A stopwatch 1 denotes a measuring instrument of time .
Its name is derived from the Greek khrónos (όρόνος), meaning time and from the Latin metrum meaning to measure.
The term “chronometer” is misused for short-duration measuring devices, such as those used in sports competitions, which are in fact ” chronographs “.
In watchmaking , a “chronometer” is a watch equipped with a display of the second, the movement of which has passed successfully the control of its accuracy by an official neutral body 1 , several days in different positions and at different temperatures. A chronometer is distinguished by its reliability and precision.
A “pocket watch” or “pocket watch” means a pocket watch that can fit into the pocket of a garment, as opposed to the “wristwatch” attached to the wrist .
The term “stopwatch” refers to an hourly instrument carried on board a vehicle such as automobiles , aircraft or space shuttles .
Chronometer officially certified
The name “chronometer” is defined by the ISO 3159 standard and protected by certain national laws , which accredit organizations to practice the certification of movements . The Swiss Official Control of Chronometers (COSC) 2 is the most important of these organizations, it is the only one capable of certifying industrial quantities of movements (about one million per year). However, the controls performed at the COSC are made on non-nested movements, while the Observatory in Besançon, for example, performs the same controls on finished and nested watches, thus guaranteeing optimum reliability for the end user.
Organizations issuing chronometric certificates
- The Swiss Official Control of Chronometers
- The Observatory of Besançon
- The Federal Institute of Metrology METAS in Bern
- The foundation Timelab Laboratory Watchmaking and Microtechnology Geneva
- The Observatory Wempe Chronometerwerke in Glashütte
Chronometer of navy
Originally, stopwatches were intended to be used on board ships to determine longitude according to the principles of celestial navigation .
Until 1754, the position of a building in the high seas could not be known with great precision, since it was estimated from the last known position, that is to say from the last known land . The navigators could determine their latitude accurately. In order to be able to determine the longitude , a reliable, stable and precise time measuring apparatus must be available; In fact longitude is determined by measuring the time of passage of the sun at the meridian and by comparison with the time of this passage at the port of departure: Every minute of error on this measure leads to a positional deviation of not more than 15 nautical miles at the equator . Thus, one second of time error corresponds to a positioning error of 463 meters .
Solving the problem of clocks was difficult. At the time, the most accurate timepieces were based on the principle of the pendulum clock , which were continually disturbed by the rolling of the ship at sea . John Harrison , a carpenter – watch English, developed a clock containing a pair of oscillating clocks in opposite directions, connected by springs , whose movements were exempt from the influence of gravity and turbulence of a boat. Its chronometers H1 , H2 , H3 , designed according to this concept,
He eventually solved the problem with his prototype H4 , which is a large diameter watch, winning the British Admiralty Award . Its new concept was based on the use of an oscillating wheel, the thermo-compensated balance . This principle is sometimes still used in current mechanical chronometers. The determination of longitude continued by astronomical observation , mainly for reasons of cost.
Subsequently, the United Kingdom was a great applicant in “naval chronometers” and precision contests were regularly organized by various observatories .
A stopwatch is always present on ships 3 . Positioned in the gangway and protected as much as possible from vibrations, its march is controlled daily by listening to the hourly tops of the terrestrial radio stations or more simply by comparison with the clocks of the satellite positioning systems . The stopwatch’s timetable is the advance or delay in one hour. A quality chronometer has a daytime running (or walking everyday ) low and almost constant (of the order of seconds) 4 .
Chronometer of railway
Aaron Lufkin Dennison pioneered the industrial revolution in the watch manufacturers since 1849 and developed the American System of Watch Manufacturing organizing for the Waltham Watch Company production in quantity of pieces of watches so what are perfectly interchangeable. This process is at the origin of the current production methods at work all over the world.
In 1893 , Webb C. Ball established the criteria that define the railway chronometer , the latter are still the basis of the current criteria applied to officially certified chronometers.
While this kind of competition has disappeared early in the second half of the xx th century , exists since 2009 an international chronometry contest which aims to reward the watch manufacturers with the most precise mechanical parts.
Remarks Since the discovery of the piezoelectric effect of quartz and the development of integrated circuits , everyone can have a quartz watch that will be able to provide chronometric accuracy at an affordable price.
Nowadays, atomic clocks are used for the measurement of standard times.
The design of miniaturized radio-controlled systems makes it possible, by incorporating them in a watch, to synchronize the local oscillator of this watch with a remote atomic clock in order to obtain a watch whose precision is maximum.
Since the invention of satellite positioning systems , each geographical position can be obtained without calculation, with a very small margin of error.
Notes and references
- ↑ a and b chronometer [ archive ] , on the CNRTL website, accessed on October 30, 2015
- ↑ Official Swiss Chronometer Control (COSC) [ archive ] , on the website cosc.ch
- ↑ Article 222-6.14, p. 89 . [ Archive ] , on the maritime.gov.pf website
- ↑ Definition of the diurnal march [ archive ] , on the website obwww.unige.ch