Multimeters

[images]

Thought I would test a greenlee clamp on multimeter that I bought at a rummage sale.
The greenlee read 123 volts.
The fluke I have is quite old and read 119 volts.
The harbor freight cheapie I have read read 121 volts.
Never tried this experiment before, all were digital and the max spread is as much as 4 volts.
I am surprised that the meters differ so much, apparently I should not have assumed all these years the readings I have been getting were pretty accurate because it was from a digital voltmeter.
Any experience in this area?

[Wayne_Dohnal]

From downloaded manuals, the AC voltage accuracy spec of the HF meters is probably either 1.2%+5D or 1.2%+10D. That's either about 1.94 volts or 2.44 volts. Just for curiosity I tested a few HF meters I have lying around.

My most trusted meter varied 123.0 to 123.2 during the testing.
A low-end Sears clamp meter varied 122.6 to 122.8 (about 1/3% difference).
HF #1 - 123.1 to 123.6
HF #2 - 123.1 to 123.8
HF #3 - 121.6 to 122.0
HF #4 - 123.0 to 123.4
HF #5 - 121.4 to 122.5

So if one assumes the 'trusted' meter is correct, the HF meters are all within their spec. It would take a reading below about 121.0 to be out-of-spec. The 4 volt spread the OP saw does look bad.

[tvman44]

Depends on the accuracy of the particular instrument and if it is in calibration. For really accurate work they are periodically re-calibrated and certified.:)

[WyoTraveler]

I would believe the Fluke meter. John M. Fluke made some good meters.

[2oldman]

images wrote:
I should not have assumed all these years the readings I have been getting were pretty accurate because it was from a digital voltmeter.

The digital part only applies to how it displays information, not how accurate the internal electronics are. It is deceiving.

I just installed 2 of the exact same digital VMs in my RV and off the same power source they read 0.2 apart.