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AC Voltmeter

  • #1
138
1
I took some measurements for a Physics lab and don't recall whether the Voltmeter I used reports the peak voltage or rms voltage. I need rms voltage to calculate the rms current. Can anyone tell me what the norm is for voltmeters: peak or rms?

To divide by the [squ]2 or not to divide by the [squ]2, that is the question.

Thanks.
 

Answers and Replies

  • #2
jamesrc
Science Advisor
Gold Member
476
1
My guess, RMS.

Hey, that rhymed.

If it was giving you a steady reading for AC voltage, it was probably RMS.
 
  • #3
chroot
Staff Emeritus
Science Advisor
Gold Member
10,226
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Actually, the vasssssst majority of AC voltmeters are peak-to-peak. Some of them which say "RMS" actually only give the correct RMS voltage at one frequency, usually 60 Hz. Only a meter which says "true RMS" will actually give you the RMS amplitude at all frequencies.

Just because the meter is not true RMS does not mean it will not give a steady reading -- it will. It'll just be an incorrect steady reading.

- Warren
 
  • #4
jamesrc
Science Advisor
Gold Member
476
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Fair enough. The Fluke handhelds I always use always give me true RMS. I shouldn't have assumed that applied to others considering what happens when you assume... Sorry if I was the source of misinformation.
 
  • #5
138
1
I vaguely remember the instructor saying something about the meter measuring the peak voltage, but needed to confirm before I finish my lab assignment.

Thanks very much for the help.
 

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