Martin K wrote: > 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. That's going to be tricky since a simple high pass filter will still pass significant fundamental at the level that THD is often measured. You need to find the power in everything except the fundamental down to a fraction of a percent to be useful in most applications. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist