MQ131 High Concentration Ozone Gas Sensor Module

Specifications

• Target Gas: Ozone (O3)
• Detection Range: 10 ppm – 1000 ppm (High Concentration)
• Sensor Type: Semiconductor (SnO2 / WO3 based)
• Operating Voltage (VCC): 5V DC ±0.1V
• Heater Voltage (VH): 5V DC or AC
• Heater Power Consumption: ~900mW (High current draw, external power recommended)
• Response Time: < 10 seconds (Fast response)
• Preheat Time: > 48 Hours recommended for first-time use to stabilize chemical baseline.
• Sensitivity (S): Rs(in 200ppm O3) / Rs(in air) ≥ 2

     Outputs:

• Analog Output (AO): Voltage increases with ozone concentration (0-5V range).
• Digital Output (DO): TTL level (Active Low) with adjustable threshold via onboard potentiometer.

Applications

• Industrial Ozone Generator Monitoring: Monitor output levels in water treatment and sterilization plants to ensure machinery is functioning within safe limits.
• Leakage Detection Alarms: Critical safety device for factories using O3 for bleaching or chemical synthesis, triggering alarms if concentrations breach 10ppm.
• Environmental Control Systems: Automate ventilation fans in laboratories or workshops when ozone levels rise during experiments.
• Sewage Treatment Plants: Monitor ozone injection levels used for disinfecting wastewater.

Wiring Guide

• Warning: The internal heater of the MQ131 consumes significantly more current (~150-180mA) than standard sensors. Do NOT power this directly from an Arduino 5V pin if you are running other modules. A separate 5V 1A power supply is highly recommended for stability.

Wiring Pinout:

• VCC: Connect to External 5V Source (Share Ground with Microcontroller)
• GND: Connect to System Ground
• DO (Digital Out): Connect to Digital Pin (e.g., D2 on Arduino) for Threshold Alarm
• AO (Analog Out): Connect to Analog Pin (e.g., A0 on Arduino) for Concentration Measurement

Technical Table:

Package Includes:

1x MQ131 High Concentration Ozone Gas Sensor Module

Frequently Asked Questions (FAQ)

• What is the difference between MQ131 Low and High concentration?
  The Low version detects ppb (parts per billion) for air quality. This High version detects ppm (parts per million) for industrial leaks and generator monitoring.
• Why is my sensor getting hot?
  This is normal. The internal heater must reach ~300°C to activate the chemical sensing layer. The module will feel warm to the touch.
• Can I use this with an ESP32?
  Yes, but you must use a voltage divider or logic level converter on the Analog Output (AO) because the sensor outputs up to 5V, which can damage the ESP32's 3.3V pin.
• Why are my initial readings unstable?
  The sensor requires a "burn-in" period of at least 24-48 hours when used for the first time to remove chemical impurities from storage.
• Does this detect other gases?
  While specific to Ozone (O3), it has some cross-sensitivity to strong oxidizers like Chlorine (Cl2) and Nitrogen Dioxide (NO2).
• How do I calibrate the MQ131?
  Calibration requires a known concentration of Ozone. For most hobbyist applications, calibrating R0 (Clean Air resistance) after the burn-in period is sufficient for relative measurements.
• What is the "Preheat Time"?
  It is the time required for the heater to stabilize the sensor before taking a reading. For best accuracy, keep the sensor powered for 3-5 minutes before reading data.
• Can I use the Digital Pin (DO) without a microcontroller?
  Yes, you can use the DO pin to directly drive a relay module (with a transistor driver) or an LED when the threshold set by the potentiometer is exceeded.
• Is this sensor waterproof?
  No, water or condensation will damage the sensitive heating element. Use a breathable enclosure for outdoor deployment.
• What is the lifespan of this sensor?
  Under normal operating conditions, the sensor has a lifespan of nearly 5 years.
• Why does the value drop when air blows on it?
  Airflow cools the heater, temporarily changing the resistance. Avoid placing it directly in front of fans; use a baffle if necessary.
• What is the maximum current draw?
  The heater consumes about 150mA to 180mA. Ensure your power supply can handle this.
• Can I use this for medical oxygen concentrators?
  No, this detects Ozone (O3), not Oxygen (O2). For Oxygen, you need a sensor like the KE-25.
• Does it measure O3 in water?
  No, this is an air/gas sensor only. It cannot be submerged.
• How do I convert the Analog value to PPM?
  You need to use the Rs/R0 ratio and the log-log sensitivity curve from the datasheet. Using the linked GitHub library simplifies this math.
• What is the default threshold for the Digital Output?
  The threshold is not fixed; you must adjust the blue potentiometer on the board to set your desired trigger point.
• Can I use a 9V battery?
  No. 9V batteries cannot supply the sustained current required for the heater and will drain very quickly. Use a wall adapter.
• Is the sensor module compatible with Raspberry Pi?
  Yes, but the Raspberry Pi has no analog inputs. You will need an external ADC (like ADS1115) to read the Analog Output.
• Does the sensor work in sub-zero temperatures?
  The operating range is -10°C to 50°C. Performance may degrade or drift outside this range.
• Why is the output voltage 0V?
  Check your wiring. Ensure the heater has 5V. If the sensor is cold, it is not receiving power.
• Is the 10-1000ppm range suitable for human safety monitoring in offices?
  No. The OSHA safety limit for humans is 0.1 ppm. This sensor detects massive industrial concentrations (starting at 10 ppm). It is designed for leak detection alarms in heavy machinery or ozone generators, not for monitoring breathable air quality.