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Easy way to test the calibration of a DMM (Fluke 45)?

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KungFuJosh:

--- Quote from: shabaz on April 02, 2024, 09:28:37 pm ---
Well now you're just trying to swing the discussion into something else.

"Without traceability, those numbers mean NOTHING"

If you need $2700 of traceability to figure out which instrument is off by 20 mV or so, then there's something wrong with the way you do engineering.

--- End quote ---

I don't know what your first language is, but there seems to be something lost in translation with you. He never said anybody else should spend that money on calibration. The dude's name is "CalibrationGuy" you might infer from that that he's somewhat into calibration.

CalibrationGuy:
I'm going to reply because there are people who will read this thread and misunderstand what is being said. So, let me be clear.

1) I pay top dollar because I must be sure of my data.
2) Using a newly calibrated meter verified that a very reasonably priced voltage reference achieved excellent results.
3) You cannot verify with any certainty, 20mV which meter is off using a reference from unknown sources without proof of calibration.
4) To tell the OP that it's a good idea to rely on an unknown reference to test his meters is bad advice.

TomG.

shapirus:

--- Quote from: shabaz on April 02, 2024, 09:28:37 pm ---If you need $2700 of traceability to figure out which instrument is off by 20 mV or so, then there's something wrong with the way you do engineering.

--- End quote ---
The wonders of metrology. Yes you actually do need to spend a lot of money, if you want to have a definite, expressed in numbers, and certified amount of certainty uncertainty in the readings displayed by your test equipment.

But once you can be satisfied by qualitative expressions "most likely" and "good enough", or have a friend or someone who offers to use their calibrated (officially or unofficially) equipment out of their good will for you, then it can be done much, much cheaper.

shabaz:
Regarding:
"Yes you actually do need to spend a lot of money, if you want to have a definite, expressed in numbers, and certified amount of certainty in the readings displayed by your test equipment"

No one is arguing with that - although with the slight caveat that some would say it's not a lot of money to pay to get a 5-digit DMM calibrated. Everyone has a different perspective on pricing, of course, and it would vary by region.

shabaz:
"3) You cannot verify with any certainty, 20mV which meter is off using a reference from unknown sources without proof of calibration."

That's demonstrably untrue. Modern silicon comes factory-trimmed to a greater precision. You could pick up a $5 voltage reference (half the cost of the AliExpress one!) and with little care (a couple of capacitors) end up with a result accurate to within single-digit millivolts.

So yes, it is certainly possible to identify which of two multimeters (or both, or any number of them) are faulty, if their discrepancy is 20 mV.

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