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-boun...@febo.com > [mailto:time-nuts-boun...@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 > <t...@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@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@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.