Hetzel, Max

SUBJECT AREA: Electronics and information technology, Horology

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b. 5 March 1921 Basle, Switzerland

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Swiss electrical engineer who invented the tuning-fork watch.

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Hetzel trained as an electrical engineer at the Federal Polytechnic in Zurich and worked for several years in the field of telecommunications before joining the Bulova Watch Company in 1950. At that time several companies were developing watches with electromagnetically maintained balances, but they represented very little advance on the mechanical watch and the mechanical switching mechanism was unreliable. In 1952 Hetzel started work on a much more radical design which was influenced by a transistorized tuning-fork oscillator that he had developed when he was working on telecommunications. Tuning forks, whose vibrations were maintained electromagnetically, had been used by scientists during the nineteenth century to measure small intervals of time, but Niaudet- Breguet appears to have been the first to use a tuning fork to control a clock. In 1866 he described a mechanically operated tuning-fork clock manufactured by the firm of Breguet, but it was not successful, possibly because the fork did not compensate for changes in temperature. The tuning fork only became a precision instrument during the 1920s, when elinvar forks were maintained in vibration by thermionic valve circuits. Their primary purpose was to act as frequency standards, but they might have been developed into precision clocks had not the quartz clock made its appearance very shortly afterwards. Hetzel's design was effectively a miniaturized version of these precision devices, with a transistor replacing the thermionic valve. The fork vibrated at a frequency of 360 cycles per second, and the hands were driven mechanically from the end of one of the tines. A prototype was working by 1954, and the watch went into production in 1960. It was sold under the tradename Accutron, with a guaranteed accuracy of one minute per month: this was a considerable improvement on the performance of the mechanical watch. However, the events of the 1920s were to repeat themselves, and by the end of the decade the Accutron was eclipsed by the introduction of quartz-crystal watches.

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Principal Honours and Distinctions

Neuchâtel Observatory Centenary Prize 1958. Swiss Society for Chronometry Gold Medal 1988.

Bibliography

"The history of the “Accutron” tuning fork watch", 1969, Swiss Watch \& Jewellery Journal 94:413–5.

Further Reading

R.Good, 1960, "The Accutron", Horological Journal 103:346–53 (for a detailed technical description).

J.D.Weaver, 1982, Electrical \& Electronic Clocks \& Watches, London (provides a technical description of the tuning-fork watch in its historical context).

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