Detection and characterisation of conductive objects using electromagnetic induction and a fluxgate magnetometer

TL;DR

This paper demonstrates a method for detecting and characterizing conductive objects by measuring their electromagnetic response at various frequencies using a fluxgate magnetometer, enabling material identification without contact.

Contribution

The study combines experimental and numerical approaches to evaluate conductive objects' electromagnetic responses, advancing non-destructive material identification techniques.

Findings

Successful detection of aluminium and steel cylinders

Good agreement between experiments and simulations

Frequency-dependent response enables material discrimination

Abstract

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.