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15 décembre 2010 3 15 /12 /décembre /2010 03:04

A watchis a timepiece that is made to be worn on a person. It is usually a wristwatch, worn on the wrist with a strap or bracelet. In addition to the time, modern watches often display the day, date,month and year, and electronic watches may have many other functions      (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk.

Most inexpensive and medium-priced watches used mainly for timekeeping are electronic watches with quartz movements.Expensive, collectible watches valued more for their workmanship andaesthetic appeal than for simple timekeeping, often have purely mechanical movements and are powered by springs, even though mechanical movements are less accurate than more affordable quartz movements      (Dell Studio XPS 1340 Battery)    .

Before wristwatches became popular in the 1920s, most watches were pocket watches,which often had covers and were carried in a pocket and attached to a watch chain or watch fob. Watches evolved in the 17th century from spring powered clocks, which appeared in the 15th century      (Dell Studio XPS 1640 Battery)      .

Parts

Movement

A movement in watchmaking is the mechanism that measures the passage of time and displays the current time (and possibly other information including date, month and day). Movements may be entirely mechanical, entirely electronic (potentially with no moving parts), or a blend of the two       (Dell Vostro 1710 Battery)    .

Most watches intended mainly for timekeeping today have electronic movements, with mechanical hands on the face of the watch indicating the time.

Mechanical movements

Compared to electronic movements, mechanical watches are less accurate, often with errors of seconds per day, and they are sensitive to position and temperature      (Sony VGP-BPS13 battery)    .

They are also costly to produce, require regular maintenance and adjustment, and are more prone to failure. Nevertheless, the "old world" craftsmanship of mechanical watches still attracts interest from part of the watch-buying public.

Mechanical movements use an escapement mechanism to control and limit the unwinding and winding parts of a spring, converting what would otherwise be a simple unwinding into a controlled and periodic energy release    (Sony VGP-BPS13/B battery) .

Mechanical movements also use a balance wheel together with the balance spring (also known as a hairspring) to control motion of the gear system of the watch in a manner analogous to the pendulum of a pendulum clock. The tourbillon, an optional part for mechanical movements     (Sony VGP-BPS13/S battery)    ,

is a rotating frame for the escapement, which is used to cancel out or reduce the effects of gravitational bias to the timekeeping. Due to the complexity of designing a tourbillon, they are very expensive, and only found in "prestige" watches.

The pin-lever escapement (called the Roskopf movement after its inventor, Georges Frederic Roskopf)      (Sony VGP-BPS13A/B battery) ,

which is a cheaper version of the fully levered movement, was manufactured in huge quantities by many Swiss manufacturers as well as Timex, until it was replaced by quartz movements.

Tuning-fork watches use a type of electromechanical movement. Introduced by Bulova in 1960, they use a tuning fork with a precise frequency (most often 360 hertz) to drive a mechanical watch       (Sony VGP-BPS13B/B battery)     .

The task of converting electronically pulsed fork vibration into rotary movement is done via two tiny jeweled fingers, called pawls. Tuning-fork watches were rendered obsolete when electronic quartz watches were developed, because quartz watches were cheaper to produce and even more accurate      (Sony VGP-BPL9 battery)   .

Electronic movements

Electronic movements have few or no moving parts, as they use the piezoelectric effect in a tiny quartz crystal to provide a stable time base for a mostly electronic movement. The crystal forms aquartz oscillator which resonates at a specific and highly stable frequency, and which can be used to accurately pace a timekeeping mechanism      (Sony VGP-BPS13B/B battery)   .

For this reason, electronic watches are often calledquartz watches.Most quartz movements are primarily electronic but are geared to drive mechanical hands on the face of the watch in order to provide a traditional analog display of the time, which is still preferred by most consumers     (Sony VGP-BPL11 battery)      .

In 1959 Seiko gave an order to Epson (a daughter company of Seiko and the actual brain behind the quartz revolution) to start developing a quartz wristwatch. The project was codenamed 59A and by the 1964 Tokyo Summer Olympics, Seiko had a working prototype of a portable quartz watch which took part in time measurements throughout the event    (Sony VGP-BPL15 battery) .

The first Swiss prototypes of electronic quartz watches 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 hit the shelves in December 25, 1969. One particularly interesting decision made by Seiko at that time was to not patent the whole movement of the quartz wristwatch, thus allowing other manufacturers to benefit from the Seiko technology      (Dell Inspiron E1505 battery)    .

This played a major role in the popularity and quick development of the quartz watch, which in less than a decade was dominant in the watch market, nearly ending an almost 100 years of mechanical wristwatch heritage. The modern quartz movements are produced in very large quantities, and even the cheapest wristwatches typically have quartz movements   (Dell Latitude E6400 battery)  .

Whereas mechanical movements can typically be off by several seconds a day, an inexpensive quartz movement in a child's wristwatch may still be accurate to within half a second per day—ten times better than a mechanical movement. Seiko achieved to combine the quartz and mechanical movements after 20 years of research, finally introducing the Seiko Spring Drive, first in a limited domestic market production in 1999 and to the world in September 2005    (HP Pavilion dv6000 Battery)  .

