain foreign organizations.
    - Payments made to a nominee.

Exempt payees described above should file the Substitute Form W-9 to avoid
possible erroneous backup withholding. FILE THIS FORM WITH THE PAYER, FURNISH
YOUR TAXPAYER IDENTIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM,
SIGN AND DATE THE FORM AND RETURN IT TO THE PAYER.

Certain payments other than interest, dividends, and patronage dividends that
are not subject to information reporting are also not subject to backup
withholding. For details, see sections 6041, 6041A(a), 6042, 6044, 6045, 6049,
6050A and 6050N, and the regulations under those sections.

PRIVACY ACT NOTICE.--Section 6109 requires most recipients of dividend,
interest, or other payments to give taxpayer identification numbers to payers
who must report the payments to the IRS. The IRS uses the numbers for
identification purposes and to help verify the accuracy of tax returns. Payers
must be given the numbers whether or not recipients are required to file a tax
return. Payers must generally withhold 31% of taxable interest, dividend, and
certain other payments to a payee who does not furnish a taxpayer identification
number to a payer. Certain penalties may also apply.

PENALTIES

(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER.--If you fail
to furnish your taxpayer identification number to a payer, you are subject to a
penalty of $50 for each such failure unless your failure is due to reasonable
cause and not to willful neglect.

(2) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS. --If you fail to
include any portion of an includible payment for interest, dividends or
patronage dividends in gross income, such failure is strong evidence of
negligence. If negligence is shown, you will be subject to a penalty of 20% on
any portion of an underpayment attributable to that failure.

(3) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING.--If you
make a false statement with no reasonable basis which results in no imposition
of backup withholding, you are subject to a penalty of $500.

(4) CRIMINAL PENALTY FOR FALSIFYING INFORMATION.--Willfully falsifying
certifications or affirmations may subject you to criminal penalties including
fines and/or imprisonment.

                       FOR ADDITIONAL INFORMATION CONTACT
                      YOUR TAX CONSULTANT OR THE INTERNAL
                                REVENUE SERVICE.

<PAGE>

                                                          Exhibit 12(a)(10)



Investor Contact: 781-622-1111
Media Contact:    781-622-1252


       THERMO ELECTRON ANNOUNCES PROGRESS ON COMPANY REORGANIZATION


WALTHAM, Mass., March 6, 2000 - One month following its announcement of an
ambitious plan to simplify the company and focus solely on its core
measurement and detection instruments business, Thermo Electron Corporation
(NYSE-TMO) announced today that it has initiated the first steps required to
take three of its subsidiaries private.

     On Friday, the company's Thermo Instrument Systems Inc. (ASE-THI)
subsidiary filed with the Securities and Exchange Commission (SEC) the
materials necessary to take its Thermo Optek Corporation and ThermoQuest
Corporation businesses private through short-form mergers. The SEC must
complete its review of these materials before the mergers can be finalized.
Thermo Electron expects these mergers to be completed in the second quarter
of 2000.

     In addition, the company announced that its Thermedics Inc. (ASE-TMD)
subsidiary has commenced its previously announced cash tender offer of $15.50
per share for any and all outstanding shares of its Thermo Sentron Inc.
business. The offer and withdrawal rights will expire at midnight on
Thursday, March 30, 2000, unless the offer is extended.

     The goal of the tender offer is to bring Thermedics' and Thermo
Electron's combined equity ownership in Thermo Sentron to at least 90
percent. If Thermedics and Thermo Electron achieve this 90-percent-ownership
level, Thermo Sentron would then be spun into Thermedics through a
"short-form" merger at the same cash price as the tender offer. Thermedics
expects to complete the spin-in of Thermo Sentron in the second quarter of
2000. The tender offer for THermo Sentron and proposed subsequent short-form
merger require SEC clearance of necessary filings. The short-form merger
would not require Thermo Sentron board or shareholder approval.

     Thermo Electron is pursuing an aggressive timetable to complete its
reorganization plan and expects to commence tender offers for Metrika
Systems, ONIX Systems, Thermo BioAnalysis, and Thermedic Detection over the
next two weeks.

     Thermo Electron Corporation is a leading provider of analytical and
monitoring instruments used in a broad range of applications, from life
sciences research to telecommunications to food and beverage production. In
addition, Thermo Electron serves the healthcare market through a family of
medical products, and is a major producer of paper recycling systems and
provides water-clarification and fiber-recovery products and services. As
announced on January 31, 2000, the company has initiated a major
reorganization that would transform it into one publicly traded entity
focused on its core measurement and detection instruments business. The
company's medical products and paper recycling businesses will be spun off as
dividends to Thermo Electron shareholders. More information is available on
the Internet at http://www.thermo.com.


                                    -more-

<PAGE>


The following constitutes a "Safe Harbor" statement under the Private
Securities Litigation Reform Act of 1995: This press release contains
forward-looking statements that involve a number of risks and uncertainties.
Important factors that could cause actual results to differ materially from
those indicated by such forward-looking statements are set forth under the
heading "Forward-looking Statements" in Exhibit 13, to the company's annual
report on Form 10-K, for the year ended January 2, 1999. These include risks
and uncertainties relating to: the company's spinout and acquisition
strategies, competition, international operations, technological change,
possible changes in governmental regulations, capital spending and government
funding policies, and dependence on intellectual property rights.


                                    # # #




<PAGE>

                                                          Exhibit 12(a)(11)



Investor Contact: 781-622-1111
Media Contact:    781-622-1252


             THERMO INSTRUMENT SYSTEMS COMMENCES CASH TENDER OFFER
                              FOR ONIX SYSTEMS


WALTHAM, Mass., March 13, 2000 - Thermo Instrument Systems Inc. (ASE-THI), a
Thermo Electron company, announced today that it has commenced its previously
announced cash tender offer of $9.00 per share for any and all outstanding
shares of its ONIX Systems Inc. subsidiary. The offer and withdrawal rights
will expire at midnight on Friday, April 7, 2000, unless the offer is
extended. The tender offer is part of a major reorganization plan under which
Thermo Instrument's parent company, Thermo Electron Corporation (NYSE-TMO),
will spin in, spin off, and sell various businesses to focus solely on its
core measurement and detection instruments business.

     The complete terms and conditions of the offer are set forth in the
offer to purchase, letter of transmittal, and other related materials being
filed today with the Securities and Exchange Commission (SEC). Copies of the
offer and transmittal letter are being distributed to ONIX Systems
shareholders.

     The goal of the tender offer is to bring Thermo Instrument's and Thermo
Electron's combined equity ownership in ONIX Systems to at least 90 percent.
If Thermo Instrument and Thermo Electron achieve this 90-percent-ownership
level, ONIX Systems would then be spun into Thermo Instrument through a
"short-form" merger at the same cash price as the tender offer. Thermo
Instrument expects to complete the spin-in of ONIX Systems in the second
quarter of 2000.

     The tender offer and proposed subsequent short-form merger require SEC
clearance of necessary filings. The short-form merger would not require ONIX
Systems board or shareholder approval.

     Thermo Instrument Systems Inc. is a leading provider of analytical
instruments used to identify complex chemical compounds, toxic metals, and
other elements in a broad range of liquids and solids. The company also
developments and manufactures instruments used to monitor radioactivity and
air pollution; life science instruments and consumables; and imaging,
inspection, measurement, and control instruments for various industrial
processes. Thermo Instrument Systems is a public subsidiary of Thermo
Electron Corporation. More information is available on the Internet at
http://www.thermo.com/subsid/thil.html.

The following constitutes a "Safe Harbor" statement under the Private
Securities Litigation Reform Act of 1995: This press release contains
forward-looking statements that involve a number of risks and uncertainties.
Important factors that could cause actual results to differ materially from
those indicated by such forward-looking statements are set forth under the
heading "Forward-looking Statements" in Exhibit 13 to the company's annual
report on Form 10-K for the year ended January 2, 1999. These include risks
and uncertainties relating to: the company's acquisition and spinout
strategies, competition and technological change, intellectual property
rights and litigation, dependence on certain key industries and international
operations, possible changes in governmental regulations, capital spending
and government funding policies.

