[time-nuts] Measuring the accurcy of a wrist watch
DaveH
info at blackmountainforge.com
Thu Apr 17 16:37:27 UTC 2014
Something to consider is that most pickups are biased with a fairly strong
magnetic field.
Don't know if this would cause any damage or changes in operation of a
mechanical watch but something to consider...
http://www.guitarnuts.com/wiring/pickups.php
Dave
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Ulrich Bangert
> Sent: Thursday, April 17, 2014 01:15
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] Measuring the accurcy of a wrist watch
>
> Chris,
>
> I do not own a guitar with single coil pickups but I will
> surely give it a
> try to find out whether the humbuckers of my Gibson Firebird
> & SG Standard
> will also do the trick!
>
> Best regards
>
> Ulrich
>
> > -----Ursprungliche Nachricht-----
> > Von: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] Im Auftrag von Chris Albertson
> > Gesendet: Mittwoch, 16. April 2014 20:56
> > An: Tom Van Baak; Discussion of precise time and frequency
> measurement
> > Betreff: Re: [time-nuts] Measuring the accurcy of a wrist watch
> >
> >
> > I just did an experiment. Place a simple quartz movement
> > wrist watch on top of a Fender Stratocaster guitar. I get a
> > very strong and easy to detect signal. A loud and sharpt
> > "ping" once per second. More then 1 volt
> > peak to peak. I can cancel almost all the background hum
> > and hiss in the
> > normal way by using the selector switch on the guitar.
> >
> > The guitar has a pickup coil with many thousands of turns of
> > #40 wire. With the selector with at #2 position there is a
> > second coil some inches away that is wound in the opposite
> > direction and the two are added canceling any field that is
> > filing the room.
> >
> > I tried the same with a wall clock and all I had to do was
> > hold the clock an inch away. The wrist watch was placed on
> > top of the strings a few mm above the bridge PU.
> >
> > These is likely about 3 oz of #40 magnet wire on a guitar PU.
> > If I were building a sensor I'd do it just like the guitar.
> > one coil to pick up the signal and another identical coil
> > some inches away to to pick up ambient "noise" and then wire
> > the two in parallel but in anti-phase.
> >
> > If yu happen to have a guitar around, you have a watch sensor.
> >
> >
> > On Wed, Apr 16, 2014 at 10:43 AM, Tom Van Baak
> > <tvb at leapsecond.com> wrote:
> >
> > > > Tom,
> > > >
> > > > can you explain what exactly you understand by "a large coil of
> > > > wire"?
> > >
> > > Sorry, by large I meant a large number of turns; the coil
> itself is
> > > quite small. Rather the winding one myself I just used the
> > pickup coil
> > > from an old cheap plastic self-impulsed pendulum clock.
> The wire is
> > > extremely fine and there must be thousands of turns since
> the spool
> > > diameter is only 15-20mm and the net resistance is 3.5k.
> > Here are some
> > > iPhone photos I just
> > > took:
> > >
> > > http://leapsecond.com/pages/Junghans/coil.htm
> > >
> > > > Did you make the easurements on the Junghans with a DIY
> sensor or
> > > > with
> > > one
> > > > of the commercially available?
> > >
> > > Both. The commercial ones sold by Bryan Mumford are
> excellent; his
> > > instrument includes signal conditioning, adjustable high
> gain, and
> > > other useful features. It's meant for watchmaker types with no
> > > electronics background. It works perfectly out of the box.
> > >
> > > The Junghans wristwatch is extremely well engineered for
> > long-life and
> > > the leaked magnetic signal is the weakest of any watch I've
> > measured.
> > > Still, it can be measured. The placement of the pickup
> coil on the
> > > watch face needs to be optimized for best "reception", or any
> > > reception at all for that matter.
> > >
> > > By contrast, a typical AAA-battery desk/wall quartz clock
> movement
> > > generates a huge magnetic signal. It is so clean that you
> > can clearly
> > > see both the start (+) of the impulse and the end (-) of
> > the impulse
> > > about 30 ms later. In fact I suspect it's actually 31.25
> > ms, or 1/32
> > > s, since that's 1024 cycles of a 32.768 kHz oscillator. See:
> > >
> > > sensor placement:
> > > http://leapsecond.com/pages/Junghans/quartz-clock.jpg
> > > output to scope: http://leapsecond.com/pages/Junghans/coil-aa.gif
> > >
> > > > 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.
> > >
> > > I suspect your 1.3 ohms means the number of turns is far
> too low. I
> > > don't see any RF here, nor even very much 50/60 Hz.
> > >
> > > /tvb
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> >
> >
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the Time-nuts_lists.febo.com
mailing list