Ultrasonic Air Coupled Transducer Output Impedance Measurement Technique

New Designs of Focussed Air-coupled Ultrasonic Transducer

The paper describes new developments in air-coupled ultrasonic transducers that can be used to focus energy in air. All transducers to be described are based on a capacitive design, using a rigid backplate and a thin polymer membrane. There are three approaches that can be used to achieve focussing, all of which are described: focussing with a mirror, using curved back-plates, and linear phased...

Ultrasonic Transducer Peak-to-peak Optical Measurement

Possible optical setups for measurement of the peak-to-peak value of an ultrasonic transducer are described in this work. The Michelson interferometer with the calibrated nanopositioner in reference path and laser Doppler vibrometer were used for the basic measurement of vibration displacement. Langevin type of ultrasonic transducer is used for the purposes of Electro-Ultrasonic Nonlinear Spect...

Numerical modelling for the optimization of multi-element, capacitive, ultrasonic, air-coupled transducer

This paper presents an analytical method to predict the acoustic pressure field produced in the air by concentric, annular sources. The sources correspond to a multi-element, ultrasonic, air-coupled array, which should be used further for non-destructive testing (NDT) purposes. After validation of the model based on the comparison of the predicted acoustic pressure with experimental results, a ...

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 s...

Air-coupled Ultrasonic Testing of Materials