Portable eddy current NDT instrument using two different implementations

This paper describes two implementations towards the development of a portable low-cost system capable of detecting defects on metallic surfaces through non-destructive testing. The defect detection is made via an eddy-current probe using a giant magnetoresistor (GMR) sensor. Both approaches use a computer mouse as a position device to locate the probe and deliver a graphical representation to facilitate the defect analysis. One implementation is based on a planar excitation coil, embedded power supplies and the signal processing is made by a dsPIC. The dsPIC controls the signal generation, the measurement procedure and the communication. The defect visualisation can be made in a LCD in real-time or transmitted to a PC. The other implementation uses a low-cost analog system to reduce the data processing required to detect the surface defects. The controller is a PIC microcontroller that does all the analog/digital conversions and transmits the defect data to a PC via wireless channel.