The Quartz Revolution

Abstract

The drive to improve the performance of clocks inevitably led on a path from large lumbering mechanical clock mechanisms with long periods of oscillation to increasingly smaller mechanisms that run at much higher frequency. The hair spring-balance wheel clocks evolved over the eighteenth and nineteenth centuries into mechanical instruments of such perfection that further improvement could only come painstakingly in small increments at the cost of higher complexity. There is a limit to the precision that can be attained with a relatively low frequency reference oscillator; in a fundamental sense, there is a limit to how finely one can split a period of oscillation. It was therefore inevitable when the electronic revolution arrived in the 1950s with the development of the transistor and smaller batteries that a higher frequency electrical watch would soon emerge; as indeed it did in the form of the Bulova Accutron. This watch uses a tuning fork as the reference vibrator, so called not so much because it resembles a fork, although it does have two tines, but rather it is the name given to a two pronged device that produces a pure audible tone when struck, an instrument that has a long history as a standard of acoustic frequency, or musical tone. The tuning fork in the Accutron was designed to vibrate at the audible frequency of 360 Hz, hence the watch hums rather than ticks; another immediately noticeable difference about the new watch is that the second hand rotates continuously, and not in discrete steps. The principal initiator of this development in 1960 was an electrical engineer by the name of Max Hetzel [1]. Initial tests showed that the new watch was more stable than the classical balance-wheel watches by at least an order of magnitude. It was found, however, that the initial tuning fork design made the watch perceptibly sensitive to its orientation in space, with deviations of ±5 s per day. This is still below the limit required for chronometer rating, but nevertheless the design was modified to minimize this effect. The tuning fork movement was licensed also to other quality watchmakers, such as Omega and Tissot. These and other fine chronometers designed by Piaget were the ultimate mechanical timepieces of the day; timepieces that were carried by the Apollo astronauts.