  Eddy currents induced in electrically conductive objects can be used to
locate metallic objects as well as to assess the properties of materials
non-destructively without physical contact. This technique is useful for
material identification, such as measuring conductivity and for discriminating
whether a sample is magnetic or non-magnetic. In this study, we carried out
experiments and numerical simulations for the evaluation of conductive objects.
We investigated the frequency dependence of the secondary magnetic field
generated by induced eddy currents when a conductive object is placed in a
primary oscillating magnetic field. According to the electromagnetic theory,
conductive objects have different responses at different frequencies. Using a
table-top setup consisting of a fluxgate magnetometer and a primary coil
generating a magnetic field with frequency up to 1 kHz, we are able to detect
aluminium and steel cylinders using the principle of electromagnetic induction.
The experimental results are compared with numerical simulations and we find
overall a good agreement. This technique enables identification and
characterisation of objects using their electrical conductivity and magnetic
permeability.
