Tachymeter is an indicator that is sometimes used in watches, mostly in conjunction with chronograph function. It is an instrument for measuring speed, which looks like an immobile scale on the outer or inner bezel of a watch.
It measures units per hour, generally miles or kilometers. In order for a tachymeter to work, the watch owner must move at a fixed rate of speed and distance (e.g., 1 mile or 1 kilometer).
These signs indicate the presence of tachymeter:
First, you need to start the chronograph (it can be done via a button located above the crown) or to start speed measurement when the second hand is reached zero mark. After passing one kilometer, you need to stop it (or to notice the position of the hand). Then you only need to look at the tachymeter scale - it represents a speed in km / h. By the way, various tachymeters measure speed in other units - land or nautical miles/h.
It should be kept in mind that the tachymeter has its own hands, which do not depend on the work of watch mechanism. The hand starts to move itself, showing the required results.
Watches with this device will be useful for: