About Accutron's accuracy Science

All for the sake of accuracy

Max Hetzel explaining about the Bulova Accutron using a giant sized model.  

From the 200 inch mirror used in the Palomar Observatory, we move to something that was less than 2 inches in diameter, but nevertheless changed the way we measured time. For the precision and accuracy of wristwatches was never the same after the introduction of the Bulova Accutron.

The Accutron was developed by Swiss engineer Max Hetzel, who had joined the Bulova Watch Company in 1950. It was in fact a response to the electric watches that were introduced in the 1950s and heralded as the most significant advance in watchmaking over centuries.

Race for accuracy

Arde Bulova, fearing that they might be left behind in the race, asked Hetzel to research these new watches. By 1952, Hetzel had come out with his findings, which stated that even though these new devices were battery powered, they couldn’t boast of an improved accuracy as they still employed the conventional balance-wheel movement.

Hetzel predicted that the newly-invented transistors held the key for improved accuracy in wristwatches. Hetzel received his first useful transistors (Raytheon CK 722) in 1953 and set about working on his first model by hand.

Higher frequency of oscillation

While Hetzel believed adding a transistor to the movement would help improve the watch’s precision, he also decided to replace the balance with a tuning fork in order to achieve even greater accuracy. The tuning fork - a small metallic piece with two parallel arms soldered in a U-shape and extended by a stem - was placed in between two transistors and it oscillated at 360 Hz.

With a higher frequency of oscillation than a classical balance, the tuning fork could divide every second into a hundred equal parts. As a result, the watches that were to be produced using this technique were guaranteed to be accurate to within two seconds a day, or one minute in a month!

Accutron announced

Along with William O Bennett, an American engineer working for Bulova, Hetzel completed the development of Accutron 214, the first wristwatch with a tuning fork movement, in 1959. On October 10, 1960, the revolutionary Accutron was officially unveiled by Bulova’s president and they went on sale in New York on October 25.

In the decade that followed, Accutron and the series of watches built with tuning fork movement were much sought after. Millions of pieces were sold around the globe and were even used by astronauts from NASA for their space missions.

But Bulova’s golden age soon came to an end with the advent of quartz watches. Quartz watches were not only more accurate when compared to tuning fork technology, but also turned out to be a commercial success. But for the two decades when the tuning fork method was used, those watches were the most accurate ones on earth… and in space!

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Printable version | Nov 30, 2021 10:13:35 AM | https://www.thehindu.com/in-school/sh-science/All-for-the-sake-of-accuracy/article16079453.ece

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