The electromagnetics we use are so-called two-coil systems, the function principle of which is based on induction. These systems are composed of a transmitting and a receiving coil. During the measurement, an alternating current in the transmitting coil generates a so-called primary magnetic field. In conductive interfering bodies, electrical currents are excited by the alternating field, which in turn generate their own (secondary) magnetic field. With the receive coil, the changes in the secondary magnetic field can be registered and thus anomalies can be detected.
With the electromagnetic method, the substrate itself is excited and its reaction is analyzed, so this method is also referred to as an active geophysical method. Since the conductivity of the substrate is investigated with electromagnetics, non-magnetic but conductive disturbance bodies such as infantry ammunition can also be detected.