Home WORLD How to Measure Flow with Magnets – Magnetic Flow Meters

How to Measure Flow with Magnets – Magnetic Flow Meters

What happens when a civil engineer mixes water and electricity? The results aren’t always ideal, but you always learn something!

source/image: Practical Engineering

A magnetic flow meter relies on Faraday’s Law of Induction to measure the flow of a fluid. Magnets outside the pipe create a magnetic field. Electrodes are located perpendicular to the magnets.

A conductive fluid moving through the pipe will generate a voltage (electromotive force) between the electrodes due to Faraday’s law. The faster the fluid moves through the pipe, the higher the voltage.


Once you know the velocity of the fluid, you can calculate flow using the cross sectional area of the pipe. In this video, I walk through some of the details that electrical engineers have worked out so that this ingenious device can work properly. Unfortunately I couldn’t get it working very well myself!