Abstract: A target identification system for detecting a desired ferrous object concealed beneath a surface is provided for a gradiometer. The system has first and second sensors for detecting a magnetic field at a first and second points above the surface. A device for providing drive signals for the sensors is connected to the sensors, to generate sensor output signals proportional to the magnetic fields sensed by the sensors. The outputs of the sensors are connected to means for generating a difference signal at an output thereof, the difference signal being the difference between the output signals of the sensors and being proportional to the detected gradient of the magnetic field between the first and second points. An interface receives the difference signal for producing an indication signal when said magnetic field has a selected polarity and when the magnitude of the detected magnetic field gradient exceeds a set value.

Abstract: A fluxgate sensor has a coil body defining a bore and an axis. A coil is wound on the coil body around the axis. A ferromagnetic core is located in the bore and extends beyond either end of the coil, to improve the sensitivity of the sensor. The core may be elongate and have a non-circular profile such as a zig zag pattern. In a gradiometer, the core configuration facilitates balancing of two sensors by either radial or axial adjustment of the core.