360 degree shaft angle sensing and remote indicating system using a two-axis magnetoresistive microcircuit

Apparatus for sensing the angular position of a first rotor mounted for 360 degrees of rotation about a first axis, the apparatus comprising:

• a pair of stationary magnetoresistive Wheatstone bridge sensors;
• permanent magnet means connected for rotation with the rotor and positioned to alter the resistance of the sensors according to associated periodic sinusoidal functions as the rotor rotates through 360 degrees of rotation;
• first circuit means for supplying an input voltage to the sensors, said input voltage resulting in a pair of periodic output voltages associated with respective ones of said periodic functions;
• second circuit means for conditioning said output voltages to produce a pair of associated conditioned voltage signals proportional to the periodic sine and cosine of the rotor angle and having equal peak amplitudes;
• and
• means for indicating the rotor angle through 360 degrees of rotation characterized by formulation of the arctangent of the ratio of said conditioned voltage signals over the entire 360 degrees of rotation.

Apparatus for sensing the angular position of a rotatable shaft mounted for rotation through 360 degrees of rotation about a first axis, the apparatus comprising:

• a pair of magnetoresistive Wheatstone bridge sensors having magnetically sensitive axes oriented at right angles to each other and to said axis of rotation;
• a two-pole magnet mounted for rotation about said axis with the shaft, said magnet being sized and positioned to generate a non-saturating magnetic field of substantially uniform intensity across said sensors;
• means for shielding the sensors from external magnetic sources;
• first circuit means for supplying an input voltage to the sensors, said input voltage resulting in a pair of periodic output voltages associated with respective ones of said sensors;
• second circuit means for conditioning the output voltage from said sensors to produce a pair of conditioned voltage signals proportional to the periodic sine and cosine of the shaft angle and having equal peak amplitudes;
• and
• means for indicating the shaft angle formulated from the arctangent of the ratio of said conditioned voltage signals, said indicating means including one of electromechanical means for providing a visual indication of the shaft angle and microprocessor means for providing a digital representation of the shaft angle.

Apparatus for sensing and indicating the angular position of a shaft mounted for 360 degrees of rotation, the apparatus comprising:

• a pair of magnetoresistive sensors;
• a magnet connected for rotation with the shaft and positioned to alter the resistance of the sensors according to associated periodic sinusoidal functions as the rotor rotates through 360 degrees of rotation;
• a magnetic shield encasing the sensors to shield the sensors from external magnetic interference effects;
• a magnetic shunt connected for rotation with the shaft and positioned in the shield to assist in generating a non-saturating magnetic field of substantially uniform intensity across the sensors as the shaft rotates;
• an input voltage source connected to the sensors, the input voltage resulting in a pair of periodic sensor output voltages associated with respective ones of said periodic resistance functions;
• a signal conditioning circuit adapted to condition said output voltages to produce a pair of associated conditioned output voltage signals of equal peak amplitude and proportional to the periodic sine and cosine of the shaft angle;
• and
• an angle position indicator responsive to the magnitude of said conditioned output voltages and operative to indicate the angular position of the shaft therefrom.

Apparatus for sensing and indicating the angular position of a shaft mounted for 360 degrees of rotation about a first axis, the apparatus comprising:

• a pair of magnetoresistive sensors;
• a magnet connected for rotation with the shaft and positioned to alter the resistance of the sensors according to associated periodic sinusoidal functions as the rotor rotates through 360 degrees of rotation;
• an input voltage source connected to the sensors, the input voltage resulting in a pair of periodic sensor output voltages associated with respective ones of said periodic resistance functions;
• a signal conditioning circuit adapted to condition said output voltages to produce a pair of associated conditioned output voltage signals of equal peak amplitude and proportional to the periodic sine and cosine of the shaft angle;
• and
• an air core meter including (i) a pair of coils receiving respective ones of said conditioned output voltage signals, and (ii) a rotor mounted for rotation about a second axis remote from the first axis, the rotor being rotationally responsive to the electromagnetic field developed in the coils from said conditioned voltage signals for visually indicating the angular position of the shaft.