Online Self-Calibration Technique for Trace Gas Analyzer Based on Tunable Diode Laser Absorption Spectroscopy

To compensate the measurement error induced by temperature and pressure variation in a tunable diode laser absorption spectroscopy (TDLAS) system, an online self-calibration technique is introduced. More specifically, a reference gas cell filled with known proportion target gas is placed on site, surrounded by working gas to be measured. Thereby, the temperature and pressure inside the reference cell are equal to the gas outside. The TDLAS system acquires the absorption spectrum of the reference gas cell and the working gas synchronously. And the concentration of the trace gas in working gas can be easily obtained by calculating the absorption intensity proportion of both absorption spectrums without considering the affection of temperature and pressure. The principle, design, and experiment of this technique are presented in this paper.