QEPAS Sensor for Simultaneous Measurements of H2O, CH4, and C2H2 Using Different QTFs

A multi-gas quartz enhanced photoacoustic spectroscopy (QEPAS) sensor based on three quartz tuning forks (QTFs) with different response frequencies for trace gas detection was proposed and experimentally demonstrated. Three near-infrared DFB lasers are used to monitor water vapor, methane, and acetylene in the parts per million range. The sensor system was first evaluated for individual H ₂ O, CH ₄ , and C ₂ H ₂ detection, respectively. Subsequently, the sensor system was evaluated for simultaneous H ₂ O, CH ₄ , and C ₂ H ₂ detection. Finally, trace gas measurements have been assessed and minimum detection limit (MDL) of 1.3 ppmv at 1368.597 nm for H ₂ O, 79 ppmv at 1653.722 nm for CH ₄ , and 5 ppmv at 1532.83 nm for C ₂ H ₂ have been demonstrated. The continuous monitoring of H ₂ O, CH ₄ , and C ₂ H ₂ concentration levels for >3 h indicated the stability of the reported multi-gas QEPAS sensor system.