The optical fiber detection network for methane concentration

Methane explosion accident is always the main threat to mine production. The two main physical factors of methane explosion are the concentrations of methane and oxygen comes to the explosive limits and the existence of fire source. It is very important to measure the concentration of methane in real-time and accurately for protecting the production safely. Among many methods of methane gas concentration measurement, harmonic detection is one of more effective methods for measuring the weak signal and raising the sensitivity of detection. The study based on the spectrum absorption properties of methane, adopted the Distributed Feedback LD, high performance gas absorption cell. The lock-in amplifier SR830 is adopted to measure the first and second harmonic signals for different methane concentration in this paper. And analyzed the data with Lab VIEW. The analysis data validated the good linearity among the methane concentration and I2f/If (second harmonic/first harmonic) in the range from 0% to 5%, confirmed the superiority of second harmonic theory.