Magnetic Sensor Segmentation for Stray Field Rejection
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Solution Overview
Problem
Magnetic sensors face limitations such as excessive size, inadequate sensitivity, dynamic range, cost, reliability, and sensitivity degradation due to positional misalignment of magnetic sensing elements.
Innovation Solution
The solution involves configuring magnetic field sensing elements and segments based on magnetic bias field iso-lines to reduce sensitivity to common mode fields, with specific dimensions and spacings to achieve equal bias field distribution and zero field resistance, and using a non-rectangular magnet shape to minimize sensitivity changes due to misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If magnetic sensing elements are positioned closer together to reduce sensor size, then the sensor size is reduced, but sensitivity to common mode fields increases
Solution Approach 1:
Each magnetic sensing element is divided into multiple segments positioned at different locations relative to the magnet. The segments are spaced according to magnetic field iso-lines, with each segment experiencing different bias field conditions. This segmentation allows the element to maintain compact size while reducing common mode field sensitivity through differential measurement between segments.
Solution Approach 2:
Different segments of the sensing elements are positioned at specific locations where they experience different magnetic bias field strengths and orientations. By configuring segments at positions corresponding to different iso-lines, each segment has locally optimized properties for detecting specific field components while being less sensitive to common mode variations.
2Object-affected harmful factors
If magnetic sensing elements are positioned further apart to reduce common mode field sensitivity, then common mode field sensitivity is reduced, but the sensor size increases
Solution Approach 1:
Instead of spacing segments only in one dimension, the invention positions segments in multiple dimensions according to three-dimensional magnetic field iso-lines. This multi-dimensional arrangement allows segments to be distributed in space to achieve common mode rejection while maintaining a compact overall sensor footprint through optimized spatial configuration.
3Measurement precision
If magnetic sensing elements are placed precisely to optimize sensitivity, then sensitivity is improved, but manufacturing complexity and alignment requirements increase
Solution Approach 1:
The sensing elements and segments are configured with asymmetric positioning relative to the magnet, where segments are placed at specific non-symmetric locations corresponding to magnetic field iso-lines. This asymmetric configuration provides inherent insensitivity to certain types of misalignment while maintaining high sensitivity to the target magnetic field variations.
Solution Approach 2:
The segment configuration is designed beforehand to compensate for potential misalignments. By positioning segments at locations where they experience different bias field conditions, the structure inherently cushions against the effects of manufacturing tolerances and assembly misalignments, maintaining performance without requiring extreme precision.
4Ease of manufacture
If traditional magnetic sensing element configuration is used, then manufacturing is simpler, but sensitivity to misalignment degrades performance
Solution Approach 1:
The sensing elements are segmented into multiple parts that can be independently positioned according to magnetic field iso-lines. This segmentation allows for standardized manufacturing of individual segments while achieving the complex spatial configuration needed for misalignment insensitivity through systematic arrangement of the segments.
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
This configuration significantly reduces the impact of misalignment on sensor performance, enhancing sensitivity and reliability while maintaining robustness against positional errors.
Implementation Method 1
magnetic field sensing elements and segments of a magnetic field sensor positioned with respect to a bias field of a magnet to reduce sensitivity to a common mode field
Implementation Method 2
first and second segments are located at positions of opposite magnetic field, wherein the first and second segments are spaced from each other based upon iso-lines of the magnetic field
Data Source
AI summary
Methods and apparatus for a sensor having a first magnetic field sensing element with first and second segments where the first and second segments are located at positions of opposite magnetic field. The first and second segments are spaced from each other based upon iso-lines of the magnetic field. A processing module can process an output of the magnetic field sensing element.