Clocks and Watches [2]
Webpages concerning "Clocks and Watches [2]"
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Wikipedia-Article "Clocks"
- For other uses, see Clock (disambiguation).
A clock (from the Latin cloca, "bell") is an instrument for measuring time. A clock is usually a physical instrument; an especially accurate one is called a chronometer. The clock in its modern form (24 hour clock) has been in use since at least the 14th century. Clock can refer to an abstract system of time measurement (see calendar for other measurements). Modern clocks define constant units of time: an hour is always sixty minutes, of sixty seconds each.
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History
The clock is one of the oldest human inventions. Vitruvius reported that the ancient Egyptians used clepsydras, a time mechanism run by flowing water. Historians disagree over the Antikythera mechanism but this is largely thought to be an early mechanical clock. By the 9th century AD a mechanical timekeeper had been developed that lacked only an escapement mechanism. There is a record that in 1176 Sens Cathedral installed a ‘horologe’—the word still used in French for large clocks. It is derived from the Greek hora meaning ‘hour’ and legein meaning 'to tell'. This word has led scholars to believe that these tower clocks did not employ hands or dials, but “told” the time with audible signals.
A variety of mechanical clocks were produced by Spanish Muslim engineers, both large and small, and this knowledge was transmitted to Europe through Latin translations of Islamic books on mechanics. These clocks were weight-driven. Designs and illustrations of epi-cyclic and segmental gears were provided. One such clock included a mercury escapement. The latter type was directly copied by Europeans during the 15th century. In addition, during the 9th century, Ibn Firnas of Islamic Spain, according to Will Durant, invented a watch-like device which kept accurate time. The Muslims also constructed a variety of highly accurate astronomical clocks for use in their observatories.
The earliest reasonably accurate clocks are the 13th century tower clocks probably developed for (and perhaps by) monks in Northern Italy. These were used to announce the canonical hours or intervals between set times of prayer. Canonical hours differ in length, and varied as the times of sunrise and sunset shifted.
The earliest table clocks that survive in any quantity are mid-16th century ones from the metalworking towns of Nuremberg and Augsburg. These clocks have only one hand. The dial between the hour markers is divided into four equal parts making the clocks readable to the nearest 15 minutes.
The next major development in accuracy occurred in 1657 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to propel the motion of a time telling device earlier in the 17th century. Christiaan Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 inches for the one second movement) and had the first pendulum driven clock made. In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement. Within just one generation, minute hands and then second hands were added.
The excitement over the pendulum clock attracted the attention of designers resulting in a proliferation of clock forms. Notably, the longcase clock (aka grandfather clock) was created to house the pendulum and works. The English clockmaker William Clement, inventor of the anchor escapement, is credited with developing this form in 1670. It was also at this time that clock cases began to be made of wood and clock faces to employ enamel. On November 17, 1797, Eli Terry received his first patent for a clock. Terry is known as the founder of the American clock-making industry.
Purposes
Clocks are in homes and offices; smaller ones (watches) are carried; larger ones are in public places, e.g. a train station or church. A small clock is often shown in a corner of computer displays or mobile phones.
The main purpose of a clock is not always to display the time. It may also be used to control a device according to time, e.g. an alarm clock, a VCR, or a time bomb (see: counter).
Practically all computers depend on an accurate internal clock signal to allow synchronized processing. (A few research projects are developing CPUs based on asynchronous circuits). Some computers also maintain time and date for all manner of operations whether these be for alarms, event initiation or just to display the time of day.
Ideal clocks
An ideal clock is a scientific principle that measures the ratio of the duration of natural processes, and thus will give the time measure for use in physical theories. Therefore, to define an ideal clock in terms of any physical theory would be circular. An ideal clock is more appropriately defined in relationship to the set of all physical processes.
This leads to the following definitions:
- A clock is a recurrent periodic process and a counter.
- A good clock is one which, when used to measure other recurrent processes, finds many of them to be periodic.
- An ideal clock is a clock (i.e., recurrent process) that makes the most other recurrent processes periodic.
The recurrent, periodic process (a metronome) is an oscillator and typically generates a clock signal. Sometimes that signal alone is (confusingly) called "the clock," but sometimes "the clock" includes the counter, its indicator, and everything else supporting it.
This definition can be further improved by the consideration of successive levels of smaller and smaller error tolerances. While not all physical processes can be surveyed, the definition should be based on the set of physical processes which includes all individual physical processes which are proposed for consideration. Since atoms are so numerous and since, within current measurement tolerances, they all beat in a manner such that if one is chosen as periodic then the others are all deemed to be periodic also, it follows that atomic clocks represent ideal clocks to within present measurement tolerances and in relation to all presently known physical processes. However, they are not so designated by fiat. Rather, they are designated as the current ideal clock because they are currently the best instantiation of the definition.
