<PAGE>

                                                                    EXHIBIT 10.1

                                                         [CONFORMED AS EXECUTED]

                       FIRST AMENDMENT TO CREDIT AGREEMENT

                  FIRST AMENDMENT TO CREDIT AGREEMENT (this "Amendment"), dated
as of April 23, 2003, among AMETEK, INC. (the "Borrower"), the lending
institutions party to the Credit Agreement referred to below (the "Banks"),
WACHOVIA BANK, N.A. (f/k/a First Union National Bank) and PNC BANK, NATIONAL
ASSOCIATION, as Syndication Agents (the "Syndication Agents"), DEUTSCHE BANK
TRUST COMPANY AMERICAS (f/k/a Bankers Trust Company), as Documentation Agent
(the "Documentation Agent"), and JPMORGAN CHASE BANK (f/k/a The Chase Manhattan
Bank), as Administrative Agent (the "Administrative Agent"). All capitalized
terms used herein and not otherwise defined shall have the respective meanings
provided such terms in the Credit Agreement.

                              W I T N E S S E T H:

                  WHEREAS, the Borrower, the Banks, the Syndication Agents, the
Documentation Agent and the Administrative Agent are parties to a Credit
Agreement, dated as of September 17,2001 (the "Credit Agreement"); and

                  WHEREAS, the parties hereto wish to amend the Credit Agreement
as herein provided;

                  NOW, THEREFORE, it is agreed:

I.       Amendment.

                  1.       Section 1.01 (a) of the Credit Agreement is hereby
amended by deleting the word "Dollars" appearing at the end of said Section and
inserting the following text in lieu thereof:

                  "an Approved Currency, provided that the aggregate outstanding
                  principal amount of all Revolving Loans denominated in a
                  Primary Alternate Currency shall not exceed $100,000,000 at
                  any time"

                  2.       Section 1.01 (b) of the Credit Agreement is hereby
amended by (i) deleting the comma at the end of the first proviso in the first
sentence of said Section and (ii) deleting the second proviso of said sentence
in its entirety.

                  3.       Section 1.05(a) of the Credit Agreement is hereby
amended by deleting the word "Dollars" appearing in clause (x) of the second
sentence of said Section and inserting the text "an Approved Currency as
specified in such Notice of Borrowing" in lieu thereof.

                  4.       Section 1.07 of the Credit Agreement is hereby
amended by (i) deleting the text "and" appearing at the end of clause (ii) of
the proviso contained in said Section and inserting a comma in lieu thereof and
(ii) inserting the text "and (iv) Revolving Loans denominated in a Primary
Alternate Currency may not be converted into Base Rate Loans" immediately
following the text "1.02" appearing in the proviso contained in said Section.

<PAGE>

                  5.       Section 1.09(b) of the Credit Agreement is hereby
amended by deleting said Section in its entirety and inserting the following
text in lieu thereof:

                           "(b) The unpaid principal amount of each Eurodollar
                  Loan shall bear interest from and including the date of the
                  Borrowing thereof until the earlier of (i) maturity (whether
                  by acceleration or otherwise) and (ii) conversion of such
                  Eurodollar Loan to a Base Rate Loan pursuant to Section
                  1.07,1.10 or 1.1 l(b), as applicable, at a rate per annum
                  which shall, during each Interest Period applicable thereto,
                  be equal to the sum of the relevant LIBOR for such Interest
                  Period, plus the Applicable Margin, as in effect from time to
                  time."

                  6.       Section 1.10 of the Credit Agreement is hereby
amended by inserting the following text immediately after the text "Interest
Period" appearing at the end of said Section:

                  ", provided that if such Eurodollar Loans are denominated in a
                  Primary Alternate Currency then such Eurodollar Loans shall
                  not convert to Base Rate Loans but shall instead be prepaid
                  by the Borrower on the last day of such Interest Period".

                  7.       Section 1.11 (a) of the Credit Agreement is hereby
amended by deleting the text "clause (i)" appearing in clause (x) of said
Section and inserting the text "clauses (i) and (iv)" in lieu thereof.

