A Quantum Well Hall Effect Magnetovision System for Non-Destructive Testing

A novel magnetovision system was developed based on miniature, highly sensitive Quantum Well Hall Effect (QWHE) Sensors. This system consists of a handheld, portable 1616 QWHE sensors array, and an adjustable electromagnet, which can generate both DC and AC magnetic fields. The system has high spatial resolution due to the use of the small size sensors (QWHE) compared to conventional coils. By using a superheterodyne technique, magnetic fields in the range of nano to micro Tesla can be detected both for DC and AC operations, respectively. In DC measurements, this system can also be used as a MFL testing equipment, which can provide 2 dimensional graphical images results similar to MPI but without its inherent drawbacks. By using low frequency magnetic fields, non-magnetic materials such as aluminum, copper and stainless steels can also be examined allowing for deeper defects below the surface to be detected. By varying the frequency of the excitation magnetic field, different skin depth can be accessed and therefore the full thickness of the materials can be tested leading to 3 dimensional visualization of the positions and sizes of the defects. Finally, the system can be used in multiple sampling measurements to give better signal to noise ratios and in real time measurements for fast scan speed requirements.