Construction & Working of D.C. Tachometer Generator or Dynamometer Type Speedometer

Construction & Working of D.C. Tachometer Generator or Dynamometer Type Speedometer Points : Construction and Working of D.C. Tachometer Generator or Dynamometer Type Speedometer D.C. tachometer generator consists of a small armature which is coupled to the machine whose speed is to be measured. This armature revolves in the field of a permanent magnet. The e.m.f. generated is proportional to the product of flux and speed. Since the flux of the permanent magnet is constant, the voltage generated is proportional to the speed. The polarity of out put voltage indicates the direction of rotation. This e.m.f. is measured with the help of a moving coil voltmeter having a uniform scale and calibrated directly in terms of speed.

Shows a d.c. tachometer generator. A series resistance is used in the circuit for the purpose of limiting the current from the generator in the event of a short circuit on the output side.