EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: bson on April 07, 2018, 05:38:49 am
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A moment ago, with CH3 set to to 3.3V and nothing plugged in it showed 3.55V and 166mA. Only on CH3; CH2 was fine (didn't check CH1). Power cycled it and it behaved normally again.
Even after turning down the voltage to 0.000V it still showed 0.358V and 0.166A. It wasn't a fixed offset. Almost like it had corrupted its calibration data...
Disconcerting... :scared:
(http://www.rockgarden.net/download/eevblog/dp832.jpg)
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Looks like a software issue, never seen in mine a rare behaviour though. The current consumed was most probable never really there
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Can you provide us details about firmware version of the unit and its calibration date?
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Definitely only a firmware issue. Like it stepped on an in-memory copy of the calibration data.
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I haven't calibrated it in about a year, but it's off only about 1mV and less than 1mA on both set and readback, so no need to recalibrate yet.
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I was asking the calibration date to understand when it was manufactured and so its board version; that, toghether with the firmware version, would allow to identify better the unit
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When I first got my DP382 (a few years ago) I used the manual calibration process to attempt to calibrate it. One thing I learned is that the power generation subsystem is separate from the output metering subsystem, and each has to be calibrated separately. Thus it's possible for the unit to accurately produce output according to it's current setpoint, but for the meters to inaccurately report the output values.
Give your problem statement, it's a reasonable hypothesis that you might have a problem in the metering subsystem. Since resetting the unit cleared the error, then perhaps calibration data is loaded on startup into volatile storage, and there was data corruption in the instance in question?
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Nah, it worked fine for a couple of hours, then glitched out. Clearly the firmware stepped on its internal calibration data. I didn't actually check it with a DMM, I just disconnected everything, noted no change, took a pic, then power cycled it. I was in the middle of something else and didn't want to lose my focus.