Optic Fiber Methane Gas Sensor Based on Tunable Diode Laser Absorption Spectroscopy

Abstract

Tunable diode laser absorption spectroscopy (TDLAS) is a widely used technique in measuring the concentration of trace gas due to its high sensitivity, high selectivity, and fast time response. The fluctuations of temperature in the gas cell can cause the characteristics of the absorption spectra to change in the TDLAS methane sensing system. The three absorption lines in the R(3) transitions of 2v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> band of methane at 1653.72 nm have been studied, and the influence of the temperature fluctuations on the spectral absorption coefficient and the amplitude of second harmonic is analyzed. A simple piece of equipment with temperature acquisition devices is developed for measuring methane gas concentration, temperature signals are obtained for eliminating the impact of temperature fluctuations. Using calibration coefficient, the amplitude of second harmonic is transformed into standard signal at reference temperature in order to restrain the influence of temperature fluctuations. The results show that this optic fiber methane gas sensor using tunable diode laser absorption spectroscopy can restrains the influence of temperature fluctuations and improves detection accuracy effectively.