Gas temperature measurement using first harmonic based on tunable diode laser absorption spectroscopy

A single-diode-laser sensor using first harmonic based on tunable diode laser absorption spectroscopy (TDLAS) is demonstrated to provide rapid and accurate temperature measurements, and two carbon dioxide absorption lines at 6241.402828 and 6242.672190 cm^-1 with different temperature dependence are analyzed. First of all, the first harmonic peak-peak values and the average values of the two absorption lines are measured, and the ratio of these two values is used as the output value of a single absorption line, and then the gas temperature is measured using the ratio of two absorption lines output value. Experiment results show that the gas temperature measurement error is less than 30 K in the temperature range of 200~1000 K. The scheme can eliminates the influence of light intensity fluctuation on the temperature measurement, and this scheme has stable performance and simple structure, which can meets the need of real-time and non-contact temperature measurement.