Handheld instrument to detect defects in conductive plates with a planar probe

This paper presents a novel low-cost handheld instrument to detect cracks and other defects in a plate of conductive material. The instrument includes a planar eddy-current probe having a giant magnetoresistor (GMR) based sensor, a mouse pointing device that acts as the positioner, a dsPIC that controls the measurement process and that possesses also signal processing capabilities to enhance the accuracy of the system and all the electronic circuitry (power supplies, signal amplification, current generation, analog to signal conversion) necessary to carry out the defect detection. The visualization of the defect can be depicted in real-time on a LCD display or transmitted to a PC. The metrological performance and the effective cost make this handheld device well suited for several applications such as cracks detection at subsurface depths.