MAX visa returns no instruments

[nyc_(is_out_of_here)]

We have two test racks with same instrument Keithley 7002 switch system.

Using MAX, VISA finds the instrument in one test rack but not the other. When it doesn't, it just shows 1-32 empty instrument strings GPIB0::1::Instr  ---> GPIB0::32::Instr.
The VISA is same version.

No problems when using NI488 under MAX though.

This is not a showstopper, but I am interested in what may be causing this.

The two test racks are not using same model of NI GPIB card and the OS is Windows 2000 vs XP.

Any thoughts or suggestions?

[Dennis_Knutson]

When you use Scan for Instruments in MAX, VISA isn't used. Only the low level GPIB functions are used to find what is connected and send the *IDN? query.

You say they are not the same GPIB controllers? Are they both from NI?

Have you tried swapping GPIB cables or tried swapping instruments? It seems to me that there may be an actual hardware problem somewhere.

[nyc_(is_out_of_here)]

In MAX, Tools --> NI-VISA --> VISA Interactive Control

That is where on the station that works, I see the two GPIB instruments and on the station that doesn't work, I see the 32 GPIB insruments.

Any ideas how this differs from the Scan For Instruments?

[Dennis_Knutson]

Your visaconf.ini file may be corrupt or just messed up. The VISA control gets it's information from this file. When you do a Scan For Instruments, some of the information in visaconf.ini is updated with the scan. The file is in c:\Vxipnp\WinNT\NIvisa. Make sure MAX is closed and then delete the file. Start MAX, do a refresh, and a scan for instruments. Assuming that the scan only finds three instruments, your VISA control should be okay.