This is YF-S201 Water Flow Measurement Sensor with 1-30Liter/min Flow Rate white sensor. This sensor sits in line with your water line and contains a pinwheel sensor to measure how much liquid has moved through it. There’s an integrated magnetic hall effect sensor that outputs an electrical pulse with every revolution. The hall effect sensor is sealed from the water pipe and allows the sensor to stay safe and dry. By counting the pulses from the output of the sensor, you can easily calculate water flow. Each pulse is approximately 2.25 milliliters. Note this isn’t a precision sensor, and the pulse rate does vary a bit depending on the flow rate, fluid pressure, and sensor orientation. It will need careful calibration if better than 10% precision is required. However, it’s great for basic measurement tasks! We have an example Arduino sketch(check the ATTACHMENTS tab) that can be used to quickly test the sensor, it will calculate the approximate flow of water in liters/hour. The pulse signal is a simple square wave so it’s quite easy to log and convert into liters per minute using the following formula. Connection Red wire:  5V. Black wire: GND. Yellow wire: PWM output. Features : 1/2″ nominal pipe connections, 0.78″ outer diameter, 1/2″ of thread. The simple and compact module. Easy to Install. High Sealing Performance. High-Quality Hall Effect Sensor. Package Includes : 1 x YF-S201 Water Flow Measurement Sensor with 1-30Liter/min Flow Rate. . SKU: PGI-0012219 Category: Water Flow And Level Sensor