Most people do not remember a time when they had to wind a watch every few days. Since the 1970s, quartz watches have been the popular technology for timekeeping. But exactly how does it work?
A LITTLE HISTORY
For several hundred years, the wind-up watch was the best personal timekeeping instrument. The wind-up watch consisted of:
- A spring (wound to provide power)
- Oscillator a balance wheel (to provide the timekeeping aspect of the watch)
- Dial with numbers and 2 hands (so you could tell the hours and minutes)
- Gears that connected everything together and provided smooth movements
It was a very simple, but elegant way of keeping time. Unfortunately, if you forgot to wind the watch, you were out of luck the watch would run out of the power provided by the coiled spring. Also, the accuracy of the timepiece was questionable. The precision of the watch was dependent upon how well the watch was made (i.e. were the gears, spring, and oscillator matched well enough to keep good time) and how often the watch was wound. As the watch wound down it would slow making the time inaccurate.
In the 1960s, a battery replaced the spring and the problem of remembering to wind the watch. A tuning fork was used for the oscillator (it vibrates at a fairly reliable frequency), but accuracy was still an issue. Integrated circuits were introduced, but they tended to be heavy and the technology that would produce tiny integrated circuits was not available. Enter the introduction of the Quartz crystal.
Quartz is a silicon dioxide in a crystal form. Quartz can be found in most kinds of rocks and on beaches (it is chemically similar to sand) and it abundant throughout the world. Some of the properties of quartz that make it a unique and valuable material is the crystalline structure is not altered by extremes of temperature or environment. It is extremely hard and glassy. The shape of the quartz crystal can also increase the energy it creates. Natural quartz can have minute cracks and imperfections that would make it unusable in some applications, but quartz, like many other crystals, can be artificially manufactured to the quality necessary.
Quartz crystals have been used for many years in radios, computers, and other devices as an oscillator. An oscillator vibrates or moves back and forth and can create energy. The frequency of the oscillation denotes its use. Shaping a quartz crystal in a certain way can generate power differently due to the changes in oscillation frequency. The quartz crystal can oscillate at a very low frequency (for a watch) or high frequency for a powerful radio receiver. The best thing about the quartz crystal is that oscillates at a constant speed making it a perfect device for keeping time.
The quartz crystal used in most watches is a straight bar and oscillates at 32 kilohertz, which is very low. A battery keeps the crystal oscillating and the oscillation keeps the time precise.
A quartz watch will last for many years and only needs to have the battery replaced when necessary. A good quartz watch will not lose more than 1 minute a year in time. The only timekeeping device more accurate than a good quartz watch is an atomic clock – currently not available in a wristwatch.