Function of tachometer

Answer 1

A tachometer is a gauge that measures mechanical rotation, and typically reads out in "RPM" or revolutions per minute. Such a gauge can be used anywhere where a measurement of speed of rotation is needed, but the most common use is to measure how many times in a minute the crankshaft of your car's engine turns, which would indicate to the car's driver how hard the car's engine is working at any given moment.