The concept of tachometer
Rotational speed is the physical quantity of the ratio of the number of revolutions of a rotating body to time. In engineering, it is usually expressed as rotational speed=number of rotations/time. It is an important parameter to describe the rotational motion of an object. Electricians often need to measure the speed of the motor and its driving equipment, and use a portable tachometer. A tachometer is an instrument used to measure the rotational speed and linear speed of a motor. There are many types of tachometers, and portable ones generally include mechanical centrifugal tachometers and digital electronic tachometers.
