Second harmonic magnetic field detection circuit with means to rectify the sensed signal
AssigneeRockwell International Corporation
InventorMelvin H. Rhodes
Life of this patent
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Abstract
A magnetic field sensing circuit using three windings on a magnetic sensor with one winding using a locally generated excitation voltage, a second winding providing an output induced by the excitation voltage and a third winding both providing external magnetic field sense signals and serving as a feedback winding. The induced excitation voltage is used to generate a signal indicative of the flux in the core for the ultimate purpose of logically switching the sense winding so as to rectify it and supply it back to the third winding as a feedback signal for counteracting the flux in the sensor due to the external field being sensed.
Claims7
Magnetic field detection apparatus for use with a magnetic sensor of the type having a magnetic core, an excitation producing winding, an excitation detecting winding, and a magnetic field sensing winding operatively associated with said core, comprising:
- means for supplying a periodic excitation signal to said excitation producing winding to induce a flux in said magnetic core to drive said magnetic core periodically into saturation, to induce a voltage in the excitation detection winding and to enable the magnetic field to be detected to induce a signal onto said sensing winding;
- first means connected to said excitation detecting winding for detecting the direction of the flux produced in said magnetic core by the excitation signal and generating signals indicative thereof;
- second means connected to said excitation detecting winding for detecting the polarity of the induced voltage and when the induced voltage exceeds a predetermined level and generating signals indicative thereof;
- integrating means having an input and an output;
- means connected to the sensing winding and to the signals from said first and second means to rectify the signals induced onto said sensing winding in timed relation with changes in the polarity of the induced excitation voltage and the direction of the excitation signal induced flux, and supplying the rectified signals to the input of said integrating means;
- and feedback means connected between the output of said integrating means and said sensing winding for supplying feedback signals to said sensing winding to substantially cancel the effect of flux generated in said magnetic core by the magnetic field to be detected.
A magnetic field detector, comprising:
- a magnetic sensor having a magnetically saturable core;
- means for applying a periodic excitation signal to said core to produce an excitation flux in said core and to drive said core periodically into saturation;
- means for generating an induced voltage in response to said excitation flux;
- means responsive to said induced voltage for detecting the direction of the excitation produced flux in said core and the polarity of the induced voltage and when the induced voltage exceeds a predetermined level, and generating signals in response thereto;
- means for sensing a signal in said core induced therein by a magnetic field to be detected between the periodic saturation of said core;
- and means connected to said means for sensing and said means for detecting for rectifying the sensed signal in timed relation with changes of the detected excitation produced flux and polarity of the induced voltage from said detecting means, to produce a phase detected output signal.
Dependencies are inferred from the claim text.