[5A3] Real-time magnetic imaging of paramagnetic and ferromagnetic materials using time-frequency division-multiplexed quantum well Hall-effect sensor arrays
R Murshudov, J Sexton, A Lindley, N Sathappan and M Missous
University of Manchester, UK
Quantum well Hall-effect (QWHE) sensors are highly sensitive linear magnetic flux density sensors that are well suited for electromagnetic NDT imaging. A number of systems have previously been developed using both scanned single sensors and arrays. The work described here explores a new method of combining these sensors through simultaneous time and frequency division multiplexing. This is achieved by biasing each row of sensors in an array at a unique frequency, shifting their measured signals to the sum and difference of the magnetic and relative biasing frequencies. The signals can then be summed together and the magnetic field seen from each sensor can be extracted through an FFT procedure, isolating only the relevant frequencies. This method has been explored through the development of a 16 × 16 sensor array with a coil surrounding the sensors. The system developed is capable of both MFL imaging and, to a lesser extent, ECT imaging. The inclusion of FDM channels allows the system to perform real-time imaging at up to 20 fps, including image processing.