Navigation
Accurate navigation by ships beyond the sight of land depends on the ability to measure latitude and longitude. Latitude is fairly easy to determine through celestial navigation, but the measurement of longitude requires accurate measurement of time. This need was a major motivation for the development of accurate mechanical clocks. John Harrison created the first, highly accurate marine chronometers in the mid-18th century. The Noon gun in Cape Town still fires an accurate signal to allow ships to check their chronometers.
Types
There are two major types of clocks.
Analog clocks
Analog clocks may be mechanical or have a quartz movement. A clock face is the part of an analog clock that tells time through the use of a fixed numbered dial or dials and moving hand or hands. It usually has a circular scale of 12 hours, which also serves as a scale of 60 minutes, and often also as a scale of 60 seconds. The analog clock with digital display emulates a digital clock but with an analog movement. The ultimate analog clock is the sundial, which tracks the sun continuously, registering the time by the shadow of its gnomon.
Digital clocks
Digital clocks use electronic methods of keeping time, typically the 60 hertz oscillation of AC power or a crystal oscillator as in a quartz movement. A digital clock typically displays a numerical hour range of 0-23, or 1-12 (with an indication of AM or PM) using an LCD or LED display, although digital versions of analog-style faces exist. Mains-driven digital clocks are often reset after a power failure, and, typically, begin flashing to alert us that the time they display is incorrect. After a reset digital clocks lacking a backup battery either start counting from 00:00, or stay 00:00 to indicate that their time needs to be set.
Modern clocks
Quartz timepieces were invented in the 1920s.
The digital clock was invented in 1956.
Specific types of clocks
- alarm clock
- analog clock with digital display
- astronomical clock
- atomic clock
- binary clock
- bracket clock
- cartel clock
- chiming clock
- clock network
- Data clock for timescapes created with time-technology
- doll's head clock
- Railroad chronometers
- countdown clock
- cuckoo clock
- game clock
- grandfather clock
- hourglass
- longcase clock
- mantel clock
- pedestal clock
- swinging pendulum clock
- torsion pendulum clock
- projection clock
- quartz clock
- sidereal clock
- skeleton clock
- stopwatch
- striking clock
- sundial
- tide clock
- time clock
- watch
- water clock
- world clock
See also
- chronometer
- radio clock
- timer
- Iron Ring Clock
- Allan variance
- biological clocks
- clock face
- Cox's timepiece
- Clock of the Long Now
- Clock signal (digital circuits)
- clock tower
- clockmaker
- Horology
- Intellectual history of time
- Metrology
- Star clock
- Timeline of time measurement technology
- Time standard
- watchmaker
- Colgate Clock, the world's largest clock
External links
- American Watchmakers-Clockmakers Institute
- British Horological Institute
- 24 hour analog clocks
- Science Museum - more details on early clocks
- Humanclock.com a website with a unique image for every minute of the day
- [1] article, by a key figure in the development of quartz crystal clocks, on the history of timekeeping up to the late 1940s (based on remarks he made when given a prize for his contributions to horology) from The Bell System Technical Journal, Vol. XXVII, pp. 510-588, 1948
www.Timeforclocks.nl: information on Dutch clocks
References
- Bruton, Eric. The History of Clocks and Watches. London: Black Cat, 1993.
- Edey, Winthrop. French Clocks. New York: Walker & Co., 1967.
- Lloyd, Alan H. “Mechanical Timekeepers.” In A History of Technology. Vol. III. Edited by Charles Joseph Singer, et. al. Oxford: Clarendon Press, 1957, pp. 648-675.
- Robinson, Tom. The Longcase Clock. Suffolk, England: Antique Collector’s Club, 1981.
- Smith, Alan. The International Dictionary of Clocks. London: Chancellor Press, 1996.
- Tardy. French Clocks the World Over. Part One and Two. Translated with the assistance of Alexander Ballantyne. Paris: Tardy, 1981.
- Yoder, Joella Gerstmeyer. Unrolling Time: Christiaan Huygens and the mathematization of nature. New York: Cambridge University Press, 1988.
Wikipedia-Article "Watches [2]"
In naval parlance, watches are a timekeeping convention. The term in general use can mean any period of duty or responsibility, such as a hurricane watch.
A watch is a small portable clock that displays the time and sometimes the day, date, month and year. In modern times they are usually worn on the wrist with a watch-strap (made of e.g. leather (often synthetic), metal, or nylon), although before the 20th century most were pocket watches, which had covers and were carried separately, often in a pocket, and hooked to a watch chain.
Current watches are often digital watches, using a piezoelectric crystal, usually quartz, as an oscillator (see quartz clock).
