CUSIP No. 636518 10                                          Page 1 of 5 Pages

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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G


                    Under the Securities Exchange Act of 1934

                              (Amendment No. Two)*


                        NATIONAL INSTRUMENTS CORPORATION
- ------------------------------------------------------------------------------

                                (Name of Issuer)


                                  COMMON STOCK
- ------------------------------------------------------------------------------

                         (Title of Class of Securities)


                                    636518 10
- ------------------------------------------------------------------------------

                                 (CUSIP Number)


     *The  remainder  of this cover  page  shall be filled  out for a  reporting
person's  initial  filing of this  form with  respect  to the  subject  class of
securities,  and for any subsequent amendment containing information which would
alter the disclosures provided in a prior cover page.

     The  information  required in the remainder of this cover page shall not be
deemed to be "filed"  for the purpose of Section 18 of the  Securities  Exchange
Act of 1934 ("Act") or otherwise  subject to the  liabilities of that section of
the Act but shall be subject to all other  provisions of the Act  (however,  see
the Notes).







SEC 1745 (2-95)

                                Page 1 of 5 Pages






CUSIP No. 636518 10                                          Page 2 of 5 Pages



CUSIP No. 636518 10                       13G                 Page 2 of 5 Pages


   1    NAME OF REPORTING PERSON
        S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        L. Wayne Ashby
   2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
        (a)   |_|
        (b)   |_|
   3    SEC USE ONLY


   4    CITIZENSHIP OR PLACE OF ORGANIZATION
        U.S.A.
                      5    SOLE VOTING POWER

     NUMBER OF             2,259,056
      SHARES
   BENEFICIALLY
     OWNED BY
       EACH
     REPORTING
    PERSON WITH
   6    SHARED VOTING POWER
        -0-

   7    SOLE DISPOSITIVE POWER
        2,259,056

   8    SHARED DISPOSITIVE POWER
        -0-

   9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

        2,259,056

  10    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

  11    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
        6.92%

  12    TYPE OF REPORTING PERSON*
        IN

                       *SEE INSTRUCTION BEFORE FILLING OUT







CUSIP No. 636518 10                                          Page 3 of 5 Pages


Item 1.
      (a)   Name of Issuer    National Intruments Corporation

      (b)   Address of Issuer's Principal Executive Offices
                              6504 Bridge Point Parkway
                              Austin, TX 78730-5039

Item 2.
      (a)   Name of Person Filing   L. Wayne Ashby

      (b)   Address of Principal Business Office or, if none, Residence
                                    6005 Bon Terra
                                    Austin, TX  78730

      (c)   Citizenship
                                    U.S.A.

      (d)   Title of Class of Securities
                                    Common Stock

      (e)   CUSIP Number
                                    N/A

Item     3. If this statement is filed pursuant to Rule 13d-1(b), or 13d-2(b),
         check whether the person is a:
    (a) |_| Broker or Dealer registered under Section 15 of the Act
    (b) |_| Bank as defined  in  section 3(a)(6) of the Act
    (c) |_| Insurance Company as defined in section 3(a)(19) of the Act
    (d) |_| Investment Company registered under section 8 of the Investment
            Company Act
    (e) |_| Investment Adviser registered under section 203 of the Investment
            Advisers Act of 1940
    (f) |_| Employee Benefit Plan, Pension Fund which is subject to the
            provisions of the Employee Retirement Income Security Act of 1974
            or Endowment Fund, see ss.240.13d-1(b)(1)(ii)(F)
    (g) |_| Parent Holding Company, in accordance with ss.240.13d-1(b)(ii)(G)
            (Note: See Item 7)
    (h) |_| Group, in accordance with ss.240.13d-1(b)(1)(ii)(H)








CUSIP No. 636518 10                                          Page 4 of 5 Pages


Item 4.  Ownership

      (a)   Amount Beneficially Owned                               2,259,056*

      (b)   Percent of Class                                             6.92%

      (c)   Number of shares as to which such person has:

          (i) sole power to vote or to direct the vote              2,259,056*
         (ii) shared power to vote or to direct the vote                    0
        (iii) sole power to dispose or direct the disposition of    2,259,056*
         (iv) shared power to dispose or direct the disposition of          0



Item 5.  Ownership of Five Percent or Less of a Class

     If this  statement  is being  filed to report  the fact that as of the date
hereof the reporting  person has ceased to be the beneficial  owner of more that
five percent of the class of securities, check the following |_|.
         NOT APPLICABLE

Item 6.  Ownership of More than Five Percent on Behalf of Another Person.
         NOT APPLICABLE

Item 7.  Identification and Classification of the Subsidiary Which Acquired the
         Security Being Reported on By the Parent Holding Company.
         NOT APPLICABLE

Item 8.  Identification and Classification of Members of the Group
         NOT APPLICABLE

Item 9.  Notice of Dissolution of Group
         NOT APPLICABLE





     *Includes 607 shares underlying stock options exercisable within 60 days of
December 31, 1997, but excludes 14,162 shares held by reporting person's spouse.






CUSIP No. 636518 10                                          Page 5 of 5 Pages

Item 10.
     By signing  below I certify  that,  to the best of my knowledge and belief,
the  securities  referred  to above  were  acquired  in the  ordinary  course of
business  and were not acquired for the purpose of and do not have the effect of
changing or  influencing  the control of the issuer of such  securities and were
not acquired in connection  with or as a participant in any  transaction  having
such purposes or effect.


                                    SIGNATURE


     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.




                                          Date    February 13, 1998


                                          /s/ L. WAYNE ASHBY
                                          -------------------------------------
                                          L. Wayne Ashby, Director