There is no higher purpose actually. I just fiddle. This is how I relax.
On Sat, Nov 16, 2013 at 3:47 PM, Chris Albertson <albertson.ch...@gmail.com>wrote: > No, I meant the purpose of the whole thing. Why are you measuring power > frequency? Not why are you using a PIC. How will the data be used, what > is the question driving the measurement? > > > On Sat, 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. > > > > > > -- > > 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. > -- Doc Bill Dailey KXØO _______________________________________________ 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.
