Electronics > Metrology

Multimeter Resistance Accuracy Calculator

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Nogtail:
I've put together a tool to check the accuracy of multimeter resistance measurements: https://checkohm.code7.au/ I'd love to get some feedback/suggestions, especially if someone could double-check my maths!

The source is here if anyone is interested: https://github.com/ZoidTechnology/CheckOhm

LordXaos:
Didn't check the code, but the outcome looks plausible. Makes me wonder why benchtop DMMs with graphical displays don't show some kind of confidence interval on screen (at least as an option)...

Sensorcat:
Accidentally entered 'Reference Resistance' and 'Measured Resistance' of 100 Ω for a 'Multimeter Range' of 20 Ω. Input accepted! Either don't understand how you mean it (=> more text would be useful) or input checking should be added. Otherwise, good and useful idea.

srb1954:

--- Quote from: LordXaos on July 23, 2024, 11:30:12 am ---Didn't check the code, but the outcome looks plausible. Makes me wonder why benchtop DMMs with graphical displays don't show some kind of confidence interval on screen (at least as an option)...

--- End quote ---
I agree. With some high-end multimeters including temperature sensors and real time clocks they could easily include the aging effects and temperature coefficient into that confidence interval.

The manufacturers of these multimeters could possibly get more business for their calibration labs when users see how much worse the confidence level gets over time.

Nogtail:

--- Quote from: Sensorcat on July 23, 2024, 09:08:54 pm ---Accidentally entered 'Reference Resistance' and 'Measured Resistance' of 100 Ω for a 'Multimeter Range' of 20 Ω. Input accepted! Either don't understand how you mean it (=> more text would be useful) or input checking should be added. Otherwise, good and useful idea.

--- End quote ---

Thanks for the feedback! That's actually intended. On a lot of multimeters, the full-scale reading is slightly higher than the range. I think on my Keithley 2000 it's around 120%. I could show a warning if the resistance is significantly higher than the range, but I'm not sure where I'd set the threshold.

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