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Magnetoresistive Current Sensor

IP.com Disclosure Number: IPCOM000081792D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Bowen, AJ: AUTHOR [+4]

Abstract

Fig. 1 shows a magnetoresistive circuit 10 for noncontact sensing of excessive currents in a conductor. Four approximately equal-valued magnetoresistors (MRs) 11-14 are arranged in a bridge circuit, which is balanced by trimming resistor 15 when no current is flowing in an adjacent conductor. A supply voltage is coupled to the junction of MRs 11 and 14, while the junction between MRs 12 and 13 is grounded. The junctions between MRs 11 and 12, and between MRs 13 and 14, are coupled to a conventional discriminator 16. The magnetic field from-the adjacent conductor is made to change the resistances of MRs 11 and 13 in the same direction, thereby unbalancing the bridge. When the bridge is sufficiently unbalanced, discriminator output 17 produces an overcurrent signal.

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Magnetoresistive Current Sensor

Fig. 1 shows a magnetoresistive circuit 10 for noncontact sensing of excessive currents in a conductor. Four approximately equal-valued magnetoresistors (MRs) 11-14 are arranged in a bridge circuit, which is balanced by trimming resistor 15 when no current is flowing in an adjacent conductor. A supply voltage is coupled to the junction of MRs 11 and 14, while the junction between MRs 12 and 13 is grounded. The junctions between MRs 11 and 12, and between MRs 13 and 14, are coupled to a conventional discriminator 16. The magnetic field from-the adjacent conductor is made to change the resistances of MRs 11 and 13 in the same direction, thereby unbalancing the bridge. When the bridge is sufficiently unbalanced, discriminator output 17 produces an overcurrent signal.

Fig. 2 illustrates the physical placement of magnetoresistors 11-14 with relation to a current-carrying conductor 20. Immediately overlying conductor 20 is a thin layer 21 of alumina or other suitable electrically insulating material. Two magnetizable legs 22, such as PERMALLOY* layers, overlie insulator 21 to provide the required flux path through MRs 11 and 13.

Fig. 3 is a cross section of an integrated module for sensing currents in a conductor 20 on a printed-circuit board 30. Insulator 21, legs 22 and MR elements 11-14 are covered with a second insulating layer 31, and are then mounted on the underside of a conventional integrated circuit module substrate
32. The upp...