It does not depend on the weight of the pendulum bob and for low amplitudes it is independent of the amplitude of the swing. In the case of the pendulum, the resonant frequency is determined by its length. If the operating conditions change however, the device will run at a different resonant frequency unless some form of compensation is applied.Ī timekeeping mechanism is said to be "isochronous" if it continues to run at the same rate regardless of changes in its operating conditions, such as the drive force, the amplitude of the motion or the ambient temperature, so that it keeps correct time as the mainspring unwinds or as the temperature affects the balance spring or the pendulum. It is the property of resonant devices that they resist oscillating at other rates and tend to return to their resonant rate if subject to a temporary disturbance and it is this property which controls the timekeeping. The oscillator is a resonant device with a fixed characteristic resonant frequency of oscillation, often called the "beat" frequency which depends on its construction, its materials, its degrees of freedom its restoring force and its operating conditions. The torque from the energy source is transmitted through the gear train to the escapement which only allows power to "escape" from the energy source in short impulses of fixed duration and frequency which are transmitted through the gear train to the counting mechanism or pointers. The component which controls the timepiece's heartbeat is the escapement and its pulse rate, or timekeeping, is regulated by a harmonic oscillator consisting of a pendulum or a balance wheel incorporating a small balance spring. In both cases the drum or the spring must be wound regularly to replenish the energy. The energy source which drives a mechanical clock or watch is usually either a heavy weight suspended on a cord, or a chain, looped around the circumference of a drum causing it to rotate, or alternatively, a large spring serving the same purpose. The Mechanical Timekeeper's Main Components The more frequent the event, the greater the potential accuracy of the clock. For want of an accurate timekeeper, Galileo used his heart beat to determine time periods, while John Harrison of "Longitude" fame used the apparent movement of the stars to calibrate his clocks. Time is measured by counting events such as the Sun's motion across the sky, a pendulum's swing, the oscillations of a quartz crystal or the vibrations of an atom. This page describes some key technical developments in the measurement of time with accuracies improving from 15 minutes per day to 1 second in 300 years. Woodbank does not monitor or record these emails
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