Anti-magnetic (non-magnetic) watches are those that are able to run with minimal deviation when exposed to a certain level of

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

. The

International Organization for Standardization The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. M ...

issued a standard for magnetic-resistant watches, which many countries have adopted.

ISO 764 magnetic-resistant watches standard

The international standard ISO 764 Horology—Magnetic resistant watches defines the resistance of watches to magnetic fields. According to ISO 764 or its equivalent

DIN DIN or Din or din may refer to: People and language * Din (name), people with the name * Dīn, an Arabic word with three general senses: judgment, custom, and religion from which the name originates * Dinka language (ISO 639 code: din), spoken ...

8309 (Deutsches Institut für Normung - German Institute for Standardization) a

watch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

must resist exposure to a direct current

of 4800 A/ m. The watch must keep its accuracy to ±30 seconds/day as measured before the test in order to be acknowledged as a magnetic-resistant watch. Annex A of ISO 764 deals with watches designated as magnetic resistant with an additional indication of intensity of a magnetic field exceeding 4800 A/m. There are two ways of building an anti-magnetic watch: * The first way consists of making the moving parts of

alloys An alloy is a mixture of chemical elements of which in most cases at least one is a metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have properties ...

chosen to be insensitive to magnetic fields. These alloys include

Invar Invar, also known generically as FeNi36 (64FeNi in the US), is a nickel–iron alloy notable for its uniquely low coefficient of thermal expansion (CTE or α). The name ''Invar'' comes from the word ''invariable'', referring to its relative lac ...

(

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

–

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

–

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

–

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

alloy), Glucydur (

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

–

bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals (such as phosphorus) or metalloid ...

alloy), Nivarox (iron–nickel–chromium–

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

–beryllium alloy) and Elinvar (an alloy similar to Invar, though less resistant to

magnetism Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, ...

and more resistant to thermal influence). These alloys are preferred by different watchmakers due to their differing properties. In the 1960s, almost all Swiss watches had Glucydur balance and Nivarox

hairspring A balance spring, or hairspring, is a spring attached to the balance wheel in mechanical timepieces. It causes the balance wheel to oscillate with a resonant frequency when the timepiece is running, which controls the speed at which the wheels of ...

s. The anchors, escape wheels and other watch mechanisms were also made of non-magnetic metals or alloys. * Another way of making a watch non-magnetic is to house the entire movement into a case made of a highly permeable (magnetically conductive) material. The movement is covered by an additional soft-iron clasp to prevent the forming of magnetic fields inside the watch itself.

History

The first recorded experiments in anti-magnetic watch-making are in 1846. Watchmakers from Vacheron Constantin were among the first to experiment with anti-magnetic features of a watch. However, they succeeded in assembling the first antimagnetic watch only several decades later. That watch was able to withstand magnetic fields because some of its parts were made of non-magnetic

metals A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against no ...

: the

palladium Palladium is a chemical element; it has symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1802 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas (formally 2 Pallas), ...

-made

balance wheel A balance wheel, or balance, is the timekeeping device used in mechanical watches and small clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position b ...

, balance spring and the lever shaft. In 1896

Charles Édouard Guillaume Charles Édouard Guillaume (; 15 February 1861 – 13 June 1938) was a Swiss physicist who received the Nobel Prize in Physics in 1920 "for the service he had rendered to precision measurements in physics by his discovery of anomalies in nickel ...

discovered the nickel based alloy Invar. Afterwards, in 1920, when he received the

Nobel Prize The Nobel Prizes ( ; ; ) are awards administered by the Nobel Foundation and granted in accordance with the principle of "for the greatest benefit to humankind". The prizes were first awarded in 1901, marking the fifth anniversary of Alfred N ...

Physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

, he developed another alloy - Elinvar. These alloys assisted in the assembly of anti-magnetic watches. Invar and Elinvar are able to resist magnetic fields, allowing the watch to continue to keep accurate time. The first anti-magnetic pocket watch was assembled by Vacheron Constantin in 1915. In 1930,

Tissot Tissot SA () is a Swiss luxury watch brand owned by the Swatch Group. The company was founded in Le Locle, Switzerland by Charles-Félicien Tissot and his son, Charles-Émile Tissot, in 1853. Tissot is not associated with Mathey-Tissot, anoth ...

produced the first ever non-magnetic

wristwatch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

Usage

Since their appearance, anti-magnetic watches have been favored by people who deal with high magnetic fields. They are widespread among electronic engineers and in other professions where strong magnetic fields are present. Today, even divers' watches (according to ISO 6425) must be anti-magnetic as well as being water resistant, sufficiently luminous, shock resistant and have solid straps.

Contributions

After discovering the alloys for assembling anti-magnetic watches, many watch-making brands utilize such materials in production in order to improve the performance of such timepieces.

IWC

In 1989 IWC first manufactured the Ingenieur Reference 3508, which was able to withstand huge magnetic fields of up to 500000 A/m.

Omega

The Omega Anti-Magnetic Seamasterwas announced
17 January 2013 (e.g. Seamaster Aqua Terra > 15,000 Gauss). According to the press release, the OMEGA movement does not rely on a protective container inside the watchcase but on the use of selected non-ferrous materials in the movement itself. The OMEGA prototype was subjected to 1.5 Tesla (15,000 Gauss) and continued to perform. Testing showed that the watch was as accurate after its magnetic exposure as it had been before.

Rolex

The Rolex Milgauss series of antimagnetic certified chronometers was first manufactured in 1954 with the model 6541 for those working in nuclear, aircraft, and medical settings associated with strong magnetic fields. The watch has an advertised magnetic flux density resistance of 1,000 Gauss within magnetic fields of 80,000 A/m. In 2007, after being out of production for nearly two decades a new Milgauss was introduced as the model number 116400.

Sinn

Certain diving watches produced by Sinn as mission timers (in German: "Einsatzzeitmesser") for professional users are also protected against magnetic fields up to 1,000 Gauss / 80,000 A/m, using a protective sheath consisting of a closed, magnetically soft inner case that includes the dial, the movement holding ring and the case back.

METAS N001 requirements

The Swiss Federal Institute of Metrology (METAS) has METAS N001 requirements for movements and mechanical watches resistant to magnetic fields of 1.5 Tesla (15,000 Gauss). The METAS N001 certification demands a series of tests were amongst other relevant requirements the watches are subjected to strong magnetic field exposures without resulting in the movement stopping or a 0 to ≤5 seconds daily rate deviation.Certification of mechanical watches is in accordance with the METAS requirements N001
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References

External links

Vacheron Constantin and Nonmagnetic Watches
{{DEFAULTSORT:Antimagnetic Watch Watches