Abstract: A device for detecting random objects that are being carried inside a container includes an excitation coil and a sensing coil with a gap therebetween. When the construction of the container includes a conducting loop, the container is positioned on a path between the two coils, with the plane of the loop substantially perpendicular to the path. The excitation coil is then activated to generate a magnetic field that is directed along the path. This magnetic field has both a sinusoidal component and a cosinusoidal component. Importantly, the cosinusoidal component is adjusted to match a characteristic dimension of the loop, to thereby cause zero mutual inductance with the loop in the magnetic field. On the other hand, conducting objects inside the loop will cause inductance perturbations in the magnetic field which can be detected to establish the presence of the objects in the container.