Low-frequency electromagnetic scattering from conductive and permeable bodies is the main principle of detection devices. To be able to classify the objects in the base material, a fast forward model based on the dipolar approximation was developed and verified at high frequency and single targets. For efficient model inversion for nearby targets, the superposition principle is required. To check the general validity of this principle, the dipole model was compared with a validated 3-D finite-element method model for a wider frequency range. For the investigated targets, the coupling effect can be neglected only for high-frequency range.