Magnetic sensor with electromagnetic radiation compensation

A measurement system for magnetic fields and electric currents uses a single-core fluxgate device 70 driven with a radio frequency excitation source 72 and is provided with a means 78 to indicate saturation of the core of the sensor. A means is provided for detecting overload of the sensor as the core approaches continuous saturation using a pair of demodulators 73, 74 and a comparator 77. The demodulators may be envelope detectors. Saturation is thus determined by monitoring the time averaged impedance of the core, and an indication is given when the core becomes continuously saturated. This prevents a large magnetic field being erroneously determined to be a zero field.