[humaniac]

Replaced the 2,7 MOhm resistor now with a 1.8 MOhm type.
That was a success. Calibration was possible without any problems.
Thanks again for your support and a Happy New Year.

[humaniac]

O.K., it took me a little longer to get 2,7 MOhm SMD resistors of size 0603. I finally replaced the resistor and ran the calibration process. The results are better now, but it still shows a residual current of 0.06A even when no current is flowing. The resistor is still too high. Would you recommend trying 2.0 MOhm or even 1.8 MOhm next?

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[humaniac]

Thanks,
I will try this maybe tomorrow and give you some feedback soon.

[humaniac]

Thank you very much for your efforts!
Did some Excel work with my measured data.
Seems the offset voltage is not correct.
I will check R17 as suggested. Are you sure it is 2.7 MOhm? Thought mine is labeled 3.3 MOhm.
I think, R17 has to be removed for measuring – right?

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[humaniac]

I did some additional voltage-measurements at PIN 17 (PA7) that is the ADC for Current measuerement.
Here are the results:

Current Voltage at PA7
0.000 A 0.0000 V
0.104 A 0.0001 V
0.203 A 0.0066 V
0.501 A 0.0404 V
1.003 A 0.0991 V
2.000 A 0.2167 V
5.519 A 0.6309 V

Looks like there is a problem with the OpAmp SGM8582 rather than with the ADC of the STM32.
What do you think?

[humaniac]

As you can see in the screenshot, the IoutH value of the ADC seems to be determined correctly.
Only the value for IoutL is 0 (sometimes 1 or 2) – in any case unusually small.
Even with a real current measurement, it is close to the correct value. So the ADC seems to be working. Even with no current flowing, 0.10 A is displayed.
I also tried calibrating with different HW versions – it made no difference.
I don’t know where the problem is.

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[humaniac]

Thanks for the quick reply.
I have also tried various earlier firmwares (4.3 and 3.9). Both with the same result.
I can eliminate point 2 – I was very careful to leave the multimeter connected during calibration.
What exactly does point 1 mean – is there anything I can do?
I’m also afraid it’s a problem with the ADC for the input current.
Could a new STM32 controller solve the problem?

Kind regards
Philip

[humaniac]

Hello profi-max,

first of all, thank you very much for your great work and for making it available free of charge.
I have two DPS 5015 which I have flashed to the new firmware 4.4.
Everything worked smoothly with the first DPS 5015.
With the second one I have massive difficulties with the calibration of the output current. Although I have proceeded strictly according to the instructions, a residual current of 0.1 A always remains on the display, even when the output is open.
I have repeated the process several times, also with different hardware versions 1.0 and 2.0. Unfortunately without success. The ADC value for “I out L” looks strange. It always remains at 0, even after repeating the calibration several times.
Do you have any idea where the error may lie?

Best regards
Philip

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