|
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 |
|
Alloy
|
Components
|
|
Glucydur
|
beryllium, bronze
|
|
Invar
|
carbon, chromium, iron,nickel
|
|
Nivarox
|
beryllium, chromium, iron, nickel,
titanium
|
|
Elinvar
|
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.
 |
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: |
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. |
| |
|
Ball
Engineer Hydrocarbon series can withstand 12,000A/m.
Other anti-magnetic series can withstand 4,800 A/m.
|
| |
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. |
| |
|
|
