Integrated near-infrared QEPAS sensor based on a 28 kHz quartz tuning fork for online monitoring of CO2 in the greenhouse

Signal-to-Noise Ratio Analysis for the Voltage-Mode Read-Out of Quartz Tuning Forks in QEPAS Applications

“…Since, in QEPAS applications, several QTFs have been employed [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], the same study has also been carried out for a representative QTF characterized by an f S = 12.484 kHz and a quality factor of 10 4 [ 9 ], and the same results were found.…”

“…Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a well-known technique used for the detection of specific trace gases in complex mixtures [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. The high performances in terms of selectivity and sensitivity allow for the exploitation of this technique in a wide range of applications, such as environmental monitoring [ 8 , 9 , 10 ], chemical analysis [ 11 , 12 ], and advanced biomedical diagnostics [ 13 , 14 ]. In QEPAS, acoustic waves are generated between the prongs of a quartz tuning fork (QTF) by the absorption of modulated light from the gas molecules, via non-radiative relaxation processes [ 2 , 15 ].…”

“…Suitable front-end electronics must be designed to read-out the signal generated by the QTF. The common read-out architecture employed in QEPAS sensors is the transimpedance amplifier (TIA) [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ], schematically depicted in Figure 1 .…”

Multivariate spectral analysis in quartz-enhanced photoacoustic spectroscopy

“…Due to quartz piezoelectric properties, this device acts as both resonator and transducer, providing stable resonance frequencies and high quality factors 6 . Photoacousticbased sensing has already proven its capabilities in several fields such as: i) environmental monitoring [7][8][9][10] ; ii) hazardous and toxic gases detection [11][12][13][14] ; iii) oil&gas industry [15][16][17][18] ; iv) energy systems monitoring [19][20][21][22] . As photoacoustic transducer, the QTF is characterized by wavelength-independent response respect to the laser source employed to target the absorption features of the selected target gases [23][24][25] .…”

All-optical light-induced thermoacoustic spectroscopy for remote and non-contact gas sensing

“…Quart tuning fork (QTF) as a resonant acoustic-electric transducer based on its piezoelectric property has been successfully applied in trace gas photoacoustic sensing since 2002, which is called quartz-enhanced photoacoustic spectroscopy (QEPAS) [1] , [2] , [3] , [4] , [5] , [6] , [7] , [8] . The QTF has the advantages of a high resonance frequency, a high quality factor, a small size and a low cost, which enable the QEPAS sensor to have the immunity to ambient acoustic noise and the capability to analyze ultra-small volume gas samples with respect to the conventional PAS sensor based on a photoacoustic cell and a microphone [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] . However, the QTF required to be immersed in the target gas in the QEPAS sensor, so that the QTF can be corroded.…”