                  8.       Section l.ll(a)(i) of the Credit Agreement is hereby
amended by (i) deleting the first reference to "the Eurodollar Rate" appearing
in said Section and inserting the text "any LIBOR" in lieu thereof, (ii)
deleting the second reference to "the Eurodollar Rate" appearing in said Section
and inserting the text "US LIBOR" in lieu thereof, (iii) deleting the text
"London" appearing in said Section and inserting the text "relevant" in lieu
thereof, (iv) deleting the third reference to "Eurodollar" appearing in said
Section and (v) deleting the third reference to "Eurodollar Rate" appearing in
said Section and inserting the text "the respective LIBOR" in lieu thereof.

                  9.       Section l.ll(a)(ii) of the Credit Agreement is hereby
amended by (i) deleting the text "London" appearing in clause (y) of said
Section and inserting the text "relevant" in lieu thereof, (ii) deleting the
text "Eurodollar" appearing in clause (y) of said Section and (iii) deleting the
text "or" appearing at the end of said Section.

                  10.      Section l.ll(a)(iii) of the Credit Agreement is
hereby amended by (i) deleting the text "London" appearing in said Section and
inserting the text "relevant" in lieu thereof, (ii) deleting the second
reference to "Eurodollar" appearing in said Section and (iii) inserting the text
"or" immediately after the semi-colon appearing at the end of said Section.

                  11.      Section 1.11 (a) of the Credit Agreement is hereby
further amended by inserting the following new clause (iv) immediately after
clause (iii) of said Section:

                                      -2-

<PAGE>

                  "(iv) at any time that any Approved Alternate Currency is not
                  available in sufficient amounts, as determined in good faith
                  by the Administrative Agent, to fund any Borrowing of Loans
                  denominated in such Approved Alternate Currency;"

                  12.      The concluding unnumbered paragraph of Section 1.11
(a) of the Credit Agreement is hereby amended by (i) inserting the text "or
(iv)" immediately after the reference to "clause (i)" appearing in the first
sentence of said Section, (ii) re-lettering clauses (x), (y) and (z) appearing
in the second sentence of said Section as clauses (w), (x) and (y),
respectively, (iii) deleting the reference to "the Eurodollar Rate" appearing in
the second sentence of said Section and inserting the text "US LIBOR" in lieu
thereof, (iv) deleting the word "and" appearing immediately before the reference
to the old clause "(z)" in said Section and (v) inserting the following new
clause (z) immediately before the period appearing at the end of said Section:

                           "and (z) in the case of clause (iv) above, Loans in
                  the affected Approved Alternate Currency shall no longer be
                  available until such time as the Administrative Agent notifies
                  the Borrower and the Banks that the circumstances giving rise
                  to such notice by the Administrative Agent no longer exist and
                  any Notice of Borrowing or Notice of Conversion given by the
                  Borrower with respect to any Loans denominated in such
                  Approved Alternate Currency which have not yet been incurred
                  shall be deemed rescinded by the Borrower".

                  13.      Section l.ll(b) of the Credit Agreement is hereby
amended by deleting said Section in its entirety and inserting the following
text in lieu thereof:

