Gas Concentration Measurement Based On Laser Absorption Spectroscopy

Gas concentration measurement is more and more important in industrial process control, environmental pollution monitoring and other areas. So far, we have developed a wide range of gas concentration measurement method. One method based on laser absorption spectroscopy is widely applied. The principle is that each gas has its own characteristic absorption spectrum which satisfies the Beer Lambert absorption law.Correlation spectroscopy is a method which has high sensitivity, wide measurement range, and strong anti-interference. To match absorption spectrum of the target gas, we use a multi-wavelength fiber laser to make multiple discrete mode output, and the tested gas concentration can be easily measured by correlation with well-calibrated gas concentration of the reference cell. This method can not only eliminate the source instability and interference gases, but also measure multiple gases simultaneously.Light detection and ranging technology is applied widely in environmental monitoring and atmospheric pollution gas detection. It is an effective method that using short pulse laser to measure the backscattering of a remote target under test and analyzing trace gas distribution in atmosphere with differential absorption. We measured the concentration distribution of Hg and NO in a major city of southern China.Regardless of any gases experimental study, gases under test need some space for measurement, i.e. gas cell, and the multi-pass gas cell is very important in high sensitivity gas concentration measurement. We design a new type multi-path gas cell measurement, that is, the lasing beam incidents at an angle to the internal wall of a circular glass plated with a total reflection film, and the beam comes out and is received by a detector after multiple reflections.