The Measurement Of NO₂ Concentration Based On Spectroscopy Technology

For the past few years, people pay more attention to the improvement of the life as the improvement of their living conditions. Among these, how to control the environment pollution effectively has become one of the focus issues. However, the detection of the pollution is the important basis for the control of the environment pollution. NO2 is one of the important pollutants. It is also the source of the acid rain. Therefore, it has great significance to realize the measurement of the NO2 gas concentration.This paper mainly uses TDLAS technology to detect the NO2. Compared with the traditional chemical detection methods, this way can achieve non-contact measurement. Compared with the other optical measurement methods, this way can ensure the accuracy and reduce the cost at the same time.The mainly work of this paper are as follows:We firstly solved the temperature control problem of the laser without built-TEC. The assembled laser achieves temperature control with good dynamic performance and steady-state performance through the external TEC, thermistor, radiator and the PID system. After that, the laser we used has the mode hopping phenomenon. The laser mode hopping phenomenon can be avoided by setting the laser operating temperature and the operating current, and it can also emit the 670nm wavelength at the same time. And then, the experiment platform is built up. The position of the absorption peak, the optimum modulation parameters and the calibration curve are achieved through the experiments. At last, to check the accuracy and the feasibility of the system, NO2 gas concentration measurement is carried out at outdoor. The results of the experiment show that the test system can measure NO2 gas concentration accurately. It has a good feasibility.