Watch Terminology Dictionary

A clock that uses atomic vibrations. It is currently used as the standard clock in astronomical observatories. It was developed by the US National Bureau of Standards in 1946 (patented in 1949). The UK then developed a cesium atomic clock. Even the most accurate clocks at the time had an error of about 1/1000 of a second per day, but the best electronic clocks have an accuracy of about 1 second in 30 million years. Taking a cesium electronic clock as an example, its frequency is 9,192,631,770 Hz, which is about 280,000 times higher than a typical quartz clock.