<PAGE>

                                                                   EXHIBIT 10.44

THIS NOTE IS SUBJECT TO AN INTERCREDITOR AGREEMENT, DATED AS OF DECEMBER 21,
2001, AMONG FLEET CAPITAL CORPORATION, A RHODE ISLAND CORPORATION, PETROCON
ENGINEERING, INC., AND EQUUS II INCORPORATED, A DELAWARE CORPORATION, ET AL.
THIS NOTE IS SUBORDINATED IN RIGHT AND TIME OF PAYMENT TO THE PRIOR PAYMENT IN
FULL IN CASH OF ALL SENIOR DEBT (AS DEFINED IN THE INTERCREDITOR AGREEMENT) IN
ACCORDANCE WITH, AND TO THE EXTENT SPECIFIED IN, SUCH INTERCREDITOR AGREEMENT
AND EACH HOLDER OF THIS NOTE, BY ITS ACCEPTANCE HEREOF, IRREVOCABLY AGREES TO BE
BOUND BY THE TERMS AND PROVISIONS OF SUCH INTERCREDITOR AGREEMENT.

                                PROMISSORY NOTE
                                ---------------

$3,000,000                         Houston, Texas             December 21, 2001

      FOR VALUE RECEIVED, PETROCON ENGINEERING, INC., a Texas corporation
("Maker"), does hereby promise to pay to the order of EQUUS II INCORPORATED, a
Delaware corporation with its principal office at 2929 Allen Parkway, Suite
2500, Houston, Texas 77019 ("Payee"), or at such other place as the holder
hereof may from time to time designate in writing, in lawful money of the United
States, the principal sum of THREE MILLION AND NO/100 DOLLARS ($3,000,000), with
interest thereon as provided in this Promissory Note (the "Note").

     1.     Certain Definitions. For the purposes hereof, the terms set forth
            -------------------
below shall have the following meanings:

               (a)     "Applicable Law" shall mean (i) the laws of the United
                        --------------
     States of America applicable to contracts made or performed in the State of
     Texas, now or at any time hereafter prescribing maximum rates of interest
     or eliminating maximum rates of interest on loans and extensions of credit,
     (ii) the laws of the State of Texas now or at any time hereafter
     prescribing or eliminating maximum rates of interest on loans and
     extensions of credit, and (iii) any other laws at any time applicable to
     contracts made or performed in the State of Texas which permit a higher
     interest rate ceiling hereunder.

               (b)     "Base Rate" shall mean 9.5%.
                        ---------
               (c)     "Final Maturity Date" shall mean December 21, 2005.
                        -------------------
               (d)     "Highest Lawful Rate" shall mean at the particular time
                        -------------------
     in question the maximum rate of interest which, under Applicable Law, Payee
     is then permitted to charge Maker in regard to the loan evidenced by this
     Note. If the maximum rate of interest which, under Applicable Law, Payee
     is permitted to charge Maker in regard to the loan evidenced by this Note
     shall change after the date hereof, the Highest Lawful Rate shall be
     automatically increased or decreased, as the case may be, from time to
     time as of the effective date of each change in the Highest Lawful Rate
     without notice to
<PAGE>

     Maker. In determining the Highest Lawful Rate, all fees and other charges
     contracted for, charged or received by Payee in connection with the loan
     evidenced by this Note which are either deemed interest under Applicable
     Law or required under Applicable Law to be deducted from the principal
     balance hereof to determine the rate of interest charged on this Note shall
     be taken into account.

     (e)     "Merger" shall mean the merger of PEI Acquisition, Inc. a Texas
              ------

     corporation ("PEI Acquisition") with and into Maker pursuant to that
     certain Agreement and Plan of Merger dated July 31, 2001 by and among
     Parent, IDS Engineering Management, LC, a Texas limited liability company,
     PEI Acquisition and Maker.

     (f)     "Parent" shall mean Industrial Data Systems Corporation, a Nevada
              ------
     corporation.