The Spring Drive manages to keep time within quartz standards without the use of a battery, using a traditional mechanical gear train powered by a spring, while at the same time doesn't have the need of a balance wheel either    (Sony Vaio VGN-FZ31S battery)   .

Radio time signal watches are a type of electronic quartz watch which synchronizes (time transfer) its time with an external time source such as in atomic clocks, time signals from GPS navigation satellites, the German DCF77 signal in Europe, WWVB in the US, and others      (Sony Vaio VGN-FZ31S battery)     .

Movements of this type may -among others- synchronize not only the time of day but also the date, the leap-year status of the current year, and the current state of daylight saving time (on or off). However, other than the radio receiver these watches are normal quartz watches in all other aspects      (SONY VGN-FZ38M Battery)    .

Power sources

Traditional mechanical watch movements use a spiral spring called a mainspring as a power source. In manual watchesthe spring must be rewound periodically by the user by turning the watch crown. Antique pocketwatches were wound by inserting a separate key into a hole in the back of the watch and turning it     (SONY VGN-FZ31z Battery)    .

Most modern watches are designed to run 40 hours on a winding and thus must be wound daily, but some run for several days and a few have 192-hour mainsprings and are wound weekly.

A self-windingor automaticmechanism is one that rewinds the mainspring of a mechanical movement by the natural motions of the wearer's body      (Sony VGN-FZ31Z Battery)    .

The first self-winding mechanism was invented for pocketwatches in 1770 by Abraham-Louis Perrelet, but the first "self-winding", or "automatic," wristwatch was the invention of a British watch repairer named John Harwood in 1923. This type of watch allows for constant winding without special action from the wearer       (SONY VAIO VGN-FZ38M Battery)      ;

it works by an eccentric weight, called a winding rotor, which rotates with the movement of the wearer's wrist. The back-and-forth motion of the winding rotor couples to a ratchet to automatically wind the mainspring. Self-winding watches usually can also be wound manually so they can be kept running when not worn or if the wearer's wrist motions are inadequate to keep the watch wound  (SONY VGN-FZ31E Battery)       .

Some electronic watches are also powered by the movement of the wearer of the watch. For instance, Seiko's Kinetic powered quartz watches make use of the motion of the wearer's arm turning a rotating weight which causes a tiny generator to supply power to charge a rechargeable battery that runs the watch       (SONY  VGN-FZ31J Battery)     .

The concept is similar to that of self-winding spring movements, except that electrical power is generated instead of mechanical spring tension.

Electronic watches require electricity as a power source. Some mechanical movements and hybrid electronic-mechanical movements also require electricity     (SONY VGN-FZ31M Battery)     .

Usually the electricity is provided by a replaceable battery. The first use of electrical power in watches was as a substitute for the mainspring, in order to remove the need for winding. The first electrically-powered watch, the Hamilton Electric 500, was released in 1957 by the Hamilton Watch Company ofLancaster, Pennsylvania      (SONY VGN-FZ31B Battery)     .

Watch batteries (strictly speaking cells, as a battery is composed of multiple cells) are specially designed for their purpose. They are very small and provide tiny amounts of power continuously for very long periods (several years or more). In most cases, replacing the battery requires a trip to a watch-repair shop or watch dealer       (SONY VGP-BPS13 Battery)     ;

this is especially true for watches that are designed to be water-resistant, as special tools and procedures are required to ensure that the watch remains water-resistant after battery replacement. Silver-oxide and lithium batteries are popular today; mercury batteries, formerly quite common, are no longer used, for environmental reasons     (Dell Inspiron 1320 Battery)   .

Cheap batteries may be alkaline, of the same size as silver-oxide cells but providing shorter life. Rechargeable batteries are used in some solar powered watches.

Solar powered watches are powered by light. A photovoltaic cell on the face (dial) of the watch converts light to electricity, which in turn is used to charge a rechargeable battery or capacitor     (Dell Inspiron 1320n Battery)   .

The movement of the watch draws its power from the rechargeable battery or capacitor. As long as the watch is regularly exposed to fairly strong light (such as sunlight), it never needs battery replacement, and some models need only a few minutes of sunlight to provide weeks of energy (as in the Citizen Eco-Drive)         (Dell Inspiron 1464 Battery)      .

Some of the early solar watches of the 1970s had innovative and unique designs to accommodate the array of solar cells needed to power them (Synchronar, Nepro, Sicura and some models by Cristalonic, Alba, Seiko and Citizen). As the decades progressed and the efficiency of the solar cells increased while the power requirements of the movement and display decreased, solar watches began to be designed to look like other conventional watches     (Dell Inspiron 1564 Battery)      .

A rarely used power source is the temperature difference between the wearer's arm and the surrounding environment (as applied in the Citizen Eco-Drive Thermo).

Display

Analogue

Traditionally, watches have displayed the time in analogue form, with a numbered dial upon which are mounted at least a rotating hour hand and a longer, rotating minute hand        (Dell Inspiron 1764 Battery)      .

