[time-nuts] Tissot wrist watch

David Martindale dave.martindale at gmail.com
Wed Apr 6 14:26:51 UTC 2011


Picking up the crystal frequency should work with older quartz watches
that use a trimmer capacitor to adjust the crystal frequency.  But
recent quartz watches use a crystal that's deliberately too high
frequency, and a divider chain that drops one oscillator pulse every
so often to bring the overall rate down to close to the correct value.
 This all-digital method is cheaper and more stable than using a
trimcap.  The time between dropped pulses is programmed individually
for each watch after measuring the actual crystal frequency.

To measure the timekeeping of such a watch, you pick up the sound or
magnetic pulses from the second hand's motor (not the crystal), and
observe how they drift compared with a reference 1 Hz source over a
period of 10 minutes or 16 minutes or whatever the cycle time of the
pulse-dropping process is for that model of watch.  If you're watching
on a timegrapher, you will see the timing running fast for a while,
then jump back periodically giving a sawtooth-shaped display.

     Dave

On Wed, Apr 6, 2011 at 7:33 AM, Greg Broburg <semiflex at comcast.net> wrote:
> For mechanical watch movements such as Rolex
> and Patek quality used a microphone to resolve
> the sounds of the escapement reference. They
> had a strip chart recorder on the top and displayed
> the recovered acoustical signature onto a plot of
> against the internal crystal reference which ran a
> stepper motor moving the paper. I believe that the
> manufacturer was Heuer. Last look was 20 yrs ago.
>
> Same idea for 32k768 bender time references
> different type of acoustical pickup then lots of
> gain and a BP filter at 32k8.
>
> No experience with newer 4M194 style watches.
> Maybe build an RF induction pickup with a 4M2
> filter and amplifier to try to find it then more
> cleanup to get it to a counter
>
> Greg
>
>
>
> On 4/6/2011 5:32 AM, asmagal at fc.up.pt wrote:
>>
>> Dear Time-Nuts,
>>
>> I am afraid of being off topic with the following.
>> If so, I sincerely apologize.
>>
>> I would like to know the precision to be expected
>> on time keeping from a Tissot mod. J378/478 S wrist
>> watch and how could be verified the fulfilment of
>> that specification without waiting for a long time
>> (probably more than one month) to observe an error
>> of one second.
>>
>> Instructions on how to build a test basket or similar
>> layout would be most appreciated.
>>
>> Thanks in advance,
>> Antonio
>> CT1TE
>>
>>
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>
>
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