Quote:
Originally Posted by mgarrett  I
Crest Factor is an expression for the deviation from a sinusoid... If I have a very narrow pulse (low duty cycle, lots of off time) that has a peak to peak of 2 Volts, it will not generate as much heat as a sinusoid, but if we correct it utilizing the 'crest factor' we can get the RMS answer, based on knowledge of the wave shape (crest factor). |
Crest factor is an expression for the deviation from the RMS value, an expression that corrects the RMS or peak(whichever one you know) based on waveform characteristics (Provided you know the crest factor...)
CF=|Peak|/RMS, to say it simple, the ratio of peak to rms value... In the world of dB, division is subtraction so dB(CF)=dB(|Peak|)-dB(RMS) as Bob K refered to earlier, the difference between the Peak in dB and the RMSin dB.
To make it confusing, Peak is not the PKPK value, but the Peak (notice the magnitude operator) from 0 to the positive peak... complicated for non symetrical waveforms..
So for a sine wave, with a Peak of 1 Volt (PKPK of 2 volts), the Crest factor is 1.414 or 1 / 0.707...
Applying a 2 Volt PKPK sinewave to a resistor, gets it the same temperature as 0.707 Volts DC...
mcg