                                    # # #




<PAGE>

                                                                   Exhibit 12 b

                                                                   March 1, 2000

Thermo Instrument Systems Inc.
81 Wyman Street
Waltham, MA 02454
Attn:  Earl R. Lewis

Dear Earl:

     Reference is made to Thermo Instrument's proposed acquisitions of the
minority interest investment in each of its majority owned subsidiaries,
ThermoQuest Corporation, Thermo Optek Corporation, Thermo BioAnalysis
Corporation, Metrika Systems Corporation and ONIX Systems Inc. In connection
with those transactions, Thermo Electron Corporation intends to loan Thermo
Instrument up to $400,000,000 for the acquisition of such interests in each
of ThermoQuest Corporation, Thermo Optek Corporation, Thermo BioAnalysis
Corporation, Metrika Systems Corporation and ONIX Systems Inc. This loan will
be available at an interest rate equal to the 30-day Dealer Commercial Paper
Rate plus 150 basis points, set at the beginning of each month, provided such
rate shall be reduced to the Dealer Commercial Paper Rate plus 50 basis
points to the extent of any funds invested by Thermo Instrument's majority
owned subsidiaries in Thermo Electron's cash management arrangement. Interest
will be due and payable on a monthly basis and the loan will be payable in
full on September 1, 2000. If these terms are acceptable to you, please sign
the letter as indicated below to evidence your acceptance of the terms.

                                    Sincerely,
                                    THERMO ELECTRON CORPORATION

                                    /s/ Theo Melas-Kyriazi
                                    ----------------------
                                    Theo Melas-Kyriazi
                                    Vice President and Chief Financial Officer

ACCEPTED AND AGREED TO:

THERMO INSTRUMENT SYSTEMS INC.

/s/ Earl R. Lewis
- ---------------------------------
Earl R. Lewis
President and CEO


<PAGE>

                                                                   Exhibit 12 c

January 29, 2000

Board of Directors
Thermo Electron Corporation
81 Wyman Street
Post Office Box 9046
Waltham, MA  02454-0946

Attention:  Dr. Richard F. Syron
                Chairman and Chief Executive Officer

Special Committee of the
Board of Directors
Thermo Instrument Systems Inc.
81 Wyman Street
Post Office Box 9046
Waltham, MA  02454-0946

Attention:  Mr. Polyvios C. Vintiadis
                Director

Ladies and Gentlemen:

J.P. Morgan Securities Inc. ("J.P. Morgan") and The Beacon Group Capital
Services, LLC (collectively "we", "us" and "our") understand that Thermo
Instrument Systems Inc. ("Thermo Instrument"), a subsidiary of Thermo Electron
Corporation ("Thermo Electron"), proposes to acquire all of the outstanding
common stock, par value $.01 per share, (the "Shares") of ONIX Systems Inc. (the
"Company") not currently held by Thermo Electron or its subsidiaries from the
holders thereof at a purchase price of $9.00 per Share, net to the seller in
cash (the "Consideration"), pursuant to (i) an offer (the "Offer") by ONIX
Acquisition Inc. (the "Purchaser"), a wholly-owned subsidiary of Thermo
Instrument, to purchase all of the outstanding Shares and (ii) the subsequent
merger (the "Merger") of the Purchaser with and into the Company. You have
requested our joint opinion as to the fairness, from a financial point of view,
to Thermo Instrument and to Thermo Electron of the Consideration proposed to be
paid pursuant to the Offer and the Merger.

