Study on temperature influence correction of gas concentration laser spectrum detection

The gas detection method based on tunable semiconductor laser absorption spectroscopy has the advantages of non-contact, high resolution and sensitivity. However, the on-line detection of industrial gas by laser spectroscopy is susceptible to temperature changes, resulting in an increase in concentration measurement deviation. Study on ammonia, the mechanism of temperature effect on the absorption spectroscopy characteristics was explored, the experimental platform for ammonia laser detection at various temperatures (298 K to 323 K) was built, and the gas absorbance-temperature correlation method was proposed to correct the concentration inversion results. The results show that, the ratio of total partition function rQ is the dominant parameter affecting the spectral line intensity of ammonia at the same concentration. The spectral line intensity decreases with the increase of temperature due to the linear decrease of rQ with the rise of temperature. When the ambient temperature of ammonia reaches 323 K, the inversion value is 3.13%, and the relative error between the inversion value and the standard concentration value is as high as 37.4%. After correction, the relative error between the inversion value and the standard concentration value is in the range of 0.2%~1.4%.