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From Wikipedia -

A watch is a timepiece that is made to be worn on a person. The term now usually refers to a wristwatch, which is 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.

Most inexpensive and medium-priced watches used mainly for timekeeping are electronic watches with quartz movements. Expensive, collectible watches valued more for their workmanship and aesthetic 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.

Before the inexpensive miniaturization that became possible in the 20th century, 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 1600s from spring powered clocks, which appeared in the 1400s.

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. 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. As well, they are costly to produce, they require regular maintenance and adjustment, and they 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 of the spring, converting what would otherwise be a simple unwinding, into a controlled and periodic energy release. 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, is a rotating frame for the escapement which is used to cancel out or reduce the effects of bias to the timekeeping of gravitational origin. Due to the complexity of designing a tourbillon, they are very expensive, and only found in "prestige" watches. The pin-lever (also called Roskopf movement after its inventor, Georges Frederic Roskopf), is a cheaper version of the fully levered movement which was manufactured in huge quantities by many Swiss manufacturers as well as Timex, until it was replaced by quartz movements.[1][/suP][2][/suP][3][/suP]

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. 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.

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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 a quartz oscillator which resonates at a specific and highly stable frequency, and which can be used to accurately pace a timekeeping mechanism. For this reason, electronic watches are often called quartz 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.

The first 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 appeared in 1969. Modern quartz movements are produced in very large quantities, and even the cheapest wristwatches typically have quartz movements. 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.[4][/suP] Some watchmakers combine the quartz and mechanical movements, such as the Seiko Spring Drive, introduced in 2005.

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

Power Sources:
Traditional mechanical watch movements use a spiral spring called a mainspring as a power source. In manual watches the spring must be rewound by the user periodically 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. Most modern watches are designed to run 40hours on a winding, so must be wound daily, but some run for several days and a few have 192-hour mainsprings and are wound weekly.

A self-winding or automatic mechanism is one that rewinds the mainspring of a mechanical movement by the natural motions of the wearer's body. The first self-winding mechanism, for pocketwatches, was invented in 1770 by Abraham-Louis Perrelet;[5][/suP] 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 a constant winding without special action from the wearer: 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 don't keep the watch wound.
Some electronic watches are also powered by the movement of the wearer of the watch. Kinetic powered quartz watches make use of the motion of the wearer's arm turning a rotating weight, which turns a generator to supply power to charge a rechargeable battery that runs the watch. 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. Usually the electricity is provided by a replaceable battery. The first use of electrical power in watches was as 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 of Lancaster, Pennsylvania.

Watch batteries (strictly speaking cells, 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; 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. Cheap batteries may be alkaline, of the same size as silver-oxide 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. 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).

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.[6][/suP] 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).

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Easy Guide to Watch Movements

The majority of watches produced today are powered by a quartz or mechanical movement. What are the peculiarities of these mechanisms?

Mechanical Movements
The major component of a mechanical movement is the mainspring, a special gradually unwinding spring responsible for transmission of energy. The same way as in case of a quartz movement a mechanical movement has an oscillator for time keeping.

The oscillator of a mechanical movement is the balance wheel, a small wheel moving very quickly to and fro. In most watches produced at present day the balance wheel oscillates 28, 800 times per hour.

One more important component of the mechanical movement is the balance spring, also called the hairspring, a tiny delicate spring necessary for controlling oscillations of the balance wheel.

Mechanical movements are divided into two major groups - automatic, also called self-winding, and manual-wind, also known as hand-wound or wind-up.

Automatic Mechanical Movement
An automatic mechanism has a special fan-shaped rotor that is swinging on a pivot in response to the motion of the arm of the watch wearer. With help of the swinging rotor the watch's mainspring winds up and keeps the watch running. Many watches equipped with automatic movements have transparent case backs to allow the owner of the timepiece admire the spinning rotor.

So, owners of automatic watches do not have to regularly wind their timepieces - all they have to do is to remember to put the watch on the wrist and wear it for about 12 hours every day. This way the owner of an automatic mechanical watch provides the mechanism with enough motion to keep the mainspring wound. If an automatic timepiece is not worn for a few days, it stops running and its owner must wind it with help of a winding crown positioned on the side of the watch case.

