A matrix eddy current transducer using surface mount inductors

Abstract

The paper reports the results of testing the by us developed detachable matrix eddy current transducer designed to detect discontinuities on the surface of thin (tens of micrometers) inspected conductive objects, in particular, electrically conductive coatings of aircraft fuel tanks. The transducer can be useful for other applications, e.g. magnetic tomography. The device consists of 32 miniature inductors series-produced by the electronic industry and allowing you to cover an 80 mm wide band with a 2.5 mm wide test path. The use of inductance coils as magnetic receivers is due to the small thickness of the coatings to be tested. With this thickness, testing is effective only at an operating frequency of hundreds of kilohertz. Otherwise, the sounding magnetic field will not be reflected from the item under inspection. At these frequencies, modern microelectronic magnetic field sensors are inoperable. Scanning was carried out at an operating frequency of about 100 kHz. The scan results were displayed on the monitor of the personal computer. By selecting the operating frequency, the information content of the examination can be increased. The transducer detects the pattern of the copper foil of glass textolite both on the foil side and on the reverse side when the material thickness is 1.5 mm. The foil pattern is also detected through an aluminum foil gasket with a thickness of more than 10 μm. Steel plate surface discontinuities have also been detected, and this can be of interest for in-tube flaw detection. Cheap serial inductors designed for surface mounting take up a minimum of space on the printed circuit board and provide higher inspection resolution compared to coils obtained by printing. The scanning step (2.5 mm) achieved in this device is unique to matrix eddy current transducers. The study demonstrates the practicality and efficiency of using serial miniature inductors in eddy current testing.