Take a look at the ADI demo board schematics on how they do front end filtering using the ADE7758 and others in the family Martin K wrote: Olin Lathrop wrote: > Martin K wrote: > >> So calculating the power factor could be done quite easily on an 18F >> however THD would require a FFT to calculate the sum of powers at >> frequencies above the fundamental. > > > Calculating power factor should be possible on a 18F since its mostly a few > multiplies per sample. Calculating total harmonic distortion doesn't > require a FFT, although that's one way. You don't need to know the full > spectrum to calculate THD, only how much power is in the fundamental and > how > much everywhere else. There are simpler ways of doing that than a FFT. The only way I can think of would be to high pass filter the current/voltage signals and then figure out the total power of that signal [>60Hz] sound reasonable? It seems like it gives you the "power here, power everywhere else" data. A digital IIR/FIR filter would have a better result but probably take much more computation. -- Martin K http://wwia.org/ -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist