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1. (WO2001033233) A CLOSED-LOOP MAGNETORESISTIVE CURRENT SENSOR SYSTEM HAVING ACTIVE OFFSET NULLING

Pub. No.:    WO/2001/033233    International Application No.:    PCT/US2000/029443
Publication Date: Fri May 11 01:59:59 CEST 2001 International Filing Date: Fri Oct 27 01:59:59 CEST 2000
IPC: G01R 15/20
Applicants: HONEYWELL INC.
Inventors: SANDQUIST, David, A.
BERNDT, Dale, F.
LENZ, James, E.
Title: A CLOSED-LOOP MAGNETORESISTIVE CURRENT SENSOR SYSTEM HAVING ACTIVE OFFSET NULLING
Abstract:
A magnetoresistive sensor system having resistive elements changing in ohmic value in the presence of a magnetic field of a current being measured. The variant values of the elements are amplified by some electronics that inherently add offset to the resultant values. The elements themselves also add an offset. The output of the electronics is modulated and then buffered as an output. This output is demodulated and integrated. The resultant signal is fed back to the input of the electronics to null out the offsets. The output of the buffer also goes to an inductive coil that is magnetically coupled to the resistive elements to null out the magnetic field from the current being measured. The buffer output indicates the magnitude of the current being measured. An oscillator outputs a signal to actuate the modulator and the demodulator. The oscillator signal also goes to a set/reset circuit for setting and resetting the resistive elements of the magnetoresistive sensor.