Today watchmakers develop automatic movements that will keep an unworn watch running for a week or more. The are also electronically powered watch winders to keep the watch on. Watch winders rotate the timepiece for a few hours at a time, so an owner of the watch does not have to manually wind it or reset the time and date.

Hand-Wound Watches
As for hand-wound watches, it is necessary to wind them up regularly, usually once a day, using the crown.

Quartz Movements
Quartz movements power the timepiece by electricity stored in a battery. The electricity is worked out by a tiny piece of quartz crystal oscillating at the rate of 32, 786 times per second.

The majority of timepieces equipped with a quartz movement feature analog time display, implying a dial with rotating hands. Other quartz watches feature digital displays, very often LCDs - liquid crystal displays - that are used in many types of electronic devices. You will also see quartz watches with both analog and digital time readouts for simultaneous display of different information. These watches are known as 'ana-digi.'

A lot of people are puzzled by the question a watch with which type of movement to buy. It is easier to make up your mind when you consider the factors mentioned below:

1. Accuracy
Watches equipped with quartz movements generally provide more accurate timekeeping. The accuracy is provided due to the faster and steadier oscillations of a quartz crystal than those of a balance wheel. A quartz timepiece usually gains or loses about 10 seconds monthly, while a mechanical watch gains or loses several minutes a month.

2. Winding or Changing the Battery
An owner of a quartz watch will never have to wind it. But it will be necessary to replace the battery from time to time. Silver oxide batteries serve for two-three years. As for long-life lithium batteries, they run for about a decade.

You will also find quartz watches equipped with batteries that are recharged by light, or by the wearer's arm-motion. Light enters a light-powered watch through its dial. Beneath the dial there is a special solar cell that transforms the light into electricity. The electricity created is stored in the cell. The 'motion-powered' quartz watch incorporates a tiny rotor spinning in response to motion and generating electricity.

3. Maintenance
Mechanical watch movements require cleaning and lubricating once in 3-5 years. Usually, a mechanical watch is accompanied by a booklet that specifies the necessary service intervals.

Quartz movements consist of fewer parts and are influenced by less stress as they are powered electronically rather than mechanically, so they do not need much attention. Sometimes, however, some dirt accumulates on the gears of an analog quartz movement, making the watch lose time. Then, it is necessary to take the watch to the service center to have the gears cleaned.

Revolution In Quartz Movements' Field
In the 1970-s the world of mechanical watchmaking had to face the appearance of quartz technology. The first quartz wristwatch, named the Astron, was produced by Seiko in 1969. Quartz watches became serious rivals to their mechanical forerunners as they offered supreme accuracy and convenience - they saved their owners from the necessity to wind the watch.

However, the battery-equipped quartz watches had their own disadvantage - a dead battery that had to be replaced by a watch repairer. Citizen, Seiko and the Swatch Group, the leading producers of quartz watches in the world, have invented a new revolutionary type of quartz watches. To recharge the battery, these watches use the motion of the wearer's arm or the light power.

The new generation of quartz watches provided three major advantages:
- convenience - the new-type quartz watch will never stop running unexpectedly. Its owner will not have to visit a watch repairer to have it equipped with a new battery.
- no need for maintenance - as there is no need to change the battery, there is no need to open the case. So the mechanism inside and the water-resistant seal are well-protected from any dust and dirt.
- environment-friendliness - there are no used batteries to throw away.

Seiko Kinetic Technology
The Seiko Company is the most experienced producer of the motion-powered quartz watches. Seiko developed the Kinetic technology generating electricity from arm-motion. The Kinetic system is based on a tiny rotor spinning at amazing speed - 10,000 to 100,000 revolutions a minute.

The motion of the rotor is generating voltage across a coil block. The system is also provided with the ESU (electrical storage unit), an extremely small component used for storing the electrical current that is released when it is necessary to power the watch.

The ESU stores electricity that powers the watch even when it is off the wrist of its owner. Fully charged Kinetic watches operate for 6 months when not worn. Seiko also introduced Kinetic Auto Relay watches that are devised to tell the precise time when off the wrist for the whole four years.

