Description

WATER FLOW SENSOR 1/2-INCH YFS201

Precision water flow sensor designed for accurate flow rate measurement and liquid consumption monitoring. The YF-S201 features a 1/2-inch threaded connection and Hall effect sensor technology for reliable, real-time flow detection. Ideal for water meters, dispensing systems, irrigation control, and automated monitoring applications where accurate flow measurement is essential.

KEY FEATURES

Hall Effect Technology – Magnetic sensing for reliable, contactless measurement

1/2-Inch Threading – Standard G1/2 thread for easy plumbing integration

Wide Flow Range – Measures flow rates from 1 to 30 liters per minute

High Accuracy – ±10% measurement precision across operating range

Food Grade Material – Safe for drinking water and food processing applications

Low Power Consumption – Operates on 5V DC with minimal current draw

Pulse Output – Digital square wave output proportional to flow rate

Temperature Resistant – Operates reliably in 0°C to 80°C water temperature

Durable Construction – Long-lasting turbine and housing design

Easy Integration – Compatible with Arduino, Raspberry Pi, ESP8266, ESP32

TECHNICAL SPECIFICATIONS

Physical Specifications:

Model Number: YF-S201 / YFS201

Thread Type: G1/2 inch (DN15) male threads both ends

Thread Standard: BSP (British Standard Pipe)

Outer Diameter: 20mm nominal bore

Overall Length: 58mm (approximately)

Body Diameter: 30mm (approximately)

Weight: 30-40 grams

Material: Food-grade plastic (POM or nylon)

Seal Material: NBR rubber O-rings

Color: Typically black or white housing

Electrical Specifications:

Operating Voltage: 5V – 24V DC (typically 5V)

Supply Current: 10-15mA (at 5V)

Output Type: NPN pulse signal (open collector)

Output Level: 0V (LOW) to VCC (HIGH)

Pulse Frequency: Proportional to flow rate

Maximum Output Current: 10mA

Wire Length: 15cm (approximately)

Wire Colors: Red (VCC), Black (GND), Yellow (Signal/Pulse)

Performance Specifications:

Flow Range: 1 – 30 L/min (liters per minute)

Optimal Range: 2 – 25 L/min

Working Pressure: ≤ 1.75 MPa (≤ 17.5 bar / 254 PSI)

Fluid Temperature: 0°C to 80°C (water)

Accuracy: ±10% (within optimal flow range)

Repeatability: ±1%

Frequency Formula: F = 7.5Q (approximately)

• F = Frequency in Hz
• Q = Flow rate in L/min

Pulse Characteristics: ~450 pulses per liter (calibration may vary)

Response Time: <1 second

Pressure Drop: Minimal (typically <0.05 MPa at 10 L/min)

Environmental Specifications:

Operating Temperature: -10°C to +60°C (ambient)

Storage Temperature: -20°C to +70°C

Humidity: 0-95% RH (non-condensing)

Protection Rating: IP65 (when properly installed)

WORKING PRINCIPLE

Hall Effect Sensor Operation:

Water flows through the sensor body causing the internal turbine/rotor to spin

Embedded magnets in the rotor pass by the Hall effect sensor

Each magnet passage generates a pulse on the output wire

Pulse frequency increases proportionally with flow rate

Microcontroller counts pulses to calculate flow rate and total volume

Pulse to Flow Calculation:

Frequency (Hz) = 7.5 × Flow Rate (L/min)

Flow Rate (L/min) = Frequency (Hz) ÷ 7.5

Pulses per Liter ≈ 450 (calibration factor may vary ±10%)

Total Volume (Liters) = Total Pulse Count ÷ 450

WIRING CONNECTIONS

Wire Color Code:

Red Wire: VCC (Power supply positive) – Connect to 5V

Black Wire: GND (Ground) – Connect to power supply ground

Yellow Wire: Signal/Pulse Output – Connect to microcontroller input pin

Connection Diagram:

Sensor → Arduino/ESP32/Raspberry Pi

Red → 5V power pin

Black → GND pin

Yellow → Digital input pin (D2, D3, or interrupt-capable pin)

