Abstract
A near-IR CO trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is evaluated using humidified nitrogen samples. Relaxation processes in the CO-N2-H2O system are investigated. A simple kinetic model is used to predict the sensor performance at different gas pressures. The results show that CO has a ~3 and ~5 times slower relaxation time constant than CH4 and HCN, respectively, under dry conditions. However, with the presence of water, its relaxation time constant can be improved by three orders of magnitude. The experimentally determined normalized detection sensitivity for CO in humid gas is .
Highlights
Photoacoustic spectroscopy (PAS) has been one of the most widely used spectroscopic techniques for trace gas detection in the past decades because of its advantages of high sensitivity, high selectivity and compact detection module
Diode laser with an emitting wavelength centered at 1566.31 nm (Model PN: feedback (DFB) diode laser with an emitting wavelength centered at 1566.31 nm
Pressure in Dry and Modulation and Wet is wavelength a 2f wavelength modulation technique, the sensor performance is a 2f modulation basedbased technique, the sensor performance depends on the modulation the laser source andpressure
Summary
Photoacoustic spectroscopy (PAS) has been one of the most widely used spectroscopic techniques for trace gas detection in the past decades because of its advantages of high sensitivity, high selectivity and compact detection module. The principle of PAS is to detect the sound waves which are generated in the media upon absorption of modulated optical radiation. Quartz-enhanced photoacoustic spectroscopy (QEPAS), an alternative approach to PAS utilizing a quartz tuning fork (QTF) as a sharply resonant acoustic transducer instead of a microphone [1,2,3], has been widely applied to environmental monitoring, industrial process control, combustion processes analysis, and medical diagnosis [4,5,6,7,8,9,10,11,12,13,14].
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