In this paper, three parameters of an object, which is inserted between a pair of piezoelectric ceramic transducers in the homogeneous medium, - a position, diameter, and relative permittivity, - are estimated. In our proposed method, time of flight is measured by each piezoelectric ceramic transducer, and capacitance between a pair of piezoelectric ceramic transducers is also measured by using each piezoelectric ceramic surface electrode. Therefore, the ultrasonic and electrical properties are simultaneously obtained by the proposed sensing method. In the experiment, a column was inserted between a pair of piezoelectric ceramic transducers which were arranged inside the cylindrical equipment filled with distilled water, and time of flight and capacitance were measured. Three kinds of columns- polyvinyl chloride (relative permittivity ε
s: 2.25), polyoxymethylene (ε
s: 3.5), and polyvinylidene fluoride (ε
s: 6.8)-, were prepared. In addition, three types of diameters- 30, 35, and 40mm-, each with column were used. The position of the column, diameter, and relative permittivity were estimated from time of flight and capacitance.
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