chronometer

chronometric /kron'euh me"trik/, chronometrical, adj.chronometrically, adv.
/kreuh nom"i teuhr/, n.
1. a timepiece or timing device with a special mechanism for ensuring and adjusting its accuracy, for use in determining longitude at sea or for any purpose where very exact measurement of time is required.
2. any timepiece, esp. a wristwatch, designed for the highest accuracy.
[1705-15; CHRONO- + -METER]

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Mechanical timekeeping device of great accuracy, particularly one used for determining longitude (see latitude and longitude) at sea.

Early weight-and pendulum-driven clocks were inaccurate because of friction and temperature changes and could not be used at sea because of the ship's motion. In 1735 John Harrison invented and constructed the first of four practical marine timekeepers. The modern marine chronometer is suspended to remain horizontal whatever the inclination of the ship and differs in parts of its mechanism from the ordinary watch. A chronometer may provide timekeeping accurate to within 0.1 second per day. See also Ferdinand Berthoud.

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▪ timekeeping device
      portable timekeeping device of great accuracy, particularly one used for determining longitude at sea.

      Although there were a couple of earlier isolated uses, the word was originally employed in 1779 by the English clock maker John Arnold to describe his sensationally accurate pocket chronometer “no. 1/36.” Ordinary clocks were of no use at sea due to temperature changes and the ship's motion. It was not until the 18th century that John Harrison (Harrison, John), a self-taught English carpenter, invented and constructed four marine timekeepers, the fourth of which effectively won him the reward of £20,000 offered in 1714 by the British government for any means of determining a ship's longitude within 30 geographical miles (about 34.6 miles, or 55.7 km) at the end of a six weeks' voyage. (The geographical mile is defined as one minute of arc along the Earth's equator; compare the nautical mile, defined as one minute of arc along any great circle route.) A timekeeper fulfilling this condition would have to keep time within three seconds per day, a standard that, at the date the reward was offered, had not been attained by the best pendulum clocks on shore. Though Harrison's original invention was complicated, delicate, and costly, his successful design led to further investigations by others and eventually to the modern marine chronometer.

      The modern chronometer is, broadly speaking, a large, well-made watch but with a detached chronometer escapement, suspended in gimbals (a set of rings connected by bearings) poised so as to remain horizontal whatever the inclination of the ship. It is thus safeguarded from those alterations of position that slightly affect the timekeeping of even the best watches. In addition, it differs somewhat in its mechanism from the ordinary watch, the spiral balance spring and lever escapement of the latter being replaced by a helical balance spring and a spring detent, or chronometer escapement. In a chronometer this form of escapement is mechanically superior to any other and requires no oiling other than at the pivots, but it is not suitable for use in pocket watches, because it is very fragile and also, if given a more or less circular twist, may “trip,” causing a rapid gain. For the purpose of equalizing the force of the mainspring, almost all chronometers are fitted with a fusee (a cone-shaped grooved pulley) and a chronometer compensation balance, by which the effects of heat and cold upon the timekeeping are practically nullified. By these devices the chronometer usually provides timekeeping accurate to within 0.5 second per day.

Jonathan D. Betts
 

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Universalium. 2010.

Synonyms:

Look at other dictionaries:

  • Chronometer — Chronometer, »Zeitmesser«, könnte eigentlich jede Uhr und jeder sonstige Apparat zur Zeitmessung genannt werden. Das Wort bezeichnet aber jetzt ausschließlich die feinsten transportabel und gegen Gangänderungen durch Temperaturwechsel… …   Lexikon der gesamten Technik

  • Chronometer — Chro*nom e*ter, n. [Gr. ? time + meter: cf. F. chronom[ e]tre.] 1. An instrument for measuring time; a timekeeper. [1913 Webster] 2. A portable timekeeper, with a heavy compensation balance, and usually beating half seconds; intended to keep time …   The Collaborative International Dictionary of English

  • Chronometer — Sn genau gehende Uhr per. Wortschatz fach. (18. Jh.) Neoklassische Bildung. Neubildung (im englischen Bereich) aus gr. chrónos Zeit und gr. métron Meßgerät .    Ebenso nndl. chronometer, ne. chronometer, nfrz. chronomètre, nschw. kronometer,… …   Etymologisches Wörterbuch der deutschen sprache

  • Chronometer — (griech., »Zeitmesser«), nächst den mit Kompensationspendel versehenen Uhren die besten Zeitmesser, unterscheiden sich von gewöhnlichen Taschenuhren hauptsächlich durch die Konstruktion der »Unruhe« und der Hemmung. Bei den gewöhnlichen… …   Meyers Großes Konversations-Lexikon

  • Chronometer — Chronometer. Nichts ist für den Seemann wichtiger, als genau zu wissen, auf welchem Punkte der Erde er sich befindet. Hierzu bedient man sich der Chronometer oder Seeuhren, welche von einem Engländer Harryson erfunden wurden, gegen Wärme und… …   Damen Conversations Lexikon

  • Chronometer — Chronoskop, v. gr.), 1) Zeitmesser, also jede Uhr; 2) (Stopwatch), eine höchst genau gearbeitete Taschensecundenuhr, die so wenig wie möglich u. täglich weniger als 1 Secunde abweicht. Sie sind in England im 18. Jahrh. von Harrison zuerst… …   Pierer's Universal-Lexikon

  • Chronometer — (grch., »Zeitmesser«), genau gehende tragbare Uhr mit Spiralfeder, deren Unruhe mit Kompensation gegen Temperaturänderungen versehen ist, zu Längenbestimmungen auf See und Landreisen; auf See durch Aufhängung im Cardanischen Ring (s.d. und Abb.… …   Kleines Konversations-Lexikon

  • Chronometer — (Zeitmesser), sehr sein und genau construirte tragbare Uhren, ähnlich unsern Taschenuhren, welche die Genauigkeit der Zeitangabe bis auf Bruchtheile einer Sekunde mit den astronomischen Pendeluhren gemein haben, vor diesen aber den Vorzug, daß… …   Herders Conversations-Lexikon

  • Chronometer — Chronometer,das:⇨Uhr(1) …   Das Wörterbuch der Synonyme

  • chronometer — 1735, from CHRONO (Cf. chrono ) time + METER (Cf. meter). Related: Chronometric …   Etymology dictionary

  • Chronometer — Chronometer: Die Bezeichnung für »Zeit , (früher auch) Taktmesser« ist eine Neubildung des 18. Jh.s zu griech. chrónos »Zeit« (vgl. ↑ chrono..., ↑ Chrono...) und griech. métron »Maß« (vgl. ↑ Meter) …   Das Herkunftswörterbuch

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