What is a tachymeter and how does it work?
It is a scale on the dial. In fact, many sports version watches have it either on the rim or bezel. In conjunction with the second hand, it gives the speed of a moving object. A tachymeter takes a value determined in less than a minute and converts it into miles per hour. For example, a wearer could measure the time it takes a car to pass between mile markers on the highway. When the car passes the second marker, the second hand will be pointing to the cars speed in miles per hour on the tachymetric scale.
