Vrms

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tomroth
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Vrms

Post by tomroth » Sat Oct 24, 2009 2:58 am

Vrms = Vp*.707, right? My Picoscope software only offers Vpp, or AC rms. I have displayed right now a source of 22.18Vpp @ 105.5Hz. Dividing by 2 for Vp I get 11.09Vp. Multiplying by .707. I get 7.841 Vrms. My display says 7.683 Vrms. Why the difference? I am running 6.2.13.0.

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Erik
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Re: Vrms

Post by Erik » Tue Oct 27, 2009 7:40 am

That formula is only true for a perfect sinewave.
RMS is actually calculated by integrating to get the area under the signal (between the signal and zero) and then dividing by the time to get the average DC voltage corresponding to the same power (area).
AC RMS is the same thing but the DC component removed first.

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