PeakTech 2025 multimeter shows 330mV after power on

[maelh]

Hello,

My PeakTech 2025 multimeter shows about 330mV after I power it on (and set it to volt measurement), with and without leads attached.
It very slowly goes down to a lower value, when I short out the leads this happens much faster (than without shorting the leads) and reaches 0mV. After separating the test leads it shows some minor mV variations as you would expect from environment noise.

What could be the reason for this initial power up voltage?

I already exchanged the fuses, just in case they might have been the issue.

Is there something relatively simple I can check to find the cause of this behavior?

[mcinque]

Does it change the symptom in DC or AC mode?
Does this initial issue happen also in other modes (ohm etc.)?

[maelh]

AC has less resolution so it's hard to tell.

Seems to be a bad contact issue.

When I turn the dial from V to Ohm usually it shows 0 Ohm, in seldom cases it was also showing significant resistance.
But usually when I go from the Ohms setting to the V setting it has a value of a few mV only, as it should.

You can see how it quickly goes from 300 or 600mV to almost zero almost instantly.

So I think it's a bad contact/issue with the dial.

Though when I leave it on the volt setting, the voltage slowly rises, so it's probably a bit more complex.

The COM plug solder joint is broken, I will fix it and see if it makes a difference.

[electr_peter]

What is PeakTech 2025 input impedance on different voltage ranges? It could be that mV DC range has high (~1-10 GOhm) impedance and may show peak of the range due to offset currents (or some stray charge).

Such is the case with Amprobe AM-240 DMM. Turning knob OFF to DC V shows 320mV on 400 mV DC range (this range has high input impedance). 320 mV initial offset (or input "charge") disappears after range change, function change, etc. It is not an issue or problem, just a design artifact.