Temperature compensation of QCM sensors in liquid media

This work presents thermal characterization and compensation of a quartz crystal microbalance sensor for the determination of the state-of-charge of lead acid batteries. The concentration of sulfuric acid in the electrolyte changes significantly with the battery state-of-charge. However, changes in the temperature of the electrolyte take place during the operation of the battery, to which the resonant frequency of the quartz is very sensitive. Likewise, density and viscosity are greatly dependent on temperature. The compensation described here takes into account not only the thermal variations of density and viscosity but also the thermal behavior of the quartz resonator.