Low frequency quartz tuning fork as hydrogen sensor

The use of hydrogen as a sustainable energy source is pushing the development of innovative sensing strategies for the monitoring of H2 concentration during its production processes and transportation. In this work, we propose a custom quartz tuning fork (QTF) as sensor for the detection of high concentrations of hydrogen in air. The selectivity derives directly from values of molar mass and the viscosity of hydrogen molecules, significantly different from those of the other main constituents of air. Exciting the fundamental flexural mode of a commercially available 12.4 kHz-QTF, we demonstrated the linear dependence of its resonance frequency and quality factor on the H2 concentration, passing through their relationship with molar mass and the viscosity of the H2-air mixture. Monitoring the shift of the resonance frequency of the QTF, the H2-component in air can be estimated with a precision level of 0.74% and accuracy error of 1.82%. The same parameters resulted 0.40% and 4.29%, respectively, when Q values are evaluated. Finally, a beat-frequency approach was proposed to speed up the acquisition in few seconds, monitoring both resonance parameters of the QTF.