How to Use MQ131: Examples, Pinouts, and Specs

The MQ131 is a gas sensor designed to detect ozone (O₃) concentrations in the air. It operates on the principle of resistive change, where the sensor's resistance varies based on the presence of ozone. This analog output can be used to measure ozone levels in various environments. The MQ131 is widely used in air quality monitoring systems, industrial safety applications, and environmental research.

• Air quality monitoring systems
• Industrial ozone detection
• Environmental research and analysis
• Ozone leakage detection in sterilization equipment
• Smart home air quality devices

The MQ131 sensor is available in two variants: low concentration and high concentration. Below are the key technical details:

The MQ131 sensor typically comes with four pins. Below is the pinout description:

1. Power Supply: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Analog Output: Connect the AOUT pin to an analog input pin of a microcontroller (e.g., Arduino) to read ozone concentration as a voltage.
3. Digital Output: Optionally, connect the DOUT pin to a digital input pin of a microcontroller. This pin provides a HIGH or LOW signal based on a preset ozone threshold.
4. Load Resistor: Use an appropriate load resistor (RL) between the AOUT pin and ground. The value of RL affects the sensitivity and range of the sensor.
5. Preheating: Allow the sensor to preheat for at least 24 hours before taking accurate measurements.

• Calibration: The sensor requires calibration to convert the analog voltage into meaningful ozone concentration values. Use a known ozone source for accurate calibration.
• Preheat Time: The MQ131 requires a long preheat time (≥ 24 hours) for stable operation.
• Environmental Factors: Avoid exposing the sensor to high humidity or temperatures outside its operating range, as this may affect accuracy.
• Placement: Ensure proper ventilation around the sensor for accurate ozone detection.

Below is an example of how to interface the MQ131 with an Arduino UNO to read analog values:

// MQ131 Ozone Sensor Example Code
// Connect AOUT to Arduino analog pin A0
// Ensure the sensor has been preheated for at least 24 hours

const int MQ131_AOUT = A0; // Analog output pin connected to A0
int ozoneValue = 0;        // Variable to store the analog reading

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  pinMode(MQ131_AOUT, INPUT); // Set AOUT pin as input
  Serial.println("MQ131 Ozone Sensor Initialized");
}

void loop() {
  ozoneValue = analogRead(MQ131_AOUT); // Read analog value from sensor
  Serial.print("Ozone Sensor Value: ");
  Serial.println(ozoneValue); // Print the analog value to the Serial Monitor

  // Add a delay to avoid flooding the Serial Monitor
  delay(1000); // Delay for 1 second
}

• The analog value (ozoneValue) corresponds to the sensor's resistance change due to ozone concentration. You will need to calibrate the sensor to convert this value into ozone concentration (e.g., in ppm or ppb).
• Ensure the sensor is preheated for accurate readings.

1. No Output or Incorrect Readings:

   • Ensure the sensor is powered with 5V DC.
   • Verify that the sensor has been preheated for at least 24 hours.
   • Check the connections, especially the load resistor (RL).

2. Fluctuating Readings:

   • Ensure the sensor is placed in a stable environment with proper ventilation.
   • Avoid exposing the sensor to sudden changes in temperature or humidity.

3. Low Sensitivity:

   • Adjust the load resistor (RL) to optimize sensitivity for your application.
   • Ensure the sensor is not exposed to contaminants or high humidity.

4. Digital Output Not Triggering:

   • Verify the threshold setting on the sensor module (if applicable).
   • Check the DOUT pin connection and ensure it is connected to a digital input pin.

Q: Can the MQ131 detect gases other than ozone?
A: The MQ131 is specifically designed for ozone detection. While it may respond to other gases, its sensitivity and accuracy are optimized for ozone.

Q: How do I convert the analog output to ozone concentration?
A: You need to calibrate the sensor using a known ozone source. The relationship between the analog voltage and ozone concentration is non-linear and depends on the load resistor value.

Q: Can I use the MQ131 outdoors?
A: Yes, but ensure the sensor is protected from extreme weather conditions, such as heavy rain or high humidity, which can affect its performance.

Q: How long does the MQ131 last?
A: The sensor's lifespan depends on usage and environmental conditions. Under normal conditions, it can last several years, but regular calibration is recommended to maintain accuracy.