Magnetic Sensor TMR AMR Series Circuit Error Correction
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Solution Overview
Problem
Conventional magnetic sensors face reduced sensitivity and accuracy in measuring the rotation angle of an external magnetic field due to errors in the resistance value measurement, which are not effectively corrected by existing bridge circuit configurations.
Innovation Solution
A magnetic sensor configuration that includes a magnetoresistive element and an anisotropic magnetoresistive element, where the anisotropic element has a smaller resistance value than the magnetoresistive element, allowing for increased voltage application and correction of output errors, thereby enhancing sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a corrective TMR element with great resistance value is used to reduce measurement error, then the error in rotation angle measurement is reduced, but the voltage applied to the bridge circuit decreases and the sensitivity is reduced
Solution Approach 1:
The patent changes the resistance value parameter of the corrective magnetoresistive element from high (conventional TMR element) to low (new corrective element). This parameter change allows the corrective element to reduce measurement errors while maintaining adequate voltage levels across the bridge circuit, thereby preserving sensitivity. The low resistance value ensures that the corrective element does not create a voltage drop that would reduce the voltage available to the bridge circuit.
2Measurement precision
If the resistance value of the corrective magnetoresistive element is great, then the output error is corrected, but the voltage applied from the power supply to the bridge circuit decreases
Solution Approach 1:
The patent applies parameter change by setting the resistance value of the corrective magnetoresistive element to be lower than that of conventional corrective elements. This ensures that while the element still provides error correction functionality, it does not excessively consume voltage from the power supply, thereby maintaining adequate voltage levels for the bridge circuit operation.
3Measurement precision
If the resistance value of the corrective magnetoresistive element is great, then the error is reduced, but the amount of change in resistance value dependent on rotation angle decreases
Solution Approach 1:
The patent changes the resistance value parameter of the corrective element to be low, which maintains the error correction capability while preserving the dynamic range of resistance change. The low resistance value ensures that the corrective element can still exhibit sufficient resistance variation with rotation angle, thereby maintaining sensitivity without compromising error correction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The magnetic sensor achieves high sensitivity and reduced error in measuring the rotation angle of an external magnetic field by combining the resistance values of both elements, aligning the output closer to an ideal curve and increasing the amount of change dependent on the rotation angle.
Implementation Method 1
a magnetoresistive element 20 whose resistance value varies with a rotation angle of an external magnetic field; a ferromagnetic layer 23 whose magnetization direction rotates in accordance with an external magnetic field; a tunnel layer 4 which varies a tunnel current in accordance with a spin state prevailing between the free layer 2 and the pin layer 3
Implementation Method 2
an anisotropic magnetoresistive element 30 whose resistance value varies with a rotation angle of an external magnetic field
Data Source
AI summary
A TMR element and a corrective AMR element are series-connected between a power supply and a ground. The resistance value of the corrective AMR element is set so as to offset an output error in the rotation angle of an external magnetic field, which is included in the resistance value of the TMR element. The resistance value of the corrective AMR element is smaller than that of the TMR element. An increased voltage can be applied from the power supply to the TMR element. It is possible to increase, in the resistance value of the TMR element, the amount of change that depends on the rotation angle of the external magnetic field. This makes it possible to increase, in the output of a magnetic sensor, the amount of change that depends on the rotation angle of the external magnetic field. The sensitivity of the magnetic sensor can be increased.