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                                                                   EXHIBIT 3.1.b
 
            CERTIFICATE OF AMENDMENT OF CERTIFICATE OF INCORPORATION
 
                                       OF
 
                         MANCHESTER EQUIPMENT CO., INC.
 
                            UNDER SECTION 805 OF THE
                            BUSINESS CORPORATION LAW
 
     We the undersigned, BARRY R. STEINBERG, the President of MANCHESTER
EQUIPMENT CO., INC., and JOEL ROTHLEIN, the Assistant Secretary thereof, hereby
certify:
 
     FIRST:   The name of the Corporation is MANCHESTER EQUIPMENT CO., INC.
 
     SECOND:  The Certificate of Incorporation was filed by the Department of
State on August 21, 1973.
 
     THIRD:   The Certificate of Incorporation is amended as authorized by
Section 801- of the Business Corporation Law to increase the number of shares
from 200 without par value, all of one class, to 5,000 shares without par value
all of one class. Paragraph 3 of the Certificate of Incorporation which refers
to the authorized shares is amended to read as follows:
 
        "The aggregate number of shares which the Corporation shall have
        authority to issue is 5,000 shares of common stock without par value."
 
     FOURTH:   The changes included in the Certificate of Change were authorized
and approved by the Board of Directors and thereafter by vote of a majority of
shareholders.
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     IN WITNESS WHEREOF the President and Assistant Secretary, respectfully
hereunder set their hands and seals this 29th day of November 1984.
 
                                          MANCHESTER EQUIPMENT CO., INC.
 
                                          By: /s/  BARRY R. STEINBERG
 
                                            ------------------------------------
                                            BARRY R. STEINBERG - President
 
                                          By: /s/  JOEL ROTHLEIN
 
                                            ------------------------------------
                                            JOEL ROTHLEIN - Assistant Secretary
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STATE OF NEW YORK  )
                   )
COUNTY OF NASSAU   )
 
     BARRY R. STEINBERG and JOEL ROTHLEIN, being duly sworn, depose and say that
deponents are the President and Assistant Secretary respectively of MANCHESTER
EQUIPMENT CO., INC., the corporation named within; that deponents have read the
foregoing Certificate of Amendment of Certificate of Incorporation and know the
contents thereof; and that the same is true to deponents own knowledge.
 
                                          --------------------------------------
                                          BARRY R. STEINBERG - President
 
                                          --------------------------------------
                                          JOEL ROTHLEIN - Assistant Secretary