What is the principle of the UV spectrum detection of gas?

With the rapid development of society and people's lack of attention to environmental protection, environmental pollution is becoming more and more serious. The sources of pollution are mainly produced by industry, road transportation, and daily life.

In industry, soot, sulfur oxides, nitrogen oxides, organic compounds, halides, and carbon compounds are mainly produced.

In daily life, cooking stoves and other supplies will mainly produce a large amount of dust, SO2, CO, and other harmful substances pollution of the atmosphere;

In transportation, especially the automobile, CO, SO2, NOX, and hydrocarbons are mainly produced, especially in the first three are more harmful.

Facing such a severe environmental situation, how to monitor and control air pollution is very important.

Atmospheric pollution, monitoring is the key, only to check the pollution of the gas composition, to scientific and effective governance, the ultraviolet analyzer is now commonly used a smoke analysis instrument, it uses UV difference spectrum analysis technique (DOAS) as the core, with high measurement precision, high reliability, fast response time, etc.

When ultraviolet light is irradiated to gas molecules composed of heteroatoms such as sulfur dioxide, nitrogen oxides, carbon dioxide, carbon monoxide, etc., its inherent vibration and rotation energy levels will undergo transitions, and will absorb ultraviolet light of specific wavelengths. 

Differential absorption spectroscopy (DOAS) is a new type of data processing method for absorption spectroscopy. It decomposes the absorption spectrum of gas into two parts: fast and slow, and then uses the fast part for calculation and analysis to determine the measured gas concentration.

The UV spectrometer adopts the in-situ thermal and moisture monitoring mode, which can directly monitor the concentration and emission of gas such as O2, SO2, NO, NO2, NH3, CS2, CO, CO2, and others in the flue gas. Compared with the traditional electrochemical method, it has obvious advantages such as NO signal attenuation, NO sensor life limit, NO gas cross-interference, and easy maintenance.

Normally, the fast-changing part of the gas absorption spectrum is related to the structure of gas molecules and the elements it is composed of. It is the characteristic part of the gas molecule absorption spectrum and is different. Therefore, differential absorption spectroscopy can effectively eliminate the interference of other gas components, thereby the sensitivity and resolution of monitoring are improved, and the types of analysis gases will be more.