At the heart of a quartz watch is a 4-mm bar of quartz piezoelectric crystal that is made to vibrate by applying a small voltage. The crystal is laser trimmed so that it oscillates exactly 32,768 times per second. Higher-frequency crystals would need too large a driving current and guickly drain a watch battery, and lower-frequency ones would be physically too large. The signal, one cycle per second, either drives a second hand or triggers an LCD (liquid crystal display).
Quartz is used because it has a very low coefficient of thermal expansion and thus is not affected by changes in the weather. A fairly standard mass- produced quartz watch typically gains or loses less than one second per day.
The first quartz oscillator was produced in 1921. By 1927 Warren Marrison, a telecommunications engineer at Bell Laboratories in Canada, had made the first quartz clock. Unfortunately, its valve-driven counting electronics were bulky and unreliable. The great breakthrough came in the 1960s with the introduction of robust inexpensive digital logic systems that used simple semiconductors. In 1967 the Centre Electronique Horloger (CEH) in Neuchatel, Switzerland, developed the famous Beta 21, the world's first analog quartz wristwatch, and two years later Seiko produced the world's first commercial quartz wristwatch, the Astron. Soon clocks, timers, and alarm mechanisms were routinely being fitted with quartz crystals, as opposed to "old-fashioned," inaccurate, and high- maintenance mechanical oscillating balance wheels.
For purposes requiring extreme accuracy, the atomic clock is preferred to the quartz clock.
