Fig. 1. Structural diagram of the miniature resonant photoacoustic cell

Fig. 2. Simulated frequency response of the photoacoustic cell

Fig. 3. Structure diagram of vacuum degassing module

Fig. 4. Schematic diagram of the dissolved gas detection system based on miniature resonant photoacoustic cell

Fig. 5. Absorption spectra in the near-infrared band of 1 μL/L C₂H₂，500 μL/L CO₂ and 1 000 μL/L H₂O

Fig. 6. Experimental frequency response of the micro-resonant photoacoustic cell

Fig. 7. Relationship between the photoacoustic signal amplitude and the modulation current

Fig. 8. The second harmonic response of the system to dissolved C₂H₂ oil samples with different concentrations

Fig. 9. The relationship between the peak values of second harmonic signals and the oil sample concentrations