The working principle of Electromagnetic Flowmeters is based on Faraday's Law of Electromagnetic Induction, that is, when the conductive liquid flows through the electromagnetic flowmeter, the induced electromotive force will be produced in the liquid conductor, and the induced electromotive force is directly proportional to the velocity of conductive liquid, magnetic flux density and width of conductor (interior diameter of flowmeter). Such induced electromotive force is detected by a pair of electrodes on the tube wall of the flowmeter, and the equation of induced electromotive force is as follows: U = K×B×V×D U: Induced electromotive force K: Instrument Constant B: Magnetic flux density V: Velocity D: Interior diameter of measuring pipe.

Electromagnetic flowmeters can be only used for conductive liquid media. They are wildy used in petroleum, chemical, metallurgy, water supply and drainage, steel, coal, paper, food, textile, environmental protection and other municipal administration, water conservancy construction field, etc.