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.
