Electromagnetic inductance tomography (EMT): sensor, electronics and image reconstruction algorithm for a system with a rotatable parallel excitation field

The main features and principle of operation of an electromagnetic inductance tomography system are described. The system can image the distribution of electrically conducting and/or magnetically permeable materials and is analogous to the other electrical tomography systems which measure capacitance or resistance. The paper presents a nonintrusive system with a rotatable parallel uniform excitation magnetic field which improves the detectability at the centre of the object space with respect to that near the periphery. The sensor construction, electronics design and image reconstruction are described. A novel electronic compensation scheme is used to condition the output signals from the sensor. This scheme subtracts the empty space background field measurements and consequently increases the overall dynamic range of the data acquisition system. An image reconstruction technique based on a correlation method is described and some images are presented