Greg Broburg wrote:
For mechanical watch movements such as Rolex
and Patek quality used a microphone to resolve
the sounds of the escapement reference.
ALL watch manufacturers used such a system, even Timex.
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.
There were a dozen or more manufacturers of watch timing
machines. One of the most popular was the Vibrograf.
Greinier was another.
They were basically a mechanical version of an oscilloscope.
Inside the machine was a crystal, or tuning fork, reference,
which was divided down to a handful of frequencies that
corresponded to the popular balance wheel rates of the
various sized watches. The resulting frequency (sinewave)
was fed to a power amplifier stage that drove a synchronous
motor.
The motor directly drove a drum that had a one turn spiral
of wire wrapped around it. That wire formed the "sweep".
Geared to the motor was a paper feed system that fed a strip
of paper over the top of the drum. It also drove a standard
typewriter ribbon to make a mark on the paper.
On the other side of the system, a piezoelectric transducer
picked up the mechanical vibrations of the watch, and a high
gain adjustable amplifier amplified the vibrations to a high
enough level that they could drive the coil on a solenoid
device that drove a bail that could strike the drum. When the
bail struck the drum, it left a mark on the paper strip at the
intersection of the bail, and the spiral wire. The watchmaker
knew the gain was adjusted correctly when the bail ticked
with a nice regular pattern at the same rate as the watch's
balance wheel.
Because of the inter relationships of the various parts, the
marks on the paper would represent a straight line when the watch's
rate matched the timing machine's. They would veer off at a
positive, or negative angle if the watch was above, or below
the desired rate.
The timing machines typically have a plastic wheel with a set
of lines on it that can be rotated to match the pitch of the
line on the tape. There was a dial that could be referenced
to read out the watch's error.
The absolute accuracy of the timing machine was not of great
importance. The way it typically was used, was to quickly
set the watch to what the machine thought was correct, and
then the watch was given to the owner with the instructions
to wear it normally, and bring it back in a week... but don't
reset the time. At the end of the week, the watchmaker would
compare the watch's time with the shop's standard clock,
calculate the owner's "personal error", and then set the
dial on the timing machine to compensate for that error. The
watchmaker would then put the watch on the machine, and adjust
the balance wheel to match the dial on the machine.
-Chuck Harris
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, asma...@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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