Electromagnetic Flow Meter

Electromagnetic flow meters (or magmeters) are a type of velocity or volumetric flow meter that operate pursuant to Faraday’s law of electromagnetic induction – which states that a voltage will be induced when a conductor moves through a magnetic field. Magmeters can detect the flow rate of conductive fluids only. Early magmeter designs required a minimum fluidic conductivity of 1-5 microsiemens per centimeter for their operation. The newer designs have reduced that requirement a hundredfold to between 0.05 and 0.1.

An electromagnetic flowmeter consists of a non-magnetic pipe that is lined with an insulating material. A pair of magnetic coils is situated as shown in Figure 1, and a pair of electrodes penetrates the pipe and its lining.

If a conductive fluid flows through a pipe of diameter (D) through a magnetic field density (B) generated by the coils, the amount of voltage (E) developed across the electrodes--as predicted by Faraday's law--will be proportional to the velocity (V) of the liquid. Because the magnetic field density and the pipe diameter are fixed values, they can be combined into a calibration factor (K) and the equation reduces to:

E = KV