YF-S201 Water Flow Sensor G1/2 Inch

A pinwheel inside this sensor spins as water passes through, and a hall-effect sensor counts each rotation as a pulse - roughly 450 pulses per liter - which a microcontroller reads on a digital pin and converts into a flow rate or total volume with simple pulse-counting code. That is a fundamentally different measurement approach from a pressure or capacitive sensor, and it is what makes it possible to measure actual volume passed rather than just detecting flow is happening.

The G1/2 inch threaded fitting means it installs inline with standard plumbing fittings rather than needing custom adapters, and the 1 to 30 L/min range covers typical household and small irrigation flow rates. Worth knowing before relying on it for anything precise: pulse rate varies somewhat with pressure and orientation, so it needs calibration against a known volume if better than roughly 10% accuracy matters.

Common uses are automated irrigation systems tracking water usage, water metering projects, and leak-detection builds that alert when flow continues longer than expected.