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Anti-magnetic Watch

Anti-magnetic (non-magnetic) watches can run with minimal deviation when exposed to a certain magnetic field.

According to the DIN 8309 (Deutsche Industrie Norm - German Industry Norm), an anti-magnetic watch must resist a magnetic field of 4,800 A/m (Ampere per meter) or about 60 Gauss and have a maximum deviation of 30 seconds per day.

2 Ways of making an anti-magnetic watch:
1. Using different alloys
beryllium, bronze
carbon, chromium, iron,nickel
beryllium, chromium, iron, nickel, titanium

chromium, iron,nickel

Less resistant to magnetism and more resistant to thermal influence than Invar

Different components of these alloys have different properties. Since the 50's Nivarox and Glucydur were extensively used by the watchmakers. Starting with the 60's almost all Swiss watches had Glucydur balance and Nivarox hairsprings. The anchors, escape wheels and other parts of the timing mechanisms were also made of non-magnetic materials or alloys.

2. Another way of making an anti-magnetic watch is to surround the entire movement by a case made of a highly conductive (permeable) material. The movement is covered by an additional soft-iron clasp to prevent the forming of magnetic fields inside the watch itself.

Drawback: the watch case is relatively big and thick.

The second method is used widely because of its low cost and low technology; however, Most famous brand would use both methods to increase the anti-magnetic ability.
Magnetic field:

A magnetic field is a force field that surrounds electric current circuits or it can also be found in the vicinity of ferromagnetic materials such as iron.

Ampere Per Meter The Ampere per Meter (symbolized A/m) is the International Unit of magnetic field strength. 1 A/m is the magnetic field strength in the interior of an elongated, uniformly-wound solenoid which is excited with a linear current density in its winding of 1 ampere per meter of axial distance.

In daily life, all electric appliances produce magnetic field. Moreover, audio speaker is a common source of magnetic field.

That is why not only engineers need anti-magnetic watches.

Examples of anti-magnetic watch:
In 1989 IWC assembled the Ingeneur which was able to withstand a huge magnetic field of 500,000 A/m. In 1993, when IWC celebrated its 125th birthday, the company substituted this model with a more conventional Ingeneur, resisting a magnetic field of 80,000 A/m.

Engineer Hydrocarbon series can withstand 12,000A/m.
Other anti-magnetic series can withstand 4,800 A/m.

In 1950's Rolex assembled the Oyster Perpetual Chronometer Milgauss Ref. 6541 which was able to withstand 1000 Gauss or about 80,000 A/m.

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