A tach generator is a device that produces an output voltage proportional to its shaft speed. It is used in industrial applications to measure the speed or motors, engines and other rotating equipment.
Tach generators are outfitted with an armature, one end of which is attached to a motor or machine shaft. As the machine produces torque, the armature rotates within a magnetic field to induce voltage. The voltage measurement, directly proportional to the rotation speed, is converted into a speed value by a voltmeter connected to the armature.
The primary purpose of the tach generator is the measure motor speed, or the speed of motor-powered equipment like conveyors, fans, mixers and machine tools. They can also be used to provide feedback for motor voltage control, power tachometers, and provide directional indication for a rotating shaft that reverses direction.