The tachometer is nothing more than a simple electronic digital sensor.Usually, it is used to measure the speed of the axis of rotation.Revolutions per minute (RPM) are invaluable information to learn about any rotating system.For example, there is an optimal speed for knowing information about any rotating system.For example, drilling a hole of a particular size on a particular metal part has the best speed;The ideal pan speed depends on the finished material.You may also need to measure the speed of the fan being used