Re: Average, RMS and Power Factor made easy!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Charles Hobson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <charles.a.hobson-at-btinternet-dot-com>

Dave Sharp wrote:

"Terry
The 0.7071 factor for pk to rms value is ONLY VALID for sinusoidal periodic
waveforms.  Square waves are a different fish to fry...

I'll look in my Yokogawa references and see what the rms equations are for
a periodic square wave...  I believe the HP meter over the Tek any day of
the
week in this case.

Regards

Dave Sharpe, TCBOR
Chesterfield, VA. USA"

Hello Dave and Terry,

A neat symetrical square wave consists of its fundemental frequency and the
odd harmonics of the fundamental. These are all sinusoidal waves obeying the
law of superposition to form the square wave. The fourier series describes
this and provides the relative amplitudes these frequencies. Voltage
Amplitude is regarded as Peak Voltage of any wave form. I think the rms of a
square wave is equal to its peak value. (The .7071 factor to get rms as you
say is good only for  sine waves)

I suspect that different makes of instruments for measuring voltages will
give different results because their  frequency responses are not the same.
That is to say that the HP instrument probably has a wider band width than
the Tek. I hope this is of some help.

Regards Chuck