See New Magnetic Inferential Water Meter in Action!

Inferential meters are those which infer the flow while not measuring the flow directly. So they have to measure some other parameter instead. Magnetic inferential flow meters need a conducting fluid like water which contains ions. They use electromagnetic induction to measure the velocity of water flowing through a pipe. There is virtually no pressure loss in the meter as it works by electromagnetic induction. When there is water flow, you can see the black spoked wheel rotating continuously and the small red indicator needle beside it also rotating. As time passes, the digits in the meter display also change. The transducer measures fluid flow by the voltage induced across the liquid by its flow through a magnetic field. Potential difference generated is proportional to the flow velocity perpendicular to the flux lines of the magnetic field.