Electrical resonance/antiresonance characterization of NDT transducer and possible optimization of impulse excitation signals width and their types

Abstract

This work presents an experimental method for obtaining the best excitation pulse type and width for optimal driving of an industrial non-destructive testing (NDT) ultrasound transducer by using its electrical impedance parameters as input. Within the optimization method, a classic low-voltage frequency sweeping signal and two different types of high-voltage impulse excitation signals (unipolar and bipolar), with different pulse widths, are used for the electromechanical characterization of the transducer. The optimization of the excitation signal is verified by measuring the voltage, current and electrical power of the excitation and received signals obtained by ultrasound pulse reflection from two cracks (2 mm and 3 mm) in a stainless-steel block. Additionally, the influence of the output electrical impedance of the power amplifier on the optimal transfer of electrical power from the amplifier to the loading (the NDT transducer on the block) and vice versa is also discussed in this work. The optimum working point for the ultrasound NDT transducer, regarding the impulse excitation type and its pulse width, is a bipolar impulse excitation with the width and amplitude calculated from maximum values of the measured voltage, electric current and power generated in the transducer receive mode by the reflected ultrasound signals.