It does not take a large pickup coil to pick up the magnetic field of a quartz watch movement tick.
Radio Shack used to sell suction cup "telephone pick up coils" but I doubt they have them anymore. These piggybacked on a phone receiver. They are still out there, http://www.elliottelectronicsupply.com/camera-security-equipment/listening/telephone-pickup-coil-suction-cup.html Just as effective is any unshielded mH-range inductor. e.g. http://www.mouser.com/ProductDetail/Murata-Power-Solutions/13R336C/?qs=gLyyx31KZaCXYrPIar3DqA== I work with e.g. Rick Campbell's R2 series receivers, which do AF filtering using inductors and these pick up the tick, tick, tick from my watch clear as day from over a foot away. Back when I had a CRT computer monitor on my desk, they picked up the flyback and deflection frequencies real well. Tim. On Wed, Apr 16, 2014 at 1:51 PM, Chris Albertson <albertson.ch...@gmail.com>wrote: > 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 <df...@ulrich-bangert.de > >wrote: > > > Tom, > > > > 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 > > > > Ulrich > > > > > -----Ursprungliche Nachricht----- > > > Von: time-nuts-boun...@febo.com > > > [mailto:time-nuts-boun...@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 > > > > > > _______________________________________________ > > > 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. > > > > > > -- > > 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.