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Anti-magnetic Watch
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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.
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| 2 Ways of making an anti-magnetic watch: |
| 1. Using different alloys |
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Alloy
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Components
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Glucydur
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beryllium, bronze
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Invar
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carbon, chromium, iron,nickel
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Nivarox
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beryllium, chromium, iron, nickel, titanium
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Elinvar
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chromium, iron,nickel
Less resistant to magnetism and more resistant
to thermal influence than Invar
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| 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. |
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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.
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| 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. |
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| Magnetic field: |
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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.
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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.
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| Examples of anti-magnetic watch: |
IWC
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. |
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Ball
Engineer Hydrocarbon series can withstand 12,000A/m.
Other anti-magnetic series can withstand 4,800 A/m.
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Rolex
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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