                           "(b) At any time that any Eurodollar Loan or
                  Competitive Bid Loan is affected by the circumstances
                  described in Section l.ll(a)(ii) or (iii), the Borrower may
                  (and in the case of a Eurodollar Loan or Competitive Bid Loan
                  affected pursuant to Section l.ll(a)(iii), shall) either (i)
                  if the affected Eurodollar Loan or Competitive Bid Loan is
                  then being made pursuant to a Borrowing, cancel said Borrowing
                  by giving the Administrative Agent telephonic notice
                  (confirmed promptly in writing) thereof on the same date that
                  the Borrower was notified by a Bank pursuant to Section
                  l.ll(a)(ii) or (iii), (ii) if the affected Eurodollar Loan or
                  Competitive Bid Loan is then outstanding, upon at least three
                  Business Days' notice to the Administrative Agent, (A) in the
                  case of Eurodollar Loans denominated in Dollars, require the
                  affected Bank to convert each such Eurodollar Loan into a Base
                  Rate Loan (which conversion, in the case of the circumstances
                  described in Section l.ll(a)(iii), shall occur no later than
                  the last day of the Interest Period then applicable to such
                  Eurodollar Loan (or such earlier date as shall be required by
                  applicable law)), and (B), in the case of Eurodollar Loans
                  denominated in a Primary Alternate Currency, repay all such
                  Eurodollar Loans in full or (iii) if the affected Competitive
                  Bid Loan is then outstanding, prepay such Competitive Bid Loan
                  in full (which prepayment may be made with the proceeds of
                  Revolving Loans); provided that if more than one Bank is
                  affected at any time, then all affected Banks must be treated
                  the same pursuant to this Section l.ll(b)."

                                      -3-

<PAGE>

                  14.      Section 1.11(d) of the Credit Agreement is hereby
amended by deleting the text "the Eurodollar Rate" appearing in said Section and
inserting the text "any LIBOR" in lieu thereof.

                  15.      Section 1.12 of the Credit Agreement is hereby
amended by (i) deleting the first reference to "the Eurodollar Rate" appearing
in said Section and inserting the text "any LIBOR" in lieu thereof and (ii)
deleting the second reference to "the Eurodollar Rate" appearing in said Section
and inserting the text "the respective LIBOR" in lieu thereof.

                  16.      Section 4.02(A)(a)(ii) of the Credit Agreement is
hereby amended deleting said Section in its entirety and inserting the following
text in lieu thereof:

                           "(ii) If on any date the aggregate outstanding
                  principal amount of Revolving Loans denominated in Primary
                  Alternate Currencies (after giving effect to all other
                  repayments thereof on such date) is greater than $105,000,000,
                  the Borrower shall repay on such date the principal of such
                  Revolving Loans in an aggregate amount equal to such aggregate
                  outstanding principal amount in excess of $100,000,000."

                  17.      Section 4.02(A)(a)(iii) of the Credit Agreement is
hereby amended by (i) inserting the text "Revolving Loans and" immediately
before the first appearance of the text "Competitive Bid Loans" in said Section
and (ii) inserting the text "Revolving Loans," immediately before the second
appearance of the text "Competitive Bid Loans" in said Section.

                  18.      Section 4.02(B) of the Credit Agreement is hereby
amended by inserting the text "denominated in Dollars" immediately after the
first reference to "Eurodollar Loans" appearing in clause (iii) of said Section.

                  19.      Section 10 of the Credit Agreement is hereby amended
by deleting the definition of "Eurodollar Rate" appearing in said Section.

                  20.      The definition of "Interest Rate Basis" appearing in
Section 10 of the Credit Agreement is hereby amended by deleting the text
"Eurodollar Rate" appearing therein and inserting the text "respective LIBOR" in
lieu thereof.

                  21.      Section 10 of the Credit Agreement is hereby further
amended by inserting the following new definitions in the appropriate
alphabetical order:

                           "Approved Currency" shall mean each of Dollars and
         each Primary Alternate Currency.

                           "Associated Cost Rate" shall mean, with respect to
         each Interest Period for Loans denominated in Pounds Sterling, the
         costs (expressed as a percentage rounded up to the nearest four decimal
         places and as determined on the first day of such Interest Period and
         any three month anniversary thereof by the Administrative Agent) of
         compliance with then existing requirements of the Bank of England in
         respect of Loans denominated in Pounds Sterling.

