Discover what could be more accurate than a quartz watch? Why, a quartz watch that adjusts itself daily to an atomic clock.
- What is a radio-controlled watch?
A radio-controlled watch is one that maintains an extremely high level of accuracy by synchronizing itself at regular intervals with an atomic clock. The watch contains a small antenna that picks up a signal broadcast by a government agency. In the U.S., that agency is the National Institute of Standards and Technology; part of the U.S. Department of Commerce. NIST maintains an atomic clock in Boulder, Colo. and sends a timekeeping signal from a radio station in Fort Collins, Colo.
- What is an atomic clock?
Atomic clocks are the most accurate type of timekeeper yet invented. They use as their time base, or oscillator, atoms that vibrate at unimaginably rapid rates. The type of atomic clock now in use is regulated by cesium atoms, which vibrate at the rate of 9,192,631,770 times per second. Cesium clocks – or at least the best-made specimens – are accurate to within one second in 10 million years.
Accurate as that is, atomic clocks may become more precise still. Scientists at NIST have developed a new type of atomic clock, regulated by a single ion of mercury, which may one day replace cesium clocks. The mercury clock has the potential to be 100 to 1,000 times more accurate than the cesium clock.
- Is a radio-controlled watch more accurate than a quartz watch?
An atomic watch is a type of quartz watch. It is powered by electricity (from a battery or, in some instances, light converted into electricity by a solar cell). It is regulated by a quartz crystal. Where it differs from other quartz watches is in its self-correcting mechanism, which keeps its timing errors imperceptibly small – much smaller even than in a standard quartz watch.
- How accurate is a radio-controlled watch
Because it readjusts itself to absolute accuracy every 24 hours, it will never be off by more than a fraction of a second, assuming the movement is of at least average quality and is in good running order. A standard quartz movement gains or loses perhaps five or 10 seconds a month. That translates to 0.17 seconds to 0.34 seconds per day. The maximum error for a radio-controlled watch is therefore about one-sixth to one-third of a second. However, some radio-controlled-watch manufacturers claim far better than average quartz accuracy for their movements.
- How does a radio-controlled watch work?
The tiny antenna in the watch case “searches” at a specific time for the signal from the NIST atomic clock. Some watches search once each 24 hours, at 1 a.m. Others search several times during the night in order to increase the probability of picking up the signal. The searching always takes place at night because magnetic influences of the sun can interfere with reception. So can “electronic pollution” from cell phones, faxes, satellite dishes, etc., which is greater during working hours. Because the watch uses electricity as it searches, watch manufacturers want to make the process as efficient as possible in order to minimize power drainage.
When the watch picks up the signal, it uses a microchip to readjust the watch’s hands or digital display. The watch also readjusts itself automatically twice a year for daylight savings time and standard time. The broadcast signal tells the watch when it needs to jump forward or fall back.
- Can the watch pick up the signal anywhere?
No. The broadcast signal emanates from Fort Collins in concentric circles about 3,750 miles in diameter. A watch might not always be able to pick up the signal at the limits of this range – terrain and atmospheric conditions influence receptivity – and will be unable to pick it up at all outside of it, in Alaska, northern Canada, or southern Mexico, for instance.
Nor, as a rule, can the watch pick up the signal underground or in a building with a steel roof (many shopping malls have steel roofs, so radio-controlled watches sold by mall retailers are often unable to correct themselves until they’re purchased.) Furthermore, the watch cannot pick up the signal from inside a safe.
- I’ve seen references to “atomic” watches. What are they?
An “atomic” watch is merely a nickname-some would call it a misnomer-for a radio-controlled watch. It’s a simple way of saying that the watch adjusts itself to an atomic clock.
- Is it ever necessary to adjust a radio-controlled watch?
It is rarely necessary to do so. One occasion is when the wearer travels from one time zone to another. He would manually reset the watch to the new time zone, then, during the night, the watch would pick up the NIST signal and readjust itself as usual. (This assumes he is traveling in the continental U.S., northern Mexico or Canada. See above.)
Another occasion could be after a battery change. Although some radio-controlled watches adjust themselves automatically after their batteries are changed, using a device that “remembers” what time it was when the battery died, others don’t. They must be reset the way a standard quartz watch would.
- Who makes radio-controlled watches?
The best-known manufacturer of radio-controlled watches is the German company Junghans, owned by EganaGoldpfeil (Holdings) Ltd. Junghans brought the first radio-controlled watch to market in 1990. (Its U.S. distributor is in Franklin Lakes, New Jersey) There are a few other companies selling them in this country. One is Chaney Instrument Co., in Lake Geneva, Wis., which markets the Atomix line of radio-controlled clocks and watches. Another is LaCrosse Technology, in La Crescent, Minn. Several companies market radio-controlled clocks, including Seiko Corp. of America and Bulova Corp.
- Will radio-controlled watches work in other countries?
A radio-controlled watch designed for use in North America will only be able to adjust itself if it’s within range of the NIST atomic clock in Colorado. There are other atomic-clock signals broadcast elsewhere in the world – from Mainflingen, Germany; Nasaki, Japan; Rugby, England and Kauai, Hawaii – but these signals are either sent at different frequencies than the NIST signal or are indecipherable to watches not designed specifically for them. When a radio-controlled watch travels beyond the reach of its signal transmitter, it runs like a standard quartz watch.
- How much do radio-controlled watches cost?
Radio-controlled watches are available from about $50 to about $1,100.