Angular velocity is measured using devices called tachometers.Tachometers are instruments that measure angular speed by registering anyone of the following

Number of rotations during the contact period (or)

●      Number of rotations per minute (rpm)

●      Tachometers are classified as follows:

Mechanical Tachometers

1.    Revolution counter and timer

2.    Tacho Scope

3.    Hand speed indicator

4.    Slipping clutch tachometer

5.    Centrifugal force tachometer

6.    Vibration reed tachometer

Electrical tachometers

●      Drag cup tachometer

●      Commutated capacitor tachometer

●      Tachogenerators

●      DC – Tachogenerator

●      AC – Tachogenerator

Contact Less Electrical Tachometers

1.    Inductive pick up tachometer

2.    Stroboscope tachometer

3.    Photoelectric tachometer

4.    Capacitor tachometer