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Keithley 2750 issue when reading timestamps in Labview

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reinhardh
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Joined: December 5th, 2016, 4:10 am
Country: Germany

Keithley 2750 issue when reading timestamps in Labview

Post by reinhardh » July 22nd, 2020, 11:39 pm

Hi all,

I'm using a 2750 with a 7702 card to do 4-wire-measurements. I use Labview to control the DMM via RS232.
I'm trying to do a continuous mulit-read from the system's buffer following the Labview Example of the instrument's Labview library.
I've set NPLC = 1 and the measured data seems to be correct but the timestamps I get in Labview are incorrect.

I've set the timestamp to be relative. I expected the timestamp to consist of two numbers according to the manual, first an absolute timestamp an then a delta timestamp.

But I get timestamps like the string array in the screenshot.
Each reading has indeed two numbers, but the first one is too small to be an relative time (something about 6e-4 to 9e-4, when I change to DCV and set NPLC to 0.01 even negative values occur) and the second one is always 9.9E+37.

When I check the stored readings on the frontpanel, they seem correct:
the relative timestamp dS varies between 0.062 to 0.171 with fixed range, NPLC=1, Autozero=OFF, OCOMP=OFF, DCIR=OFF.

how can I get these values in Labview?
or is there at least a possibility to acquire 4-wire-ohms readings with a fixed sample rate? I need to synchronize them with other measured data.
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readings_relative_timestamp2.png
readings_relative_timestamp2.png (10.8 KiB) Viewed 177 times

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