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Electromechanical characterization of active piezoceramic elements by using different types of excitation signals

The nondestructive ultrasound probes and high intensity focused medical ultrasound transducers are usually constructed and theoretically modelled by using electromechanical parameters of active piezoceramic elements determinated from the input electrical impedance. The input electrical impedance of active piezoceramic elements is usually measured by using low voltage magnitude frequency sweeping signal around the resonance frequencies. In this research we compared the results for the input electrical impedance measured in the real operating conditions when the sample is driven with the short impulse of high voltage magnitude. The equivalent circuit parameters including complex electrical, mechanical and piezoceramic constants of materials used in probe construction are determinated by fitting the theoretical input electrical impedance equation with measured input electrical impedance by using these two different types of excitations. The parameters of equivalent electrical circuits including complex materials parameters at each way and level of excitation are determinated by fitting the assumed theoretical model with measurement results of the input electrical impedance. It is shown that electrical, mechanical and piezoceramic parameters of the active piezoceramic are different depending on the measurement method and levels of excitation. The resonances in the case of impulse excitation are not so expressed as in the case of constant voltage magnitude frequency sweeping excitation signals and imaginary parts of electromechanical material properties are larger. The parameters of theoretical models (KLM) should be corrected with increased losses to obtain the appropriate theoretical modeling results which can be compared with measurement results in the impulse mode of working.

non-destructive evaluation ultrasound probe; constant voltage magnitude frequency sweeping signal excitation; short impulse high voltage excitation; electromechanical parameters of piezoceramic elements

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