Device for detecting magnetisable material in buildings

The invention relates to a device for detecting magnetisable material (5, 6) in a building (4). The device contains a scanning head (1) which has, for example, a permanent magnet (28) for introducing a magnetic field into the building (4) and two field plates (30, 31), which are adjacently arranged on only one pole face of the permanent magnet (28) and which are connected to one another in a differentiating circuit and measure the magnetic field of the permanent magnet (28) disturbed by the magnetisable material. The differential measurement values supplied by the field plate pairs at respective positions are used for forming a differential measurement signal from which, after differentiation, the position of the magnetisable material in the building is determined. The position of the magnetisable material (5, 6) within the building (4) can be imaged on a monitor (7) of an evaluating unit (3).