The measurement equipment are controlled by LABVIEW and measured data are recorded in computer programs, and it is possible to graphically show both measured data and theoretical curves together. In this way input impedance of piezo-material is measured and compared with theoretical curves with variable parameters, and the parameters are determined at a condition of exact agreement, which is parameter fitting method.
Vendors of piezo-materials show parameters on their catalogue but those are for general applications, not for specific frequency range and therefore parameters determined by this fitting method are different from vendor's catalogue values. Parameters of PVDF or its copolymer transducers are more varied for unit to unit and more frequency dependent than piezo-ceramic and therefore, parameters determined by fitting method become more critical for performance prediction of the piezo-polymer transducers.
Parameters of materials, metals or polymers are available from its vendors. However, the parameters are for general use at a static condition or at a low frequencies. Such parameters are very different from those at high frequencies, or in some case high frequency values of velocity and impedance are available from published data but the measured condition or used frequency for that is not necessarily same as those for the actual application. Therefore, it is necessary to measure the acoustic parameters for each material and those parameters are fed to computer program for simulation. The predicted performance in this way is more accurate and close to practical performance.
