Range: 20000 to 30000 r.p.m.
Accuracy: ±1% of full scale.
Construction of Hand Tachometer
Hand Tachometer consists of a spindle having conical tip. Therefore, spindle is also called as conical spindle. Due to conical tip, spindle can be connected or attached to the shaft, whose angular speed is to be measured. Hand speed indicator has an integral (inbuilt) stopwatch and counter with automatic disconnect fadlity (system).
Working of Hand Tachometer
When the spindle is brought in contact with the shaft under measurement, hand speed indicator operates, but the counter and hence, the stopwatch do not start functioning, until ‘START’ or ‘RESET’ button is pressed. As soon as, the button ‘START’ or ‘RESET’ pressed, the revolution counter gets engaged With automatic clutch. Now, revolution counter gets actuated and starts functioning. The instrument shows the angular speed over short interval of time. After measurement, the revolution counter gets automatically disconnected or disengaged. The disengagement takes a fxed time. It is very short duration (approximately 3 to 6 seconds) after performing process of measurement.
Fig. 1: Hand Tachometer