Electronics > Metrology

Shoud we ask the Cal Lab to adjust the multimeter to 24h specs?

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mendip_discovery:

--- Quote from: bdunham7 on January 19, 2025, 07:04:57 pm ---
--- Quote from: IanJ on January 19, 2025, 06:22:49 pm ---Wokingham.

--- End quote ---

That appears to be the better of the two by far.

https://www.ukas.com/wp-content/uploads/schedule_uploads/969151/0147Calibration-Multiple.pdf

Since they show sub-ppm uncertainties for DC voltages then your 3458A must be pretty much spot-on to begin with, much better than just "in spec".  Or perhaps results of the artifact calibration procedure are a little uncertain.  What were the source uncertainties listed on your certificate?

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Remember this is the lab's best capability, this might just be for comparison to other 10 V refs and not for the calibration of 8.5digit multimeters. Some labs will have a Golden calibrator and the spare, if they use the spare then your uncertainties might not be as good as you expected, I got caught out by this myself once. So now all our equipment goes out with a comment for them to use their best capabilities.

rodpp:

--- Quote from: Kleinstein on January 25, 2025, 10:07:53 am ---Even if the meter is adjusted digitally, there may be no easy digital read back. Ideally one would get that, but AFAIK not many meters offer this in a well documented form.
Using only the measured value before and after adjustment adds some error to this. So one may not know by how much the scale facters were changed exactly. The drift history would thus be more accurate without the adjustment step.

It also depends on the use case, if it is important that the meter directly displays the correct values, or if it sufficient to know the correction factors to apply afterwards.

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I haven't had considered the calibrator errors in the before/after report measurements. And at least in my factory cal report the TUR is very low accros the board, ranging from 0.8 for 1.9KOhm up to only 3.9 for 19mV. So the calibrator error were on the same ballpark of the meter itself.

Not good to track the drift...

rodpp:

--- Quote from: CalibrationGuy on January 25, 2025, 02:11:22 am ---In March, I will be sending my reference 3458a meter to the Keysight standards lab in California. Since the meter has been extremely stable, I will tell them to now calibrate it to 24 hour specs because I'm tired of using offsets for critical precision measurements. But that's just me...

TomG.

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Nice, in your case you already know your meter and the adjustment will bring the convenience of not having to use offsets.

My meter only had the factory cal report, I'll think more about adjusting it or not. The point Kleinstein bring is relevant.

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