Once upon the time there was a "Vibrograph", see nice pictures here:
https://www.google.com/search?q=vibrograph&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwigtcmSn9fJAhUW8GMKHVNyAMcQsAQIHA&biw=1760&bih=888
,which picked up the sound of watches, clocks, and the watch maker was
able to set the watch very accurately, these machines did not used any
fancy DSP despite that they worked very well, I myself used one some 55
years ego in Switzerland,.
to get a reliable digital signal from a noisy analog signal is the most
reliable way to use an analog PLL with a linear multiplier type phase
detector [ at least one input of the phase detector must be linear e.g.
a transitional gate [cd4016 and it's derivatives ], the noise could be
filtered out with a low pass filter or integrator, the price of the
method is that it also eliminates the phase-noise of the the input signal, .
That was the method which was used by the Vibrograph.
73
LJ6UHN
Alex
On 12/12/2015 7:15 AM, Dave Martindale wrote:
Someone is in the process of writing open-source watch timing software.
You may want to look into it.
It was announced here:
http://forums.watchuseek.com/f6/open-source-timing-software-2542874-post21977314.html#poststop
It contains these links:
First the goodies. Here are Windows binaries
http://ciovil.li/tg.zip
and here is the full source code
https://github.com/vacaboja/tg
Apparently this software is better at dealing with noisy signals from
microphones than Biburo. Since it's open source, you can see what it's
doing internally. It expects an analog input, and does its own filtering
to find the interesting edges within the sound of each tick.
The precision with which you can time events is likely to be limited by the
frequency response of your sensor and the amplifier. If that's limited to
20 kHz, a standard PC sound card is adequate. For up to 80 kHz or so, you
can buy a relatively inexpensive USB "audio interface" that digitizes at
192 kHz (typically 24 bit resolution). At somewhat higher cost, you can
get professional audio interfaces that accept an external clock source.
- Dave
On Fri, Dec 11, 2015 at 1:44 PM, Andrea Baldoni <[email protected]>
wrote:
Hello!
I decided to do some experiments with mechanical clocks, so I worked a
little
on picking up escapement ticking sound, with the idea of processing it and
obtaining a "clean" digital pulse to feed a counter.
So far, I have not yet been able to find the best way to obtain a digital
pulse,
but I have already built the preamp for the piezoelectrick pickup, that
I used to feed the mic input of a PC sound card for spectrum analysis.
The timing could eventually be done in software because the whole idea of
measuring watches by picking up their noise almost surely doesn't allow
high
resolution anyway, but I will plan to try hardware solutions as well in the
future. I hope to be able to measure the jitter of the clock, but it will
be
very hard.
In the meantime, with the free software Biburo you can download here
http://tokeiyade.michikusa.jp
you can regulate your wrist watch.
Best regards,
Andrea Baldoni
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