According to Faraday's principle of electromagnetic induction when a conductor passes vertically through magnetic field B, it will induce a voltage. U In the measurement of the flowmeter, the moving conductor is a flowing conducting medium, and the magnetic field B is emitted from the direction perpendicular to the flowing medium. The induced electromotive force U on the two electrodes E1 and E2 is directly proportional to the velocity V of the medium.