Many watches also incorporate a third hand that shows the current second of the current minute. Watches powered by quartz usually have a second hand that snaps every second to the next marker. Watches powered by a mechanical movement have a "sweep second hand", the name deriving from its uninterrupted smooth (sweeping) movement across the markers      (Dell Studio 1450 Battery)      ,

although this is actually a misnomer in most cases; the hand merely moves in smaller steps, typically 1/5th of a second, corresponding to the beat (half period) of the balance wheel. In some escapements (for example the duplexescapement), the hand advances every two beats (full period) of the balance wheel       (Dell Studio 1457 Battery)      ,

typically 1/2 second in those watches, or even every four beats (two periods, 1 second), in the double duplexescapement. A truly sweeping second hand is achieved with the tri-synchro regulatorof Spring Drive watches. All of the hands are normally mechanical, physically rotating on the dial, although a few watches have been produced with “hands” that are simulated by a liquid-crystal display       (Dell Latitude D610 Battery)       .

Analog display of the time is nearly universal in watches sold as jewelry or collectibles, and in these watches, the range of different styles of hands, numbers, and other aspects of the analogue dial is very broad. In watches sold for timekeeping, analog display remains very popular, as many people find it easier to read than digital display    (Toshiba NB100 Battery)       ;

but in timekeeping watches the emphasis is on clarity and accurate reading of the time under all conditions (clearly marked digits, easily visible hands, large watch faces, etc.). They are specifically designed for the left wrist with the stem (the knob used for changing the time) on the right side of the watch     (Toshiba Satellite M65 battery)      ;

this makes it easy to change the time without removing the watch from the wrist. This is the case if one is right-handed and the watch is worn on the left wrist (as is traditionally done). If one is left-handed and wears the watch on the right wrist, one has to remove the watch from the wrist to reset the time or to wind the watch        (Toshiba Satellite M60 battery)     .

Analog watches as well as clocks are often marketed showing a display time of approximately 10:09 or 10:10. This creates a visually pleasing smile-like face on upper half of the watch, in addition to enclosing the manufacturer's name. Digital displays often show a time of 12:38, where the increases in the numbers from left to right culminating in the fully-lit numerical display of the 8 also gives a positive feeling       (Dell Latitude D830 Battery)    .

Digital

A digital display simply shows the time as a number, e.g.,12:08instead of a short hand pointing towards the number 12 and a long hand 8/60 of the way round the dial.

The first digital mechanicalpocket watches appeared in late 19th century. In the 1920s the first digital mechanical wristwatches appeared      (Dell Latitude D620 Battery)      .

The first digital electronicwatch, a Pulsar LED prototype in 1970, was developed jointly by Hamilton Watch Company and Electro-Data. John Bergey, the head of Hamilton's Pulsar division, said that he was inspired to make a digital timepiece by the then-futuristic digital clock that Hamilton themselves made for the 1968 science fiction film 2001: A Space Odyssey      (Dell Inspiron Mini 10 Battery)      .

On April 4, 1972, the Pulsar was finally ready, made in 18-carat gold and sold for $2,100. It had a red light-emitting diode (LED) display.

Digital LED watches were very expensive and out of reach to the common consumer until 1975, when Texas Instruments started to mass produce LED watches inside a plastic case       (Sony VGN-FW11S Battery)     .

These watches, which first retailed for only $20, reduced to $10 in 1976, saw Pulsar lose $6 million and the Pulsar brand sold to Seiko.

Most watches with LED displays required that the user press a button to see the time displayed for a few seconds, because LEDs used so much power that they could not be kept operating continuously. Usually the LED display color would be red      (Sony VGN-FW11M Battery)    .

Watches with LED displays were popular for a few years, but soon the LED displays were superseded by liquid crystal displays (LCDs), which used less battery power and were much more convenient in use, with the display always visible and no need to push a button before seeing the time       (Sony VGN-FW139E/H battery)    .

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, and the Cox Electronic Systems Quarza.

From the 1980s onward, digital watch technology vastly improved    (Dell Latitude E5400 Battery)     .

In 1982 Seiko produced a watch with a small television screen built in, andCasio produced a digital watch with a thermometer as well as another that could translate 1,500 Japanese words into English. In 1985, Casio produced the CFX-400 scientific calculator watch. In 1987 Casio produced a watch that could dial your telephone number and Citizen revealed one that would react to your voice  (Dell Latitude E4200 Battery)   .

In 1995 Timex released a watch which allowed the wearer to download and store data from a computer to his wrist. Some watches, such as the Timex Datalink USB, feature dot matrix displays. Since their apex during the late 1980s to mid 1990s high technology fad, digital watches have mostlydevolved into a simpler, less expensive basic time piece with little variety between models      (Dell Vostro A840 Battery)     .

Despite these many advances, almost all watches with digital displays are used as timekeeping watches. Expensive watches for collectors rarely have digital displays since there is little demand for them. Less craftsmanship is required to make a digital watch face and most collectors find that analog dials (especially with complications) vary in quality more than digital dials due to the details and finishing of the parts that make up the dial (thus making the differences between a cheap and expensive watch more evident) (Dell Inspiron 300M Battery)  .

