Evaluation of portable ECT instruments with positioning capability

► Probes with a giant magnetoresistance (GMR) as the magnetic field sensor. ► Raw data digitally processed architecture versus analog signal processing. ► Incorporated positioning system. ► Very large frequency range (10Hz–1MHz). ► Subsurface defects detection capability. In this paper two different low-cost eddy current testing (ECT) systems used in detecting and measuring defects in conductive surfaces are evaluated and its performance compared with a commercial equipment. Both developed systems include a probe with a giant magnetoresistance (GMR) as the magnetic field sensor and a computer mouse pointer as the positioning system. This configuration, despite its low cost, allows better performances than commercial equipments because deeper defects can be detected due to the higher sensitivity of the GMR sensor, which is constant in a very large frequency range (10Hz–1MHz), but also because a precisely located graphical representation of the defect is delivered to the user due to the incorporated positioning system. Although having the same goal, both developed ECT system implementations differ on their architectures and signal processing algorithms. One system is based on a digital signal processor (DSP) where raw data is digitally processed and the other system uses analog circuits to process the acquired signals. This paper includes a detailed description of each implementation, the obtained results and a performance comparison with commercial equipment.