Magnetic flow meters

Magnetic flow meters are used to measure flow of liquids that are conductive.  Magnetic flow meters do not have to physically be in contact with the medium.

Magnetic Flow meters, or Magmeters as they are otherwise called work on the basis of Faraday's law which states that the voltage produced by a moving conductor in a magnetic field is proportional to the velocity of the conductor.

In a Magnetic flowmeter, the conductive liquid such as water is passed through a constant magnetic field.

As the conductive liquid flows between a magnetic field, a voltage is induced in direction perpendicular to the magnetic field.  This voltage is measured by a pair of probes.

The flowrate can be calculated from the voltage induced in these probes.

The magnetic field is produced by a pair of electromagnets whose polarity is constantly reversed. The reversal of polarity is essential to prevent interference due to electrochemical potentials induced where the probes come in contact with the liquid.

The voltage is proportional to the velocity of the liquid, the width of the pipe (diameter), and the magnetic field strength.