It depends of your goals. If you want a 60 Hz time/frequency standard then using a mains disciplined oscillator is good. Like AN12 shows.
But if your goal is to measure mains itself, warts and all, then measure mains as it is, not a pure oscillator tied to mains by PLL or FLL. See this Atmel app note: http://www.atmel.com/images/doc2508.pdf Also: http://leapsecond.com/pages/ac-detect/ /tvb (i5s) > On Feb 9, 2014, at 12:04 PM, "M. Simon" <msimon6...@yahoo.com> wrote: > > I kind of like the synchronized oscillator on page 6 of this pdf > > http://cds.linear.com/docs/en/application-note/an12fa.pdf > > > They claim good results. I may have to build one and see. > > > > > > Engineering is the art of making what you want from what you can get at a > profit. > > > > On Sunday, February 9, 2014 7:44 PM, Chris Albertson > <albertson.ch...@gmail.com> wrote: > > All you need to monitor line frequency is a small transformer connected to a > computer's DCD pin on a serial port. You can get fancier and use > comparator, opto isolation and so on but a simple 5V transformer is enough. > This takes advantage of the electronics inside the RS232 port that is > designed to handle positive and negative voltages up to about +/- 12 volts. >> >> >> Then the linux pulse per second driver will time stamp and log every cycle >> with the internal clock. It is accurate to a couple microseconds. >> >> >> Don't worry about line noise because that is what you are measuring and it >> averages out after a few cycles. You might try a >60Hz RC filter to remove >> noise but I think to do any better you will have to treat the signal as if >> it were audio frequency. So scale it to 1 volt peak to peak and read it >> with an audio interface and then use an FFT. But the transformer on the >> DCD pin of any normal computer with the Linux PPS driver works. People are >> doing just fine with the simple transformer and time stamping the >> transitions. And then it is just pure luck that Linux will already do this >> out of the box. >> >> >> >> On Sun, Feb 9, 2014 at 5:53 AM, M. Simon <msimon6...@yahoo.com> wrote: >> >> This probably came up during the recent discussion of Line Frequency >> Monitoring but I may have missed it. >>> >>> >>> Does any one have a circuit (tested - operational) for monitoring line >>> frequency? I'd like something that checks zero crossing so that it is >>> relatively insensitive to line voltage variations. >>> >>> >>> Simon >>> >>> >>> Engineering is the art of making what you want from what you can get at a >>> profit. >>> _______________________________________________ >>> 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. _______________________________________________ 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.
