How Are Atomic Clocks Controlled?

Atomic clocks are controlled through low frequency radio waves.

Available in a variety of styles and price ranges, atomic clocks keep very precise time. The atomic clock you buy at the department store is actually a radio-controlled clock that synchronizes with a true atomic clock.

National Institute of Standards and Technology Atomic Clock

The National Institute of Standards and Technology (NIST) maintains a cesium atomic clock near Fort Collins, Colorado. Controlled by an atomic oscillator, the NIST clock sends out an encoded radio message with the current time. Your atomic clock has a radio inside which receives this encoded message.

Synchronization

Your radio-controlled atomic clock synchronizes with the true atomic clock on a regular basis (how often depends on the clock manufacturer). Your clock keeps its own time in between synchronizations.

Clock Accuracy

The quartz crystal used in radio-controlled atomic clocks can keep accurate time (within a second) for several days. Since most radio controlled clocks synchronize at least once per day, you won't see any accuracy problems.

Radio Frequency

The radio in your atomic clock and the Fort Collins cesium atomic clock both operate at a very low frequency, and thus do not interfere with other radio frequencies, such as those used by radio stations.

References

• National Institute of Standards and Technology: Radio-controlled Clocks
• National Institute of Standards and Technology: NIST-F1 Cesium Fountain Atomic Clock