Research on Gas Pressure Measurement Method Based on Absorption Spectroscopy and Laser Interference Technology

Optical non-contact measurement of gas pressure is currently one of the important application fields of laser technology,and the temperature coupling problem in the process of gas pressure measurement is a difficult point in the current research work. Therefore, a combined measurement method of spectral and laser interference technology is proposed, which realizes the calculation of gas pressure value and temperature value by integrating absorbance and refractive index. The principle of direct absorption measurement of tunable semiconductor laser spectroscopy (TDLAS) and the principle of laser interferometry based on the refractive index are analyzed, and the pressure measurement model based on absorption spectrum and the laser interferometric pressure measurement model based on the refractive index are established. The method of fitting the intensity function of the absorption spectrum by the cubic polynomial equation establishes a mathematical model for the solution of the gas pressure value and temperature value based on the integral absorbance and refractive index. In the experiment, a gas pressure detection system based on TDLAS technology and laser interference technology was built. A tunable semiconductor laser with a center wavelength of 2 004 nm and a laser interferometer with a fixed wavelength of 632.8 nm wasused. The length of the gas cell was 24.8 cm. CO2 was selected forthe research. Use the measurement results of the high-precision pressure controller and temperature sensor as the pressure and temperature reference values, and use the vacuum signal as the background signal to measure and calculate the integrated absorbance and refractive index values after the gas pressure changes in a room temperature environment. Finally, the gas pressure and temperature values are obtained by the solution. The realization results show that the maximum relative error of the pressure measurement result is 3.61%, the minimum relative error is 0.5%, and the average relative error is 1.99%. Under the premise of temperature in Kelvin, the maximum absolute error of the temperature solution is 7.66 K, the absolute minimum error is 0.78 K, and the average absolute error of the measurement is 3.29 K. The measurement results are in good agreement with the reference results. This work can provide a reference for future analysis and research on the influence of optical methods on gas pressure and temperature.