1/8 inch Water Flow Sensor – YF S401 The water flow sensor measures the rate of a liquid flowing through it. The YF-S401 water flow sensor consists of a plastic valve body, flow rotor, and hall effect sensor. It is usually used at the inlet end to detect the amount of flow. When liquid flows through the sensor, a magnetic rotor will rotate and the rate of rotation will vary with the rate of flow. The hall effect sensor will then output a pulse width signal. Connect it to a microcontroller and you can monitor multiple devices such as your coffee maker, sprinkler or anything else, and control the water flow rate to suit your needs! Features: Analog Sensor Accuracy Up-to 5% Water Proof Sensor Standard 1/8″ Nozzle Size Max. Supported Water Flow: 6L/Min