In arriving at our opinion, we have reviewed (i) certain publicly available
information concerning the business of the Company and of certain other
companies engaged in businesses deemed by us to be comparable to those of the
Company; (ii) the reported market

<PAGE>

                                      -2-

prices of the securities of certain other companies deemed by us to be
comparable to the Company; (iii) publicly available terms of certain
transactions involving companies deemed by us to be comparable to the Company
and the consideration paid for such companies; (iv) current and historical
market prices of the Shares; (v) the audited financial statements of Thermo
Instrument, Thermo Electron and the Company for the fiscal year ended January 2,
1999 and the unaudited financial statements of Thermo Instrument, Thermo
Electron and the Company for the period ended October 2, 1999; (vi) certain
agreements with respect to outstanding indebtedness or obligations of Thermo
Instrument, Thermo Electron and the Company; (vii) the terms of other business
combinations that we deemed relevant; and (viii) projections for the period from
October 3, 1999 through January 1, 2000 and for fiscal 2000 prepared by the
Company in November 1999 (the "2000 Projections").

In addition, we have held discussions with certain members of the managements of
Thermo Instrument, Thermo Electron and the Company with respect to certain
aspects of the Offer and the Merger, the past and current business operations of
the Company, the financial condition and future prospects and operations of the
Company and certain other matters we believed necessary or appropriate to our
inquiry. We have reviewed such other financial studies and analyses and
considered such other information as we deemed appropriate for the purposes of
this opinion.

In giving our opinion, we have relied upon and assumed, without independent
verification, the accuracy and completeness of all information that was publicly
available or was furnished to, or discussed with, us, by Thermo Instrument,
Thermo Electron or the Company or was otherwise reviewed by us, and we have not
assumed any responsibility or liability therefor. We have also assumed that
there have been no material changes in the Company's financial condition,
results of operations, business or prospects since the date of the most recent
financial statements made available to us. We have not conducted, and we have
not assumed any responsibility for conducting, any valuation, appraisal or
physical inspection of any assets or liabilities (contingent or otherwise), nor
have any such valuations or appraisals been provided to us. In relying on the
financial analyses, projections and estimates provided to, or discussed with,
us, we have assumed that they have been reasonably prepared based on assumptions
reflecting the best currently available estimates and judgments by management as
to the expected future financial performance of the Company. We have relied as
to all legal matters relevant to rendering our opinion upon the advice of
counsel.

Our opinion is necessarily based on economic, market and other conditions as in
effect on, and the information made available to us as of, the date hereof. It
should be understood that subsequent developments may affect the conclusions in
this opinion and that we do not have any obligation to update, revise or
reaffirm this opinion.

We have acted as financial advisors to Thermo Instrument and Thermo Electron
with respect to the proposed Offer and Merger and will receive a fee from Thermo
Electron for our services. We have also acted as financial advisors to Thermo
Electron for the purpose of advising Thermo Electron in connection with its
strategic alternatives, including the

<PAGE>

                                      -3-

proposed reorganization of Thermo Electron and its subsidiaries. As part of the
proposed reorganization of Thermo Electron, it is contemplated that Thermo
Electron will acquire the publicly-held minority interest in Thermo Instrument.
We will receive separate fees for services with respect to other elements of
Thermo Electron's reorganization, including acting as financial advisors to
Thermo Electron in connection with the acquisition of the publicly-held minority
interest in Thermo Instrument. These other fees include a minimum retainer for
each of us and additional compensation if some or all of the other elements of
Thermo Electron's reorganization are completed. In the ordinary course of their
businesses, J.P. Morgan and its affiliates may actively trade the debt and
equity securities of Thermo Instrument, Thermo Electron or the Company and their
affiliates for their own account or for the accounts of customers and,
accordingly, they may at any time hold long or short positions in such
securities.

On the basis of and subject to the foregoing, it is our opinion as of the date
hereof that the Consideration to be paid pursuant to the Offer and the Merger is
fair, from a financial point of view, to Thermo Instrument and to Thermo
Electron.

