Development of an Electronic Instrument for Eddy Current Testing

Abstract

This article presents the development of a portable electronic variable frequency instrument for eddy current testing. Variations in the conductivity, permeability, or physical characteristics of non-ferromagnetic and ferromagnetic materials cause the impedance of the probe (or coil) connected to a Wheatstone bridge circuit to change. Impedance change causes bridge unbalance, which is indicated by analog and digital indicators on the front panel. The main applications of the equipment are: detection of cracks and surface faults in conductive materials, evaluation of the depths of detected discontinuities, classification of these materials through the variation of conductivity, and evaluation of the thickness of non-conductive layers on a conductive basis. Eddy current testing instruments are superior to equipment that does not use electromagnetic principles for the applications described above. The reason is due to the accuracy and ease of carrying out the inspection. The device developed in this work also has the advantage of the circuits simplicity, the low cost of the electronic components, and the ease of finding them in the market for eventual maintenance. Some test results performed are presented. The instrument performed well for the intended applications.