Magnetoresistive Sensor Bias Field for Position Detection
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Solution Overview
Problem
Magnetic sensor systems face challenges in accurately detecting the position of a magnetic field generator due to deviations in the distance between the magnetic sensor and the field generator, leading to signal saturation and reduced detection accuracy, which requires frequent calibration and is prone to errors from physical impacts.
Innovation Solution
A magnetic sensor system with magnetoresistive elements that include a pinned layer, a free layer, and a gap layer, where a bias magnetic field is applied orthogonally to the free layer, allowing the magnetic field component to change resistance with the field strength, and includes a bias magnetic field generator and soft magnetic layers to amplify the field, reducing harmonic distortions and signal saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnetic sensor is located at a predetermined distance from the magnetic field generator, then the detection signals can be processed by standard circuits, but the distance deviation causes signal magnitude changes and saturation
Solution Approach 1:
The patent changes the magnetic field parameter by introducing a bias magnetic field that shifts the operating point of the magnetoresistive element. This parameter change makes the detection signal magnitude less sensitive to distance variations, allowing standard circuits to process signals without saturation while maintaining detection accuracy.
Solution Approach 2:
The bias magnetic field is applied in advance to pre-position the magnetoresistive element's operating point in a region where the magnetic field component's resistance change is proportional to field strength. This preliminary action prevents signal saturation before distance deviations occur and reduces the need for calibration.
2Measurement precision
If the distance between magnetic sensor and magnetic field generator decreases, then detection sensitivity increases, but signal saturation occurs
Solution Approach 1:
By applying a bias magnetic field, the patent changes the operating parameter of the magnetoresistive element to a region where the resistance change is linearly proportional to the magnetic field component. This allows the sensor to operate at closer distances for higher sensitivity without entering the saturation region.
Solution Approach 2:
The bias magnetic field acts as a preliminary countermeasure that positions the operating point in a safe region before strong magnetic fields from close proximity could cause saturation. This preemptive action prevents the harmful effect of saturation while allowing high sensitivity operation.
3Adaptability or versatility
If gain is increased to prevent signal saturation, then dynamic range is improved, but resolution and detection accuracy decrease
Solution Approach 1:
The bias magnetic field changes the resistance characteristic of the magnetoresistive element so that the resistance change becomes proportional to the magnetic field component. This parameter change allows the system to maintain high resolution and detection accuracy across a wider dynamic range without needing excessive gain amplification.
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 system effectively suppresses changes in detection signals due to distance deviations, maintaining accuracy and reducing the need for frequent calibration by ensuring the magnetic field component's resistance changes proportionally with the field strength, thereby enhancing detection precision and robustness against physical impacts.
Implementation Method 1
magnetoresistive elements that each include a magnetization pinned layer having a magnetization whose direction is fixed, a free layer having a magnetization whose direction is variable depending on a direction and the strength of the magnetic field component, and a gap layer located between the magnetization pinned layer and the free layer
Implementation Method 2
a bias magnetic field generator and soft magnetic layers to amplify the field
Implementation Method 3
soft magnetic layers to amplify the field, reducing harmonic distortions and signal saturation
Data Source
AI summary
A magnetic sensor system includes a magnetic field generator and a magnetic sensor. The magnetic sensor includes a plurality of MR elements. The plurality of MR elements are each configured so that a bias magnetic field in a second direction orthogonal to a first direction is applied to a free layer, and to change in resistance with a strength of a magnetic field component. A maximum strength of the magnetic field component applied to each of the MR elements is greater than or equal to 1.2 times the strength of a bias magnetic field.