Electromagnetic flow meter

A flow meter with no moving parts that uses Faraday's law: water moving through a magnetic field generates a small voltage, which electrodes in the measuring tube pick up. The voltage is proportional to flow velocity. It needs water with some electrical conductivity, which ordinary drinking water and raw water have.

With nothing in the flow path, it adds almost no pressure loss and copes well with raw or silty water, which suits pumping stations, treatment plants and transfer mains. It needs a power source, mains or battery, and a pipe that runs full.