     (g)     "Sale of Maker" shall mean (i) a sale of substantially all of the
              -------------
     assets of Maker to a person or entity that is not an affiliate of Maker,
     (ii) any sale in a single transaction or in a series of related and
     substantially similar contemporaneous transactions of the common stock,
     par value $.01 per share of Maker ("MAKER COMMON STOCK"), representing
     50% or more of the total number of shares of Maker Common Stock then
     outstanding (determined on a fully diluted basis) to any person or entity
     which is not an affiliate of the selling shareholders, or (iii) any
     merger, consolidation or reorganization of Maker with or into one or more
     entities which are not Subsidiaries or affiliates of Maker or Parent
     (other than the Merger), as a result of which less than 50% of the
     outstanding voting securities, partnership interests or membership
     interests of the surviving or resulting entity are owned by the holders
     of Maker Common Stock (or their Affiliates) immediately prior to such
     merger, consolidation or reorganization.

     (h)     "Sale of Parent" shall mean (i) a sale of substantially all of the
              --------------
     assets of Parent to a person or entity that is not an affiliate of Parent,
     (ii) any sale in a single transaction or in a series of related and
     substantially similar contemporaneous transactions of the common stock of
     Parent, par value $0.001 per share ("PARENT COMMON STOCK"), representing
     50% or more of the total number of shares of Parent Common Stock then
     outstanding (determined on a fully diluted basis) to any person or entity
     which is not an affiliate of the selling shareholders, or (iii) any merger,
     consolidation or reorganization of the Parent with or into one or more
     entities which are not Subsidiaries or affiliates of the Parent, as a
     result of which less than 50% of the outstanding voting securities,
     partnership interests or membership interests of the surviving or resulting
     entity are owned by the holders of Parent Common Stock (or their
     Affiliates) immediately prior to such merger, consolidation or
     reorganization.

     (i)     "Security Documents" has the meaning specified in Section 13 of
              ------------------
     this Note.

     (j)     "Senior Debt" shall mean (i) all now existing or hereafter incurred
              -----------
     indebtedness of the Parent, the Maker or any of their respective
     Subsidiaries for money borrowed, loans made or letters of credit issued or
     other credit extended to the Parent, Maker or any of their respective
     Subsidiaries by any bank or other financial or lending

                                        2
<PAGE>

     institution, including, without limitation, Fleet Capital Corporation, that
     is specifically designated by the Parent or the Maker, in the document or
     instrument creating or evidencing such indebtedness or in an officer's
     certificate delivered to the holder of this Note, as "Senior Debt", (ii)
     all assumptions or guaranties of any indebtedness of the type described in
     the preceding clause (i), and (iii) all indebtedness of the Parent, the
     Maker or any of their respective Subsidiaries arising in connection with
     any refunding or refinancing of, or increases in the principal amount of,
     any indebtedness of the type described in the preceding clause (i) and
     (ii), in each instance together with all interest, fees, costs, taxes,
     expense reimbursements, indemnification and other like amounts arising
     under the documents and instruments evidencing such indebtedness, including
     all such amounts that become payable (or that would have become payable if
     enforceable or allowable in such case or proceeding) on the terms specified
     in such documents and instruments after the commencement of any bankruptcy,
     reorganization, receivership, insolvency, liquidation or dissolution
     proceeding, whether or not the claim for such amount is enforceable,
     allowable or allowed as a claim in such proceeding and even if such claim
     is not enforceable or allowed therein; provided, however, that, except for
     the outstanding principal balance as of the date hereof of the term loan
     indebtedness evidenced by that certain Term Note, dated June 15, 1999, from
     Maker and each of its Subsidiaries, as Borrower, to Fleet Capital
     Corporation, in the stated principal amount of $5,000,000, in no event
     shall the principal amount of any indebtedness described in the preceding
     clause (i) be Senior Debt unless the documents, agreements and instruments
     evidencing such indebtedness provide that the principal amount of such
     indebtedness which may be advanced from time to time shall be determined by
     reference to a borrowing base (i.e., accounts receivable and inventory) of
     Maker, Parent and/or any one or more of their respective Subsidiaries
     regardless of whether the aggregate amount of such indebtedness may from
     time to time exceed the amounts permitted to be advanced on such borrowing
     base.

