Design of nitrogen oxide detection system based on non-dispersive infrared technology

In recent years, air pollution has become an increasingly serious global problem and the massive emission of pollutant gases, mainly nitrogen oxides, have seriously harmed to people's health. In order to solve the problems of poor stability, low measurement accuracy and single analysis components of the gas analyzer, a multi-component gas analyzer based on non-dispersed infrared technology was developed to analyze the nitric oxide (NO) and nitrogen dioxide (NO2) in automobile exhaust. It can be applied to simultaneously and economically detect the gas concentration in the range of 0–5000 ppm for NO, and 0–1000 ppm for NO2. The optical system of the gas analyzer uses two electrically modulated infrared light sources and pyroelectric infrared detectors to detect the concentration of NO and NO2 respectively. The design of high-precision circuit lays a foundation for the subsequent signal processing, and enhances the anti-interference ability and working stability of the system. According to the experimental data, the concentration inversion model was established using the least squares. It was observed that the detection repeatability error was lower than 4%, and the detection stability was less than 3.1%. The experimental results show that the system has the advantages of high accuracy, good repeatability and stability, as well as easy operation and convenient maintenance.