Single Coil Metal Detector and Classifier Based on Phase Measurement

Metal detection is present in more daily life applications than one can imagine. This is due to the fact metal detectors (MD) are simple and effective sensing instruments. These devices are mostly based on Ampere's and Faraday's induction laws and the majority only indicates the presence of a metal object or target, not differentiating its type. In this paper, we present a different approach to metal detection and classification. Our MD consists of a single copper coil and simple electronic components. The method is based on the fact that when a metal object approaches an air core coil, the surrounding magnetic permeability is affected. This changes the coil inductance and, consequently, its inductive reactance. Such a phenomenon can be used to detect and classify ferrous and non-ferrous metal objects based on the phase measurements. Preliminary results show that such an approach allows for a simple, cheap and accessible electronic design of a metal detector capable of detecting and classifying ferrous and non-ferrous materials.