Self-compensating magnetoelastic torque sensor system

A system for canceling any external interfering magnetic fields and temperature offset effects for a magnetic field sensing arrangement, comprising:

• a first sensor proximate to a magnetoelastic transducer zone;
• a second sensor outside of said magnetoelastic transducer zone or a portion of said zone with a lower field strength than that of said first sensor;
• and
• a signal processing system, wherein said system is operable to measure the magnetic field with said first and second sensors, operable to determine the magnetic field from said first and second sensors, operable to determine any external interfering magnetic field or temperature offset by processing the magnetic field detected from said second sensor, operable to subtract the processed magnetic field of said second sensor from that of said first sensor, and operable to convert the final magnetic field into an output signal representing the torque about a longitudinal axis of a rotatable shaft member;
• wherein said first sensor is an active field sensor and said second sensor is a passive field sensor, wherein there is at least one passive field sensor on one side of said active field sensor.

A method for matching the sensitivity of multiple magnetic field sensors operably associated with a magnetoelastic transducer, comprising:

• positioning two or more magnetic field sensors in line with each other proximate to said magnetoelastic transducer, wherein said magnetic field sensors are operably associated with a signal processing system operable to generate an output signal representing the torque about a longitudinal axis of a rotatable shaft member;
• placing said magnetic field sensors inside a uniform magnetic field;
• determining a magnetic field from each of said magnetic field sensors;
• and
• matching an output from each of said magnetic field sensors to make their outputs identical:
• wherein said magnetic field sensors include a first sensor that is an active field sensor and a second sensor that is a passive field sensor, wherein there is at least one passive field sensor on one side of said active field sensor.