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Quartz clocks and quartz watches are timepieces that use an electronic oscillator regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency , so that quartz clocks and watches are at least an order of magnitude more accurate than mechanical clocks .
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. [1] [2] [3] The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers.
Picture of a quartz crystal resonator, used as the timekeeping component in quartz watches and clocks, with the case removed. It is formed in the shape of a tuning fork. Most such quartz clock crystals vibrate at a frequency of 32 768 Hz. The piezoelectric properties of crystalline quartz were discovered by Jacques and Pierre Curie in 1880.
The first clock known to strike regularly on the hour, a clock with a verge and foliot mechanism, is recorded in Milan in 1336. [96] By 1341, clocks driven by weights were familiar enough to be able to be adapted for grain mills, [97] and by 1344 the clock in London's Old St Paul's Cathedral had been replaced by one with an escapement. [98]
In modern quartz watches, the timekeeper is a quartz crystal in an electronic circuit, powering a small stepper motor. Because of the small amount of torque needed to move the hands, there is almost no pressure on the bearings and no real gain by using a jewel bearing, hence they are not used in a large proportion of quartz movements.
Lavet-type stepping motor of a quartz clock. A black rotor sprocket provides the mechanical output. The Lavet-type stepping motor has widespread use as a drive in electro-mechanical clocks [1] and is a special kind of single-phase stepping motor. Both analog and stepped-movement quartz clocks use the Lavet-type stepping motor (see Quartz clock).
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