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6221/2182 pair, problems reading out

Posted: December 2nd, 2013, 9:21 pm
by sfostner
I am trying to do pulse delta measurements, controlled using GPIB, with both boxes connected using the serial and link cables.

It took me a while to realize that a few second setup time is required to arm the measurement (though I believe that is only the first time, assuming I leave it armed after reading in the buffer measurement?). We would ideally like to do a few (or perhaps only 1) pulse at a time, spaced typically several hundred ms apart, which seems possible so long as the arming process is done beforehand. I haven't quite been able to tell, what is the min time for the buffered data to be read BACK? After fiddling a lot, I found that it is extremely sensitive to the delays I put in between the pulse, read, arm.

My ideal setting would be: ARM the setup, then send ~50 us pulses every 100ms or so (using our own software ramping). Is this doable? The short pulse length is important for heating reasons in the device, I might be able to get away with longer but I suspect not. I also imagine we will need to set the voltage range to manual as it complains if the delay is <55 us without doing so.

My primary problem though is that no matter what I do, I cannot seem to actually get meaningful voltages out, the buffer typically returns a pair of numbers for each measurement (9.9E37, 0.1000 for example). The same voltages going to the 2182 are also going to a digital scope which seems to show the expected readings, depending on the pulse size and resistance under test (though I haven't had much luck triggering on pulses <1mA, its a bit noisy but that's more likely the test setup I'm using).

I've struggled with this for a while, suggestions? I should point out, normally we control both boxes independently through GPIB with no problems, the 2182 seems to measure perfectly fine otherwise.

Re: 6221/2182 pair, problems reading out

Posted: December 5th, 2013, 9:49 am
by Kenneth P

The method you are describing is the equivalent to the Pulse Delta Mode. Have you tried this system configuration? Pulse width is configurable from 50 usec to 12 msec. The period is set by adjusting the PLC. For 100 msec, use a PLC of 5 (50 Hz AC) or 20 msec per PLC.
A digital scope will not have sufficient resolution and accuracy compared to the 2182.

Re: 6221/2182 pair, problems reading out

Posted: December 5th, 2013, 12:19 pm
by sfostner
Hi Kenneth,

Sorry, perhaps I was unclear. I am trying to do measurements in the pulse delta mode, however I do see the pulse on the digital scope correctly (though this is for diagnostic purposes only), I do not see the correct readings in the buffer after the read command (on the PC).

Re: 6221/2182 pair, problems reading out

Posted: December 5th, 2013, 2:16 pm
by sfostner
Never mind, I realized that it was in fact an out of range issue on the voltmeter, I had thought it was in auto as it often is, but the reset returned it to manual and I didn't see the overflow message.