This letter is provided to the Special Committee of the Board of Directors of
Thermo Instrument and the Board of Directors of Thermo Electron in connection
with and for the purposes of their evaluation of the Offer and the Merger.
This opinion does not constitute a recommendation to any stockholder of the
Company as to whether such stockholder should tender its Shares in the Offer.
This opinion may not be disclosed, referred to, or communicated (in whole or
in part) to any third party for any purpose whatsoever except with our prior
written consent in each instance. We hereby consent to the filing of this
opinion as an exhibit to the Tender Offer Statement on Schedule TO to be
filed by Thermo Instrument, Thermo Electron and certain of their subsidiaries
and to the provision of this opinion to persons who request it as
contemplated by the Schedule TO.

Very truly yours,

J.P. MORGAN SECURITIES INC.

/s/ Jacques Aigrain
- --------------------------------
    Name:  Jacques Aigrain
    Title: Managing Director


THE BEACON GROUP CAPITAL SERVICES, LLC

/S/ THE BEACON GROUP CAPITAL SERVICES, LLC
- ------------------------------------------


<PAGE>

                                                                   Exhibit 12 g

                             [LOGO] Thermo Electron
                             ----------------------



<PAGE>


THE NEW THERMO ELECTRON
- -----------------------



                                   > Vision

                                   > Focus

                                   > Clarity

                                   > Growth

1                                                         [LOGO] Thermo Electron

<PAGE>

SHAREHOLDER VALUE
- -----------------

Medical    >   Dividend
Products

                                      Existing
  New      >   Stock          >    Thermo Electron
Thermo                               Shareholders


 Thermo
Fibertek   >   Dividend


2                                                         [LOGO] Thermo Electron

<PAGE>

OUR GOAL
- --------

                         To channel all our resources -

                                   financial,

                                     human,

                                technological -

                            to become the preeminent

                        instrument company in the world.

3                                                         [LOGO] Thermo Electron

<PAGE>

WHY INSTRUMENTS?
- ----------------

                          > Critical mass

                          > Strong market presence

                          > Experienced management

                          > Strong cash flow

                          > Broad technology platform

4                                                         [LOGO] Thermo Electron

<PAGE>

THE PLAN
- --------

     >    Sell businesses totaling $1.2 billion in revenues

     >    Spin off equity of Thermo Fibertek and new Medical Products company

     >    Spin in instrument companies

5                                                         [LOGO] Thermo Electron

<PAGE>

MAJOR DIVESTITURES
- ------------------

                             > Thermo Cardiosystems

                             > Trex Medical

                             > Thermo TerraTech

                             > Thermo Coleman

                             > Peek

6                                                         [LOGO] Thermo Electron

<PAGE>

PLAN PROCEEDS
- -------------
<TABLE>

<S>                               <C>
Proceeds from Divestitures        $ 1.0 BILLION

Cost of Spin Ins                  $(0.4 BILLION)
                                  --------------

Net Increase in Cash              $ 0.6 BILLION

</TABLE>

                             Invest all proceeds in
                             new instrument company

7                                                         [LOGO] Thermo Electron

<PAGE>

SPIN OFFS
- ---------

                        > Market leadership

                        > Experienced management

                        > Independent market identities

                        > Balanced product mix

                        > Strong growth prospects


8                                                         [LOGO] Thermo Electron

<PAGE>

MEDICAL PRODUCTS
- ----------------

                               Thermo Biomedical

                               Thermedics Medical



                          1999E Revenues: $335 million

9                                                         [LOGO] Thermo Electron

<PAGE>

MEDICAL PRODUCTS
- ----------------

[Collage of photos representing the various businesses within the new Medical
Products company, including neurodiagnostic testing, respiratory care, infant,
audiology products, wireless patient monitoring, and medical polymers.]

10                                                        [LOGO] Thermo Electron

<PAGE>

THERMO FIBERTEK
- ---------------

                                Thermo Fibertek

                                Thermo Fibergen



                          1999E Revenues: $225 million

11                                                        [LOGO] Thermo Electron

<PAGE>

THERMO FIBERTEK
- ---------------

[Collage of photos representing the various businesses within the new Thermo
Fibertek company, including papermaking and recycling equipment,
water-management systems, waste-recovery, and fiber-based consumer products and
composites.]

