Eddy current enhancement for EMATs

S. B. Palmer; X. Jian; S. Dixon

doi:10.1117/12.715162

10 April 2007 Eddy current enhancement for EMATs

S. B. Palmer, X. Jian, S. Dixon

Proceedings Volume 6530, Sensor Systems and Networks: Phenomena, Technology, and Applications for NDE and Health Monitoring 2007; 653013 (2007) https://doi.org/10.1117/12.715162
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2007, San Diego, California, United States

Abstract

When an electromagnetic acoustic transducer (EMAT) is used to generate ultrasound in an electrically conducting sample, eddy currents are generated in the sample's skin depth as the first stage in transduction. The resultant acoustic wave amplitude is proportional to the amplitude of this eddy current, and so anything that we can do to increase the eddy current will lead to the generation of larger amplitude ultrasonic waves. In eddy current testing, wire coils are often wound onto a ferrite core to increase the generated eddy current, with the effect that inductance of the coil increases greatly. When we are dealing with an EMAT, any increase in the coil inductance is usually unacceptable as it leads to a reduction in the amplitude of a given frequency of eddy current from a limited voltage source. This is particularly relevant where current arises from capacitor discharge, as is typically used in EMAT driver current circuitry. We present a method for electromagnetic acoustic transduction where ferrite is used to increase eddy current amplitude, without significantly increasing coil inductance or changing the frequency content of the eddy current or the generated acoustic wave.

Citation Download Citation

S. B. Palmer, X. Jian, and S. Dixon "Eddy current enhancement for EMATs", Proc. SPIE 6530, Sensor Systems and Networks: Phenomena, Technology, and Applications for NDE and Health Monitoring 2007, 653013 (10 April 2007); https://doi.org/10.1117/12.715162

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