RESUMEN
Differential photoacoustic spectroscopy (PAS) for flow gas detection based on single microphone is innovatively proposed and experimentally demonstrated. Unlike the traditional systems, only one microphone is used to suppress flowing gas noise. Wavelength modulation spectroscopy and second harmonic detection technique are applied in this PAS system with Q-point demodulation for acetylene (C2H2) gas detection. The experiment is conducted at 1â¯atm and 300â¯K. Different concentrations and flow rates of C2H2 from 0â¯sccm to 225â¯sccm are detected by using nitrogen (N2) as the carrier gas, which indicates that the system can respond well to flowing gases while maintaining the noise at the same level. The system response time decreases to 3.58â¯s while the gas velocity is 225â¯sccm. The detection limit of 43.97â¯ppb with 1â¯s integration time and normalized noise equivalent absorption (NNEA) coefficient of 4.0â¯×â¯10-9 cm-1 Wâ¯Hz-1/2 is achieved at the flow rate of 225â¯sccm. The firstly proposed differential PAS based on single microphone greatly simplifies the system structure for flow gas detection, which provides a novel route for development of PAS with significant practical implementation prospects.