[time-nuts] Mains frequency
Charles Steinmetz
csteinmetz at yandex.com
Sun Nov 17 00:54:17 UTC 2013
Chuck wrote:
>In the case of a 60Hz mains derived signal, most of the noise is
>going to be riding on the signal, and will be amplified with your
>gain stage.
The potential evils of bandpass filters in a timing chain are well
known, but as long as you can accept the delay of a filter (or
correct for it, which should be trivial with a PIC or other uC), you
may be much further ahead with a noisy signal like the AC mains if
you use a sharp bandpass filter on the incoming 60 Hz then amplify &
clip the signal to increase the slew rate. Active filters with fast,
quiet op-amps should do the job well. For the lowest jitter, a
Collins-style multi-stage zero cross detector may be helpful.
Best regards,
Charles
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