sudden "too many listeners on GPIB" error

[neets]

Out of the blue, I am suddenly dealing with this "too many listeners on the GPIB" error, and my PC could no longer find any intsruments in NI-MAX. I have a GPIB-USB-HS connected to my PC, and 8 instruments (few HP4142b, Keithley instruments, power meter, etc) daisy-chained with various GPIB cables..I was able to control them in LabVIEW and was having no issue with it for months.

Then yesterday, LabVIEW (I have 2012)  suddenly hung when I was trying to access one of the instruments (went into "not responding" state). Upon recovering, it could no longer see any of my GPIB instruments in the drop down menu. I restarted LabVIEW, but still got the same thing..could no longer see my GPIB instruments. I restarted the PC, and same issue. Then I could no longer see any GPIB instruments in NI-MAX. I have spent a few hours debugging this, trying different setups, connecting to 1 or 2 instrument at a time..now with this new configuration I am able to get it to see 7 of my instruments, but not all 8. I have one Keithley 7001 system it does not seem to like anymore...when i connect it to the rest of the GPIB instruments, I get the "too many listeners" error and can't see any instruments in MAX. Odd because I have two of these 7001s in my setup, and it is seems ok connecting to one but not the other.

Overall this is all really strange and i cannot figure out what could be the issue...would appreciate any suggestions/tips.

things i have checked/tried

-all GPIB instruments have unique addresses..there are no conflicts. as i mentioned, things were working fine before..suddenly they weren't.

-doesn't appear to be a GPIB cable issue. i have tried different cables..same cable will be ok connecting to one instrument, but when i use it connect to this particular Keitlhley instead, none of the instruments can be found.

Also, i just noticed something, don't know if it's important.. for my GPIB-USB-HS, the "Ready" light seems to always glow amber...it is never green. And the "Active" light never seems to come on...even when i'm sending commands to instruments.  Not sure if this matters or not.

[Dennis_Knutson]

That's almost certainly a hardware failure of the instrument. You've isolated it and it should be sent out for repair. The only other possible cause would be s bad cable but you said you've eliminated those as s cause.

[neets · Accepted solution]

ok i seem to have resolved this issue. i changed the  GPIB address of the troublesome Keithley instrument to a number much futher from the other instruments (e.g. addr 30 and the other instruments were 10, 11, 12, etc) and it worked. I don't know why it didn't work before as it was NOT an address conflict (it was originally addr 9, and no other instrument had that address and it worked fine... just one day it complained about there too many listeners and it couldn't see anything..strange. just posting this here in case it helps anyone.

[crossrulz]

This sounds like something that would happen when an instrument comes back from calibration.  I have all kinds of interesting troubleshooting adventures purely because the calibration lab changed all of the communication settings on the instrument.

[JÞB]

You went from address 9 to address 30 and it works? 0b01001 to 0b11110  Good bet that either b1 or b2 is stuck high on the address lines in that keithley.

Send it out for repair and calibration- have them explicitly test all address bits.