Clocks have been around since ancient times. Ancient man, utilizing a phenomenon that precedes at a predetermined rate, such as the phases of the moon, was able to measure the passage of time. Sundials, candles and hourglasses preceded the modern clocks and watches we use today.
Types of Clocks
Today we use a variety of clocks to tell time. Wind-up watches that originated in the 14th century are still around. Today, they are thinner and more reliable; many are self-winding. Pendulum clocks like grandfather clocks are admired for their beauty, and some people use them at home to keep time. The use of quartz crystals in watches represented a breakthrough in timekeeping accuracy.
Mechanical or wind-up clocks work by winding the mainspring to provide energy for the clock. The mainspring uncoils, driving a power wheel that uses gears to transmit motion to the hour and minute wheel. The escarpment wheel regulates the power wheel with a back and forth movement of a pivot, resulting in the signature tick-tock sound. A mechanism consisting of a set of hands sweeping the dial provides a visual indication of the time.
Pendulum clocks have been in use since the 1600s. The mechanism of a pendulum clock consists of the face of the clock with an hour and minute hand, weights and a pendulum, and possibly a keyhole to wind a spring to energize the weights. The weight stores energy, and when you wind the clock a cord lifts up the weight. As the pendulum swings back and forth, a gear advances by releasing each tooth of the gear, producing a tick or tock sound. The anchor attached to the pendulum releases the escarpment gear. The escarpment gear has 60 teeth and the pendulum swings within a period of one second. The second hand turns with one revolution per minute, giving the pendulum clock great accuracy.
In the 1960s a transistor oscillator was used to move the hands of the clock. The transistor oscillator maintained a tuning fork and cogs and wheels moved the hands. A battery replaced the wind-up mainspring. Subsequently, integrated circuits were used in clocks and watches and higher accuracy was achieved with the use of quartz crystals. The quartz crystal replaced the tuning fork. Electronics in the watch amplify noise at the crystal frequency, resulting in oscillation or ringing. The clock then pulses to produce a digital readout. Or, in the case of a quartz watch with hands, a divider sends a one-second pulse to drive a motor connected to gears that drive the hands on the watch.