Mechanical timepieces are still used, usually powered by a spring wound regularly by the user, e.g. a stem winder. The invention of "Automatic" or "Self-Winding" watches allowed for a constant winding without special action from the wearer: it works by an eccentric weight, called a winding rotor, that rotates to the movement of the wearer's body. The back-and-forth motion of the winding rotor couples to a ratchet to automatically wind the watch.
Watches may be collectible; they are often made of precious metals, and can be considered an article of jewelry.
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Types of watch
Pocket clock
The earliest need for portability in time keeping was navigation and mapping in the 15th century. The latitude could be measured by looking at the stars, but the only way a ship could measure its longitude was by comparing timezones; by comparing the midday time of the local longitude to a European meridian (usually Paris or Greenwich), a sailor could know how far he was from home. However, the process was notoriously unreliable until the introduction of John Harrison's chronometer. For that reason, most maps from the 15th century to c.1800 have precise latitudes but distorted longitudes.
The first reasonably accurate mechanical clocks measured time with weighted pendulums, which are useless at sea or in watches. The invention of a spring mechanism was crucial for portable clocks. In Tudor England, the development of "pocket-clockes" was enabled through the development of reliable springs and escapement mechanisms, which allowed clockmakers to compress a timekeeping device into a small, portable compartment. In 1524, Peter Henlein created the first pocket watch[1][2]. It is rumoured that Henry VIII (the portrait of Henry VIII at this link shows the medallion thought to be the back of his watch) had a pocket clock which he kept on a chain around his neck. However, these watches only had an hour hand - a minute hand would have been useless considering the inaccuracy of the watch mechanism. Eventually, miniaturization of these spring-based designs allowed for accurate portable timepieces which worked well even at sea. Aaron Lufkin Dennison founded Waltham Watch Company in 1850, which was the pioneer of the industrial manufacturing by interchangeable parts, the American System of Watch Manufacturing.
Wrist watch
The wristwatch was invented by Patek Philippe at the end of the 19th century. It was however considered a woman's accessory. It was not until the beginning of the 20th century that the Brazilian inventor Alberto Santos-Dumont, who had difficulty checking the time while in his first aircraft (Dumont was working on the invention of the aeroplane), asked his friend Louis Cartier for a watch he could use more easily. Cartier gave him a leather-band wristwatch from which Dumont never separated. Being a popular figure in Paris, Cartier was soon able to sell these watches to other men. During the First World War, officers in all armies soon discovered that in battlefield situations, quickly glancing at a watch on their wrist was far more convenient than fumbling in their jacket pockets for an old-fashioned pocket watch. In addition, as increasing numbers of officers were killed in the early stages of the war, NCOs promoted to replace them often did not have pocket watches (traditionally a middle-class item out of the reach of ordinary working-class soldiers), and so relied on the army to provide them with timekeepers. As the scale of battles increased, artillery and infantry officers were required to synchronize watches in order to conduct attacks at precise moments, whilst artillery officers were in need of a large number of accurate timekeepers for rangefinding and gunnery. Army contractors began to issue reliable, cheap, mass-produced wristwatches which were ideal for these purposes. When the war ended, demobilized European and American officers were allowed to keep their wristwatches, helping to popularize the items amongst middle-class Western civilian culture. Today, many Westerners wear watches on their wrist, a direct result of the First World War.
Complicated watch
A complicated watch has one or more functionalities beyond basic time-keeping capabilities; such a functionality is called a complication. Two popular complications are the chronograph complication, which is the ability of the watch movement to function as a stopwatch, and the moonphase complication, which is a display of the lunar phase. Among watch enthusiasts, complicated watches are especially collectible.
Chronographs and chronometers
The similar-sounding terms chronograph and chronometer are often confused, although they mean altogether different things. A chronograph is a type of complication, as explained under the heading "Complicated Watch." A chronometer is a watch or clock whose movement has been tested and certified to operate within a certain standard of accuracy by the COSC (Contrôle Officiel Suisse des Chronomètres). The concepts are different but not mutually exclusive; a watch can be a chronograph, a chronometer, both, or neither.
Electromechanical watches
The first use of electrical power in watches was as a source of energy to replace the mainspring, and therefore to remove the need for winding. The first battery-powered watch, the Hamilton Electric 500, was released in 1957 by the Hamilton Watch Company of Lancaster, Pennsylvania.
Quartz analog watch
The quartz analog watch is an electronic watch that uses a piezoelectric quartz crystal as its timing element, coupled to a mechanical movement that drives the hands. The first prototypes were made by the CEH research laboratory in Switzerland in 1962. The first quartz watch to enter production was the Seiko 35 SQ Astron, which appeared in 1969. There are also several variations of the quartz watch as to what actually powers the movement. There are solar powered, kinetically powered, battery powered and other less common power sources. Solar powered quartz watches are powered by available light. Kinetic powered quartz watches make use of the motion of the wearer's arm turning a rotating weight, which in turn, turns a generator to supply power. A seldom used power source is temperature difference between the wearer's arm and the surrounding environment (as applied in the Citizen Eco Drive Thermo). The most common power source is the battery. Watch batteries come in many forms, the most common of which are silver oxide and lithium.
