[email protected] said: > You are looking for parts per thousand at most. Precision GPSDO 10 MHz is > overkill.
That depends on the time scale you are interested in. If you want to plot the line frequency on the scale of seconds or minutes, then a junk crystal is probably good enough. If you are want to measure the drift over hours or days, then you want a reference with long term stability. You can do that with either a PPS or a 10 MHz reference. -------- [email protected] said: > - The dropping resistor will slowly change the amplitude of the waveform > (and thus the point in the cycle that the schmitt trigger fires) due to > thermal and aging effects, if we're measuring anything that's not the exact > zero crossing There is all sorts of crap on the line. I think temperature and aging of a resistor will be lost in the noise of normal shifts in the line voltage. When I run out of other things to do, I want to capture what happens when the washing machine or refrigerator turns on and compare that with random dips that the power company delivers. The APC UPS units have a serial or USB port to tell your system when to shut down. At least the one I have will also tell you the line voltage and the min and max since the last time you asked. On a good day, my 120V line voltage wanders over about 5 volts. On other days, there are 10-15 volt dips. -- 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.