Pull-up Resistor:

Some modules require 10kΩ pull-up resistor on signal line

Many microcontrollers have internal pull-up (enable in code)

External pull-up: Signal line → 10kΩ resistor → VCC

APPLICATIONS

Water Metering – Residential and commercial water consumption monitoring

Irrigation Systems – Automated watering with flow feedback control

Beverage Dispensing – Coffee machines, soda fountains, drink dispensers

Industrial Monitoring – Process water flow measurement and logging

Smart Home – IoT water usage tracking and leak detection

Aquarium Systems – Water change volume measurement and automation

Hydroponics – Nutrient solution flow monitoring and control

Washing Machines – Water intake measurement for optimal cycles

Cooling Systems – Liquid cooling flow verification

Laboratory Equipment – Precise liquid dispensing and measurement

MICROCONTROLLER INTEGRATION

Arduino Code Example:

volatile int pulseCount = 0;
float flowRate = 0.0;
float totalVolume = 0.0;
unsigned long oldTime = 0;

void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), pulseCounter, RISING);
  oldTime = millis();
}

void loop() {
  if ((millis() - oldTime) > 1000) {
    detachInterrupt(digitalPinToInterrupt(2));
    
    flowRate = (pulseCount / 7.5); // L/min
    totalVolume += (pulseCount / 450.0); // Liters
    
    Serial.print("Flow: ");
    Serial.print(flowRate);
    Serial.print(" L/min, Total: ");
    Serial.print(totalVolume);
    Serial.println(" L");
    
    pulseCount = 0;
    oldTime = millis();
    attachInterrupt(digitalPinToInterrupt(2), pulseCounter, RISING);
  }
}

void pulseCounter() {
  pulseCount++;
}

ESP32/ESP8266 Compatible:

Use hardware interrupt pins (GPIO 4, 5, 12, 13, 14, etc.)

Same interrupt logic as Arduino

WiFi capability for IoT data logging

Raspberry Pi Integration:

Use GPIO pins with interrupt capability

Python RPi.GPIO library for pulse counting

Ideal for data logging and cloud integration

CALIBRATION PROCEDURE

Factory Calibration:

Default: ~450 pulses per liter

Formula: F = 7.5Q (frequency in Hz, flow in L/min)

Variation: ±10% between individual sensors

Manual Calibration Steps:

Collect water in measured container (5-10 liters recommended)

Count total pulses during collection

Calculate: Calibration Factor = Total Pulses ÷ Volume Collected

Update code with new calibration factor

Repeat test to verify accuracy

Calibration Tips:

Calibrate at your typical operating flow rate

Use graduated cylinder or precision scale for measurement

Multiple test runs improve accuracy

Recalibrate if flow characteristics change (temperature, pressure)

INSTALLATION GUIDE

Mounting Orientation:

Can be installed horizontally or vertically

Ensure turbine can spin freely (no air bubbles trapped)

Arrow on housing indicates flow direction – MUST be observed

Vertical installation (upward flow) often provides best accuracy

Plumbing Connection:

Apply thread seal tape (PTFE/Teflon tape) to male threads

Hand-tighten first, then 1-2 turns with wrench

Do not over-tighten – may crack plastic housing

Use G1/2 female adapters, couplers, or direct connection

Install after any filters to prevent debris damage

Best Practices:

Install straight pipe sections before and after sensor (10x diameter)

Avoid installation near elbows, valves, or flow restrictions

Use inline filter upstream to protect turbine from debris

Install shut-off valves for easy maintenance and removal

Protect wiring from water exposure with waterproof connectors

Mount securely to prevent vibration

FLOW RATE VS FREQUENCY TABLE

Note: Actual values may vary ±10% due to manufacturing tolerances.