Functions

All watches provide the time of day, giving at least the hour and minute, and usually the second. Most also provide the current date, and often the day of the week as well. However, many watches also provide a great deal of information beyond the basics of time and date. Some watches include alarms      (Dell Studio 1737 battery)    .

Other elaborate and more expensive watches, both pocket and wrist models, also incorporate striking mechanisms or repeater functions, so that the wearer could learn the time by the sound emanating from the watch. This announcement or striking feature is an essential characteristic of true clocks and distinguishes such watches from ordinary timepieces     (Dell Inspiron E1505 battery) .

This feature is available on most digital watches.

A complicated watchhas one or more functions beyond the basic function of displaying the time and the date; such a functionality is called a complication       (Dell RM791 battery)    .

Two popular complications are the chronographcomplication, which is the ability of the watch movement to function as a stopwatch, and the moonphasecomplication, which is a display of the lunar phase. Other more expensive complications include Tourbillon, Perpetual calendar, Minute repeater, andEquation of time      (Dell XPS M1530 battery)   .

A truly complicated watch has many of these complications at once (see Calibre 89 from Patek Philippe for instance). Some watches can both indicate the direction of Mecca and have alarms that can be set for all daily prayer requirements.Among watch enthusiasts, complicated watches are especially collectible        (Dell XPS M2010 battery)    .

Some watches include a second 12-hour display for UTC (as Pontos Grand Guichet GMT).

The similar-sounding terms chronographand chronometerare often confused, although they mean altogether different things. A chronograph has astopwatch complication, as explained above    (Dell Vostro 1000 battery)     ,

while a chronometer watch has a high quality mechanical or a thermo-compensated quartz movement that 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; so a watch can be a chronograph, a chronometer, both, or neither     (Acer Aspire One battery) .

Types

Fashion

A sapphire cabochon on the crown of a men's dress watch

Wristwatches are often appreciated as jewelry or as collectible works of art rather than just as timepieces   (Toshiba Satellite P10 Battery)  .

This has created several different markets for wristwatches, ranging from very inexpensive but accurate watches (intended for no other purpose than telling the correct time) to extremely expensive watches that serve mainly as personal adornment or as examples of high achievement in miniaturization and precision mechanical engineering    (SONY VGN-FZ210CE Battery)   .

Traditionally, men's dress watches appropriate for informal (business), semi-formal, and formal attire are gold, thin, simple, and plain, but recent conflation of dressiness and high price has led to a belief among some that expensive rugged, complicated, or sports watches are also dressy because of their high cost     (Dell Precision M70 Battery)    .

Some dress watches have a cabochon on the crown and many women's dress watches have faceted gemstones on the face, bezel, or bracelet. Some are made entirely of facetted sapphire (corundum) .

Many fashion and department stores offer a variety of less-expensive, trendy, "costume" watches (usually for women), many of which are similar in quality to basic quartz timepieces but which feature bolder designs      (Toshiba Satellite L305 Battery)   .

In the 1980s, the Swiss Swatch company hired graphic designers to redesign a new annual collection of non-repairable watches.

Still another market is that of "geek" watches—watches that not only tell the time, but incorporate computers, satellite navigation, complications of various orders, and many other features that may be quite removed from the basic concept of timekeeping  (Toshiba Satellite T4900 Battery)    .

A dual-time watch is designed for travelers, allowing them to see what time it is at home when they are elsewhere.

In a variation of the "nerd" watches the time is displayed in a non-standard way: with 24-hour mechanism, the hands turn anticlockwise, the numbers are displayed with LEDs in a binary numbers, etc     (Toshiba PA3399U-2BRS battery)    .

Most companies that produce watches specialize in one or some of these markets. Companies such as Patek Philippe, Blancpain and Jaeger-LeCoultrespecialize in simple and complicated mechanical dress watches; companies such as Omega SA, Ball Watch Company, TAG Heuer, Breitling, Panerai andRolex specialize in rugged, reliable mechanical watches for sport and aviation use  (Toshiba Satellite A200 Battery)    .

Companies such as Casio, Timex, and Seiko specialize in watches as affordable timepieces or multifunctional computers.

Computerized multi-function watches

Many computerized wristwatches have been developed, but none have had long-term sales success, because they have awkward user interfaces due to the tiny screens and buttons, and a short battery life     (Toshiba Satellite 1200 Battery)  .

As miniaturized electronics became cheaper, watches have been developed containing calculators,tonometers, barometers, altimeters, video games, digital cameras, keydrives, GPS receivers and cellular phones      (Toshiba Satellite M300 Battery)     .

In the early 1980s Seiko marketed a watch with a television in it. Such watches have also had the reputation as unsightly and thus mainly geek toys. Several companies have however attempted to develop a computer contained in a wristwatch (see also wearable computer)      (Dell KM958 battery)       .

For space travel

Zero gravity environment and other extreme conditions encountered by astronauts in space requires the use of specially tested watches. On April 12, 1961,Yuri Gagarin wore a Shturmanskie (a transliteration of ??????????? which actually means "navigator's") wristwatch during his historic first flight into space      WD passport essential (500GB/640GB).

