The flowing media engages a vaned rotor causing it to rotate at an angular velocity proportional to flow rate. The   pick - up coil senses the spinning motion of the rotor inside the pipe & converts it into a pulsating electrical signal. Summation of the pulsating electrical signal is directly related to the total flow. The frequency is linearly proportional to flow rate which is converted to mA signal by electronic circuitry. Local Indication as well as totalisation is available.