This YF-S201 1/2 inch Water flow sensor consists of a black plastic valve body, a water rotor and a hall effect sensor. 1-30 Litre/min Water can flow through this sensor. This YF-S201 is placed in line with water and its pinwheel sensor detects how much liquid has flowed through it. With every pinwheel revolution magnetic hall effect sensor generate an electrical pulse which is fed to the controller and thus controller is able to detect how much liquid is flowing through the sensor at any point of time. The hall effect sensor is sealed from the liquid pipe and thus remains protected from the water.
The Electrical pulse generated by the sensor is approximately equal to 2.25 milliliters. So by counting the number of pulse we can easily calculate the amount of water flowing through the sensor.