Influence of first and second harmonic detection on the lower detection limit of acetylene gas concentration

Photoacoustic spectroscopy technology has good application prospects in the detection of acetylene gas concentration in transformer oil, but the lower detection limit of existing devices is 0.5 ppm, which cannot meet the needs of early warning for power equipment failure. In this work, a photoacoustic spectroscopy detection system for acetylene gas concentration was built. It was found experimentally that the modulation current had an important influence on the photoacoustic signal, and there was an optimal modulation current (4.5 mA) that maximized the amplitude of the photoacoustic signal. Using wavelength modulation-harmonic detection method could effectively reduce the lower detection limit of acetylene gas concentration. When the optimal modulation current was configured, the detection limit of acetylene gas concentration of wavelength modulation-first harmonic detection was 0.29 ppm, and the detection limit of acetylene gas concentration of wavelength modulation-second harmonic detection was 0.30 ppm.