Keithley 182 Nanovoltmeter CAL ERROR

[e61_phil]

Hi,

I noticed, that my Keithley 182 has a gain error of +1% in the 3mV and 30mV range. Therefore, I tried to recalibrate the meter. According to the manual one have to calibrate the internal divider first. Unfortunately the calibration of the divider fails (which explains why only  the 3mV and 30mV ranges are out).

I can run a calibration of the 30mV range (haven't tried 3mV but I should also work) without further errors, but the +1% errors stays the same. I think this is due to the (broken?) internal divider respectively the wrong gain factor.

Does anyone know this problem? I haven't open the unit until now.

Best regards
Philipp

[TiN]

Stupid question : did you calibrate main ranges before attempting divider cal?

[e61_phil]

Stupid question : did you calibrate main ranges before attempting divider cal?

Yes. I calibrated 30V, 3V and 300mV without problems. After that I directly tried to calibrate the divider.

[e61_phil]

I tried to calibrate the 30mV and 3mV ranges by estimating the right divider ratio.

After calibration of 30V, 3V and 300mV I skipped the divider calibration and I calibrated the 30mV by applying the +/-3V. After that I measured 20mV in the 30mV range (30mV overranges). I noticed the results (20.20...mV) and run the calibration again. This time I applied 2.02..V and told the K182 I will apply 2.000V (2V because of the ranges from my Fluke 5440B). I used the same correction factor while I applied 202.0..mV for calibration of the 3mV range.

As far as I can verify the ranges (only my Fluke 5440B DIV output) everything is fine.

That means the divider is there and works, but the K182 can't determine the ratio. I also tried to calibrate the divider with 25V instead of 30V in case the 30V will overrange the 300mV range during calibration, but that also results in a CAL ERROR.