Hal, Thanks for the info. I think I'm going to give it a go. At any rate it's a good excuse to buy another Raspberry pi :)
Thanks for the python source too. Looks useful. Jimmy... N5SPE > On Feb 5, 2014, at 11:39 AM, Hal Murray <[email protected]> wrote: > > > [email protected] said: >> Interesting.. I'm assuming the green graph is actual voltage and the red >> graph is..? > > The green is the frequency as measured over the last 10 seconds. > > The red is the long term clock offset in cycles relative to what it would be > if the frequency was exactly 60 Hz. It's the error you would see if you > looked at a clock that was tracking the power line. The 0 point is arbitrary > since I can't see the reference clock the power system is using. For those > graphs, I used the start of the day/file as 0. > > >> I've never done any mains monitoring/measuring and was wondering, what's >> your equipment setup? > > It's simple. The hardware is an AC wall wart and a couple of resistors as a > divider connected to a modem control pin. I forget which one. It's the one > that ntpd expects to use with a PPS input. > > There was a discussion on that topic here a year or 3 ago. It's in the > archives, but I couldn't find it with a quick look. > > The software is a simple python hack. It runs on Linux. > http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/pps.py > > Linux has a back door to the PPS info. Things like > /sys/class/pps/pps0/assert give text like this: > 1391619268.999925084#1125070 > The number left of the # is the time of the last PPS. The number to the > right is the pulse count. The software above just waits 10 seconds, grabs > another sample, and writes a line of text to a log file and switches to a new > file every day. It's 1/2 megabyte per day. > > If you have FreeBSD or NetBSD rather than Linux, it shouldn't be too hard to > use the same API as ntpd uses. I don't know how PPS works on Windows. > > Another approach would be to feed it into the audio input and scan for zero > crossings. I captured the raw binary for a while when I was chasing some > noise glitches. It's a lot of data. > > > -- > These are my opinions. I hate spam. > > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
