> I'm wondering about the possibility of checking the frequency of my > oscillator by using a NTP synced RT Linux system. What I'm thinking of
An "all-PC" frequency counter is a great idea. True, the performance is limited compared to GPS time sources and hardware frequency counters, but there's something to be said for an all (or almost all) software approach. Time-stamping from an external pin transition should work fine. Consider also using the sound card as a time comparator. If you put your divided down UUT the left channel and an NTP sync'd parallel or serial port tick into the right channel you can compare the relative phase by looking at the stereo input data. Phase change over time gives you frequency error. The instability of the sound card's own LO drops out of the equation. With 44.1 kHz sampling you could handle tick rates of 1 kHz without any problem. This should be quite a bit more accurate than 1 Hz sampling, so you might have to wait less for your goal of 1 ppm resolution. If the limiting factor is the quality of your NTP connection, then you've done a good job. /tvb _______________________________________________ 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.
