The measuring principle of electromagnetic flow meter is based on Faraday's law of electromagnetic induction. The sensor is mainly composed of a measuring tube with an insulated lining, a pair of electrodes installed by penetrating the wall of the measuring tube, a pair of coils and an iron core to generate a working magnetic field. When a conductive fluid flows through the sensor's measuring tube, a voltage signal directly proportional to the average fluid flow rate will be induced at the electrodes. The signal is amplified and processed by the transmitter to realise various display functions.