The removal of Explosive Remnants of War (ERW) such as Anti-personnel (AP) mines is a problem that affects countries and communities as a lasting legacy after many armed conflicts around the world, with more than an estimated 110 million landmines still alive. The mines can still indiscriminately injure or kill civilians for decades after the conflicts or wars end. The Ottawa Mine Ban Treaty in 1997 has banned the use of mines because of their significant effect on communities and set targets for the decontamination of mine-affected areas. Current metal detectors used for humanitarian demining struggle with a high False Alarm Rate (FAR) during the landmine clearance operations, and this research project is aiming to characterise a measurement system to identify specific metal or landmines to reduce FARs with the better demining efficiency and the operation cost. This thesis considers the electromagnetic polarizability tensor as a concise representation of a metal object in an AC magnetic field. A measurement system has been researched and developed to measure the spectroscopic characteristics of the polarizability tensor for metal objects of the type and size that would be relevant for humanitarian demining. To verify the operation of the system, simulation and experimental results of a set of US coinage are presented and compared. As part of the development of the tensor measuring system, an optimised coil configuration was proposed, and the comprehensive description of the coil design with corresponding manufacturing process was provided. AP landmines up to 13 cm diameter can fit into this coil configuration and the magnetic fields of the transmitter and receiver coils are substantially uniform which lead to better measurement results of the tested objects. Both analytical calculation and experimental measurement validated the suitableness of the coil array. The methodology of determining the coil arrangements has assisted the future coil configuration. Finally, a new method of modelling metal detector applications in the time domain using a pulsed eddy current metal detection system is proposed and presented. This simulation has been validated by the corresponding modelling method in frequency domain, and the results showed the method is capable of simulating landmine detection systems with a much faster simulation speed.