Detection of two parameters in the liquid by means of multifunctional sensing method using a pair of piezoelectric ceramics

In this paper, two parameters in temperature and concentrations of glycerol and sodium chloride (NaCl) of the liquid are estimated by a proposed multifunctional sensing method based on a pair of piezoelectric ceramics. In the proposed method, propagation time as the ultrasonic characteristic of the liquid is measured by using a pair of piezoelectric ceramics. Moreover, conductance and capacitance as the electrical characteristic of the liquid are also measured by using a pair of electrodes on the surface of piezoelectric ceramics. Therefore, the electrical and ultrasonic characteristics in the same space of the liquid are obtained by using a pair of piezoelectric ceramics. As the experiment, two parameters of the liquid such as temperature and concentration of glycerol or NaCl, or concentrations of NaCl and glycerol, are estimated from measurement values of the electrical and ultrasonic characteristics by means of the proposed multifunctional sensing method. The experimental results demonstrated that the two aforementioned parameters of the liquid could be estimated by the proposed sensor.