Measurement of complex impedance of ultrasonic transducers

The automated system for ultrasonic transducer complex impedance measurement using the sine wave correlation for signal amplitude and phase extraction is presented. The system contains the direct digital synthesis (DDS) generator and two ADC channels with a common reference frequency source. In such a case the frequency error between the excitation and the measurement channels is reduced. The shielded measurement chamber with local low noise high impedance preamplifiers has been added to reduce the induced noise and to improve robustness. The measurement procedure and equations are presented. The results of various ultrasonic transducers impedance measurements are given.