An investigation into the detection and identification of buried metal objects

Abstract

The operation of a detector used to locate buried metal objects is dependent on the generation of a magnetic field. This thesis examines methods used to generate a suitable magnetic field and the distorting effect caused by the presence of a nearby metal object. In addition to being generated, the magnetic field must also be monitored so the distortion can be measured. The effect of the change in magnetic field shape when the distortion is caused by different types of metal objects, varying in shape, size and metallic composition, is measured and analysed both when the objects are detected in free space or buried under various ground conditions.
The thesis describes the development of hardware used to create and measure the magnetic field. Analogue and digital design and signal processing techniques are employed to provide information relating to variation in the magnetic field. The implementation of a microcontroller and appropriate software is used to create a system able to detect and identify a buried object, whilst ignoring distortion caused to the magnetic field by other external influences, for example conductive ground conditions.
The work has been undertaken in collaboration with Viking Metal Detectors and has been used
to develop a new range of metal detectors for production. This range of metal detectors
incorporates advanced features previously unavailable on detectors in the Viking range, which
make the detectors attractive to customers. The design for manufacture has imposed various
restrictions on the design. These restrictions include total component cost and physical
dimensions of the final design, along with consideration of how repeatable the design is without
the need for excessive calibration in the factory.