Keithley error 420 "Query UNTERMINATED" in MAX scan for instruments

[Blokk]

Hi!

We have an about 9 years old system. There is a PC with WinXP and LabView 6.1 . In the PC there is a GPIB PCI card, and via the GPIB cable, 8 Keithley DVMs (including Models like 2010, 2400, 2182) connected. A few days ago this old system started to malfunction. There are 4 VIs run parallel on this old system -worked fine so far-, but now none of them are able to communicate with the Keithley instruments.

I had a virus check, WinXP also checked, memory check, and so on (we had several BSODs also on the old PC).Since I could not trace down the problem in the old system, I decided to counter-check the Keithleys with a brand new configuration.

I have a new PC equipped with a GPIB+ PCI card, and LabView 2010. I connected this new PC to the above GPIB chain with the Keithley instruments. (old PC disconnected) When I open MAX, and I navigate to the GPIB controller, and I scan for instruments, all of the Keithley DVMs start to beep, and show "error 420" on their displays. And I have attached what I get in MAX.

So now I have to think this is a hardware related error? Since I have even problem communicating the DVMs in this brand new PC configuration...?

A malfunctioning DVM can make the GPIB communication unreliable? I have no idea, where to go now...

By the way, in the case of the old PC controller, I do not get any visible error, only that the VIs are not communicating (time out error). I think I will also try to use again the old system, and I will connect the new PC to the GPIB chain, and I will listen into the communication with the GPIB Analyzer feature.

thanks in advance for advices !

[smercurio_fc · Accepted solution]

Basic troubleshooting: Have you tried simply connecting just one instrument at a time to the bus? You may also want to check the cables.

[Blokk]

Thanks, it worked. I turned off every Keithley DVMs, and one by one started to turn them on, and I have scanned for instruments from the MAX. I have found 2 of the Keithley's were malfunctioning. The symptom was that it could not communicate with the GPIB control, and somehow disturbed the other working instruments to communicate. The strange is, I have replaced the 2 broken Keithleys, but the old PC with the old GPIB PCI card still cannot communicate with any of the instruments. However, my new PC with the new GPIB controller and LabView 2010 can communicate now with all of the instruments, and use the PID VI-s perfectly (I was happy to see that the LabView2010 managed to run the LAbView6.1 VIs without any problem 🙂 ).

Is it possible that a malfunctioning GPIB controller can destroy DVMs on the chain?

Anyway, a Keithley nanovoltmeter is not a cheap toy, so I just purchase a new PC with a new NI GPIB card.

regards

[smercurio_fc]

Well, "detroy" is a bit of an excessive word... More than likely the instrument simply broke. I've seen this happen with the Agilent Signal generators in our lab. In one case it was corrupted firmware. Updating the firmware fixed the communication issue. I've also seen cables go bad "all of a sudden". At least the engineers say "all of a sudden". That's after all the man-handling they do to them.