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How does a watch work?


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May 01, 2012 4:24PM

Electronic watches use a resonant electronic circuit containing a crystal (usually quartz) which oscillates at a specific frequency. The oscillation is converted to a stream of pulses, which drive a series of binary counters. Because the frequency of the crystal is known, when a specific number of pulses is counted, one second has passed. Another counter counts the seconds to determine when one minute has passed, and so on.

Mechanical watches use an oscillating balance wheel and spring which act together, somewhat like a pendulum. The mass of the wheel and the elasticity of the spring determine the frequency of the movement. The oscillating motion is transferred to gears by way of an escapement mechanism, which allows a wheel to advance by a fixed amount with each oscillation of the balance wheel. A series of gears with the correct ratios of teeth determine the rotation of the second, minute and hour hands.
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.