The core principle of the automobile exhaust emission analyzer is based on the differential response of different gases to specific physical or chemical signals, and achieves qualitative and quantitative analysis of multi-component gases through precision sensors and algorithms.

The technical paths of automobile exhaust emission analyzers are mainly divided into the following categories:

1. Infrared spectroscopy technology

Detecting the selective absorption characteristics of gas molecules towards specific wavelengths of infrared radiation. Carbon monoxide (CO) has a strong absorption peak at a wavelength of 4.6 μ m, carbon dioxide (CO ₂) has strong absorption at a wavelength of 4.2 μ m, and hydrocarbons (HC) have strong absorption at a wavelength of 3.4 μ m. The system measures the intensity attenuation of infrared radiation after absorption and uses the Beer Lambert law to infer gas concentration. This technology has the characteristics of fast response speed (millisecond level), high detection accuracy (error less than 1%), and strong long-term stability, and is widely used in gasoline vehicle exhaust analysis.

2. Electrochemical sensing technology

Detection is based on the change in current generated by the oxidation-reduction reaction of gas between electrodes. The oxygen (O ₂) sensor uses platinum/zirconia solid electrolyte, and the migration of oxygen ions generates a current signal that is linearly correlated with concentration; The nitrogen oxide (NOx) sensor reduces NOx to nitrogen gas (N ₂) and releases electrons through a multi-layer catalytic film structure, and the current intensity is proportional to the NOx concentration. This technology has a compact structure and low cost, but the sensor has a short lifespan (usually 2-3 years) and needs to be replaced regularly.

3. Chemiluminescence method

High sensitivity detection technology for nitrogen oxides (NOx). The principle is to react nitric oxide (NO) in the exhaust gas with ozone (O3) to generate excited nitrogen dioxide (NO ₂ *), which releases photons when de excited. The number of photons is linearly related to the concentration of NO. By using photomultiplier tubes to measure light intensity, ppb level detection sensitivity can be achieved. By using a catalyst to reduce nitrogen dioxide (NO ₂) to NO, total NOx detection can be achieved. This technology has strong anti-interference ability and is commonly used for laboratory level high-precision analysis.

4. Hydrogen flame ionization method (FID)

A technology specifically designed for the detection of total hydrocarbons (THC). The principle is to ionize hydrocarbons in a hydrogen flame and measure the ion current intensity. The current value is proportional to the number of carbon atoms, with a detection range of 0-10000 ppm and an accuracy of ± 2%. This technology requires a hydrogen source and a high-temperature environment, and is commonly used for engine bench testing or diesel vehicle exhaust analysis.

5. Ultraviolet Differential Absorption Spectroscopy (UV-DOAS)

By utilizing the characteristic absorption of NOx molecules by ultraviolet light (200-400nm wavelength band) passing through exhaust gas, the absorption peak area is analyzed by a spectrometer, and the concentration is calculated by combining the Beer Lambert law. This technology has high sensitivity (ppb level) for NOx detection and strong anti-interference ability, especially suitable for low concentration emission monitoring.

Advantages and characteristics of automobile exhaust emission analyzer:

1. Multi component synchronous detection capability

Modern analyzers can simultaneously detect conventional pollutants such as carbon monoxide (CO), carbon dioxide (CO ₂), hydrocarbons (HC), nitrogen oxides (NOx), and oxygen (O ₂) through multi-sensor fusion technology. Some equipment can also be extended to detect components such as particulate matter (PM) and ammonia (NH3). This integrated design reduces the detection process and improves data comprehensiveness.

2. High precision and high stability

By using advanced sensing technologies such as non dispersive infrared (NDIR), electrochemistry, and chemiluminescence, combined with temperature compensation and pressure compensation algorithms, detection accuracy can be maintained under complex working conditions. The detection error of infrared sensors for CO is less than 1%, and the sensitivity of chemiluminescence method for NOx detection can reach 0.02ppm, meeting the National VI emission standards and stricter environmental requirements.

3. Real time dynamic monitoring and portability

Portable analyzers are compact in size and light in weight (usually less than 5kg), supporting on-board testing or on-site sampling. The onboard equipment is equipped with heated sampling pipelines and shock resistant design, which can capture real-time emission data of transient working conditions such as acceleration and climbing during vehicle operation, solving the problem that traditional bench tests cannot reflect actual road emissions.

4. Intelligent data processing and expansion functions

Built in microprocessor and LCD display screen, supporting Chinese interface operation, can automatically calculate derived parameters such as excess air coefficient (λ) and carbon hydrogen ratio.

5. Environmental adaptability and maintenance convenience

The equipment integrates functions such as automatic zero adjustment, automatic cleaning, and gas leakage inspection, reducing manual intervention. The modular design of sensors facilitates quick replacement, and some models support hot swapping. Electrochemical sensor replacement only takes a few minutes and has a lower cost; Infrared sensors have a lifespan of over 5 years, reducing maintenance costs.