Fig. 1. Absorption spectrum of CH₄, H₂O around 3.3 μm

Fig. 2. Principle block diagram of infrared methane sensor system

Fig. 3. Spectra of main absorption peaks of LED34, LED27, PD36 and CH₄

Fig. 4. Design diagram of sampling chamber

Fig. 5. Emission spectra of LED34 under different current

Fig. 6. Circuit diagram of photosensitive signal processing

Fig. 7. Curve of temperature compensation coefficient

Fig. 8. Physical figure of infrared methane sensor and detection system platform