Measurement and Automation Software does not find GPIB instrument

[Alison]

I have installed a PCI-GPIB card and attached a HP scope. Initially the measurement and automation software found the scope and I could communicate with it in this. Also in Labview, I could control the scope but for some reason was unable to collect data from it. Now the measurement and automation software doesn't find the scope. It claims there are no instruments attached to the GPIB. I have checked the cable is attached properly and windows control panel detects that the card is there and thinks it is working.

[Brian_Vibert]

Is the scope still configured to communicate over the GPIB bus? Some instruments can be set to communicate over different interfaces (GPIB or RS232 for example) from their front panels. Maybe yours got changed by accident?

Brian

[Alison]

I can't change the settings for RS232. One thing I did notice though is that the scope has settings for HP-IB. Initially, when I was able to communicate with the scope via the computer, the address set for HP-IB in the scope matched the GPIB address for the computer, but is this a problem? Also the scope is configured for talk/listen.

[Brian_Vibert]

HP-IB was HP's version of GPIB, as far as I know they are compatable (it has worked for me). Maybe the scope has stopped working. Do you have another GPIB instrument that you could try to eliminate the PC/GPIB controller as the problem.

[Kamran S.]

The matching addresses would be an issue. Every device (the instrument or the controlling board) needs to have a unique address. Most instruments have default GPIB addresses, you should verify that the address for the board is different for the address of the scope.

Try changing the setting on the scope to make sure it's different from the board and if that works then you're set.

Also, are you able to see other instruments?

It is strange that you were able to communicate and then weren't. Is there anything you did between when it did work and when it stopped? Send a command that caused an error, turn the scope on and off (which could have reset the GPIB address of the scope)?

[Alison]

Ok, well I've checked the set up for the scope and the cable. I reinstalled the drivers and now it finds the scope, but the scope comes up with unknown command when I try and interrogate it.

[Kamran S.]

Do other instruments work fine? BTW, what is the model of scope you're using and what command are you sending ... "*idn?"?

Are you using a manual to find the commands to send or are you making use of an instrument driver? Let me know and hopefully we can come up with some steps to troubleshoot this.

If it is a command that you're looking up from a manual. Then we should start peeling of the layers between the instrument and your application.

IBIC is pretty low level:
http://www.ni.com/support/gpib/max/ibic.htm

Are you able to get things to work with it. The other thing to check on are the termination settings. That can cause problems if the board is not be configured with the same settings as the instruments, sin
ce this is what let's an instrument know when a command has been completely received.

[Alison]

The original scope is a HD54111D. I tried a HD54120A which acted in exactly the same way. The commands I was trying were IDN? and EOS? Both of these commands are in the manual for the scope. I have been using IBIC. Yesterday I reinstalled the drivers and the MAX program managed to find the scope but could not communicate with it, the scope saying unknown command and output buffer empty. Today it didn't recognise the scope again. It also did not recognise the new scope and just said that there was no instrument present. Is it likely that I have corrupted the drivers some how?

Thanks for the assistance by the way

[Kamran S.]

The only thing I can think of is the termination settings. It might be worthwhile just trying a few different ones and if that doesn't work then you've done most of the troubleshooting I can think of.

If changing those doesn't work then something could have gotten corrupted during the installation. Uninstalling and then running a utitlity to clean your registry and then re-installing is the last option (I'd call NI support to point you in the right direction, make sure you point out what you've already tried so you're not asked to do the same things you've already done).

Sorry this is causing so many problems. If you're having issues with multiple instruments then it really seems like an installation is
sue (so if the above procedure doesn't work the last thing would be questioning the board). I'd go ahead and call NI support and see if they have any new ideas.

[Rob Cole]

A great number of interfacing problems do turn out to be cabling. Try another cable if you can. GPIB cables are often problematic if you have to put a sharp bend in the cable. This, in part, can come from the fact that there are so many conductors in the cable.

To check the VISA setup, try writing without using VISA. I have included a short program that will talk to the GPIB without using VISA. If this works then the problem is in the VISA setup (yes this program looks a lot like one of the utilities include in MAX). Run the "Test GPIB.vi" in the .LLB.

I hope this helps.

Rob