Electric current sensing device of the magnetic field compensation type

Claim 1

An electric current sensing device for measuring an electric current flowing in a primary conductor and/or for producing an image thereof, comprising: magnetic circuit means capable of being magnetically coupled with said primary conductor, said magnetic circuit means comprising at least one air gap and at least one measuring coil magnetically coupled with said magnetic circuit means, said measuring coil comprising first and second ends, said first and second ends comprising first and second nodes; magnetic field detector means disposed in said air gap; electric current control means including a current source and a current control circuit, said current control circuit having first and second current supply terminals, said current control circuit further having a control input and a measuring current supply output, said control input being connected to said magnetic field detector means and said measuring current supply output being connected to said first node of said measuring coil; and electric current output means, comprising at least one of measuring means and display means, connected to said second node of said measuring coil; a printed circuit board; said electric current control circuit comprising a printed circuit formed on said printed circuit board; said measuring coil, said magnetic field detector means, said current output means, and said current source being connected to said printed circuit; said printed circuit having first conductive portions directly connected to said first node, and second conductive portions directly connected to said control input; said first and second portions being arranged at a substantial distance from each other; said printed circuit board having an aperture for receiving said primary conductor, said aperture being surrounded on at least one face of said printed circuit board, along the major part of the perimeter of said aperture, by conductive portions at a constant potential.