No trouble. Easy. I love it. Keeping track of the rolling counters was a hack because I am so far removed from serious programming.
Sent from mobile > On Nov 16, 2013, at 1:53 PM, "Tom Van Baak (lab)" <t...@leapsecond.com> wrote: > > Doc, > > I measure mains time & frequency with a picPET all the time. In fact that's > one of the reasons I designed it. If you're having any trouble contact me by > email. > > /tvb (i5s) > >> On Nov 16, 2013, at 11:23 AM, Bill Dailey <docdai...@gmail.com> wrote: >> >> My purpose is to do it with a picpet. That's it. So, that eliminates a >> bunch of the options. I can decouple the measurements from the pc clock >> that way. >> >> Doc >> >> Sent from mobile >> >>> On Nov 16, 2013, at 11:26 AM, Chris Albertson <albertson.ch...@gmail.com> >>> wrote: >>> >>> The signal is 120 volts. You hardly need to amplify it. Clip it with a >>> diode to +- 9 volts so as not to blow up your serial port. But I'd use a >>> transformer for safety. The zero crossing detectors are built into the >>> RS232 interface. You take advantage of the RS232 spec which has a DCD >>> pin input of about +-9 volts that is already set up to find a leading edge >>> of a pulse and cause a very low latency interrupt. The system software >>> already will capture the time all inside a kernel level interrupt handler. >>> >>> The jitter turns out to be on the order of a single digit microseconds. >>> Good enough for measuring a 60Hz signal. >>> >>> I guess if you want to see transients depends on the purpose of the >>> experiment. Are you looking at local AC power quality or wanting to >>> measure the grid. The grid is well monitored, just use FNET and you get >>> real-time data for all of North America. I think the reason for measuring >>> it yourself is to see local power quality and things load switching inside >>> your own building, that's transients. >>> >>> >>> >>> The other way to measure AC with zero added equipment is to treat it as an >>> audio signal and after reducing it to 1 volt run it into an audio interface >>> And then use FFT. This will let you see very small spikes and noise. It >>> depends again on your purpose for doing this. >>> >>> >>> >>> >>> On Sat, Nov 16, 2013 at 1:18 AM, Magnus Danielson < >>> mag...@rubidium.dyndns.org> wrote: >>> >>>>> On 11/16/2013 09:52 AM, Chris Albertson wrote: >>>>> Your method tosses out a lot of data. You can't see transients. Ideally >>>>> rather then record a 1 second average you'd record the time of EVERY zero >>>>> crossing. It sounds like a lot of data but not really. You only record >>>>> 32 bits 60 times each second. That is 240 bytes per second. >>>> But you want it filtered to avoid the transients. Those are really not >>>> that interesting when you measure the grid. >>>> >>>> Also, if you use the event trigger method you probably want to use an >>>> amplifier to increase the slew-rate such that noise does not convert >>>> into time jitter. >>>> >>>> Cheers, >>>> Magnus >>>> _______________________________________________ >>>> 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. > _______________________________________________ > 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.