The Kinetic watch will stop when the ESU runs out of energy. To recharge it, it necessary to swing it gently from side to side to make the oscillating weight rotate and generate electricity. The second hand begins to move in one-second intervals and the watch has at store about three hours of power.

Citizen Eco-Drive
The Swatch Group and Citizen have developed and introduced their own motion-powered quartz movements. The Swatch Group has developed the Autoquartz technology. Citizen supplies its motion-powered movements to other brands, but does not use them for its own timepieces. The Japanese company is most experienced in producing light-powered watches.

In 1995 Citizen introduced its famous Eco-Drive series of watches powered by any type of light - natural, fluorescent and incandescent. The light passes through the dial of a watch and reaches a solar cell. The solar cell is produced from specially treated silicon semiconductor. The collision of the photons in the light and the surface of the cell results in the release of electrons.

The electrons are united into a current stored in a constantly refillable tiny reservoir - a 'secondary' energy cell. The created energy is used to power the timepiece. Citizen Eco-Drive watches have no battery as it is substituted by the energy cell.

Under normal conditions a light-powered watch will never stop running as it will be constantly recharged by any type of light. Even if the owner of a light-powered watch will keep it in complete darkness for months and years, some models will still provide perfect timekeeping due to the power stored in the secondary cell. The completely depleted cell will become 'full' after a few hours of being exposed to sunlight.

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I saw this on another thread and thought it might be of interest:

Sought after movements:

A few sought after ETA automatic movements would be:
ETA Valjoux 7750,
7753 Automatic Chronograph movements.

ETA 2836-2 day/date movement,
ETA 2892A2 high grade 3 hand automatic,
ETA 2834-2 Full day and date movement.

A few sought after Quartz movements:
Ronda 5040.F,
Ronda 5050.C,
ETA 251.272,
ETA 251.262,
ETA 251.242,
ETA G15 Retrograde.

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This is my favorite "power source"-focused movement . . .

Urwerk UR-202 Twin Turbine Hammerhead


The UR-202 is the world’s first watch with the winding rate regulated by fluid dynamics.

As long ago as the 18th century, clockmakers were using air friction to regulate the speed of chiming clocks, and their techniques evolved to become the preferred method of regulating the rate of chimes on minute-repeaters.

With the UR-202, URWERK have taken the traditional idea of using air friction and refined it to control the rate of automatic winding.

The traditional rotating vanes of the past have been replaced by cutting-edge miniature twin turbines - miniature air compressors - which can be seen spinning on the back of the watch.

Urwerk turbines

The UR-202’s twin turbines are coupled with the winding rotor. According to the position of the selector lever, the turbines act as shock absorbers.
In normal activity they cushion sharp movements of the rotor. This reduces wear and increases the lifespan of the movement.

While the selector position is continuously variable, the three principal positions are: normal activity, where the turbines spin freely; vigorous activity, where the air pressure generated by the turbines reduces the winding rate by approximately 35%; and extreme activity, where the turbines and rotor are fully blocked.

The turbine system is totally self-contained within the waterproof case. The air flows from under the turbines and is channeled up past them under a sapphire plate and down through holes leading to a tiny air chamber.

The turbines are controlled by a 3-position selector switch. This functions by adjusting the level of air compression the turbines generate by selectively regulating the amount of air flowing from inside the case.

The spinning turbines force air through holes into a tiny air chamber. The selector switch controls the amount of air escaping from the turbines.
By restricting the airflow, it increases the air pressure and slows down the turbines and the winding rotor.

The UR-202 also features URWERK’s patented Revolving Satellite Complication with telescopic minutes hands.

The Revolving Satellite Complication displays time using telescopic minutes hands operating through the middle of three orbiting and revolving hours satellites. The telescopic minutes hands precisely adjust their length to follow the three sectors marking the minutes: 0-14, 15-44, 45-60.

Extended, they enable the UR-202 to display the time across a large, easy-to-read dial. Retracted, they allow for a very wearable and comfortably sized case.


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That is so cool.
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