Apparatus and method for forming one or more magnetic field gradients through a straight conductor

Magnetic field gradients are used e.g., for potential-free current measurement without voluminous ferrite cores in order to minimise the influence of homogenous external interference fields on the measurement. So far, they have been provided mainly through U-shaped primary current conductors. The aim of the invention is to make it unnecessary to guide high currents through U-shaped current conductors, this being costly, and to provide a device and a method for creating one or more magnetic field gradients through a straight conductor. To this end, a primary current conductor (3) which is straight at the point where the magnetic field is measured has a recess or groove or slot (8) for creating a magnetic field gradient. Inside or in the area surrounding said recess, the field lines (7) take a course that enables one or more gradiometers or an arrangement of absolute field measurement devices (1) to be positioned in such a way that the influences of especially homogenous interference fields on the measurements are successfully minimised using simple mathematical methods such as subtraction.