General Question

[GEOelectronics]

1) Tomato, maybe we should move this to the PRODUCTS Forum. I was told that's where this sort of ting belongs.

2) I agree with your suggestion and yes top DMMs do, I looked long and hard for one that self-calibrated to a known good internal standard, and found the HP-34470A, it one-button autocals in 15 seconds. Manual calibration of old DMMs takes a long time, requires tons of calibration gear, charts etc.(like my HP-3478A- totally beyond my skill-set).
The Keysight 34470A was a good investment for me.

Geo

[JohnnyMalaria]

So how do you calibrate the constant current source in a DMM required for resistance measurement?

In my case, I just want to adjust two hand-held DMMs so that they read as close to each other as their precision allows. Right now there's a couple of percent between them for V, I and R.

(Sorry if this is getting off-topic - I can ask this in a new thread if necessary).

[GEOelectronics]

I don't have that knowledge but would suggest asking at PRODUCTS. It is really a test equipment and measurement sub category despite the name.

I'll be watching there too, as I am interested in general.

Geo

[rhb]

Most cheap DMMs have a single trim pot that sets the voltage and everything else is derived from that.  I have s slew of the cheap (now free with any purchase) Harbor Freight DMMs.  All but the more expensive model have a trim pot in the upper right.  There's a footprint to add one on the one that lacks it.   They are 3.5 digit DMMs good to ~0.1% if adjusted.

The best thing to do is find the service manual for the DMMs you have. But often they will mark on the PCB what the trim pots adjust if there is more than one.