Research on Methane Gas Sensor with Spectrum Absorption and Signal Processing Method

Based on the mechanism of gas absorption to light varying with concentration and the analysis of the infrared absorption spectrum of methane, the mathematical model of gas concentration harmonic measurement is built up and a measurement system was developed. This system, consisting of an illumination source LD in 1654 nm waveband, and a PbS preamplified photodetector with wavelength response range 1.0 mum -2.9 mum . Light source modulation harmonic measurement is adopted, making use of a frequency-selection amplifier to carry out second-harmonic detection from the transmitting signals. The ratio of the first harmonic and second harmonic signal can be used for eliminating the interference owing to light power changing. The sensitivity, accuracy and stability can meet practical demands for the detection of methane.