The 1/8 Inch Water Flow Sensor YF-S401 measures liquid volume passing through a pipe by spinning a small hall-effect paddle wheel inside the housing. Each rotation generates a pulse on the signal wire, and the water flow sensor counts those pulses to calculate flow rate. Operating on DC 5V to 24V, it covers a measurement range of approximately 0.3 to 6 L/min and fits inlet pipe diameters between 2.5 and 4 mm. Weighing roughly 15 to 20 grams, it adds almost no mass to a portable build.
The YF-S401 water sensor outputs a pulse-frequency signal, not an analog voltage. That means you read it on a digital interrupt pin rather than an analog input, which many builders miss when first wiring it up. A non-obvious point: the pulse frequency is proportional to flow rate, so at very low flows near 0.3 L/min the pulse interval stretches long enough that a short polling loop will undercount it. Reading on an interrupt instead of a loop solves this completely. One honest limitation is that the 1/8 inch water flow sensor is rated for clean water; sediment or particulates will jam the paddle and give false zero readings over time.
Hobbyists making coffee volume counters, and engineers prototyping water flow sensor YF-S401 Arduino projects all use this module regularly. It works with the Arduino IDE, MicroPython, and any platform that supports external interrupt pins. StemVolt provides this sensor with trusted quality, ensuring reliable performance and easy usability.
Related Products:
Features:
- Pulse frequency output directly proportional to flow rate
- Pulses-per-litre calibration constant enables precise volume calculation
- 0.3 L/min minimum sensitivity detects slow drips and low-pressure flows
- 5V to 24V wide voltage range for Arduino and industrial circuits
- Interrupt-pin compatible for accurate pulse counting in code
Technical specifications:
 Applications:
- YF-S401 used for Arduino precision liquid dosing volume calculation
- College project uses 1/8 Inch water flow sensor for pulse-counting demo
- Lab uses water flow sensor yf s401 arduino for India reagent dispensing
- Mini purifier uses yf s401 water sensor for accurate volume tracking
- Dosing pump uses water flow sensor for chemical dispensing calibration
Package includes:
- 1 x Water Flow Sensor YF-S401
Vinit Saxena –
Safe packaging and smooth UPI payment made the purchase convenient, while customer support was helpful with installation and project-related guidance
Meghanshu Sharma –
Highly recommended product
Sapna Shrivastava –
Received this water flow sensor in excellent condition, readings were accurate and consistent, making it perfect for my college water monitoring project.
Abhishek Sharma –
100% genuine product
Nidhi Agarwal –
Accurate water flow measurement and is ideal for arduino projects, water monitoring systems, and college-level electronics applications
Vikas Soni –
Fast delivery service