A Mid-Infrared Fiber-Coupled QEPAS Nitric Oxide Sensor for Real-Time Engine Exhaust Monitoring

Quartz‐Enhanced Photoacoustic Sensors for Detection of Eight Air Pollutants

“…Y. Ma et al reported about QEPAS detection of CO and NH 3 with MDLs of 11.2 and 418 ppb, [ 30,31 ] which are significantly higher than those achieved in this work both at 0.1 and 1 s integration time. A similar comparison can be drawn between the results reported by Breitegger et al, [ 32 ] Zhang et al, [ 33 ] Shi et al, [ 34 ] Waclewek et al: [ 35 ] the MDLs reported in these works are, respectively, 21 ppb for NO 2 , 79 ppm for CH 4 , 120 ppb for NO, and 100 ppb for SO 2 . These MDLs are all above those reported in Table 3 at 0.1 s integration time for the same target species.…”

Near-Infrared Off-Axis Integrated Cavity Output Spectroscopic Dual Greenhouse Gas Sensor Based on FPGA for in situ Application

“…The linewidth of both of the selected DFB lasers is nearly 2 MHz, as measured using a commercial laser linewidth measurement instrument (OE4000, OE-waves), and the output power was nearly 8 mW during the scanning period. The emission spectrum was measured using near-infrared Fourier transform (FTIR) to adjust the control temperature and current, and the results are According to previously conducted research, the modulation depth in the WMS should be 2.2 times the half width at half maximum (HEHM) of the gas absorption lines [18]. Additionally, signal processing difficulties and the frequency domain distribution of ambient noise should be comprehensively considered, so the modulation frequency was set to 1 kHz.…”

Highly sensitive HF detection based on absorption enhanced light-induced thermoelastic spectroscopy with a quartz tuning fork of receive and shallow neural network fitting

“…However, due to the long response time and limited detection performance, these methods cannot perform quantitative real-time detection. Until now, a large number of new gas detection methods have emerged [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , among which laser absorption spectroscopy has been of interest to researchers due to its unique advantages. This method has been widely used for the detection of water vapor (H 2 O), methane (CH 4 ), carbon dioxide (CO 2 ) and some toxic or corrosive gases such as hydrogen chloride (HCl) and hydrogen cyanide (HCN).…”