Hi,

I agree with tom, winding may be an issue.

If that could be overcome, would it be possible to injection lock the clock with a piezo or other small mechanical actuator? Something mounted to the clock body that 'pings' it periodically may all that's needed to pull it where you want it to go.

One would think it would be nice to do this project without having to modify the clock significantly, or risk damaging it.

If you do succeed I'd be interested in reading the results. A fun project, in my opinion.

Dan




On 1/30/2020 3:18 PM, [email protected] wrote:
Message: 7
Date: Thu, 30 Jan 2020 10:35:11 -0800
From: Tom Van Baak<[email protected]>
To:[email protected]
Subject: Re: [time-nuts] Cesium Mechanical Chronometer
Message-ID:<[email protected]>
Content-Type: text/plain; charset=utf-8; format=flowed

That would be a fun project. There are examples of measuring a M21 on
Bryan's site:

https://www.bmumford.com/mset/tech/chrono/

Here are phase and ADEV plots for my M21:

http://leapsecond.com/pages/m21/

That page also shows you a typical chronometer rate card, which provides
the key "paper clock" advantage over using the clock dial alone.

I use a piezo pickup to extract timing pulses from the clock. The audio
waveform isn't pretty but you can form a low jitter 1PPS out of it.
Laser sensors give a cleaner signal but are more difficult to use with
an M21.

Running a GPS/CSAC + M21 in a master/slave arrangement should be easy,
although I don't know how you'll handle the rate card corrections.

Running them in phase lock will be much harder. You can probably
discipline the CSAC from the M21 using RS232 commands to the CSAC. But
to discipline the M21 from the CSAC requires that you have a way to
dynamically adjust the rate of the M21 at ppm levels. That's going to be
tricky, given that high-end compensated chronometers like this are
specifically designed to be as immune to internal and external changes
as possible. One avenue may be the winding interval: notice the slopes
of the phase plot.

The biggest problem I had with long-term data collection was re-winding
the chronometer. If you design a non-invasive auto-winder as part of
your project, please contact me.

/tvb

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