     (k)     "Subsidiary" means, with respect to any person or entity, any
              ----------
     corporation, partnership, limited liability company, association or other
     business entity of which more than fifty percent (50%) of the total voting
     power of shares of stock (or equivalent ownership or controlling interest)
     entitled (without regard to the occurrence of any contingency) to vote in
     the election of directors, managers or general partners thereof is at the
     time owned or controlled, directly or indirectly, by that person or entity
     or one or more of the other Subsidiaries of that person or entity or a
     combination thereof.

     2.   CALCULATION AND PAYMENT OF PRINCIPAL AND INTEREST.
          --------------------------------------------------

     (a)     Interest on the unpaid principal balance hereof from time to time
     outstanding shall be computed at a per annum rate equal to the lesser of
     (i) the Base Rate in effect from time to time and (ii) the Highest Lawful
     Rate, and shall be due and payable quarterly, in arrears, on the 15(th) day
     of each February, May, August and November of each year, commencing on
     November 15, 2001, and continuing on the 15(th) day of each such month
     thereafter until such time as the full principal balance, together with all
     other amounts owing hereunder, shall have been paid in full.

                                        3
<PAGE>

     (b)     The principal balance shall be due and payable in equal quarterly
     installments of $110,000 each, commencing on August 15, 2002, and
     continuing on the 15(th) day of each February, May, August and November of
     each year thereafter to and including the 15(th) day of December, 2005, and
     the entire remaining principal amount then outstanding, together with any
     and all other amounts due hereunder shall be due and payable on the Final
     Maturity Date.


     (c)     All payments on this Note shall be applied first to the payment of
     accrued interest and then to the payment of principal.

     (d)     Interest on this Note shall be calculated on the basis of 365 -day
     or 366-day years, as the case may be.

     (e)     If the date for any payment or prepayment hereunder falls on a day
     which is a Saturday, Sunday or other legal holiday, then for all purposes
     of this Note, the same shall be deemed to have fallen on the next following
     day, and such extension of time shall in such case be included in the
     calculation of interest.


     3.    Prepayment. Maker shall have the right to prepay the unpaid principal
           ----------
     balance of and all accrued interest upon this Note in whole or in part at
     any time without premium or penalty. Maker shall prepay the outstanding
     principal balance of and all accrued but unpaid interest on this Note prior
     to the Final Maturity Date upon a Sale of Maker or a Sale of Parent.

     4.    Waiver. Maker and all sureties, endorsers, accommodation parties,
           ------
guarantors and other parties now or hereafter liable for the payment of this
Note, in whole or in part, hereby severally (i) waive demand, notice of demand,
presentment for payment, notice of nonpayment, notice of default, protest,
notice of protest, notice of intent to accelerate, notice of acceleration,
notice of dishonor and all other notices, and further waive diligence in
collecting this Note, in taking action to collect this Note, in bringing suit
to collect this Note, or in enforcing this Note or any of the security for this
Note; (ii) agree to any substitution, subordination, exchange or release of any
security for this Note or the release of any party primarily or secondarily
liable for the payment of this Note; (iii) agree that Payee shall not be
required to first institute suit or exhaust its remedies hereon against Maker
or others liable or to become liable for the payment of this Note or to enforce
its rights against any security for the payment of this Note.

