[time-nuts] Mechanical clock sound pickup circuit

Azelio Boriani azelio.boriani at gmail.com
Sun Dec 13 12:40:55 EST 2015


Maybe this can be useful to make the pick-up:

http://www.meas-spec.com/downloads/LDT_Series.pdf

they can be found also on the usual auction site.

On Sat, Dec 12, 2015 at 10:28 PM, Alexander Pummer <alexpcs at ieee.org> wrote:
>
> 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 <erm1eaae7 at ermione.com>
>> 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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