Precise measurement of air pressure using tunable diode laser absorption spectroscopy technology

In this paper, air pressure is precisely measured based on water vapor broadening linewidths using tunable diode laser absorption spectroscopy (TDLAS) technology. In order to get comprehensive data of the absorption spectroscopy, the laser beam is sput into two parts in the experiments. One of the laser beam passes through the measurement cell for the absorption spectroscopy, while the other passes through the FP etalon for calibration. Two absorption lines near 7243 cm^-1 are chosen for measurement. Before the experiment, the air broadening line coefficients of the two absorption lines in the HITRAN database are calibrated by measuring the linewidths from 10 kPa to 20 kPa. As the reference pressure varies from 30 kPa to 100 kPa in the experiment, the deviations of the measured pressures based on the absorption lines at 7243.07526 cm^-1 and 7242.37075 cm^-1 are about 0.9% and 2.0%, respectively. The fluctuations of the measured results based on two absorption lines are both less than 0.2%. The measured results from experiments, which differ little under the same conditions, are almost the same with reference pressures. The experimental results demonstrate that precise measurement of air pressure using TDLAS technology is feasible. As a result, this technology will be applied widely in environmental monitoring as well as in the field of flow diagnosis.