     5.     Events of Default.
            -----------------

     (a)     Upon the happening of any of the following events (each an "Event
     of Default"), Payee may, at its option upon ten (10) days prior written
     notice to the Maker, declare immediately due and payable the entire
     principal balance of this Note together with all interest accrued and owing
     hereon, plus any other sums payable at the time of such declaration
     pursuant to this Note. Events of Default include the following:

                       (i)     If Maker shall fail to pay any principal and/or
              interest under this Note and such failure shall continue for a
              period of ten (10) days after the receipt by Maker of written
              notice of such failure from Payee when same becomes due and
              payable in accordance with the terms hereof, or if Maker shall
              default in any other payment obligation under this Note and such
              default shall continue for a

                                        4
<PAGE>

              period of ten (10) days after the receipt by Maker of written
              notice of such default from Payee;

                       (ii)     If Maker becomes insolvent, fails to pay its
              debts generally as they become due or becomes the subject of any
              proceeding under any debtor relief law. In the event of Default,
              Payee may declare the entire unpaid balance of this Note, or any
              part hereof, immediately due and payable;

                       (iii)    If any default shall occur in the performance
              or compliance with any term contained in any of the Security
              Documents and such default is not remedied or waived within 30
              days after receipt by Maker of written notice of such default
              from Payee; or

                       (iv)     The failure to exercise the foregoing option
              upon the happening of an Event of Default shall not constitute a
              waiver of the right to exercise the same or any other option at
              any subsequent time, and no such failure shall nullify any prior
              exercise of any such option without the express written consent of
              Payee.

     6.     Default Interest. If the entire unpaid principal balance and
            ----------------
accrued but unpaid interest is not paid on or before the earlier to occur of
the Final Maturity Date, all unpaid amounts of this Note, including principal
and interest, shall thereafter bear interest at a rate of interest (the
"Default Rate") equal to the lesser of (i) 12% per annum or (ii) the Highest
Lawful Rate; provided, however, that the obligation to pay such interest is
subject to the limitation contained in the following paragraph.

     7.     Compliance with Law. All agreements between Maker and Payee,
            -------------------
whether now existing or hereafter arising and whether written or oral, are
hereby limited so that in no contingency, whether by reason of demand of the
Final Maturity Date or otherwise, shall the interest contracted for, charged,
received, paid or agreed to be paid to Payee in regard to the loan evidenced by
the Note exceed the maximum amount permissible under Applicable Law. If, from
any circumstance whatsoever, interest would otherwise be payable to Payee in
excess of the maximum amount permissible under Applicable Law, the interest
payable to Payee shall be reduced to the maximum amount permissible under
Applicable Law; and if from any circumstance Payee shall ever receive anything
of value deemed interest by Applicable Law in excess of the maximum amount
permissible under Applicable Law, an amount equal to the excessive interest
shall be applied to the reduction of the principal hereof and not to the
payment of interest, or if such excessive amount of interest exceeds the unpaid
balance of principal hereof, such excess shall be refunded to Maker. All
interest paid or agreed to be paid to Payee shall, to the extent permitted by
Applicable Law, be amortized, prorated, allocated, and spread throughout the
full period (including any renewal or extension) until payment in full of the
principal so that the interest hereon for such full period shall not exceed the
maximum amount permissible under Applicable Law. Payee expressly disavows any
intent to contract for, charge or receive interest in an amount which exceeds
the maximum amount permissible under Applicable Law. This paragraph shall
control all agreements between Maker and Payee.

     8.     Attorneys' Fees and Costs. If an Event of Default shall occur, and
            -------------------------
if thereafter this Note is placed in the hands of an attorney for collection,
or if this Note is collected in whole or in

                                        5
<PAGE>

part through legal proceedings of any nature, including arbitration, then and
in any such case Maker promises to pay, and there shall be added to the unpaid
principal balance hereof, all reasonable costs of collection, including, but
not limited to, reasonable attorneys' fees incurred by the holder hereof, on
account of such collection, whether or not suit is filed.

     9.     Cumulative Rights. No delay on the part of the holder of this Note
            -----------------
in the exercise of any power or right under this Note or under any other
instrument executed pursuant hereto shall operate as a waiver thereof, nor shall
a single or partial exercise of any power or right preclude other or further
exercise thereof or the exercise of any other power or right. Enforcement by the
holder of this Note of any security for the payment hereof shall not constitute
any election by it of remedies so as to preclude the exercise of any other
remedy available to it.

