The explanation is quite complex but here it goes: The basic idea is that the time on an atomic watch is determined by a number of precisely maintained and synchronized oscillators. These oscillators control a quartz crystal in the watch to keep it ticking with as close to the perfect time as possible. The frequencies of these clocks are monitored for maintenance, corrected automatically for any drifts, and then broadcast at regular intervals by powerful radio transmissions which can be picked up by the watch’s receiver.
The first oscillator (oscillator 1) is the reference radio signal which comes directly from the United States Naval Observatory in Washington, D.C. This signal stays at exactly 1 pulse per second (1 Hz). The second oscillator (oscillator 2) has a much faster frequency than the reference frequency, such as 32768 Hz, and its job is to count the number of pulses from oscillator 1. These pulses are then divided by 32768 to get a time on the second scale of the watch.
Oscillators 2a and 2b do this job for the minutes and hours scales respectively; they count oscillator 1’s ticks and divide them by 2000 or 4000 respectively to supply their respective scales with a time. The third oscillator (oscillator 3) does the same job for the day’s scale, and it counts all the pulses from oscillators 1 and 2. Oscillator 3 divides these pulses by 2000 to get a time in the day’s scale. These time measurements are converted to binary coded decimal figures with a counter that is more than 24 bits long – actually over 2500 bits! It runs fast enough to convert the second’s measurement in less than a second, and faster than your computer can finish an instruction.
The automatic self-adjustment of the oscillators is something of an involved process. Oscillators 1 and 2 are adjusted with very high precision every 6 months (one month at a time). The change in frequency of these oscillators is very small, usually less than a nanosecond (10-9 s) per day or about half of the maximum error. The adjustment is made by dividing the reference frequency in two and counting each half separately. A device called a phase comparator compares the output of oscillator 2 with an accurate time base from oscillator 3, and it supplies an electric current to oscillator 2, which then changes its frequency ever so slightly to nudge it into an agreement with the time base.
The third oscillator (oscillator 3) is adjusted by adding or subtracting one second at least once every 30 days. The process that makes this adjustment is called a “leap second. “The timing of the leap second depends on which International Atomic Time (TAI) is being used. When TAI is used, the time is advanced one second at noon on the last Sunday of October to keep standard time in step with UT1. In 2004, two leap seconds were added to standard time (one before and one after December, New Year’s Day). Some other times are also calculated by adding or subtracting three whole seconds so that both the day and night transitions are always one second apart at the same instant of midnight each day. Then leap seconds are not necessary; however, some people would prefer that they do not exist because they think it makes it impossible for people to get along as well.
Are there any Affordable Atomic Watches?
There are several affordable atomic watches on the market that are accurate to better than a second per day and some of them might even last through your lifetime. Of course, a watch that lasts through a human life will cost quite significantly and although these watches have atomic settings they will not necessarily be any more accurate than their quartz counterparts. There are many different brands that manufacture affordable atomic watches and some of them are Seiko, Citizen, Casio, Bulova, and Timex. These watches will cost anywhere between $80 and $300 depending on the make. The model of the watch you choose is dependent on which brand you choose to buy from. But the good news is that all of these companies offer a 2-5 year guarantee for their products so you will have an extended warranty with your purchase.
Should I own an atomic watch?
In my opinion, there are two reasons that you should own an atomic watch. The first is that you want to be different and the second is for the practicality of having an atomic watch. For use in the modern age we live in, everyone takes time seriously. We work to pay our bills, we have children who need our attention, we have responsibilities in life, and sometimes just trying to get so much done in a short space of time can be a challenge.
The only way that I can imagine people surviving this busy modern world is with a simple motto or concept that tells them what time it is at all times – not just a wristwatch but any movement that tells you what time it is. I think that atomic watches are a great concept because they will work in any part of the world.