Digital tachometer working principle

Answer 1

A digital Tachometer is digital device which measure the speed of a rotating object. A rotating object can be a ceiling fan ,it can be a car tyre etc. In this meter we just take no. of pulses for one minute then divide by 60,this gives the no. of pulses per min. And its reciprocal ie time for these pulses will be 60/N,where N are pulses for one minute. Then we apply these pulses(which in fact decide open gate time for counting the pulses of a clock signal). Now the no. of pulses of clock signal which are counted by a counter and divide by the open gate time(60/N) gives frquency of the of the rotating object. Since this frequency ie no. of pulses so this the original speed(rpm) of a rotating shaft.