How to Use YF-S201 Water Flow Meter: Examples, Pinouts, and Specs

The YF-S201 Water Flow Meter is a sensor designed to measure the flow rate of water through a pipe or hose. It operates by using a rotor that spins in response to water flow, with a hall-effect sensor that outputs a series of electrical pulses. These pulses can be counted to determine the volume of water that has passed through the meter. Common applications include irrigation systems, water conservation systems, and any application where water usage monitoring is necessary.

• Operating Voltage: 5 to 18 VDC
• Max Current: 15 mA (at 5 V)
• Flow Rate Range: 1 to 30 liters per minute
• Working Water Pressure: ≤ 1.75 MPa
• Operating Temperature Range: ≤ 80°C
• Accuracy: ±5%
• Output Pulse High Level: > 4.5 VDC (input voltage 5 VDC)
• Output Pulse Low Level: < 0.5 VDC (input voltage 5 VDC)
• Output Pulse Duty Cycle: 50% ±10%

1. Connect the VCC pin to a 5-18 VDC power supply.
2. Connect the GND pin to the ground of the power supply.
3. Connect the Signal Output pin to a digital input pin on a microcontroller, such as an Arduino UNO.

• Ensure that the water flow direction matches the arrow on the sensor.
• Avoid subjecting the sensor to water pressure beyond its maximum rating.
• Use a pull-up resistor if the microcontroller's input pin does not have an internal pull-up feature.
• Filter the sensor's output signal to debounce the pulses if necessary.
• Calibrate the sensor by measuring a known volume of water and adjusting the pulse count accordingly.

// Define the pin connected to the flow meter
const int flowPin = 2;
volatile int flowPulseCount; // Volatile because it's changed in an interrupt

void setup() {
  Serial.begin(9600);
  pinMode(flowPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(flowPin), pulseCounter, RISING); // Interrupt on rising edge of pulse
}

void loop() {
  // Disable the interrupt while calculating flow rate and volume to prevent errors
  noInterrupts();
  int flowRate = flowPulseCount;
  flowPulseCount = 0; // Reset pulse count after reading
  interrupts();

  // Calculate the flow rate in liters per minute (L/min)
  // The factor 7.5 is calibration factor, adjust as necessary for your specific sensor
  float flowRateLpm = (flowRate / 7.5);
  Serial.print("Flow rate: ");
  Serial.print(flowRateLpm);
  Serial.println(" L/min");

  // Delay for a second to get a stable reading
  delay(1000);
}

// Interrupt service routine to count pulses from the flow meter
void pulseCounter() {
  flowPulseCount++;
}

• No pulse output: Ensure the power supply is connected correctly and within the specified voltage range. Check for any loose connections.
• Inaccurate readings: Verify that the water flow direction is correct. Calibrate the sensor as needed. Ensure there are no air bubbles in the line.
• Erratic readings: Debounce the signal output or use a low-pass filter to smooth out the signal.

• Calibration: To calibrate the flow meter, measure a known volume of water and compare it to the pulse count. Adjust the calibration factor in the code accordingly.
• Signal Debouncing: Implement a software debounce in the interrupt service routine or use a hardware filter.

Q: Can the YF-S201 be used with hot water? A: The YF-S201 can be used with water up to 80°C. Beyond this temperature, the sensor may be damaged.

Q: How can I increase the accuracy of the sensor? A: Regular calibration and ensuring a full water pipe (no air) will help increase accuracy. Also, maintaining a steady flow rate during measurements is important.

Q: Is the YF-S201 Water Flow Meter food safe? A: The YF-S201 is not certified as food safe. It is intended for water measurement applications where food safety is not a concern.

Q: What is the lifespan of the YF-S201? A: The lifespan depends on usage conditions but it is generally designed for long-term use in typical water flow measurement applications. Regular maintenance and avoiding excessive water pressure can extend its lifespan.