12                                                        [LOGO] Thermo Electron

<PAGE>

THERMO ECOTEK
- -------------

                         > Non-core asset

                         > Maximize value

                         > Goal: spin off in 1-2 years

13                                                        [LOGO] Thermo Electron

<PAGE>

- --------------------------------------------------------------------------------

                            Thermo Electron will be

                              a completely focused

                           instrument company in 2001


14                                                        [LOGO] Thermo Electron

<PAGE>

THERMO INSTRUMENT REVENUES
- --------------------------

(in millions)

[Bar chart (without actual revenue numbers) showing increasing revenues from the
Thermo Instrument business from 1986 to 1999 estimate, indicating in 1998 actual
revenues of $1.66 billion.]

15                                                        [LOGO] Thermo Electron

<PAGE>

THERMO INSTRUMENT EBITDA
- ------------------------
(in thousands)

[Bar chart (without actual EBITDA numbers) showing increasing EBITDA for the
Thermo Instrument business from 1986 to 1999 estimate, indicating in 1998 actual
EBITDA of $294 million.]

16                                                        [LOGO] Thermo Electron

<PAGE>

THERMO INSTRUMENT STOCK PRICE
- -----------------------------
(adjusted for splits)

[Line graph generally illustrating range of Thermo Instrument stock price
(without providing specific stock prices) from 1986 to present ranging from
approximately $2.00 per share to approximately $36.00 per share during the time
period shown.]

17                                                        [LOGO] Thermo Electron

<PAGE>

GROWTH PLAN 2000
- ----------------

                      > Manage according to market served

                      > New incentives for managers

                      > Divest of slow-growth units

                      > Continue strategic acquisitions

                      > Initiate e-commerce

18                                                        [LOGO] Thermo Electron

<PAGE>

OLD ORGANIZATION
- ----------------

[Graphic of partial depiction of old organizational chart of Thermo Instrument
Systems.]

19                                                        [LOGO] Thermo Electron

<PAGE>


NEW ORGANIZATION
- ----------------

                          1999E Revenues: $2.3 billion
<TABLE>
<CAPTION>

     Life                                                           Measurement
   Sciences                       Photonics                         and Control
1999E Revenues                 1999E Revenues                     1999E Revenues
<S>                             <C>                                <C>
 $800 million                   $800 million                       $700 million

</TABLE>

20                                                        [LOGO] Thermo Electron

<PAGE>

LIFE SCIENCES - GOALS
- ---------------------

                         > Internal revenue growth >10%

                         > R&D commitment 8-10%

                         > Technology acquisitions

                         > Maintain 16% ROS

21                                                        [LOGO] Thermo Electron

<PAGE>

PHOTONICS - GOALS
- -----------------

                         > Internal revenue growth 7-8%

                         > R&D commitment

                           - Telecom >10%

                           - Balance   7%

                         > Instrument acquisitions

                         > Maintain strong cash flow

                         > Improve ROS to 13%

22                                                        [LOGO] Thermo Electron

<PAGE>

MEASUREMENT AND CONTROL - GOALS
- -------------------------------

                         > Internal revenue growth 4-5%

                         > R&D commitment 4-5%

                         > Double ROS to 10%

                         > Focus on cash flow

                         > Divestitures

23                                                        [LOGO] Thermo Electron

<PAGE>

NEW INCENTIVES FOR MANAGERS
- ---------------------------

                          > New bonus plan

                            - Growth

                            - Cash

                            - Combination

                          > Increase cash compensation

                          > Continue options in parent

24                                                        [LOGO] Thermo Electron

<PAGE>

DIVEST SLOW-GROWTH UNITS
- ------------------------

              > Detailed review of measurement and control sector

              > Sale of

                - Gould

                - NIS

                - Pharos Marine

25                                                        [LOGO] Thermo Electron

<PAGE>

RECENT ACQUISITIONS
- -------------------

<TABLE>
<CAPTION>

<S>                     <C>                   <C>                 <C>
Spectra Physics AB  Feb. 1999                 BioStar             Nov. 1998
- -----------------------------                 -----------------------------
Laser-based instruments                       Point-of-Care Diagnostics
                                              -----------------------------
Purchase Price          $351M
Current Market Value
     SPLI               $450-500M
     Other              $350M                 Interactiva         Oct. 1999
     FLIR               $ 70M                 -----------------------------
- -----------------------------                 Biochips - e-commerce
Total Value             $870-920M             -----------------------------

