I. Why are electrochemical sensors the preferred choice for industrial NO₂ detection?

    Nitrogen dioxide (NO₂) is a toxic pollutant subject to strict controls in sectors such as industrial smelting, underground mining, factory exhaust emissions, and atmospheric monitoring. Excessive levels can damage the human respiratory tract. Furthermore, online environmental monitoring systems and workshop safety alarm equipment impose rigorous demands on sensors: high accuracy and stability, strong adaptability to temperature and humidity, resistance to cross-gas interference, and minimal long-term drift.

    While semiconductor NO₂ sensors on the market suffer from poor accuracy and significant zero-point drift, imported electrochemical sensors entail high procurement costs and long lead times. The MQ-E3-NO2—a constant-potential electrolytic NO₂ sensor independently developed by Shanxi Tengxing Sensing—strikes an optimal balance between high precision, cost-effectiveness, and stable service life. It is the preferred domestic alternative to imported NO₂ sensing components and is widely used in NO₂ detectors, exhaust monitoring modules, and underground safety alarm systems.

II. MQ-E3-NO2 Working Principle: Precise NO₂ Measurement via Constant-Potential Electrolysis

    The MQ-E3-NO2 is a constant-potential electrolytic electrochemical sensor with a clear, core detection mechanism:

    NO₂ gas permeates a gas-permeable membrane into the sensor, triggering an electrochemical redox reaction between the working electrode and the counter electrode. This releases charge, generating a minute current. The output current is directly proportional to the NO₂ gas concentration; downstream circuitry captures and converts this current signal to provide an accurate NO₂ concentration reading.

    The sensor features a specialized internal electrolyte system and a 0mV bias design, eliminating the need for an external driving voltage. It provides a stable analog current output when paired with a standard 10Ω load resistor. A simple data acquisition circuit can be constructed using an AD8572 operational amplifier, ensuring low development barriers and compatibility with various microcontrollers and monitoring mainboards.

III. MQ-E3-NO2 Core Technical Advantages

    Wide linear range covering standard detection requirements

    It offers a standard measurement range of 0–20 ppm and a short-term maximum tolerance limit of 150 ppm, ensuring stable data acquisition across both low- and high-concentration conditions. The output is perfectly linear with no distortion points, simplifying calibration and minimizing data error. High Precision and Fine Resolution

Sensitivity of (0.78 ± 0.42) μA/ppm and resolution down to 0.1 ppm; accurately detects trace NO₂ leaks and low-concentration exhaust emissions, meeting environmental standards for trace-level online monitoring.

    Rapid Response (T90 < 25s)

    Reaches 90% of stable output within 25 seconds of gas exposure; provides real-time alerts for exhaust fluctuations and instantaneous leaks, preventing missed detections or delayed warnings.

    Superior Environmental Adaptability; Stable Operation Across Wide Temperature and Humidity Ranges

    Operating temperature range of -20°C to 50°C, with zero-point drift of only 0.2 ppm between -20°C and 40°C; operates in 15%–90% RH (non-condensing) and at pressures within ±10% of standard atmospheric pressure; suitable for cold workshops in the north and humid mines in the south.

    Low Drift and High Repeatability; Minimal Need for Frequent Calibration

    Repeatability <2% of output value; monthly stability drift <2%; stable zero-point output at 25°C, reducing the frequency of monthly calibrations and lowering O&M costs.

    Low-Power Design; Suitable for Portable Detectors and Online Monitoring Equipment

    No high-voltage drive required; features 0mV bias and low power consumption, making it ideal for battery-powered portable NO₂ alarms and outdoor micro air quality monitoring stations.

    Excellent Interference Rejection; Reduces False Alarms from Interfering Gases

    Electrolyte optimized against common industrial interfering gases such as hydrogen sulfide, chlorine, ammonia, and ethylene; cross-sensitivity is kept extremely low, minimizing false alarms in multi-gas workshop environments. 

IV. MQ-E3-NO2 Comprehensive Technical Specifications

V. MQ-E3-NO2 Key Application Scenarios

    1. Industrial Safety

    Online monitoring of NO₂ leaks in chemical workshops, smelters, boiler exhaust systems, and nitrogen oxide reaction workshops; compatible with fixed toxic gas alarm systems.

    2. Underground Mining Detection

    Monitoring NO₂ concentrations following underground blasting; serves as the core sensing element for underground safety inspection instruments and portable mining NO₂ detectors.

    3. Environmental Air Quality Monitoring

    Used in urban micro-air quality stations, industrial exhaust emission monitoring systems, and flue gas analyzers; compliant with HJ 654 environmental monitoring standards.

    4. Portable Detection Equipment

    Handheld NO₂ detectors, emergency detection devices, and portable exhaust gas detection modules; features low power consumption suitable for battery-powered operation.

    5. Scientific Research and Laboratory Equipment

    Continuous sensing unit for trace NO₂ concentration data collection in atmospheric pollution studies and nitrogen oxide catalysis experiments.

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