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Configuring NI-VISA as the Primary VISA

Primary Software: Driver Software>>NI-VISA
Primary Software Version: N/A
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I had NI-VISA installed on my setup and I recently installed Agilent/Tektronix VISA driver. Now my COM ports and VISA devices no longer show up in Measurement & Automation Explorer. Why is this occurring?

Note: The situation is also seen if you make Agilent/Tektronix VISA driver primary and then want NI-VISA to be primary.

Solution:
Verify what distribution of the visa32.dll is currently installed:
  1. Navigate to C:\WINDOWS\system32 and locate the visa32.dll
  2. Right click on the visa32.dll and select Properties
  3. Within the Properties go to the Version Tab and look at the Description.


If the description states NI-VISA Library, then the NI-VISA driver is set to be the primary driver. However, if the description states an alternate VISA driver, then you will need to do the following to ensure that the Primary VISA driver is NI-VISA:
  1. Rename the current visa32.dll to an alternate name
  2. Repair or reinstall NI-VISA
  3. Reboot the computer

The reason you have to rename the visa32.dll if it is associated to an alternate VISA driver is because the NI-VISA driver will not override the visa32.dll if the current driver is at a later version then NI-VISA. Therefore if NI-VISA is version 4.4 and an Agilent Driver that is version 15 is installed, the NI-VISA will not overwrite the visa32.dll. 

This should enable COM ports and VISA device to show up properly in Measurement & Automation explorer.

Related Links: Drivers and Updates: NI-VISA 4.4.1 - PharLap, Pocket PC 2003, VxWorks, Windows 2000/Mobile 5/Vista x64/Vista x86/XP
KnowledgeBase 20KG1C7Z: Can I Use Both National Instruments (GPIB) and Agilent/HP (HPIB) Controllers in the Same System?

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Report Date: 10/17/2008
Last Updated: 10/21/2008
Document ID: 4QG73OR7

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