[time-nuts] Measuring the accurcy of a wrist watch
albertson.chris at gmail.com
Wed Apr 16 17:51:24 UTC 2014
The first sensor I'd think of if I wanted to measure a wrist watch would be
a microphone. Listen for the tick. You'd need a good quality
preamplifier. Place the watch directly on top of the microphone then the
mic in a closet with a blanket on it.
Good quality studio microphones are very, very sensitive. At home with two
doors shut my condenser mic picks of the motor in the fridge, wall clock
ticks and the nearly silent fan motor in computer 20 feet away. Then in
post processing software I can find and identify the frequency components
of each of those the remove most of the signal. I'm not by any means an
audio pro and I'm using entry level recording gear. I'm making digital
recording but for precision timing you'd need to use the analog signal
after a pre-amplifier and apply a sharp bandpass analog filter.
About using a coil, I'd assume they use one with many thousands of turns,
maybe 100x more then a crossover coil. and place the watch, coil and
signal conditioning amplifier all in a faraday shield and apply a powerful
analog filter. But even if this works it needs a battery powered watch,
it couldn't pick up a purely mechanical movement.
I was all set to
On Wed, Apr 16, 2014 at 6:21 AM, Ulrich Bangert <df6jb at ulrich-bangert.de>wrote:
> can you explain what exactly you understand by "a large coil of wire"?
> Did you make the easurements on the Junghans with a DIY sensor or with one
> of the commercially available?
> I have made some basic tests with a coil coming from a loudspeaker's cross
> over network. It has a few hundred windings, R=1.3 Ohms, 2.3 mH, but the
> only thing i receive with this coil is a strong 10 Mhz signal...perhaps no
> real surprise in a time nuts laboratory.
> Best regards
> > -----Ursprungliche Nachricht-----
> > Von: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] Im Auftrag von Tom Van Baak
> > Gesendet: Dienstag, 15. April 2014 15:53
> > An: Discussion of precise time and frequency measurement
> > Betreff: Re: [time-nuts] Measuring the accurcy of a wrist watch
> > > Some research has shown that there is an comparable instrument for
> > > ANALOG quarz watches. As far as I understand it does not
> > try to detect
> > > the quarz frequency but detects magnetic pulses from the
> > step motors
> > > that move the hands of the watch.
> > >
> > > Has anyone of you ever tried to do this in a time nuts laboratory?
> > Ulrich,
> > Yes, this works well, for both those with seconds hands (one
> > magnetic pulse per second) and those with only minute/hour
> > hands (one or two steps per minute). A large coil of wire is
> > all you need. Have a look at the watch timing tools and
> > sensors at http://www.bmumford.com/microset.html or
> > http://www.bmumford.com/mset/modelwatch1.html
> > Here's an example using a magnetic sensor:
> > http://leapsecond.com/pages/Junghans/
> > /tvb
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Redondo Beach, California
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