Abstract: A differential sensor for the detection of anomalies in electrically conductive materials has a permanent magnet, a first coil with one or more first windings, which run around the permanent magnet and define a first coil axis, and a second coil with one or more second windings, which run around the permanent magnet and define a second coil axis, which runs transversely, in particular perpendicularly, to the first coil axis. Preferably, a third coil, oriented perpendicularly thereto, is also provided. Components of changes in the magnetic flux can be sensed separately for multiple spatial directions and evaluated. The sensor is part of an inspection system, which includes the sensor and an evaluation device, which is configured for sensing separately for each coil electrical voltages induced in the windings of the coils of the differential sensor, or signals derived therefrom, and correlating them by applying at least one evaluation method.