Improvement of the measuring ultrasonic electromagnetic-acoustic transducer

Abstract

Based on the analysis of previously published research and studies, it has been established that despite their significant advantages over traditional “contact” sensors in measurements, testing and diagnostics of thin dielectric coated (via paint, plastic, etc.) metal products, the available electromagnetic-acoustic transducers provide insufficient sensitivity and significant uncontrolled (“dead”) zone. This situation complicates testing of thin sheets, pipes, shells, tanks etc., and sometimes makes it impossible to measure the remaining thickness of the metal.
 The analysis of available research has shown that the possibility of transducers sensitivity increases via traditional increase in the magnetic induction value, and the high-frequency current value is practically exhausted. At the same time, the prospects for improving the design of electromagnetic-acoustic transducers were determined. The problems of traditional transducers were solved through development of a new electronic control circuit. For this, the control unit was designed to be distributed between ultrasonic shear pulse excitation devices, and as a result, for the device of ultrasonic signals reflected from the metalwork reception, the device sensitivity was increased. In addition, to provide the possibility to test and measure thin metal product thickness, the electronic circuit was supplemented with means of interference suppression after the powerful supply of the high-frequency current of the converter, which allowed significantly reducing the “dead” zone.
 A special stand was constructed to experimentally test the capabilities of the transducer developed, including a powerful high-frequency current pulse generator, an amplifier of received ultrasonic pulses and a digital oscilloscope. It has been experimentally demonstrated that the new electronic circuit of the non-contact sensor allows it to be qualitatively matched with the probing pulse generator and the amplifier of the received ultrasonic packet signals. As a result, the sensitivity of the transducer was increased by 2.5...3 times in relation to the amplitudes of bottom pulses and interference. At the same time, the diagnostics of metal products with thickness 30...50% less than the traditional sensitivity threshold of non-contact device is ensured.