What do I calibrate my dmm with or from?

Off-topic Chatter
1

Recently I got a new dmm (actually a clamp meter).

The new one consistently reads about 3 volts higher than my old one on an AC outlet, and also when I check on some of my lilos.

Now I don’t know which of the two is showing the real or just perhaps the “correct” reading.

Any ideas?

2

Where are you located?
Perhaps there is a member nearby who has a quality power supply or even just a known good meter.
Failing that, perhaps someone can send you a battery that has a known V for you to measure.
All the Best,
Jeff

3

3volts higher on (220v?) AC really not that much.

3 volts higher measuring 3-4.2V liion is a problem!

Might be crappy connection/leads, can you swap the leads and retest?

Edit to add: are the batteries in both DMMs good? I’ve seen reports of weird voltage readings if the internal DMM battery is low.

4

This. And also try swapping the leads.

And here is an article about how to make an inexpensive low V reference source.
The trick with the parallel resistors to increase accuracy is nifty.
All the Best,
Jeff

5

To maintain certification, they usually need to be sent out to be calibrated annually. I have a friend who works as an aircraft mechanic and use his DMM’s or PSU’s to calibrate my own. Sometimes they need no calibration. Other times they do, regardless of how cheap or expensive the device may be. This works well for me, given the general level of precision I need. If I needed greater precision, Id send it out for annual calibration.

6

THANKS!