Electromagnetic flow meter V.S radar flow meter

Q=Av, you have to know area and velocity. If you have a full pipe area is known, so cut it and install a magmeter to measure velocity. If you have an open channel or round sewer drain with a weir or a flume (Parshall, Venturi) to stabilize flow velocity, measure area with a level device, radar or ultrasonic. If you have an open channel without restrictions, you can measure area with a level device and velocity with an optical Doppler effect sensor (mouse) to be placed on the bed of the channel. Also available on the market devices with two radars, oneshooting downward to measure the level, the second one shooting diagonally on water surface to measure velocity with frequency shift. All major instrumentation vendors have available what above