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AC Voltmeter

  1. Nov 18, 2003 #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.

  2. jcsd
  3. Nov 18, 2003 #2


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    My guess, RMS.

    Hey, that rhymed.

    If it was giving you a steady reading for AC voltage, it was probably RMS.
  4. Nov 18, 2003 #3


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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
  5. Nov 18, 2003 #4


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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.
  6. Nov 18, 2003 #5
    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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