220 vrms
the_risk_master said:
Try to grab a Digital Multimeter (select it as to measure AC voltage with range of at least higher on what you are expected to measure) Now read the Meter, it should read 220V (note all meter device should read RMS values)
To tell the truth the above is not always true. Multimeters usually
display rms value but this fact does not mean they really
measure it. If they do, you can see the notice "True RMS" somewhere on the device and such a device is also appropriately more expensive (it requires a built-in rms converter). Other devices usually measure peak or mean value of a rectified waveform and take advantage of the fact that the relations between peak/mean and rms (root mean square) values for a known waveform, in this case
sine wave, are constants so that they can recalculate it and display. This fact implies that such a device displays the more inaccurate value (sometimes really nonsens) the more the measured waveform "differs" from sine wave.
For instance waveforms in circuits with a phase controlled SCR (thyristor or triac) give quite big errors measured with non-true rms devices.
Just for interest, the mentioned values are defined as follows:
For periodic waveforms v(t):
mean value = \[\frac{1}{T}\int_0^T{v(t)dt}\]
rms value = \[\sqrt{\frac{1}{T}\int_0^T{v^2(t)dt}}\],
where T is the time period.
Sine wave:
If v(t) = M×sin(ωt),
where M ... peak value of the sine wave,
ω = \[2\p f\] = \[\frac{2\p}{T}\] ... circular frequency, we obtain:
mean value = 0
if fully rectified, then
mean value = \[\frac{2M}{\p}\] = 0.637M ... relation between mean (fully rectified) and peak value
rms value = \[\frac{M}{\sqrt{2}}\] = 0.707M ... relation between rms and peak value
rms/mean (fully rect.) = \[\frac{\p}{2\sqrt{2}}\] = 0.707/0.637 = 1.11 ... relation between rms and mean value of fully rectified sine wave
Best Regards
Eric