How does an electromagnetic flowmeter work?

Electromagnetic flowmeters apply Faraday's law: voltage is induced when a conductor moves through a magnetic field. The flowing conductive liquid acts as the conductor. Coils create magnetic field perpendicular to flow; electrodes mounted in pipe wall measure induced voltage: V = B*D*v, where B is field strength, D is pipe diameter, and v is velocity. Advantages: no pressure drop, handles slurries and corrosives, bidirectional, linear output. Requirements: conductive liquid (>5 microS/cm), full pipe, no air bubbles at electrodes. Non-intrusive design has no moving parts to wear.