[linux-audio-dev] Setting the Beat of a Clock

[James Courtier-Dutton]

capnlinux at handsonarabians.com wrote:
> There was a question about what kind of accuracy would be required.  Well,
> the more the better.  Without electronic assistance this was done by letting
> the clock run for a day and measuring it against a known good time source,
> adjusting the pendulum, repeat.  Running the clock for longer periods
> between measurements obviously makes the adjustment more accurate.
> 

I am thinking that it might be better to use an optical instrument to 
measure the timing.

Just place the optical sensor in the center (or a pair of sensors if you 
also need to know direction) and measure the interruption of the beam.
This could potentially measure the position of the pendulum accurately.
You would then not need any fancy Digital signal processing to recognise 
the tick/tock, and you could keep making noise around the office while 
it made measurements. The computer would simply receive an on/off/on 
signal from the optical sensor each time the pendulum passed, and you 
could make the measurements as accurate as you wanted. A simple I/O card 
with very accurate timers/counters on it should do the job nicely.

I don't think that any audio based timer would work at all well, as the 
temporal resolution of the audio sampler on sound cards it no where near 
accurate enough.

It would be nice if I was proved wrong though, as the simple "just put a 
mic near the clock" solution is by far the cheapest.

James