Quartz clock

A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than good mechanical clocks. Generally, some form of digital logic counts the cycles of this signal and provides a numeric time display, usually in units of hours, minutes, and seconds. Since the 1970s, they have become the most widely used timekeeping technology.

 How it works 
Quartz clocks work by Piezoelectricity. They apply electricity to a quartz crystal. This causes the crystal to vibrate in a cycle very quickly. A circuit in the clock then counts these cycles, and once it reaches a certain number, it turns on a motor to move the hands or change the display on the clock. In most clocks and watches, the crystal goes through a full cycle 32,768 times every second. This can vary due to parts of the crystal being different, this generally is not intended and causes the clock to drift from the actual time. Another reason that a quartz clock can use a different speed is simply due to differences from one brand of clock to another.

 Uses 
Quartz clocks are used almost everywhere because they are cheap and accurate. They are commonly found in watches, wall clocks, appliances, stopwatches, alarm clocks, cell phones, computers, microwave ovens, radios, and more. Almost every electronic device which needs to keep time for whatever reason has a quartz clock in it. 

 History and Development 
The piezoelectric properties of quartz were discovered by Jacques and Pierre Curie in 1880, but it wouldn't be until 1912 when the first vacuum tube oscillator was invented which would be needed to count the fast oscillations of a quartz crystal. It took until 1921 for the first quartz crystal oscillator to be built by Walter G. Cady, and the technology was demonstrated at the National Physics Laboratory in the UK by D. W. Dye and Warren Maddison in 1923.

In October 1927 the first quartz clock was described and built by Joseph W. Horton and Warren A. Marrison at Bell Telephone Laboratories. The clock used a block of quartz crystal, which was stimulated by electricity, to produce pulses at a frequency of 50,000 cycles per second. These pulses were then counted by electronics in the clock and turned into pulses from a motor which drove clock hands. Due to the large size and delicate nature of the counting electronics, the use of quartz clocks was mostly limited to laboratories for the next 30 years while research into them continued.

During the roughly 3 decades between the invention and widespread use of quartz clocks, there weren't many developments, but the developments that were made were huge. In Japan in 1932, Isaac Koga developed a crystal cut which made the oscillation frequency of the quartz vary much less with changes in temperature. This was an important step towards the widespread use of quartz clocks because it meant that the crystal didn't need to be kept in a temperature-controlled environment, which would be impractical and expensive for watches and wall clocks. These developments lead the National Bureau of Standards (now NIST) to switch from basing the time standard of the US from pendulum clocks (specifically the Shortt clock) to basing it on quartz clocks in the 1930's. 

These developments lead the luxury Swiss watch brand, Longines, to deploy the first quartz watch movement in 1953. Unfortunately, it was too expensive for most consumers, and did not see large sales or cause other watchmakers to begin producing quartz movements. The large scale use of quartz clocks would have to wait until the development of cheap semiconductor digital logic in the mid-1960's. Quartz clocks became common by the early 1970's, and were by far the most used timekeeping technology by the 1980's.
References

Category:Clocks