Abstract: A transformer for measuring current flowing through a conductor includes a U-shaped housing which is adapted to be received about the conductor. A closure member is secured by a sliding hinge assembly to one distal end of the housing, and is adapted to be latched between the distal ends. Within the housing a plurality a U-shaped core laminations are disposed in adjacent laminated groups. The closure member includes a plurality of laminated groups which are disposed to interleave with the distal ends of the U-shaped laminations to form a continuous magnetic circuit about the conductor. Equal secondary windings about the legs of the U-shaped laminations are connected in series to counteract any proximity effect of the conductor within the transformer.