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.