The Shturmanskie was manufactured at the First Moscow Factory.

Since 1964, the watches of the First Moscow Factory have been marked by the trademark "?????", transliterated as "POLJOT", which means "flight" inRussian and is a tribute to the many space trips its watches have accomplished. In the late 1970s, Poljot launched a new chrono movement, the 3133  WD passport essential (250GB/320GB).

With a 23 jewel movement and manual winding (43 hours), it was a modified Russian version of the Swiss Valjoux 7734 of the early 1970s. Poljot 3133 were taken into space by astronauts from Russia, France, Germany and Ukraine. On the arm of Valeriy Polyakov, a Poljot 3133 chronograph movement-based watch set a space record for the longest space flight in history    WD  passport essential SE (750GB/1TB)      .

During the 1960s, a large range of watches were tested for durability and precision under extreme temperature changes and vibrations. The OmegaSpeedmaster Professional was selected by NASA, the U.S. space agency. (For a list of NASA-certified watches, see this footnote)    WD  passport elite(250GB/320GB).

Heuer became the first Swiss watch in space thanks to a Heuer Stopwatch, worn by John Glenn in 1962 when he piloted the Friendship 7 on the first manned U.S. orbital mission.

The Breitling Navitimer Cosmonaute was designed with a 24-hour analog dial to avoid confusion between AM and PM, which are meaningless in space    WD passport elite(500GB/640GB).

It was first worn in space by U.S. astronaut Scott Carpenter on May 24, 1962 in the Aurora 7 mercury capsule.

Since 1994 Fortis is the exclusive supplier for manned space missions authorized by the Russian Federal Space Agency.

China National Space Administration (CNSA) astronauts wear the Fiyta  spacewatches    WD  passport studio for Mac(320GB/500GB).

At BaselWorld, 2008, Seiko announced the creation of the first watch ever designed specifically for a space walk, Spring Drive Spacewalk.

For scuba diving

Watches may be crafted to become water resistant. These watches are sometimes called diving watches when they are suitable for scuba diving or saturation diving        WD  passport studio for Mac(500GB/640GB).

The International Organization for Standardization issued a standard for water resistant watches which also prohibits the term "waterproof" to be used with watches, which many countries have adopted.

Water resistance is achieved by the gaskets which forms a watertight seal, used in conjunction with a sealant applied on the case to help keep water out      WD  Elements series(250GB/320GB).

The material of the case must also be tested in order to pass as water resistant.

None of the tests defined by ISO 2281 for the Water Resistant mark are suitable to qualify a watch for scuba diving. Such watches are designed for everyday life and must be water resistant during exercises such as swimming      WD  Elements SE(500GB/640GB).

They can be worn in different temperature and pressure conditions but are under no circumstances designed for scuba diving.

The standards for diving watches are regulated by the ISO 6425 international standard. The watches are tested in static or still water under 125% of the rated (water)pressure, thus a watch with a 200 meter rating will be water resistant if it is stationary and under 250 meters of static water      WD Elements SE(750GB/1TB).

The testing of the water resistance is fundamentally different from non-dive watches, because every watch has to be fully tested. Besides water resistance standards to a minimum of 100 meter depth rating ISO 6425 also provides eight minimum requirements for mechanical diver's watches for scuba diving (quartz and digital watches have slightly differing readability requirements)  WD  Elements desktop(500GB/640GB).

For diver's watches for mixed-gas saturation diving two additional requirements have to be met.

Watches are classified by their degree of water resistance, which roughly translates to the following (1 meter = 3.281 feet)  WD  Elements desktop(750GB/1TB):

Water resistance rating Suitability Remarks
Water Resistant 30 m or 50 m Suitable for washing hands. 50 m suitable for showering and light swimming. not suitable for swimming or diving.[citation needed]
Water Resistant 100 m Suitable for recreational surfing, swimming, snorkeling, sailing and water sports. not suitable for diving.
Water Resistant 200 m Suitable for professional marine activity and serious surface water sports. suitable for diving.
Diver's 100 m Minimum ISO standard (ISO 6425) for scuba diving at depths NOT requiring helium gas. Diver's 100 m and 150 m watches are generally old(er) watches.
Diver's 200 m or 300 m Suitable for scuba diving at depths NOT requiring helium gas. Typical ratings for contemporary diver's watches.
Diver's 300+ m helium safe Suitable for saturation diving (helium enriched environment). Watches designed for helium mixed-gas diving will have additional markings to point this out.

Some watches use bar instead of meters, which may then be multiplied by 10, and then subtracted by 10WD  Elements desktop(1.5 TB/2TB).

This is because 1 bar is equal to one atmosphere or 10 meters of water (therefore 1 bar at the surface and one more each 10 meters). to be approximately equal to the rating based on meters. Therefore, a 5 bar watch is equivalent to a 40 meter watch. Some watches are rated in atmospheres(atm), which are roughly equivalent to bar    WD  passport essential SE (750GB/1TB)--USB 3.0)   .

History

Watches evolved from portable spring driven clocks, which first appeared in the 15th century. Portable timepieces were made possible by the invention of the mainspring       WD  passport essential (500GB/640GB).

