HERTZ (HZ)

The hertz (symbol Hz) is the unit of measurement for Frequency: it expresses the number of times a periodic phenomenon repeats per second. It is commonly used for electrical, acoustic, or light frequencies. In watchmaking, the hertz is used to quantify the frequency of the regulating organ, that is, the rate of the oscillator. For a mechanical watch, it is expressed in hertz or, more traditionally, in vibrations per hour (vph): a watch beating at 4 Hz makes 8 oscillations per second, i.e. 28,800 vibrations per hour, the most common value today. Common frequencies range from 2.5 Hz (18,000 vph) to 5 Hz (36,000 vph), or even higher for high-frequency watches. The higher the frequency, the more precise and stable the oscillator is in principle, but the more it strains the Escapement and consumes energy. For a Movement with Quartz, the oscillator typically vibrates at 32,768 Hz. Hertz is therefore a key data point in characterizing a Calibre.