     10.     Headings. The paragraph headings used in this Note are for
             --------
convenience of reference only, and shall not affect the meaning or
interpretation of this Note.

     11.     Notices and Demands. Any notice or demand given hereunder shall be
             -------------------
deemed to have been given and received (a) when actually delivered to the
address of the party to be notified or delivered in person, (b) if mailed, on
the third Business Day (hereinafter defined) after it is deposited in the
United States mail, certified, return receipt requested or (c) one Business Day
after it has been deposited with an overnight courier, marked for next day
delivery. For purposes hereof, the addresses of the parties are as follows:

                            Equus II Incorporated
                            Attn: Mr. Randall Hale
                            2929 Allen Parkway, Suite 2500
                            Houston, Texas 77019

                            Petrocon Engineering, Inc.
                            Attn: Mr. Michael L. Burrow
                            3155 Executive Blvd.
                            Beaumont, Texas 77705

     12.     Governing Law. This Note shall be governed by and construed in
             -------------
accordance with the laws of the State of Texas and the laws of the United
States applicable to transactions in the State of Texas. Courts within the
State of Texas shall have jurisdiction over any and all disputes between Maker
and Payee, whether at law or in equity.

     13.     Security. This Note is secured by (i) one or more Security
             --------
Agreements by Maker and each of Maker's Subsidiaries now existing and hereafter
created; (ii) one or more Guaranties by all of Maker's Subsidiaries now
existing and hereafter created; (iii) one or more Security Agreements by Parent
and all of Parent's Subsidiaries now existing and hereafter created; (iv) one
or more Guaranties by Parent and all of Parent's Subsidiaries now existing and
hereafter created; and (v) one or more mortgages, dated on or after the date
hereof, by and between RPM Engineering, Inc., a Louisiana corporation, and
Payee, covering certain real property generally described as 10252 Mayfair
Drive, Baton Rouge, Louisiana and 9969 Professional Boulevard, Baton Rouge,
Louisiana, as more particularly described therein (collectively, and as each of
the

                                        6
<PAGE>

foregoing may be amended, modified, supplemented, renewed or extended from time
to time, the "SECURITY DOCUMENTS").

     14.     Subordination. This Note is subject to an Intercreditor Agreement,
             -------------
dated on or about the date hereof, executed by Payee, Fleet Capital Corporation,
Maker et al. This Note is subordinated in right and time of payment to the prior
payment in full in cash of all "Senior Debt" (as defined in the Intercreditor
Agreement) in accordance with, and to the extent specified in, such
Intercreditor Agreement and each holder of this Note, by its acceptance hereof,
irrevocably agrees to be bound by the terms and provisions of such Intercreditor
Agreement. Payee hereby agrees that, upon the request of Maker and within
fifteen (15) days of such request, Payee shall execute and deliver to any other
holder of Senior Debt an intercreditor agreement on substantially the same terms
as such Intercreditor Agreement or on such other terms which are acceptable to
Maker, Payee and such holder of Senior Debt.

     15.     Successors and Assigns. The terms "Payee" and "Maker" shall include
             ----------------------
all of the respective parties' successors and assigns to whom the benefits of
this Note shall inure. Nothing herein shall be construed to limit the Maker's
ability to assign or transfer this Note in connection with a merger,
consolidation, sale of substantially all of its assets or similar transaction.

                                                MAKER:
                                                -----

                                                PETROCON ENGINEERING, INC.,
                                                a Texas corporation

                                                By:____________________________
                                                   Michael L. Burrow, President
                                                   and Chief Executive Officer

                                                PAYEE:
                                                -----

                                                EQUUS II INCORPORATED,
                                                a Delaware corporation

                                                By:____________________________
                                                   Randall B. Hale,
                                                   Vice President

                                        7