Non-Contact Thickness Gauge for Conductive Materials Using HTS SQUID System

Eddy current testing using high-TC superconductive (HTS) superconducting quantum interference devices (SQUID), was developed to realize non-contact thickness gauge measurement of conductive materials, due to their high-sensitivity to magnetic fields generated by eddy currents. A HTS SQUID pulsed eddy current system with Fourier transform analysis is proposed and demonstrated. Aluminum plates (10 x 10 mm) with thicknesses in the range of 1 to 10 mm were used as test samples. The intrinsic responses G _A(f) of the samples were successfully extracted. The slopes of these responses were estimated by linear fitting, and plotted as a function of sample thickness. The G _A(f) slopes decrease with increasing thickness of the test samples. The analysed data suggests that this system can be used as a non-contact thickness gauge for conductive materials.