</TABLE>

26                                                       [LOGO] Thermo Electron

<PAGE>

EBUSINESS - WWW.INFORMATION2.NET
- --------------------------------

                             Competitive Advantages

                          > Leverage knowledge assets

                          > Breadth of "touch points"

                          > Mining: metals to genomes

                          > One-to-one marketing

27                                                        [LOGO] Thermo Electron

<PAGE>

WELL-POSITIONED VS. COMPETITORS
- -------------------------------

[Segmented bar chart showing how Thermo Instrument and its competitors compare
in terms of the industries they serve.]

Source McKinsey & Co.

<TABLE>

<S>                                <C>                   <C>
    Thermo Instrument              Life Sciences         40%
                                   Communications         9%
                                   Environmental         17%
                                   Industrial            34%

    Agilent                        Life Sciences          7%
                                   Communications        50%
                                   Environmental          5%
                                   Non Instrument        38%

    Waters                         Life Sciences         60%
                                   Environmental         40%

    Varian                         Life Sciences         35%
                                   Environmental         35%
                                   Non Instrument        30%

    Perkin Elmer                   Life Sciences         22%
                                   Environmental         13%
                                   Industrial            26%
                                   Non Instrument        39%

</TABLE>

28                                                        [LOGO] Thermo Electron

<PAGE>

VALUATION
- ---------

                                   EV/EBITDA

[Bar chart showing how Thermo Instrument has been valued by industry analysts in
terms of EV/EBITDA compared to its competitors based on trailing 12 months
EBITDA.]


Source:  Industry Analysts


Chart reflects ratio of EV (Enterprise Value)/EBITDA as follows:

<TABLE>

<S>                  <C>
   THI                8.0
   Agilent           24.0
   Waters            19.3
   Varian            20.2
   Perkin Elmer      12.0
   Mean              18.9

</TABLE>

29                                                        [LOGO] Thermo Electron

<PAGE>

INSTRUMENTS PROVIDE KNOWLEDGE
- -----------------------------

                                   You cannot

                              improve and control

                             unless you can measure

                                   and detect


30                                                        [LOGO] Thermo Electron
<PAGE>



OLD STRUCTURE
- ---------------------------------------------------------------------------

[Graphic showing the old corporate structure of Thermo Electron indicating
Thermo Electron subsidiaries with minority investors as follows:]

<TABLE>

<S> <C>   <C>
Thermo Electron
    Thermo Instrument
          Thermo Quest
          ONIX Systems
          Thermo Spectra
          Thermo Optek
          Thermo BioAnalysis
          Metrika Systems
          Thermo Vision

    Thermo Coleman
          Thermo Information Solutions

    Thermo Biomedical

    Thermo Ecotek
          Thermo Trilogy

    Thermedics
          Thermo Sentron
          Thermedics Detection
          Thermo Cardiosystems
          Thermo Voltek

    Thermo Trex
          Trex Medical
          Trex Communications
          ThermoLase

    Thermo Fibertek
          Thermo Fibergen

    Thermo Power
          Thermolyte

    Thermo Terra Tech
          The Randers Group
          Thermo EuroTech
          Thermo Retec

</TABLE>

31                                                       [LOGO] Thermo Electron
<PAGE>

NEW STRUCTURE
- -------------

The term Thermo Electron superimposed over image of man looking through a
telescope, representing new Thermo corporate structure.

32                                                        [LOGO] Thermo Electron

<PAGE>

THE NEW THERMO ELECTRON
- -----------------------

                             > Market focus

                             > Simple structure

                             > Tightly managed

                             > Dedicated resources

33                                                        [LOGO] Thermo Electron



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