Multigas Sensing Technique Based on Quartz Crystal Tuning Fork-Enhanced Laser Spectroscopy

Investigation and Optimization of a Line-Locked Quartz Enhanced Spectrophone for Rapid Carbon Dioxide Measurement

“…Thus, the response time of the QEPAS sensor was enhanced to ~0.5 s for continuous CO2 measurements while maintaining sufficient energy accumulation. Compared with several typical QEPAS-based CO2 measurements, which achieved a detection limit of tens to hundreds ppm [16,18,26], a better detection limit of 7 ppm was achieved, notably with a much faster response time.…”

“…Thus, the response time of the QEPAS sensor was enhanced to ~0.5 s for continuous CO 2 measurements while maintaining sufficient energy accumulation. Compared with several typical QEPAS-based CO 2 measurements, which achieved a detection limit of tens to hundreds ppm [ 16 , 18 , 26 ], a better detection limit of 7 ppm was achieved, notably with a much faster response time. The system stability was evaluated by performing Allan deviation analysis, achieving a minimum detection limit of 0.45 ppm at an integration time of 270 s. Besides, a linear dynamic range of 6 × 10 5 was obtained and the implementations for atmospheric and exhaled CO 2 measurements, in a field application, were demonstrated.…”

“…Thus, an inadequately generated acoustic wave results in a weaker signal. To date, most QEPAS CO 2 sensors have a concentration detection limit of tens to hundreds of ppm, especially when the in situ excitation power is limited to merely mW level [ 15 , 16 , 17 , 18 ]. Following the radiation-to-sound conversion efficiency ε of photoacoustic process, i.e., ε = [1 + (2π f 0 τ ) 2 ] –1/2 , where τ is the relaxation time [ 19 ], the CO 2 QEPAS signal can benefit from a QTF with lower resonant frequency f 0 .…”

Multi-mechanism collaboration enhanced photoacoustic analyzer for trace H2S detection

“…However, semiconductor H 2 S sensors are usually susceptible to cross-interference and the performance of electrochemical gas sensors decays rapidly. Compared with electrical gas sensors, absorption spectroscopy gas analysis technology (ASGAT) has the advantages of online real-time analysis, minor cross-interference between gases, and high detection sensitivity [5] , [6] , [7] . The ASGAT mainly realizes the detection of gas composition and concentration based on the specificity of the molecules excited by the irradiated beam.…”

Vehicle-Deployed Off-Axis Integrated Cavity Output Spectroscopic CH4/C2H6 Sensor System for Mobile Inspection of Natural Gas Leakage

“…Many techniques have been successfully used to detect NG leakages, such as optical methods based on spectroscopic measurements, − electrochemical methods, gas chromatography, and the like. Due to the short response time, convenient sampling, noninvasive measurement, great miniaturization potential, and low power consumption, optical methods are still the preferred method in hazardous applications, including tunable diode laser absorption spectroscopy (TDLAS), , wavelength modulation spectroscopy, multipass laser absorption spectroscopy, , cavity ring-down spectroscopy (CRDS), integral cavity output spectroscopy (ICOS), off-axis integrated cavity output spectroscopy (OA-ICOS), photoacoustic spectroscopy (PAS), quartz-enhanced photoacoustic spectroscopy (QEPAS), etc. Among these optical methods, OA-ICOS is a highly sensitive infrared spectroscopy technique and has good selectivity, strong robustness, and fast response .…”