Forward Problem Modelling of a Planar EMT Sensor Array for Imaging Ferromagnetic Conductors Embedded in a Non-conducting Medium

Y. Bissessur (Mauritius) and A.J. Peyton (UK)


Planar electromagnetic inductance tomography (EMT), forward problem.


Planar electromagnetic inductance tomography (EMT) may be used for non-invasive imaging of ferromagnetic conductors embedded in a non-conducting medium. An example is the imaging of steel reinforcement in concrete structures from electromagnetic measurements on one surface only. Some preliminary work had been reported on the feasibility of using a planar array of sensor coils to image steel bars in a concrete structure. An important aspect of this type of imaging is the solution of the forward problem, that is the modelling of the sensor array for a known distribution of reinforcement bars. This paper presents an efficient method for solving the forward problem in the case when a planar array of sensor coils is used to image cylindrical ferromagnetic conductors embedded in a non-conducting medium. The formulation is based on the excitation of the object space by a mid range frequency magnetic field. The background field is calculated using an FEM-based software package. The field scattering is modelled by both a surface current and a surface magnetisation on the conductors, and these in turn are used to calculate impedance changes of coil pairs on the sensor array. A comparison is made with measurements on a prototype planar EMT sensor array.

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