Tom, many thanks for your help. Will give it a new try over Eastern!
Best regards > -----Ursprüngliche Nachricht----- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von Tom Van Baak > Gesendet: Mittwoch, 16. April 2014 19:44 > An: 'Discussion of precise time and frequency measurement' > Betreff: Re: [time-nuts] Measuring the accurcy of a wrist watch > > > > 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.