Data acquisition for ultrasonic transducer evaluation under spread spectrum excitation *

Abstract

This chapter is presenting the ultrasonic data acquisition principles and techniques used for the ultrasonic transducer properties investigation under spread spectrum excitation. Spread spectrum (SS) signals differ from conventional pulse, step and toneburst signals in that sense that they have spectral components spread in time. Thanks to this property signal can be compressed gaining both energy and resolution. Reasoning for the SS signals based on time of flight estimation theory is given. Discussion on signal and transducer types is given and governing equations are presented. Ultrasonic transducer as energy converter is presented and essential parameters outlined. Discussion is separated into two threads: i) electrical energy transduction into pressure investigation; and ii) directivity of the pressure field investigation. It was aimed to investigate the transducer transduction and directivity properties relation to excitation signal type. Spread spectrum signals and conventional pulse, step and toneburst signals were used in comparison. Setup and data acquisition techniques for transducer impedance measurement, interaction with excitation generator, power delivery and bandwidth optimization are discussed. Directions, system structure and setup for transducer directivity evaluation are given.