GRADIENTMETRIC METHOD FOR THE FERROMAGNETIC INCLUSIONS DETECTION

The paper presents a magnetic field gradientmeter meant to detect the very small size ferromagnetic inclusions. The detection of the magnetic field gradient is useful in certain applications permitting to eliminate some disturbing factors and to localize the local inhomogeneities of the magnetic field or certain close field sources. The gradientmeter makes use of two identical magnetic transducers of fluxgate type, connected in opposition, such that the output signal is proportional with the difference of the field from every transducer. The error sources are presented as well as the solutions to reduce them. The main error source in gradient measurement is the difference of sensitivities and the transducers misalignement. The two components of the local magnetic field – the longitudinal and transversal ones – determine the appearance of some error signals. The longitudinal component of the magnetic field applied to the transducer produces a measuring error proportional with its size. The measuring error proportional to the field component normal to the measuring direction can be eliminated by an accurate sensors alignment. The block diagram and the operation principle of the gradientmeter are described. The experimental results reveal the possibility to use this method for the detection of small size ferromagnetic inclusions