Exhibit 3(i)
                            CERTIFICATE OF AMENDMENT
                                       OF
                      RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                         THERMO INSTRUMENT SYSTEMS INC.

             Thermo Instrument Systems Inc. (the "Corporation"), a
        corporation organized and existing under the laws of the State of
        Delaware, hereby certifies as follows, pursuant to Section 242 of
        the General Corporation Law of the State of Delaware:

             1.   That Article FOURTH of the Restated Certificate of
        Incorporation of the Corporation, as restated on March 1, 1994,
        is hereby amended to increase the number of authorized shares of
        the Corporation's Common Stock, $.10 par value per share, from
        125 million shares to 250 million shares and that such amendment
        is hereby effected by deleting said Article in its entirety and
        inserting the following in substitution therefor:

             "FOURTH:  The total number of shares of stock which the
                       Corporation shall have authority to issue is:

                       Two Hundred Fifty Million (250,000,000) shares,
                       and the par value of each such share in Ten Cents
                       ($.10)."

             2.   That the Board of Directors of the Corporation at a
        meeting held on March 13, 1996, duly adopted the following
        resolutions:

        RESOLVED,      that it is in the best interests of the
                       Corporation that the authorized common stock of
                       the Corporation, $.10 par value, be increased to
                       250 million shares, and that, upon the approval of
                       such increase by the Corporation's Stockholders,
                       the proper officers of the Corporation be, and
                       each of them hereby are, authorized, empowered and
                       directed to execute on behalf of the Corporation a
                       Certificate of Amendment to the Corporation's
                       Restated Certificate of Incorporation to reflect
                       such increase, and to file, or cause to be filed,
                       such Certificate of Amendment with the Secretary
                       of State of the State of Delaware.

        RESOLVED,      that the Board of Directors recommend to the
                       Stockholders for approval at the Annual Meeting
                       the increase in authorized shares of the
                       Corporation's common stock to 250 million shares
                       as previously approved by the Directors.

             3.   That on May 19, 1996, at the Corporation's Annual
        Meeting of Stockholders, the Amendment to the Corporation's
        Restated Certificate of Incorporation was duly adopted by the
        affirmative vote of Stockholders of the Corporation holding a
PAGE

        majority of the shares of Common Stock, $.10 par value per share,
        of the Corporation in accordance with the provisions of Section
        242 of the General Corporation Law of the State of Delaware.

             IN WITNESS WHEREOF, this Certificate of Amendment has been
        executed on behalf of the undersigned corporation by its duly
        authorized officer and attested to by its duly authorized
        Secretary this _____ day of May, 1996.


                                           THERMO INSTRUMENT SYSTEMS INC.

                                           By:  /s/ Arvin H. Smith
                                              -------------------------
                                                Arvin H. Smith
                                                President and
                                                Chief Executive Officer


        ATTEST:

        By:  /s/ Sandra L. Lambert
           -----------------------------
             Sandra L. Lambert
             Secretary