Tachometer

A tachometer is an instrument for measuring speed and can use several measuring units, for example kilometres per hour. In horology terms it pertains to a watch with a calibrated dial or bezel used for calculating average speed according to the time necessary to travel a certain distance.

A distance of 1,000 meters is usually used for the basis of the calculation. Some digital watches are also able to display a  tachometer function on their screens.