Electronic Design

Electronic Watch Has More Accuracy

A transistorized wrist watch, called Accutron, has been designed by the Bulova Watch Co., Inc., Woodside, N.Y. The timepiece is approximately 10 times as accurate as a conventional wrist watch, according to the company. It is guaranteed not to gain or lose more than a minute a month. Accutron has 12 moving parts, compared to 19 in manually wound watches and 26 in self-winding watches.

The Accutron does not tick; it hums. The humming sound in electric timepieces is caused by the vibrations of a tiny electromagnetically driven tuning fork and its index mechanism. The Accutron's power source is a 1.3-v mercury cell. The things that make the new Bulova watch unique are:

  • The use of a precision tuning fork as the time standard.
  • The successful miniaturization of the entire circuit and mechanical assembly to its 0.5 cu-in. size.
  • The development of a highly efficient mechanism and circuit which require such a small amount of power that the self-contained power cell has a life of at least 12 months.

Energy from the power cell, controlled by a transistorized pulser, causes the tuning fork to vibrate continuously at 360 cps. Vibrations are converted mechanically to rotary motions that are transmitted through a gear train to the hands. (Electronic Design, Oct. 26, 1960, p. 18)

When it came to time-keeping, the good old days weren't all that good. It wasn't until electronics got into the act that the average person could afford an accurate watch (presuming that the user set it accurately to begin with).

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