> When you measure the mains signal, nominally 60 Hz in this case, spikes > etc. is noise which is local and not of interest when comparing over a > large area. Inter-area oscillations have much slower properties. > If you go the time-stamping way, you *should* remove such noise. > > Removing or padding over it by logic will mean dropping data, which is > not helpful.
A time-stamping counter never drops *data*; instead you apply logic to drop *noise* when necessary. > Turns out that professional gear for this does not do time-stamping in > this regard. Rather, they I-Q demodulate the signal with a reference > signal at the nominal rate, low-pass filter it and pay attention to > details of filtering like group-delay and compensation thereof. It's a > rather wise approach for the type of conditions you have. I'd be happy to compare "professional gear" with a time-stamping counter. I have two or three years of data to show 60 Hz time-stamping works perfectly. Not to say your professional gear might also. But a zero-crossing counter never misses a cycle; you can set the s/w bandwidth just as you can set an IQ hardware bandwidth. Both assume some reasonable limit of mains df/f/dt. You can either do it with a fancy $100 to $1000 reference signal generator + PLL or FLL + IQ detector + professional box -- or with a $1 PIC and $0 s/w. /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
