Chronometer watch
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A chronometer (
History
The term chronometer was coined by Jeremy Thacker of Beverley, England in 1714, referring to his invention of a clock ensconced in a vacuum chamber. The term chronometer is also used to describe a
Once mechanical timepiece
Most observatory chronometers had movements so specialized to accuracy that they could never withstand being used as wristwatches in normal usage. They were useful only for accuracy competitions, and so never were sold to the public for usage. However, in 1966 and 1967,
The observatory competitions ended with the advent of the quartz watch movement, in the late 1960s and early 1970s, which generally has superior accuracy at far lesser costs. In 2009, the Watch Museum of Le Locle renewed the tradition and launched a new chronometry contest based on ISO 3159 certification. In 2017 the Observatory Chronometer Database (OCD) [1] went online, which contains all mechanical timepieces ("chronometres-mecaniques") certified as observatory chronometers by the observatory in Neuchatel from 1945 to 1967, due to a successful participation in the competition which resulted in the issuance of a Bulletin de Marche. All database entries are submissions to the wristwatch category ("chronometres-bracelet") at the observatory competition.
The term chronometer is often wrongly used by the general public to refer to timekeeping instruments fitted with an additional
Mechanical chronometers
A mechanical chronometer is a spring-driven escapement timekeeper, like a watch, but its parts are more massively built. Changes in the elasticity of the balance spring caused by variations in temperature are compensated for by devices built into it.[2]
Chronometers often included other innovations to increase their efficiency and precision. Hard stones such as diamond, ruby, and sapphire were often used as jewel bearings to decrease friction and wear of the pivots and escapement. Chronometer makers also took advantage of the physical properties of rare metals such as gold, platinum, and palladium.
Complications
In
- Tourbillon
- Perpetual calendar
- Minute repeater
- Equation of time
- Power reserve
- Moon phases
- Chronograph
- Rattrapante
- Grande sonnerie
More recent times
Certified chronometers
More than 1.8 million officially-certified chronometer certificates, mostly for mechanical wristwatch chronometers (wristwatches) with sprung balance oscillators, are being delivered each year, after passing the COSC's most extreme tests and being singly identified by an officially-recorded individual serial number. According to COSC, an officially-certified chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions, and at different temperatures, by an official, neutral body (COSC). Each movement is individually tested for several consecutive days, in five positions and at three temperatures. Any watch with denominations "certified chronometer" or "officially-certified chronometer" contains a certified movement and matches the criteria in ISO 3159 Timekeeping instruments—wristwatch chronometers with spring balance oscillator.[3]
See also
- Horology
- Chronograph
- COSC
- Marine chronometer
- Railroad chronometer
- Tachymeter
- Clock
- Mechanical watch
- Jewel bearing
- Navigation
- Observatory chronometer
- The Nautical Almanac
- American Practical Navigator
- Webb C. Ball
- Watchmaker
References
- ^ Observatory Chronometer Database (OCD)
- ^ The Columbia Encyclopedia, Sixth Edition, 2008, Columbia University Press
- ^ PDF file Archived 2007-09-25 at the Wayback Machine (of 1976 version)