3/4 inch DN20 Water flow sensor YF-S403

Description

The YF-S403 is a Hall-effect turbine water flow sensor designed for inline measurement of liquid flow rate and total volume in plumbing, irrigation, water heaters, and vending machine applications. It features a 3/4-inch (DN20) threaded connection with a plastic valve body and is intended for medium-diameter water lines.

The sensor consists of a plastic body containing a magnetic pinwheel rotor and a Hall-effect sensor sealed from the water path. As water flows through, the rotor spins at a rate proportional to flow velocity, and the Hall sensor outputs a digital pulse train. The pulse frequency is proportional to flow rate, allowing the microcontroller to calculate instantaneous flow (L/min) and cumulative volume (liters). The YF-S403 is rated for a flow range of 1–30 L/min, with a pulse characteristic of 450 pulses per liter and a frequency relationship of f = 7.5 × Q (Hz, where Q is L/min) .

The sensor operates from 5V to 18V DC (minimum tested 4.5V) with a maximum current draw of 15mA and outputs a 5V TTL-level pulse . Accuracy is specified at ±10%, making it suitable for relative monitoring and control rather than precision metering. The body is made of plastic with a stainless steel impeller shaft for durability, and the unit is designed for vertical installation with no more than 5° tilt .

Critical limitations: This is a low-cost, non-certified sensor intended for educational, hobbyist, and light commercial use. The pulse rate varies with flow rate, pressure, and orientation, and calibration against a known volume is recommended for better precision . For 3.3V microcontrollers (ESP32, ESP8266), the 5V pulse output requires a logic level shifter or voltage divider to protect the GPIO pins. The sensor is not suitable for corrosive chemicals.

Features

• 3/4″ (DN20) Threaded Connection: Standard pipe size for medium-flow water lines in plumbing and irrigation.

• Hall-Effect Pulse Output: Digital square wave proportional to flow rate, readable by any microcontroller with an interrupt-capable GPIO .

• Flow Range 1–30 L/min: Suitable for water heaters, vending machines, and flow measurement devices .

• 450 Pulses per Liter (nominal): Provides good resolution for volume tracking .

• Wide Voltage Range (5–18V DC): 5V typical for Arduino; flexible for different supplies .

• Low Power Consumption: Maximum 15mA at 5V .

• Sealed Hall Sensor: The sensing electronics are isolated from the water path .

• Durable Construction: Plastic body with stainless steel impeller shaft; minimum 300,000 cycles .

Technical Specifications