On Mon, 6 Mar 2000 22:29:23 -0400 Jeff Davis writes: > On Mon, 6 Mar 2000, Lorick wrote: > > > Now I would like to know why this works....what is the > mathematical > > relationship between squaring the readings and obtaining the RMS > in the end? > > > > I know it's almost stupid to ask since we're talking about Root > Mean Square > > to begin with....but I am indeed missing the in between steps in > the > > story... > > What squaring the values does is effectively eliminates the sign of > the > number (+/-). If you were to simply take the average of all > measurements > of a sine wave you would get zero. An RMS value is the average > magnitude > of each reading without taking into account the sign of the reading. > > Jeff This would be true IF we took the square root prior to taking the mean (squared, took square root, accumulated sum, divided by number of samples) since the square root of the square is one way of defining the absolute value. However, in RMS, we first square the sample, then accumulate a sum, then divide by the number of samples, THEN take the square root (hence Root Mean Square). The reason for the squaring is because RMS is related to the POWER of the waveform, and power has a squared term (either I^2*R or V^2/R). So, RMS is a method of weighting so the higer amplitude signals have more significance than they would with a straight averaging. Harold FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj.