A Rogowski-type current sensor, comprising: a first board supporting a first current sensing coil, the first current sensing coil formed around an opening in the first board, a first compensation wire formed on a first surface of a second board, the first compensation wire formed around an opening in the second board; wherein the first board is attached to the second board such that their respective openings are aligned, the openings being arranged to receive a current carrying conductor, and the boards are arranged such that the first current sensing coil and the compensation wire at least partially overlap; characterised in that the current sensor further comprises: a third board supporting a second current sensing coil, the second current sensing coil being formed around an opening in the third board, and a second compensation wire formed on a second surface of the second board, the second compensation wire formed around an opening in the second board; wherein the third board is attached to the second board such that their respective openings are aligned, the openings are arranged to receive a current carrying conductor, the boards are arranged such that the second current sensing coil and the second compensation wire at least partially overlap, and the first and second current sensing coils are coupled together to produce a differential output; and the first and second compensation wires are coupled to respective ends of the first and second current sensing coils and configured to cancel the effects of interference generated by external fields. a first board supporting a first current sensing coil, the first current sensing coil formed around an opening in the first board, a first compensation wire formed on a first surface of a second board, the first compensation wire formed around an opening in the second board; wherein the first board is attached to the second board such that their respective openings are aligned, the openings being arranged to receive a current carrying conductor, and the boards are arranged such that the first current sensing coil and the compensation wire at least partially overlap; characterised in that the current sensor further comprises: a third board supporting a second current sensing coil, the second current sensing coil being formed around an opening in the third board, and a second compensation wire formed on a second surface of the second board, the second compensation wire formed around an opening in the second board; wherein the third board is attached to the second board such that their respective openings are aligned, the openings are arranged to receive a current carrying conductor, the boards are arranged such that the second current sensing coil and the second compensation wire at least partially overlap, and the first and second current sensing coils are coupled together to produce a differential output; and the first and second compensation wires are coupled to respective ends of the first and second current sensing coils and configured to cancel the effects of interference generated by external fields. a third board supporting a second current sensing coil, the second current sensing coil being formed around an opening in the third board, and a second compensation wire formed on a second surface of the second board, the second compensation wire formed around an opening in the second board; wherein the third board is attached to the second board such that their respective openings are aligned, the openings are arranged to receive a current carrying conductor, the boards are arranged such that the second current sensing coil and the second compensation wire at least partially overlap, and the first and second current sensing coils are coupled together to produce a differential output; and the first and second compensation wires are coupled to respective ends of the first and second current sensing coils and configured to cancel the effects of interference generated by external fields.