Abstract: A direct current of high intensity having alternating current components superposed thereon is flowing in a conductor 1 through a magnetic circuit 5, 6. Two measuring coils 7, 8 are arranged inside opposite air-gaps of the magnetic circuit and are connected in an electric measuring circuit in series with each other and in parallel to voltage dividers 12, 13 and 14, 15. The alternating current components induce voltages in the coils 7 and 8 which add up, the sum thereof appearing across the series-connection of resistors 13, 15. This voltage is integrated by an integrating circuit 10 and then filtered in a band-pass filter 11. The magnetic circuit 5, 6 is screened by lateral screening members 30, 31 so that the remaining field lines of a lateral parasitic magnetic field produce in the magnetic circuit flux portions which are approximately equal and which are added to the useful flux in one air-gap and are substracted from the useful flux in the other air-gap.

Abstract: A sensor of the type comprising a magnetic circuit coupled to the lead, wherein circulates the current to be measured and presenting an airgap wherein is arranged a Hall cell (3) and coupled to a compensation coil (5) supplied, as well as the Hall cell, by a unipolar current source (V.sub.+, earth), comprises a four-branch bridge supply circuit wherein the coil (5) is connected to form a diagonal. The current source and a measurement resistor (R) are mounted in series with said bridge circuit. The variable conduction elements (8, 9, 15, 16) are mounted in the four branches of the bridge and are so controlled as to cause a make-up current to circulate in the coil (5), in one direction or the other, as a function of the residual flow direction indicated by the Hall cell (3), through two respective opposite branches of the bridge circuit. The other two opposite branches being non-conductive.

Abstract: The magnetic circuit (1) is made in a single piece or consists of a stack of identically-shaped sheets. The height (H) of the air gap (2) is greater than the thickness (E) of a coil (5), enabling said coil to be inserted through the air gap. This structure is easily assembled during the mass production of current sensors which use such circuits.

Abstract: A current measuring device includes first and second current transformers, having each a magnetic core, a primary conductor or winding and a secondary winding coupled with the magnetic core, the primary windings or conductors being connected to carry the current to be measured. The secondary windings of the first and second transformers have an equal number of turns and are connected in series with each other, and arranged so that the currents induced in the secondary windings by the current to be measured flow in the same direction. A current generator has an output connected to the secondary winding of the first current transformer for feeding to the same a current comprising a magnetizing current component capable of driving the corresponding core, alternately, in opposite states of saturation.