Frequency is the measure of the number of times a periodic phenomenon repeats itself in a defined unit of time and in watchmaking can be considered as the heartbeat of a watch.
It is used to measure the displacement of a pendulum. Two units are mainly used to do this: Hertz which counts the number of oscillations per second, or vibrations per hour.
Depending on the type of watch and especially its size it will be different.
Let’s take the most traditional one, that of a pocket watch which is usually 18’000 vibrations per hour. This means that its second hand will make 5 jumps per second or precisely 18’000 jumps per hour.
Another unit used is the hertz which corresponds to oscillations per second. It is important to know that an oscillation is the result of two vibrations. Thus 18’000 v/h will correspond to 2,5 Hz.
Here are some frequencies regularly found in watchmaking:
– Marine chronometer 14’400 v/h or 2 Hz
– Pocket watch 18’000 v/h or 2,5 Hz
– Wrist watch 28’800 v/h or 4 Hz
– High frequency chronograph 36’000 v/h or 5 Hz
Namely, the higher the frequency, the lower the power reserve. Also for a stationary object a strong inertia will be privileged for a good precision, thus a low frequency will be privileged. For a wristwatch that will be on a person’s wrist, a higher frequency will be preferred for precision.
From a certain frequency level, which can already start at 36’000 v/h, it is the lubrication, in particular that between the pallets and the escape-wheel, that can start to become problematic. This is the main reason why the use of silicon is preferred for this type of even higher frequency.
In another category of watchmaking, that of electronic watches, there is of course also the quartz which has a frequency. It is in a large majority of cases at 32’768 Hz which corresponds to two power fifteen.