What is an electromagnetic flowmeter?

An electromagnetic flowmeter is a transducer that measures the flow of a fluid by a voltage induced by a liquid through a magnetic field. A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux line.

The physical principle of electromagnetic flowmeter is electromagnetic induction. Electromagnetic flowmeters require conductive fluids (e. g., ion-containing water) and electrically insulating tube surfaces (e. g., PTFE-lined steel tubes).

If the direction of the magnetic field is constant, the electrochemical and other effects on the electrode make the potential difference difficult to distinguish from the potential difference caused by the fluid flow. In order to alleviate this situation in modern electromagnetic flowmeters, the magnetic field is continuously reversed, thereby canceling the electrochemical potential difference, which does not change direction with the magnetic field. However, this prevents the use of permanent magnets for electromagnetic flow meters.