Magnetic induction tomography measurement system based on a fixed point DSP module

Magnetic Induction Tomography (MIT) is a non-contact method for imaging the passive electrical properties of objects. An array of excitation coils are employed to induce eddy currents within objects placed within the MIT system and an array of detector coils are then used to detect the resulting perturbation of the primary magnetic fields produced by the eddy currents. Measurement of both the detected signal magnitude and phase must be made. Direct digitization of the detected signal using PXI-based instrumentation and the use of a FFT-based signal measurement algorithm has been employed in recently developed MIT systems. One of the major limitations of employing the PXI system configuration is the speed of the measurement, which is limited by the data transferred rate between the PXI and the PC and the time needed for digital signal processing of acquired data on the PC workstation. Both processes lengthen the overall measurements time of the Cardiff Mk2 MIT system for instance to up to 75ms for a signal acquisition length of 8.5ms at the acquisition rate of 60MS/s. This paper proposes a MIT signal measurement module based on a dual-core fixed point DSP processor (Analog Devices Blackfin BF 561) to overcome some of the above speed limitations. The design concept is described and the results of preliminary measurements of performance are given.