Exhibit 3.1


                     RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                         THERMO INSTRUMENT SYSTEMS INC.

  Thermo Instrument Systems  Inc., a corporation  organized and existing  under
the laws of the State of Delaware, hereby certifies as follows:  The corporation
was originally incorporated under the name "Thermo Scientific Systems Inc."  and
the date  of  filing of  its  original  Certificate of  Incorporation  with  the
Secretary of the State of Delaware was May 28, 1986.  This Restated  Certificate
of Incorporation restates and  integrates all amendments  to the Certificate  of
Incorporation of this  corporation, and  has been  duly adopted  by the  written
consent of  the majority  stockholder  of this  corporation in  accordance  with
Sections 228 and 245 of the General Corporation Law of the State of Delaware.

FIRST.   The name of the corporation shall be:

         THERMO INSTRUMENT SYSTEMS INC.

SECOND.  Its registered office in the State of Delaware is 1013 Centre Road, in
         the City of Wilmington, County of New Castle 19805, and its registered
         agent at such address is CORPORATION SERVICE COMPANY.

THIRD    The purpose or purposes of the corporation shall be:
         To engage in any lawful act or activity for which corporations may be 
         organized under the General Corporation Law of the State of Delaware.

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

         One Hundred Twenty-Five Million (125,000,000) shares, and the par 
         value of each such share is Ten Cents ($.10).

FIFTH.   The Board of Directors shall have the power to adopt, amend or repeal 
         the by-laws.

SIXTH.   No director shall be personally liable to the corporation or its 
         stockholders for monetary damages for any breach of fiduciary duty by 
         such director as a director.  Notwithstanding the foregoing sentence, 
         a director shall be liable to the extent provided by applicable law 
         (i) for breach of the director's duty of loyalty to the corporation or
         its stockholders, (ii) for acts or omissions not in good faith or 
         which involve intentional misconduct or a knowing violation of law, 
         (iii) pursuant to Section 174 of the Delaware General Corporation Law 
         or (iv) for any transaction from which the director derived an 
         improper personal benefit.  No amendment to or repeal of this Article 
         SIXTH shall apply to or have any effect on the liability or alleged 
         liability of any director of the corporation for or with respect to 
         any acts or omissions of such director occurring prior to such 
         amendment.


  IN WITNESS WHEREOF, this Restated Certificate of Incorporation has been
executed on behalf of the undersigned corporation by its duly authorized officer
PAGE

and attested to by its duly authorized Secretary this 28th day of February,
1994.



                                             THERMO INSTRUMENT SYSTEMS INC.



                                             By:  Arvin H. Smith           
                                                  --------------------------
                                                  Arvin H. Smith, President




ATTEST:


By:  Sandra L. Lambert           
     ----------------------------
     Sandra L. Lambert, Secretary