GB1451941A - Magnetic field sensing device - Google Patents

Abstract

1451941 Magnetometers MISHIMA KOSAN CO Ltd 2 Oct 1973 [2 Oct 1972] 46080/73 Heading G1N In a thin film magnetometer a negative feedback signal derived from an output winding associated with the thin film is applied to the thin film to nullify the effects of the magnetic field being measured, and the magnitude and direction of the field being measured is derived from the feedback signal. The thin film may be directly deposited on, wrapped round or a plurality of thin films may be laminated on to a conductor or on to an insulating material coating on the conductor. Alternatively the thin film may be formed on an insulating tube into which the conductor is inserted. An output winding is wrapped round the thin film with its axis parallel to the conductor, the arrangement being such that when an A.C. is applied to the conductor no output voltage is induced across the winding in the absence of an external magnetic field. In the presence of such a magnetic field an assymetric waveform signal 13, 14 as shown in Figs. 3a or 3b is induced in the output winding, the magnitude of the difference in the amplitudes of the positive and negative peaks thereof being indicative of the strength of the magnetic field and the sign of the difference indicative of the direction of the field along the conductive. The induced signal is amplified, shaped and integrated and the integrated signal after inversion is fed back to the thin film in such a manner as to nullify the effect of the external field. The measure of the external field is obtained from the feedback signal. Ambient magnetic fields may be compensated for by feeding an appropriate current to counteract them to a further winding or through an impedance to the output winding. A list of applications of the device are given.