An automated two-dimensional magnetic field scanner-based on Quantum Well Hall effect sensor for non-destructive testing


With greater emphasis placed on asset integrity and materials component lifetime, Non–destructive testing (NDT) systems are becoming more sophisticated in the acquisition and analysis of defects and sample under test properties. Electromagnetic based NDT systems have long become digital repositories for data storage and post-processing, with constant improvement in the techniques underway.

This study presents a desktop electromagnetic NDT system based on Quantum Well Hall Effect sensors [1] that scans magnetic fields in samples to reveal defects in 2D colour maps. An XY platform, with a 340 square millimetre scanning area, is controlled via a LabVIEW program to scan the target area at a resolution of 100µm in both directions. The result of the scan is then changed into colour pixel map and displayed in real time on a host PC as the scanning progresses. Results of DC and AC scanning show that it is possible to detect defects from surface breaking standard Magnetic Particle Inspection Quantitative Quality indicator (QQI) sample, as shown Figure 1, to changes in microstructure of a specimen, for instance, due to welding or mechanical stress. This NDT system yields better results in terms of sensitivity, capability in post data processing and imagery without using hazardous chemicals and consumables.

The scanning QWHE sensors based system has unique advantages in terms of making NDT systems clean and truly non-destructive. Due to its high sensitivity and wide dynamic range, the potential to scan early changes in microstructure of materials is a real possibility.