Magnetic sensor with electromagnetic radiation compensation

A magnetic sensor with integral electromagnetic radiation compensation coils. The invention provides a high sensitivity and wide bandwidth measurement system for magnetic fields and electric currents utilising a simple magneto-inductive sensor, such as a single-core fluxgate device, comprising a sensing coil 13 and a core 15, driven with a radio frequency excitation current in combination with a separate compensation coil 14 driven with a related alternating current of appropriate magnitude and phase such that external electro-magnetic fields emitted by the system are minimised. Means is also provided for detecting overload of the sensor as the core approaches continuous saturation and for minimising any deleterious effects of the ohmic resistance of the sensor coil on the effectiveness of the flux nulling feedback system.