It works very good, but I have a question regarding the calibration.
When I press calibrate with no input and RV1 in the middle it works like it should.
I connect a 1.5 V battery (1,496 V) and the DC mean shows 1,75 V.
I turn down RV1 so that the DC Mean is 1.5 V.
When I disconnect the battery the DC Mean is -0,19 V?
Is this normal?
[quote]When I disconnect the battery the DC Mean is -0,19 V?
Is this normal?[/quote]Yes. You can now repeat the calibration.
When I repeat the calibration I get almost the same result.
Calibration done - 0 V
Battery connected - 1,69 V
Rotate RV1 - 1,5 V
Disconnect battery - -0,17 V
It gets a little better after every calibration, but after 3 or 4 calibrations the RV1 is bottomed out.
[quote]after 3 or 4 calibrations the RV1 is bottomed out.[/quote]This is very strange problem.
Normally the RV1 final position is a little counterclockwise from its middle position.
Do you get similar DC mean readings on all the V/Div ranges (5V/div, 2V/div, 1V/div and on 0.5V/div)?
The best values after 4 calibration and RV1 all the way ccw.
I mean, it’s not bad, but if it can be better it’s good.
Not connected (0 V) / 1.499 V battery
5V/div -0.2 / 1.6
2V/div -0.06 / 1.56
1V/div -0.03 / 1.50
0.5V/div -0.02 / 1.58
Indeed, the results are good.
The only problem is that there is no more adjustment range left for RV1.
You can fix this problem either by changing R25 (now 20k) to 18k, or soldering 150k…200k resistor in parallel with the R25.