The Development Of Digital Eddy Current Testing System

Eddy current testing technology is a kind of nondestructive testing technology, it has arapid development in recent years. Eddy current testing system can quickly realize thedetection of the defects which are on the surface and subsurface of metal conductor.Based on the analysis and argument of the principle of eddy current testing technology, aset of digital eddy current testing system completely is designed. The speed of the system isfive to six meters per minute. It can effectively detect different specification and material ofaluminum parts, and the thickness of the aluminum parts can range from one to threemillimeters, through detecting artificial defects in aluminum rod, it shows that the system isfeasible and has some engineering application value. The main research contents are asfollows:On the basis of the parameter estimation method of orthogonal lock-in amplifier, basedon self-balancing algorithm of a eddy current testing signal parameter estimation is raised, abridge to zero rapidly can be realized. To solve the signal phase angle accurately and quickly,using differential evolution algorithm to fixed-point DSP assembler layer and achieve arctangent function.On the basis of Biot-savart law, the impact of the coil shape and geometric parameterson the performance of eddy current sensor is studied, and it develops the cylindricaldifferential coil and rectangular column differential coil.Using the peak voltage, peak time and zero crossing, an identification method of defectis put forward.Using DDS technology to produce multiple sinusoidal signal, phase sensitive detectionand band-pass filter was adopted to realize parameter estimation of eddy current signal, anddevelop a controller system which is based on TMS320F2812. PC test platform is developedusing LABVIEW, realizing system parameter setting、signal collection、defect identificationand display，through the ribbon diagram and impedance plane diagram display the defect.