Influence of Air Pressure on the Resonance Properties of a T-Shaped Quartz Tuning Fork Coupled with Resonator Tubes

Abstract

A theoretical analysis and experimental investigation of the influence of gas pressure on resonance properties, namely, the quality factor and resonance frequency, of a T-shaped quartz tuning fork (QTF) is reported here. Two configurations are considered: a bare QTF, and a QTF coupled with a pair of resonator tubes (spectrophone). In both configurations, the effect of air on resonance frequency due to the additional inertia on prong motion and the influence of air damping on the quality factor, were analysed. By comparing the bare QTF and the spectrophone results, the effect of pressure on the acoustic coupling between the QTF and the tubes was theoretically modelled and then validated. The results show that acoustic coupling is strongly influenced by air pressure, leading to a shift of resonance frequency and a decrease in the quality factor up to 24%.

Characterization of H2S QEPAS detection in methane-based gas leaks dispersed into environment

“…The applicability of this model to QTFs vibrating at the fundamental and overtone mode was experimentally demonstrated [53] , [54] . In addition, the model was validated for T-shaped QTFs, like the one employed in this work [55] . Based on this model, the damping contribute to the overall quality factor can be theoretically evaluated as follows: where is the QTF resonance frequency, is the crystal width, is the prong thickness and is the quartz density.…”

H2S near-IR QEPAS detection in complex gas matrices

“…The simulation clearly shows that at this pressure, H2S and CH4 do not interfere each other and H2O is the only absorber potentially interfering with the two target molecules It was experimentally verified that, at 100 Torr, the pressure broadening of the H2O line at 3792.6 cm -1 (Fig. 2, upper panel) is small enough to not influence the H2S signal background 23 . It was also verified that almost all the nearby H2O lines shown in Fig.…”

“…Variation in the bulk composition can affect QEPAS generation and detection through several mechanisms, leading to a change in the measured QEPAS signal of the excited gas, namely H2S. First, QTF resonance properties are affected by gas matrix density variation due to viscous damping 23,24 . We experimentally measured the QTF quality factor and resonance frequency and verified that they can be considered unchanged for all the analyzed mixtures.…”

Multivariate spectral analysis in quartz-enhanced photoacoustic spectroscopy

“…With this aim, 60 QEPAS spectra corresponding to different samples compositions were collected and used as training and test set for PLSR. In this case, six latent variables were recognized by the algorithm, corresponding to i) CH4; ii) H2O; iii) effects of vibro-vibrational relaxation of CH4 on H2O; iv) effects of vibro-translational relaxation of CH4 on itself, due to increasing CH4 concentration; v) variations of fluid dynamics parameters affecting photoacoustic waves generation; iv) change of speed of sound and consequent variation of resonator tubes coupling 56 . The results of PLSR analysis on the analyzed gas samples are reported in Table 3, where the investigated CH4 concentrations are reported together with the H2O concentrations in the sample.…”