Electronic clocks, such as analog and quartz clocks, replaced the mechanical clocks that were invented in A.D. 1300. The large mechanical clocks were used in public places. In the 15th century, inventors replaced the heavy weights and gears of the large clocks with a miniaturized version of a gear and spring mechanism. The change made it possible to manufacture smaller clocks for household use. The terms analog and quartz refer to different functions of the clock.
Clocks need a mechanism or process by which the passage of time is marked in equal increments. Many modern clocks use a power source to operate the mechanism. Clocks also need a means of tracking and displaying time. The quartz crystal provides the mechanism for marking time and, with an electric current, provides the power as well. The analog clock face provides the method of tracking and displaying time.
Analog refers to the use of hands on the face of a clock to measure time. An analog clock face is usually circular with hands that move around the face. The time measurements on the clock face identify hours and minutes. The movement of the hands mark the passage of time, including seconds. A digital clock face displays the time as numerals, such as 10:45. An analog clock can be a quartz clock and can also be powered electronically or mechanically. A quartz clock can be analog or digital.
The development of quartz crystal clocks and oscillators in the 1920s improved the accuracy of timekeeping. Quartz clocks, which are more accurate than the earlier mechanical clocks, lose or gain only one second over a three-year period. Quartz is a mineral that occurs naturally in the earth’s crust. Clockmakers create synthetic quartz for use in clocks. Electricity powers the quartz clock, which has no gears or escapements to interfere with the operation or accuracy of the clock.
Quartz clock movement relies on the quartz crystal’s piezoelectric property, which causes the crystal to change shape when it is exposed to an electric charge. The property also causes the quartz crystal to emit an electric field when it is bent. An electric charge causes the quartz crystal to vibrate thousands of times per second. Circuits in the clock convert the vibrations into pulses. The vibrations generate a nearly constant electrical signal that operates the clock and maintains a consistent frequency of vibrations. The frequency is influenced by size and shape, which differs for each quartz crystal.
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