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Keithley 2000 external trigger

Hi all,

I'm using Keithley 2000 DMM for resistance measurement using external trigger (0.5-1 Hz) and official LabVIEW driver. Software as in example "Keithley 2000 Read Single.vi", function: 4-wire resistance, external trigger, "Action Send Trigger" removed, with while loop over Data Read Single.

- when using RS232 software hangs after 30-70 triggers, reboot of system is required to establish communication with DMM.... It's strange because "Data Read Single" has internal timeout and it should execute with an error

- when using NI USB-GPIB cable software is stable, but reads result twice / trigger, it seems that first read does not clear internal flag in Keithley...

tested on LabVIEW 2017 32 and 64 bit, 2016 32 bit, on two Keithley 2000 DMM, two PCs and two RS232 cables...

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Message 1 of 5
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So how are you doing triggering?  How many trigger pulses are you sending, and how many measurements/trigger are you expecting.  

 

I don't think you've necessarily setup the trigger correctly on the DMM.  I think given the current settings its behaving exactly as expected, just not as you want. What you have setup is 1 external trigger pulse arms the measurement infinite times and allows infinite measurements.  So your loop will continue to measure, but if the DMM receives further trigger pulses that may cause some funny issues.

 

Yes, you've set it to measure on an external trigger but you let all the other conditions go to default values.   Look at taking care of the other trigger settings: 

 

Trigger Iinit - continuous/single?    

Trigger Count mode - Infinite --> I think you want finite with count set to 1 (i.e. 1 measurement/trigger)

Auto Delay --> if speed isn't a concern then this will help with measurement variation.

 

Perhaps look at the manual for the full trigger model to get it to do exactly what you want.  

 

 

Describe the measurement and triggering fully and we can help debug the code.

 

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Message 2 of 5
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We are triggering with TTL 100ms long signal, Keithley triggers on falling edge, trigger repeats each 2 seconds. Trigger was controlled with the oscilloscope.

When using RS232 software reads after trigger only once, when using GPIB software reads after trigger twice.

Trigger Iinit - continuous/single? - for both cases it reads twice over GPIB

Auto Delay - does not affect measurement

Trigger Count mode - setting it to Custom dosn't help, it

 

 

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Message 3 of 5
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There should be no reason that RS232 or GPIB behave differently.  GPIB is probably faster, so it seems like your trigger pulse might have some ringing that causes a second trigger.  If you are expecting a pulse at roughly 2s, then add a delay to your while loop that is ~1.5s long.  Set the Read timeout to 1s.  That should prevent out of sync triggers from causing issues.

 

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Message 4 of 5
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Hi,

We've already tried delays, but without success...

I think that without physical access to hardware it will be impossible for you to debug it.

We stick to GPIB with double read, at least it works...

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