Time domain deconvolution approach relying on Galois sequences

Design/methodology/approach - The method is based on the time-domain analysis of the '' defect response '' and joins the PEC approach with the exploitation of the peculiar auto-correlation properties of the Galois sequences. The procedure, relying on the deconvolution of Galois sequences, greatly improves the signal to noise ratio (SNR) and thus the operating depth. De-convolving even short Galois sequences allows one to investigate at depth ranges larger than those allowed by the conventional pulsed excitation techniques. Findings - The technique has been tested on a benchmark and compared with numerical simulations. The experimental results showed that the SNR and the detection depth range have been significantly improved. Research limitations/implications - Some limitations of the measuring set up were evidenced requiring a new measuring apparatus if explorations at larger depths are of interest: the 0.1 per cent impedance differences among the four coils in the bridge, although limited by an accurate construction, resulted in a limitation of the measuring system in DSP procedure adopted to null the background signal: different probe configurations must be pursued in order to allow further improvements in the deep defect detection. Originality/value - For the first time the peculiar Galois sequences excitation was applied in a PEC system. By using these inputs the signal energy was significantly enhanced, allowing one to reconstruct by the deconvolution process the crack signatures.