Limited Power of Attorney - Securities Law Compliance


     The  undersigned,  as  an  officer  or  director  of  National  Instruments
Corporation (the  "Corporation"),  hereby  constitutes and appoints David Hugley
and Alexandra  Gustafsson,  and each of them, the undersigned's  true and lawful
attorney-in-fact  and agent to complete and execute  such Forms 144,  Forms 3, 4
and 5 and other forms as such attorney shall in his or her discretion  determine
to be  required  or  advisable  pursuant  to  Rule  144  promulgated  under  the
Securities Act of 1933 (as amended),  Section 16 of the Securities  Exchange Act
of 1934 (as amended), and the rules and regulations promulgated  thereunder,  or
any  successor  laws and  regulations,  as a  consequence  of the  undersigned's
ownership,  acquisition or disposition of securities of the Corporation,  and to
do all acts  necessary  in order to file  such  forms  with the  Securities  and
Exchange  Commission,  any  securities  exchange  or national  association,  the
Corporation  and  such  other  person  or  agency  as the  attorney  shall  deem
appropriate.  The  undersigned  hereby  ratifies  and  confirms  all  that  said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

     This Limited Power of Attorney is executed in Austin, Texas, as of the date
set forth below.

                                           Robert Porterfield
                                          -------------------------
                                          Signature

                                          Robert Porterfield
                                          -------------------------
                                          Type or Print Name

                                          Date: 2 Nov. 2004
                                               -------------------------

Witness:

 Elizabeth Bordenave
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Signature

Elizabeth Bordenave
- -------------------------
Type or Print Name

Date: 11-2-04
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