[time-nuts] Re: UTC, 60 Hz

Tom Van Baak tvb at leapsecond.com
Thu Jul 28 02:20:15 EDT 2005

> Does your phase plot mean that a mains powered wall clock might be off 
> by 10 seconds?
> Have Fun,
> Brooke Clarke, N6GCE

Yes. I also keep an old AC synchronous motor
wall clock around just to see this effect. To be
fair, it is unusual for it to be off this much, or
for very long.

> Maybe we all should run a power line test at the same time and we should 
> be able to see who is leading and lagging !
> Brian N4FMN

You know, if the stackable TAPR module
project catches on another PCB on the list
could be a mains frequency monitor.

It would robustly filter and divide the 50/60 Hz
mains frequency to 1 PPS and then onboard
compare that 1 PPS against the local (OCXO,
atomic, or GPS) 1 PPS to a modest precision
(say, 1 or 10 us).

This would be a cheap board and then many
of us could monitor mains phase and log it in
a standard format. With the right software you
could get plots like this in real-time:

60 Hz AC Mains Frequency Accuracy Measurement 

For extra credit we could follow the GPScon
Z3801A web plot model. See:

International Web Plots

Also, while we're on the subject of monitoring
mains frequency do see Bryan Mumford's page.

Measuring the accuracy of 60 cycle power

If any of you also have an interest in precision
pendulum clocks and don't already have one
of his timers you should look into it:

MicroSet Precision Clock and Watch Timer


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