A High-Sensitivity Cylindrical Cavity Resonator Sensor for the Characterization of Aqueous Solutions

In this paper, a high sensitivity concentration sensor for aqueous solutions is presented. The device is a cylindrical cavity resonator operating around a frequency of 1.5 gigahertz. The measurement procedure is simple, instantaneous, non-destructive, and obtains information from two different resonance parameters (frequency and amplitude). Samples are introduced via small, standard test tubes, and a very small amount (around four milliliters) is sufficient to perform a measurement. The design is first approached from a theoretical perspective, after which, empirical adjustments are paired with a simulation-based design optimization. The resulting topology is constructed, showing agreement with said simulations. The final sensor can be used, after a regression type calibration, to indirectly measure the concentration of a liquid solution of known components. The experimental validation, employing different mixtures, demonstrates that the proposed device shows an enhanced sensitivity to solution concentration when compared to other resonator-based arrangements found in the literature.