Mastech MAS345 Calibration Guidance?

[JP16A60]

I have a re-branded Mastech MAS345 DMM (Velleman DVM345DI) that is in need of a good cal, but I can't locate any reference materials for this [halfway-decent] meter. Lots of trim pots, but I've not yet become daring enough to just start twiddling them at random, since not every measurement type is blatantly out of cal.

Any experience in calibrating these (or any relevant instructions/procedures)?

Barring that, can anyone recommend a good trim-pot-twiddling strategy to determine what goes with what measurement?

JP
Cincinnati, OH
USA

[retiredcaps]

I have a re-branded Mastech MAS345 DMM (Velleman DVM345DI) that is in need of a good cal,

Just curious, what is out of calibration?  DCV? ohms?

Barring that, can anyone recommend a good trim-pot-twiddling strategy to determine what goes with what measurement?

See this thread for hints ...

https://www.eevblog.com/forum/testgear/tekpower-tp4000zc-digitek-dt-4000zc-looking-for-schematic/

[JP16A60]

Just curious, what is out of calibration?  DCV? ohms?

Yes, both.

See this thread for hints ...

Sweet...just what the doctor ordered. =)

JP
Cincinnati, OH
USA

[retiredcaps]

Just curious, what is out of calibration?  DCV? ohms?

Yes, both.

How much is DCV out by?  How much is resistance out by?

I don't think you will be able to calibrate ohms with trim pots.

[JP16A60]

Just curious, what is out of calibration?  DCV? ohms?

Yes, both.

How much is DCV out by?  How much is resistance out by?

After a second look, ohms is not terribly off, I suppose--say 5% or so vs. precision resistors (DMMCheck Plus).

DCV is off by about 20 mV at 5v reference (also DMMCheck Plus).

I don't think you will be able to calibrate ohms with trim pots.

My HP 3456a does this, so...dunno?

JP