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
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