This type of flow sensor is used to measure liquid flow within a pipe and is ideally suited for monitoring water consumption in irrigation control systems. Each side of the sensor has a 1/2 NPS nominal pipe connections 0.78 outer diameter 1/2 of thread. The sensor is connected by way of a 3 pin connector.

Inside the housing a small pinwheel with an attached magnet is spun by passing water; as the magnet makes each revolution a hall effect sensor inside the housing outputs a pulse on the yellow wire. Each pulse output represents approximately 2.25mL of fluid. The sensor is best suited to flow rates between 1 and 30 liters per minute flow rates below one liter per minute tend not to register accurately.