Electromagnetic flow meters are suitable for measuring the flow of electrically conducting liquid.
Schematic diagram of an electromagnetic flowmeter is shown in the figure. It consists of a pair of electrodes fixed in the opposite sides of a pipe carrying the fluid whose flow is to be measured. A pipe with non-conducting and non-magnetic property is used. The pipe is surrounded by some material to produce a magnetic field.
An electromagnetic flowmeter works on the Faraday’s Law of Electromagnetic induction. A voltage is produced inside the pipe which is proportional to the velocity of the medium and it is captured by electrodes. The voltage is given by
Where B=Magnetic flux * Density, l=Length of the conductor and v= Velocity of the conductor.
That is if the magnetic field is kept constant then voltage produced across the pipe will be proportional to the velocity of the fluid.