Although some sources erroneously credit Nuremberg clockmaker Peter Henlein (or Henle or Hele) with inventing the mainspring around 1511, many references to 'clocks without weights' and two surviving examples show that spring powered clocks appeared in the 15th century    WD  passport for Mac(320GB/500GB).

Henlein is also often credited with constructing the first pocketwatches, mostly because of a passage by Johann Cochläus in 1511:

Peter Hele, still a young man, fashions works which even the most learned mathematicians admire. He shapes many-wheeled clocks out of small bits of iron, which run and chime the hours without weights for forty hours, whether carried at the breast or in a handbag and because he was popularized in a 19th century novel      WD  passport for Mac(640GB/1TB).

However, many German clockmakers were creating miniature timepieces during this period, and there is no evidence Henlein was the first. Also, watches weren't widely worn in pockets until the 17th century      My book essential 4 generation  (640GB/1TB).

1500–1600 Clock-watches

The first timepieces to be worn, made in 16th century Europe, were transitional in size between clocks and watches. These 'clock-watches' were fastened to clothing or worn on a chain around the neck. They were heavy drum shaped cylindrical brass boxes several inches in diameter, engraved and ornamented      WD  My book essential 4 generation( 1.5TB/2TB).

They had only an hour hand. The face was not covered with glass, but usually had a hinged brass cover, often decoratively pierced with grillwork so the time could be read without opening. The movement was made of iron or steel and held together with tapered pins and wedges, until screws began to be used after 1550      WD  My book elite( 1TB/1.5TB).

Many of the movements included striking or alarm mechanisms. They usually had to be wound twice a day. The shape later evolved into a rounded form; these were called Nuremberg eggs. Still later in the century there was a trend for unusually shaped watches, and clock-watches shaped like books, animals, fruit, stars, flowers, insects, crosses, and even skulls (Death's head watches) were madeWD  My book studio(1TB/2TB).

It should not be thought that the reason for wearing these early clock-watches was to tell the time. The accuracy of their verge and foliot movements was so poor, perhaps several hours per day, that they were practically useless. They were made as jewelry and novelties for the nobility, valued for their fine ornamentation, unusual shape, or intriguing mechanism, and accurate timekeeping was of very minor importance      WD  My book essential 4 generation( 1.5TB/2TB).

1600–1657 Pocketwatches

Styles changed in the 17th century and men began to wear watches in pockets instead of as pendants (the woman's watch remained a pendant into the 20th century). This is said to have occurred in 1675 when Charles II of England introduced waistcoats. To fit in pockets, their shape evolved into the typical pocketwatch shape, rounded and flattened with no sharp edges    WD  My book elite(640GB/2TB).

Glass was used to cover the face beginning around 1610. Watch fobs began to be used, the name originating from the German word fuppe, a small pocket. The watch was wound and also set by opening the back and fitting a key to a square arbor, and turning it.

The timekeeping mechanism in these early pocketwatches was the same one used in clocks, invented in the 13th century  Seagate  expansion portable (320GB/500GB);

the verge escapement which drove a foliot, a dumbbell shaped bar with weights on the ends, to oscillate back and forth. However, the mainspring introduced a source of error not present in weight-powered clocks. The force provided by a spring is not constant, but decreases as the spring unwinds      Seagate  expansion (1.5TB/2TB).

The rate of all timekeeping mechanisms is affected by changes in their drive force, but the primitive verge and foliot mechanism was especially sensitive to these changes, so early watches slowed down during their running period as the mainspring ran down. This problem, called lack of isochronism, plagued mechanical watches throughout their history    Seagate  Freeagent Desktop (500GB/1TB).

Efforts to improve the accuracy of watches prior to 1657 focused on evening out the steep torque curve of the mainspring.Two devices to do this had appeared in the first clock-watches: thestackfreedand the fusee. The stackfreed, a spring-loaded cam on the mainspring shaft, added a lot of friction and was abandoned after about a century    Seagate  Freeagent Go(250GB/320GB).

The fusee was a much more lasting idea. A curving conical pulley with a chain wrapped around it attached to the mainspring barrel, it changed the leverage as the spring unwound, equalizing the drive force. Fusees became standard in all watches, and were used until the early 19th century        Seagate  Freeagent Go(500GB/640GB).

The foliot was also gradually replaced with the balance wheel, which had a higher moment of inertia for its size, allowing better timekeeping.

1657–1765 The balance spring

A great leap forward in accuracy occurred in 1657 with the addition of the balance spring to the balance wheel, an invention disputed both at the time and ever since between Robert Hooke andChristiaan Huygens      Seagate  Freeagent Go(750GB/1TB).

Prior to this, the only force limiting the back and forth motion of the balance wheel under the force of the escapement was the wheel's inertia. This caused the wheel's period to be very sensitive to the force of the mainspring. The balance spring made the balance wheel a harmonic oscillator, with a natural 'beat' resistant to disturbances    Seagate  Freeagent Goflex(250GB/320GB).

