Again, why are you measuring the AC line? I'd think maybe to measure the noise that is on it. The fundamental freq. changes second by second. It's not a clean 60Hz my any means. The rate of frequency change is one thing you'd like to measure
I was just watching a minute ago and can see a 0.01Hz/second drift. It is likely MUCH worse as what I was watching is filtered over second On Sat, Nov 16, 2013 at 4:54 PM, Charles Steinmetz <csteinm...@yandex.com>wrote: > Chuck wrote: > > In the case of a 60Hz mains derived signal, most of the noise is >> going to be riding on the signal, and will be amplified with your >> gain stage. >> > > The potential evils of bandpass filters in a timing chain are well known, > but as long as you can accept the delay of a filter (or correct for it, > which should be trivial with a PIC or other uC), you may be much further > ahead with a noisy signal like the AC mains if you use a sharp bandpass > filter on the incoming 60 Hz then amplify & clip the signal to increase the > slew rate. Active filters with fast, quiet op-amps should do the job well. > For the lowest jitter, a Collins-style multi-stage zero cross detector may > be helpful. > > Best regards, > > Charles > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.