                                      -4-

<PAGE>

                           "Euribor" shall mean, for each Interest Period
         applicable to any Loan denominated in Euros, the rate per annum that
         appears on Reuters Page EURIBOR-01 (or any successor page) at
         approximately 10:00 A.M. (London time) on the date which is two
         Business Days prior to the commencement of such Interest Period or (ii)
         if such rate is not shown on Reuters Page EURIBOR-01 (or any successor
         page), the average offered quotation to four prime banks in the
         Euro-zone interbank market by JPMorgan Chase for Euro deposits of
         amounts comparable to the principal amount of Loans denominated in
         Euros to be as part of such Borrowing with maturities comparable to the
         Interest Period to be applicable to such Loan (rounded upward to the
         next whole multiple of 1/16 of 1%), determined as of 10:00 A.M. (London
         time) on the date which is two Business Days prior to the commencement
         of such Interest Period.

                           "Euro" shall mean the single currency of
         participating member states of the European Union.

                           "JPMorgan Chase" shall mean JPMorgan Chase Bank.

                           "LIBOR" shall mean (i) with respect to any Borrowing
         of Revolving Loans of an Approved Currency, the relevant interest rate,
         i.e., Euribor, Sterling LIBOR or US LIBOR, (ii) with respect to any
         Competitive Bid Loans of an Approved Alternate Currency, such rate per
         annum as may be agreed upon by the respective Borrower and the Bidder
         Bank, and (iii) with respect to a Competitive Bid Loan that is a Spread
         Borrowing priced by reference to any LIBOR, the arithmetic average
         (rounded to the nearest 1/100 of 1%) of the offered rates for deposits
         in Dollars for the applicable Interest Period (or the period closest to
         such applicable Interest Period) which appear on Dow Jones Telerate
         Screen 3740 or 3750) with maturities comparable to the Interest Period
         to be applicable to such Competitive Bid Loan, determined as of 10:00
         A.M. (London time) on the date which is two Business Days prior to the
         commencement of such Interest Period.

                           "Pounds Sterling" shall mean freely transferable
         lawful money of the United Kingdom.

                           "Primary Alternate Currency" shall mean each of
         British Pounds Sterling and Euros.

                           "Sterling LIBOR" shall mean, with respect to each
         Interest Period for any Loan denominated in Pounds Sterling, (I) the
         rate per annum that appears on page 3750 (or other appropriate page if
         such currency does not appear on such page) of the Dow Jones Telerate
         Screen (or any successive page) with maturities comparable to such
         Interest Period as of 11:00 A.M. (London time) on the date which is the
         commencement date of such Interest Period or, if such a rate does not
         appear on page 3750 (or such other appropriate page) of the Dow Jones
         Telerate Screen (or any successor page) the offered quotations to
         first-class banks in the London interbank Eurodollar market by JPMorgan
         Chase for Pounds Sterling deposits of amounts in same day funds
         comparable to the outstanding principal amount of such Loans with
         maturities comparable to such Interest Period determined as of 11:00
         A.M. (London time) on the date which is the

                                      -5-

<PAGE>

         commencement of such Interest Period plus (II) the Associated Cost Rate
         for such Loans for such Interest Period.

                  "US LIBOR" shall mean for each Interest Period applicable to a
         Loan denominated in Dollars (other than a Base Rate Loan), the rate per
         annum that appears on page 3750 of the Dow Jones Telerate Screen (or
         any successor page) for Dollar deposits with maturities comparable to
         such Interest Period as of 11:00 A.M. (London time) on the date which
         is two Business Days prior to the commencement of such Interest Period
         or, if such a rate does not appear on page 3750 of the Dow Jones
         Telerate Screen (or any successor page), the offered quotations to
         first-class banks in the London interbank market by JPMorgan Chase for
         Dollar deposits of amounts in same day funds comparable to the
         outstanding principal amount of such Dollar denominated Loan with
         maturities comparable to such Interest Period determined as of 11:00
         A.M. (London time) on the date which is two Business Days prior to the
         commencement of such Interest Period.

                  22.      Section 12.07(d) of the Credit Agreement is hereby
amended by inserting the text "Revolving Loans or" immediately before the text
"Competitive Bid Loans" appearing in said Section.

II.      Miscellaneous.

         1.       In order to induce the Banks to enter into this Amendment, the
Borrower hereby represents and warrants that:

                           (a) on the Amendment Effective Date, no Default or
         Event of Default exists, both before and after giving effect to this
         Amendment; and

                           (b) on and as of the Amendment Effective Date, all
         representations and warranties contained in the Credit Agreement or the
         other Credit Documents are true and correct in all material respects,
         both before and after giving effect to this Amendment.

         2.       This Amendment is limited as specified and shall not
constitute a modification, acceptance or waiver of any other provision of the
Credit Agreement or any other Credit Document.

         3.       This Amendment may be executed in any number of counterparts
and by the different parties hereto on separate counterparts, each of which
counterparts when executed and delivered shall be an original, but all of which
shall together constitute one and the same instrument. A complete set of
counterparts shall be lodged with the Borrower and the Administrative Agent.

         4.       THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAW OF THE
STATE OF NEW YORK.

         5.       This Amendment shall become effective on the date (the
"Amendment Effective Date") when the Borrower and the Required Banks shall have
signed a counterpart hereof

                                      -6-

<PAGE>

(whether the same or different counterparts) and shall have delivered (including
by way of facsimile transmission) the same to the Administrative Agent at its
Notice Office.

                                 *    *    *

                                      -7-

<PAGE>

                   IN WITNESS WHEREOF, the parties hereto have caused their duly
authorized officers to execute and deliver this Amendment as of the date first
above written.

                                      AMETEK, INC.

                                      By: /s/ Deirdre D. Saunders
                                          --------------------------------------
                                          Title: Vice President and Treasurer

                                      JPMORGAN CHASE BANK (f/k/a The Chase
                                        Manhattan Bank),
                                        Individually and as Administrative Agent

                                      By: /s/ Randolph Cates
                                          --------------------------------------
                                          Title: Vice President

                                      WACHOVIA BANK, N.A. (f/k/a First Union
                                        National Bank),
                                        Individually and as a Syndication Agent

                                      By: /s/ Sarah T. Warren
                                          --------------------------------------
                                          Title: Vice President

                                      PNC BANK, NATIONAL ASSOCIATION,
                                        Individually and as a Syndication Agent

                                      By: /s/ Denise D. Killen
                                          --------------------------------------
                                          Title: Vice President

                                      DEUTSCHE BANK TRUST COMPANY
                                        AMERICAS (f/k/a Bankers Trust
                                        Company),
                                        Individually and as Documentation Agent

                                      By: /s/ Scottye Lindsey
                                          --------------------------------------
                                          Title: Vice President

                                      ALLFIRST BANK, a division of M&T BANK

                                      Bv: /s/ Kellie Matthews
                                          --------------------------------------
                                          Title: Administrative Vice President


<PAGE>

                                      FLEET NATIONAL BANK

                                      By: /s/ Megan L. Soltys
                                          --------------------------------------
                                          Title: Vice President

                                      BANCA INTESA, NEW YORK BRANCH
                                        (f/k/a IntesaBci)

                                      By: /s/ Frank Maffei
                                          --------------------------------------
                                          Title: Vice President

                                      By: /s/ Mark Mooney
                                          --------------------------------------
                                          Title: Vice President

                                      MELLON BANK

                                      By:_______________________________________
                                          Name:
                                          Title:

                                      SUNTRUST BANK

                                      By: /s/ Stephen Derby
                                          --------------------------------------
                                          Title: Director

                                      THE BANK OF NEW YORK

                                      By: /s/ David Csatari
                                          --------------------------------------
                                          Title: Vice President

                                      ABN AMRO BANK N.V.

                                      By: /s/ Neil R. Stein
                                          --------------------------------------
                                          Title: Group Vice President

                                      By: /s/ Henry Sosa
                                          --------------------------------------
                                          Title: Assistant Vice President

                                      -9-

<PAGE>

                                      COMERICA BANK

                                      By: /s/ Robert P. Wilson
                                          --------------------------------------
                                          Title: Vice President

                                      -10-