MAINTENANCE TIPS

Regular Inspection – Check for leaks at threaded connections monthly

Clean Turbine – Remove and clean turbine every 6-12 months

Debris Check – Inspect for sediment or debris blocking rotor

Seal Inspection – Check O-rings for wear or damage annually

Wiring Check – Verify wire connections remain secure and dry

Filter Maintenance – Clean upstream filter regularly

Calibration Verification – Test accuracy annually with known volume

Scale Removal – Clean calcium/mineral deposits with vinegar solution

TROUBLESHOOTING

No Pulse Output:

Check power supply (5V on red wire, GND on black wire)

Verify wiring connections are secure

Test with multimeter: yellow wire should pulse between 0V and VCC

Check if turbine spins freely (remove sensor, blow through it)

Verify microcontroller interrupt code is functioning

Inaccurate Readings:

Recalibrate sensor with known volume measurement

Check for air bubbles in system (purge air)

Verify flow direction matches arrow on housing

Ensure straight pipe runs before/after sensor

Clean turbine of debris or buildup

Check for leaks causing flow bypass

Intermittent Output:

Inspect wire connections for loose contacts

Check for water ingress in wire junction

Verify stable power supply (ripple-free 5V)

Test for electromagnetic interference near sensor

Low or No Flow Reading Despite Water Flow:

Turbine may be jammed with debris – clean thoroughly

Check if flow rate is below minimum (1 L/min)

Verify sensor is not installed backwards

Inspect for damaged turbine blades

ACCURACY FACTORS

Factors Affecting Accuracy:

Water Temperature – Viscosity changes affect turbine speed

Flow Rate – Most accurate in middle range (2-25 L/min)

Installation Orientation – Vertical upward flow often best

Pipe Turbulence – Straight runs improve accuracy

Pressure Variations – Sudden changes may cause brief errors

Debris – Particles can slow or jam turbine

Air Bubbles – Create erratic pulse patterns

Improving Accuracy:

Calibrate at operating temperature

Maintain consistent pressure

Install proper straight pipe sections

Use inline filter

Regular maintenance and cleaning

COMPARISON WITH OTHER FLOW SENSORS

vs 3/4-Inch Flow Sensors (YF-S402):

✗ Lower maximum flow rate (30 L/min vs 60 L/min)

✓ Better for smaller pipes and lower flows

✓ Lower cost

✓ More compact size

vs Ultrasonic Flow Sensors:

✗ Requires physical installation in pipe

✗ Moving parts subject to wear

✓ Much lower cost

✓ Simpler installation and integration

✓ No external power requirements beyond 5V

vs Turbine Flow Meters (Industrial):

✗ Lower accuracy (±10% vs ±1-2%)

✗ Plastic construction vs metal

✓ Significantly lower cost

✓ Adequate for most DIY and home automation needs

SAFETY PRECAUTIONS

Do not exceed maximum pressure rating (1.75 MPa)

Verify water temperature remains within 0-80°C range

Do not use with corrosive or chemically aggressive fluids

Ensure electrical connections are waterproofed

Do not use in explosive or hazardous environments

Install pressure relief if system can exceed sensor rating

Protect from freezing temperatures when water-filled

Regularly inspect for leaks and structural integrity

PACKAGE CONTENTS

1x YF-S201 Water Flow Sensor (1/2-inch)

3x Pre-attached wires (Red, Black, Yellow) – approximately 15cm

2x Rubber O-ring seals (may be pre-installed)

Installation instructions (may vary by seller)

Items Not Included (typically sold separately):

Thread seal tape (PTFE/Teflon)

Pipe adapters or fittings

Microcontroller (Arduino, ESP32, etc.)

Power supply (5V DC)

Waterproof wire connectors

Mounting hardware

WHY CHOOSE YF-S201 FLOW SENSOR?

The YF-S201 offers an excellent balance of accuracy, reliability, and affordability for water flow measurement applications. Its standard 1/2-inch threading ensures compatibility with common plumbing systems, while the Hall effect sensor technology provides maintenance-free, contactless operation. Perfect for DIY water monitoring projects, irrigation automation, and industrial process control where precise flow measurement is essential.

IDEAL USE CASES

Smart water meter for home consumption monitoring

Automated plant watering with precise volume control

Coffee machine or beverage dispenser flow measurement

Aquarium water change automation

Hydroponics nutrient delivery systems

Leak detection and early warning systems

Industrial process monitoring and logging

Solar hot water system flow verification