One aspect of the disclosure provides apparatus for detecting an object. The apparatus comprises a sense coil. The apparatus comprises a processor configured to determine an amount of change in a reactance of the sense coil from a previous reactance value for the sense coil. The processor is configured to determine an amount of change in a resistance of the sense coil from a previous resistance value for the sense coil. The processor is configured to determine a presence of the object based on a relationship between the amount of change in the reactance of the sense coil and the amount of change in the resistance of the sense coil. The processor performs an inverse tangent operation on a quotient of the amount of change in the reactance of the sense coil divided by the amount of change in the resistance of the sense coil.