A Quantum Well Hall Effect Sensor Based Handheld Magnetic Scanner with Programmable Electromagnetic Coil for Non-Destructive Testing of Ferromagnetic and Non-Ferromagnetic Materials
A handheld magnetic scanner using an array of highly sensitive Quantum Well Hall Effect (QWHE) sensors has been designed and fabricated. The new transducer comprises a programmable electromagnet coil for AC and DC magnetic field illumination and QWHE sensor arrays oriented orthogonally to capture 2D magnetic field variation in defective materials in a single pass, which is not possible in competing Non-Destructive (NDT) systems. Usually separate NDT techniques like Alternating Current Field Measurement (ACFM) and Magnetic Flux Leakage (MFL) are now combined in a single unit that makes it possible to perform testing on both magnetic and non-magnetic materials. Although there will always be limitations to designs, there still is room to improve the accuracy and versatile use of electromagnetic based defect testing systems, the use of QWHE sensors being a case in point. The reported prototype system uses eight of these sensors in an array, where two such arrays are aligned orthogonally to capture X and Y components of the magnetic field and also to do depth profiling by changing the frequency of scanning. The Magnetic fields are generated using dual coils aligned in parallel and electrically in phase. The magnetic field creates an Eddy current across a possible defect, which distorts the Eddy current producing change in the measured back magnetic field thus revealing the existence of the defect. Computational simulation and experimental tests are performed on both ferromagnetic and non-ferromagnetic defective samples. Data is processed in real time using a USB connection onto a PC to reveal the extent of the defect in 2D and preliminary results show promising potential for this new NDT device. Its compactness and multidimensional accessibility meant that the new system presents a strong opportunity to replace bulky systems such as Magnetic Particle Inspection (MPI).
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