Examination of the junctures of aluminium and dielectric structures using subminiature eddy-current transducers

The article presents the structure of a subminiature eddy-current transducer of a transformer type, which is based on the pyramid-shaped core providing the localization of the magnetic field on the area of 2500 μm². It also describes the major transducer parameters, which provide such localization of the magnetic field. The article describes the structure of the measuring system and the measurement procedure, which allows determining the thickness of different objects depending on the signal. The measuring system includes two subminiaturized eddy-current transducers controlled by software. The output signal of the transducers is processed in the hardware filtration systems. The article contains data demonstrating dependency of the amplitude part of the signal on the different thickness of objects, and states the objects experimentally determined size limits that precondition the practicability of these measurements. Such objects as conductive coatings, laminated structures (metal-polyethylene), solid conductive objects (aluminium) and non-conductive dielectric coatings were examined. The article demonstrates the change of the signal amplitude of the eddy-current transducer depending on the type of the monitored material. The pattern of this change allows determining a type of the studying object and its thickness on a small area of the monitored item. (paper)