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All about Keithley DMM7510. Bugs and features, recipes, advice, notes.
MegaVolt:
--- Quote from: E-Design on July 15, 2020, 11:21:55 am ---Hi Megavolt, do you have a low thermal short for when doing zero calibration?
--- End quote ---
I have a special shorting from Keithley. I bought it specifically so that I had something to answer this question :)))
The device stood and carried out automatic measurements for several days. With installed short Keithley. Then I interrupted the measurement. Updated firmware and continued measurements. After that, a clear step appeared on the chart before and after the update. (I will add a graph in the evening)
MegaVolt:
Left - 5 day test
Right - 3 day test after update.
Kleinstein:
Updating the firmware may imply running an ACAL. This alone could change the offset a little.
MegaVolt:
--- Quote from: Kleinstein on July 15, 2020, 07:28:46 pm ---Updating the firmware may imply running an ACAL. This alone could change the offset a little.
--- End quote ---
For two years I played with the device and started ACAL. Mixing was kept at 300-400nV very stable.
I assume that it is possible that ACAL can start after updating the firmware without turning off the power, but it doesn’t work as intended. It is not very clear why repeated ACAL does not return anything :(
E-Design:
--- Quote from: MegaVolt on July 15, 2020, 07:35:13 pm ---
--- Quote from: Kleinstein on July 15, 2020, 07:28:46 pm ---Updating the firmware may imply running an ACAL. This alone could change the offset a little.
--- End quote ---
For two years I played with the device and started ACAL. Mixing was kept at 300-400nV very stable.
I assume that it is possible that ACAL can start after updating the firmware without turning off the power, but it doesn’t work as intended. It is not very clear why repeated ACAL does not return anything :(
--- End quote ---
Updating the firmware requires a reboot which isnt as thermally upsetting as a power cycle but it still might make a small shift. I would expect though, the zero to eventually return to its previous value after some time.
An ACAL however, will rebuild the zero measurement and now becomes dependent on how good of short and thermally stable you can make at the terminals.. It will in general, end up being slightly different.
For your thermal short, check the orientation of it. It is not thermally symmetric. Rotate it and let unit sit for > 1 hour, you will see a shift. It is designed for stable HI-LO but as you can see there is also a SHI-SLO and the two connect. Anyways, the orientation is another variable. Also, you didnt say, are there air currents or other instrument nearby creating less stable environment. I couldnt see your picture because its only the graph not the instrument.
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