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Interference on AC Voltage Measurements

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Interference on AC Voltage Measurements

Post by SoftwareMan » July 3rd, 2017, 8:23 am

I am trying to measure an AC voltage of around 5VRMS at 50Hz on a Keithley 2701 DMM but the signal is NOT locked to the power line frequency. The readings I am taking 'wander' up and down slowly and I suspect that this is due to the difference in the frequencies between my source and the line voltage. What would be the best settings to use on the DMM in order to get a more stable reading? For example, should I change NPLC setting or even turn it off?


Andrea C
Keithley Applications
Keithley Applications
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Re: Interference on AC Voltage Measurements

Post by Andrea C » July 12th, 2017, 6:14 am

You could try enabling the line sync.

You mention it wanders up and down with time. Is auto zero in use?

By how much is it changing? For the range in use, is it within the error budget? The specs are when using SLOW and a sine wave signal type.

What sort of crest factor does your signal have? Check out the AC Voltage measurements and crest factor section in the 2701 manual.

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