At least for low-end quartz+mechanical watch movements, magnetic fields can cause the watch to stop mechanically ticking or even produce false ticks to cause dial to spin at a furious rate. e.g. By holding my watches at a certain angle in the field of an AC tape degausser, I can make them run many times faster than normal, and I had one mechanical watch where if I held it at the funny angle it would actually run backwards! (Must've been something other than a one-way escapement inside I guess.) This is not the quartz crystal and electronic divider being affected by a magnetic field, this is the stepper motor and mechanics turning in response to magnetic fields. It does not take a magnetized guitar pickup to catch the magnetic field coming from the stepper coil in the watch. Any nearby unshielded coil or AF-range inductor will pick up easy. Tim N3QE On Fri, Apr 18, 2014 at 2:04 AM, Chuck Harris <cfharris@erols.com> wrote: > Early watches were more susceptible to magnetic influence than > were later... this is primarily because the early watches used > high carbon steel hairsprings for the balance wheel, and when > they got magnetized, the spring coils would stick together... > > Later watches used elinvar for the hairspring coils because its > spring constants were less affected by temperature variations... > a nice side benefit is it is not easily magnetized. > > However, when an elinvar hairspring gets magnetized, it is very > difficult to demagnetize it using conventional means. > > Demagnetizers work by rapidly alternating the polarity of the > magnetic field, and slowly decreasing the strength of the field. > This causes the magnetic poles of the ferrous atoms to get randomly > aligned, which is the demagnetized state... But if the item that > is magnetized is so light weight and flexible that it can move > with the field, it won't get demagnetized... which is what happens > with the hairspring. The only way I know to demagnetize a hairspring > of this sort is to immobilize the spring with wax, and then run it > through the demagnetizer... then melt the wax, and clean the spring > with naptha. > > Fun times! > > -Chuck Harris > > > DaveH wrote: > >> I remember growing up (50 years ago) that the good watches were marked as >> being non-magnetic. I would guess that this is standard now. >> >> My concern is that the moving balance wheel could have an eddy current >> induced into it and the resulting magnetic field might cause it to slow >> down. >> >> http://en.wikipedia.org/wiki/Balance_wheel >> >> http://en.wikipedia.org/wiki/Eddy_current >> >> The act of measurement should not cause a change in what you are >> measuring. >> >> Dave >> > _______________________________________________ > 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. >