This increased watches' accuracy enormously, from perhaps several hours per day to perhaps 10 minutes per day, resulting in the addition of the minute hand to the face from around 1680 in Britain and 1700 in France. The increased accuracy of the balance wheel focused attention on errors caused by other parts of the movement, igniting a two century wave of watchmaking innovation  Seagate Freeagent Goflex(500GB/640GB).

The first thing to be improved was the escapement. The verge escapement was replaced in quality watches by the cylinder escapement, invented by Thomas Tompion in 1695 and further developed by George Graham in the 1720s. In Britain a few quality watches went to the duplex escapement, invented by Jean Baptiste Dutertre in 1724      Seagate  Freeagent Goflex(750GB/1TB).

The advantage of these escapements was that they only gave the balance wheel a short push in the middle of its swing, leaving it 'detached' from the escapement to swing back and forth undisturbed during most of its cycle  Seagate  Freeagent Goflex Pro(500GB/750GB).

During the same period, improvements in manufacturing such as the tooth-cutting machine devised by Robert Hooke allowed some increase in the volume of watch production, although finishing and assembling was still done by hand until well into the 19th century.

1765–1800 Temperature compensation and chronometers

The Enlightenment view of watches as scientific instruments brought rapid advances to their mechanisms    Seagate  Freeagent Goflex desktop(1TB/2TB).

The development during this period of accurate marine chronometers to determine longitudeduring sea voyages produced many technological advances that were later used in watches. It was found that a major cause of error in balance wheel timepieces was changes in elasticity of thebalance spring with temperature changes      Seagate  Freeagent go for Mac(320GB/640GB).

This problem was solved by the bimetallic temperature compensated balance wheel invented in 1765 by Pierre Le Roy and improved by Thomas Earnshaw. This type of balance wheel had two semicircular arms made of a bimetallic construction. If the temperature rose, the arms bent inward slightly      Samsung  G2 protable (250gb/320GB),

causing the balance wheel to rotate faster back and forth, compensating for the slowing due to the weaker balance spring. This system, which could reduce temperature induced error to a few seconds per day, gradually began to be used in watches over the next hundred years        Samsung  G2 protable (500GB/640GB).

The going barrel invented in 1760 by Jean-Antoine Lépine provided a more constant drive force over the watch's running period, and its adoption in the 19th century made the fusee obsolete. Complicated pocket chronometers and astronomical watches with many hands and functions were made during this period        Samsung  S2 protable (320GB/500GB).

1800–1850 Lever escapement

The lever escapement, invented by Thomas Mudge in 1759 and improved by Josiah Emery in 1785, gradually came into use from about 1800 onwards, chiefly in Britain; it was also adopted byAbraham-Louis Breguet, but Swiss watchmakers (who by now were the chief suppliers of watches to most of Europe) mostly adhered to the cylinder until the 1860s  Samsung S1 Mini (120GB/160GB).

By about 1900, however, the lever was used in almost every watch made. In this escapement the escape wheel pushed on a T shaped 'lever', which was unlocked as the balance wheel swung through its center position and gave the wheel a brief push before releasing itSamsung  S1 Mini (250GB/320GB).

The advantages of the lever was that it allowed the balance wheel to swing completely free during most of its cycle; due to 'locking' and 'draw' its action was very precise; and it was self-starting, so if the balance wheel was stopped by a jar it would start again. Jewel bearings, introduced in 1702 by Nicolas Fatio de Duillier, also came into use for quality watches during this period    Samsung story station (1TB/1.5TB).

1850–1900 Mass production

At Vacheron Constantin, Geneva, Georges-Auguste Leschot (1800–1884), pioneered in the field of interchangeability in clockmaking by the invention of various machine tools. 1830 he designed an anchor escapement, which his student, Antoine Léchaud, later mass produced    Samsung Story station (1.5TB/2TB).

1839 he invented a pantograph allowing some degree of standardisation and interchangeability of parts on watches fitted with the same calibre.

Watch manufacturing really changed from assembly in watchmaking shops to mass production with interchangeable parts, as from 1854, pioneered by the Waltham Watch Company, in Waltham, Massachusetts      Samsung story station Esata(1TB/1.5TB).

The railroads' stringent requirements for accurate watches to safely schedule trains drove improvements in accuracy. The engineer Webb C. Ball, established around 1891 the first precision standards and a reliable timepiece inspection system for Railroad chronometers      Samsung  G3 station (1TB/1.5TB).

Temperature compensated balance wheels began to be widely used in watches during this period, and jewel bearings became almost universal. Techniques for adjusting the balance spring for isochronism and positional errors discovered by Abraham-Louis Breguet, M. Phillips, and L. Lossier were adopted      Maxtor  one touch 4 plus (500GB/750GB).

The first international watch precision contest took place in 1876, during the International Centennial Exposition in Philadelphia (the winning four top watches, which outclassed all competitors, had been randomly selected out of the mass production line), on display was also the first fully automatic screw making machine    Maxtor one touch 4 plus (1TB/1.5TB).

By 1900, with these advances, the accuracy of quality watches, properly adjusted, topped out at a few seconds per day.

From about 1860, key winding was replaced by keyless winding, where the watch was wound by turning the crown  Maxtor cool black(640GB/1TB).

