Design and implementation of a high-power impedance analyzer to study the frequency response of ultrasonic transducers

This article presents a novel 100-watt impedance analyzer designed to characterize piezoelectric transducers at high excitation voltages (100–200 V)—a capability absents in commercial analyzers, which are typically limited to low voltages (e.g., 2 V). This advancement enables the study of nonlinear piezoelectric effects under realistic operating conditions, which is critical for applications such as medical imaging and industrial actuators. Operating over a 15–40 kHz frequency sweep range, the analyzer delivers high-resolution measurements (0.15 V, 1 mA, and 0.2° for voltage, current, and phase, respectively) and provides comprehensive data including impedance, admittance, quality factor, bandwidth, and electrical equivalent circuit parameters. Innovations such as a stable asynchronous buck converter and a precise D flip-flop-based phase detection method ensure reliable performance at high voltages. Testing three transducers at 100, 150, and 200 V—compared to a commercial analyzer operating at 2 V—reveals new trends: a decrease in resonance frequency by approximately 1.3% and a reduction in admittance with increasing voltage. These effects are attributed to a lowered Young’s modulus and increased damping, offering new insights into nonlinear piezoelectric behavior.