In this case, the generated frequency is the 'tick'. If the correct frequency can be generated to make the atoms change, then that frequency can be counted or divided down and compared. With an atomic clock, there is a natural tendency of atoms to change energy levels when they are exposed to very specific ("resonant") frequencies. If the quartz frequency on a watch is 0.1 Hz off, the watch will be off by one second in 327,680 seconds or, roughly, 0.26 seconds per day. For instance, if a half-swing of a pendulum is actually 0.1 Hz off, then the grandfather clock will be off by one second in ten seconds. By dividing a high frequency down to a low frequency, the accuracy can be increased. The ticks are used to advance the seconds on the clock. The frequency is "counted" by dividing it by 32,768 to equal one second 'ticks'. With a quartz clock (like most wristwatches), a piece of quartz crystal is cut and used in an electronic circuit where it vibrates at a certain frequency (usually 32,768 Hz). One cycle per second equals 1 Hertz (Hz). The arm of the pendulum is adjusted in order to make each half-swing take one second. For example, the pendulum in a grandfather clock swings back and forth at the same rate, over and over, and the gears "count" the swings. What are some sources for further reading about clocks and timekeeping?Ĭlocks work by counting a periodic event with a known frequency. What are Julian Date and Modified Julian Date (MJD)? What is the origin of hours, minutes and seconds? How are stopwatches and timers calibrated? Why must time and frequency be measured so precisely? Stopwatch calibrations, calendars and history. Cesium clocks, why we need precise time and frequency.
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