The pin pallet escapement, an inexpensive version of the lever escapement invented in 1876 by Georges Frederic Roskopf was used in cheap mass produced dollar watches, which allowed ordinary workers to own a watch for the first time; other cheap watches used a simplifed version of the duplex escapement, developed by Daniel Buck in the 1870s    Maxtor Black diamond (320GB/500GB).

These improvements were mostly originated and applied in the United States, and as a result the American industry ousted that of Switzerland from its long-held position as worldwide leader in the low-to-middle-class market. The Swiss responded, towards the end of the century, by changing their emphasis from economy to quality      Hitachi  simple touch (250GB/320GB).

1900–1920 Better materials

During the 20th century, the mechanical design of the watch became standardized, and advances were made in better materials, tighter tolerances, and improved production methods      Hitachi simple touch (320GB/500GB).

The bimetallic temperature compensated balance wheel was made obsolete by the discovery of low temperature coefficient alloys invar and elinvar. A balance wheel of invar with a spring of elinvar was almost unaffected by temperature changes, so it replaced the complicated temperature compensated balance        Hitachi  life studio (320GB/500GB).

The discovery in 1903 of a process to produce artificial sapphire made jewelling cheap. Bridge construction superseded 3/4 plate construction.

1920–1950 Wristwatches become popular

Patek Phillipe created the first wristwatch in 1868. In 1880 Constant Girard (Girard-Perregaux) develops a concept of wristwatches, made for German naval officers and ordered by Kaiser Wilhelm I of Germany      Hitachi life studio (250GB/320GB).

Two-thousand watches were produced, which represents the first important commercialization of wristwatches. For civilians the wristwatches did not yet become popular among men. At the beginning of the century wristwatches were mostly worn by women  Hitachi  life studio platinum (250GB/320GB).

In 1904, Brazilian aviator Alberto Santos Dumont asked his friend Louis Cartier to come up with an alternative that would allow him to keep both hands on the controls while timing his performances during flight. Cartier and his master watchmaker, Edmond Jaeger soon came up with the first prototype for a man's wristwatch called the Santos wristwatch      Hitachi life studio platinum (320GB/500GB).

The Santos first went on sale in 1911, the date of Cartier's first production of wristwatches.

During the First World War soldiers needed access to their watches while their hands were full. They were given wristwatches, called 'trench watches', which were made with pocketwatch movements, so they were large and bulky and had the crown at the 12 o'clock position like pocketwatches      Hitachi life studio desk (500GB/1TB).

After the war pocketwatches went out of fashion and by 1930 the ratio of wrist- to pocketwatches was 50 to 1. The first successful self-winding system was invented by John Harwood in 1923.

1950–1969 Electric watches

The first generation electric-powered watches came out during this period      Hitachi life studio plus (320GB/500GB).

These kept time with a balance wheel powered by a solenoid, or in a few advanced watches that foreshadowed the quartz watch, by a steel tuning fork vibrating at 360 Hz, powered by a solenoid driven by a transistor oscillator circuit. The hands were still moved mechanically by a wheel train        Hitachi life studio plus (320GB/500GB).

In mechanical watches the self winding mechanism, shockproof balance pivots, and break resistant 'white metal' mainsprings became standard. The jewel craze caused 'jewel inflation' and watches with up to 100 jewels were produced.

1969 Quartz watches

The introduction of the quartz watch in 1969 was a revolutionary improvement in watch technology      Hitachi X mobile (250GB/320GB).

In place of a balance wheel which oscillated at 5 beats per second, it used a quartz crystalresonator which vibrated at 8,192 Hz, driven by a battery powered oscillator circuit. In place of a wheel train to add up the beats into seconds, minutes, and hours, it used digital counters      Hitachi X mobile(320GB/500GB).

The higher Q factor of the resonator, along with quartz's low temperature coefficient, resulted in better accuracy than the best mechanical watches, while the elimination of all moving parts made the watch more shock-resistant and eliminated the need for periodic cleaning      Hitachi  XL (1TB/2TB).

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Accuracy increased with the frequency of the crystal used, but so did power consumption. So the first generation watches had low frequencies of a few kilohertz, limiting their accuracy. The power saving use of CMOS logic and LCD displays in the 2nd generation increased battery life and allowed the crystal frequency to be increased to 32,768 Hz resulting in accuracy of 5–10 seconds per month      Toshiba canvio portable(320GB/500GB).

By the 1980s, quartz watches had taken over most of the watch market from the mechanical watch industry.

1990 Radio controlled

In 1990, Junghans offered the first radio-controlled wristwatch, the MEGA 1      Toshiba  canvio portable(750GB/1TB).

In this type, the watch's quartz oscillator is set to the correct time daily by coded radio time signals broadcast by government-operated time stations such as WWVH, received by a radio receiver in the watch      Toshiba  anvio for Mac(500GB/750GB).

This allows the watch to have the same long-term accuracy as the atomic clocks which control the time signals. Recent models are capable of receiving synchronization signals from various time stations worldwide. This also included some televisions and vcr players      Toshiba  canvio for Mac(750GB/1TB).

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