[time-nuts] How good are mechanical watches

[Tom Van Baak]

>> See ADEV of a Hamilton M21 Ship's Chronometer:
>> 
>>     http://www.leapsecond.com/pages/m21/
> 
> I'm curious -- how did you pull the data?
> 
> My first guess would be a microphone to pick up the ticks, followed by a
> little dsp...
> 
> John

I mostly use Bryan Mumford's "MicroSet timer" which you
can read about in his excellent web site:
http://www.bmumford.com/microset.html
http://www.bmumford.com/mset/modelwatchpro.html

For the M21 run I used one of his clip-on acoustic sensors
(just a piezo element, I think). But see all the sensors at:
http://www.bmumford.com/mset/access/access.html

The cute little MicroSet collects data and outputs RS232 (nice)
which can then be logged on a PC and processed the same
you you'd handle any other clock data.

In some cases I pull a "tick" right off the op-amp inside the
microset and then use a GPSDO-triggered 53132A to collect
data. This gives better resolution and long-term accuracy to
the collected data. It works well with analog (stepper-motor)
watches because they then act like a 1PPS source.

That's how I measured the performance of a WWVB radio
controlled watch:

    http://www.leapsecond.com/pages/Junghans/

This is a great example of "sawtooth" that you probably
haven't seen before.

/tvb