YF-S201 Water Flow Sensor, 1/2 Inch, Hall Effect, 1-30 L/min

The YF-S201 measures water flow using a Hall-effect sensor paired with a small internal pinwheel rotor: as water passes through the sensor body, it spins the rotor, and the Hall sensor counts magnetic pulses generated by each rotation, converting mechanical flow directly into an easily countable digital signal rather than requiring any analog-to-digital conversion.

Flow rate range covers 1 to 30 liters per minute, suiting typical household and small irrigation-scale water lines rather than high-volume industrial flow, and the sensor outputs 450 pulses per liter, with the relationship between pulse frequency and flow rate following a simple formula (frequency in Hz equals 7.5 times flow rate in L/min) that makes converting raw pulse counts into an actual flow reading straightforward in firmware. Accuracy is rated at plus-or-minus 10%, reasonable for general-purpose monitoring rather than precision metering.

Output is a clean 5V TTL digital signal, directly countable by any microcontroller's interrupt-capable digital pin without needing analog circuitry. The sensor is rated for a maximum water pressure of 2.0MPa and a working temperature range of -25 to 80C, and is rated for a minimum of 300,000 operating cycles, giving reasonable longevity for continuous or repeated-use installations like an irrigation controller or water-usage logger running for extended periods.

With a 1/2-inch threaded fitting, the sensor installs directly into a standard 1/2-inch water line using common plumbing fittings. Builders working on an automated irrigation system, a home water-usage monitor, a water-leak detection project, or any application needing to measure and log actual water flow through a pipe will find the YF-S201 a well-proven, widely-documented sensor with broad library support.