Digital watches
Cheaper electronics permitted the popularization of the digital watch (an electronic watch with a numerical, rather than analog, display) in the second half of the 20th century. They were seen as the great new thing. Douglas Adams, in the introduction of his novel The Hitchhiker's Guide to the Galaxy, would say that humans were 'so amazingly primitive that they still think digital watches are a pretty neat idea'.
The first digital watch, a Pulsar prototype in 1970, was developed jointly by Hamilton Watch Company and Electro-Data. A retail version of the Pulsar was put on sale in 1972. It had a red light-emitting diode (LED) display. LED displays were soon superseded by liquid crystal displays (LCDs), which used less battery power. The first LCD watch with a six-digit LCD was the 1973 Seiko 06LC, although various forms of early LCD watches with a four-digit display were marketed as early as 1972 including the 1972 Gruen Teletime LCD Watch [3], [4].
In addition to the function of a timepiece, digital watches can have additional functions like a chronograph, calculator, video game, etc.
Digital watches have not replaced analog watches, despite their greater reliability and lower cost. In fact, because digital watches are so cheap, analog watches are often worn as status symbols. For others, analog watches are just easier to read.
Fashionable watches
At the end of the 20th century, Swiss watch makers were seeing their sales go down as analog clocks were considered obsolete. They joined forces with designers from many countries to reinvent the Swiss watch.
The result was that they could considerably reduce the pieces and production time of an analog watch. In fact it was so cheap that if a watch broke it would be cheaper to throw it away and buy a new one than to repair it. They founded the Swiss Watch company (Swatch) and called graphic designers to redesign a new annual collection.
This is often used as a case study in design schools to demonstrate the commercial potential of industrial and graphic design.
Advanced watches
In 1990 radio controlled wristwatches or as they are sometimes called "atomic watches" reached the market. These wristwatches normally receive a radio signal from one of the national atomic clock facilities around the world, for example the National Institute of Standards and Technology located in Colorado in the United States. This radio signal tells the wristwatch exactly what time it is, in theory precise to a fraction of a nanosecond. It will also reset itself when daylight savings time changes. In recent years, mass production has meant that atomic watches have become as cheap as quartz watches, though market share still remains small as interest from big manufacturers is limited.
Other technological enhancements to wristwatches have been explored but most of them remained unnoticed. In 2005 for example, a company has put into market an alarm wristwatch with an accelerometer inside that monitors the user's sleep and rings during one of his almost-awake phases.
A number of functionalities non directly related to time have also been inserted into watches. As miniaturized electronics become cheaper, watches have been developed containing calculators, video games, digital cameras, keydrives, GPS receivers and cellular phones. In the early 1980s Seiko marketed a watch with a television receiver in it, although at the time television receivers were too bulky to fit in a wristwatch, and the actual receiver and its power source were in a book-sized box with a cable that ran to the wristwatch. In the early 2000s, a self-contained wristwatch television receiver came on the market, with a strong enough power source to provide one hour of viewing.
These watches have not had sustained long-term sales success. As well as awkward user interfaces due to the tiny screens and buttons possible in a wearable package, and in some cases short battery life, the functionality available has not generally proven sufficiently compelling to attract buyers. Such watches have also had the reputation as ugly and thus mainly geek toys. Now with the ubiquity of the mobile phone in many countries, which have bigger screens, buttons, and batteries, interest in incorporating extra functionality in watches seems to have declined.
Several companies have however attempted to develop a computer contained in a WristWatch (see also wearable computer). As of 2005, the only programmable computer watches to have made it to market are the Seiko Ruputer, the Matsucom onHand, and the Fossil, Inc. WristPDA, although many digital watches come with extremely sophisticated data management software built in.
See also
- List of watch manufacturers
- Wearable computer
- 10:08 - The time to which most watches are set in advertisements
- Wikipedia Commons Watch Images, from category "watches."
External links
- American Watchmakers-Clockmakers Institute
- How does a watch work? FH, Switzerland
- Chronocentric: "The largest independent, non-commercial, consumer-oriented resource on the Internet for owners, collectors and enthusiasts of fine wristwatches."
- Watches
- Mechanical Watch FAQ 1.0 from TimeZone.com
- ThePuristS.com: an independent, non-commercial resource for horological enthusiasts.
- Horological Academy of Independent Creators - Independent Watchmakers