Tilted Segmented AMR Sensor Angular Error Cancellation
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Solution Overview
Problem
Anisotropic magnetoresistive (AMR) sensors face angular errors due to shape anisotropies in magnetoresistive segments, particularly with elongated shapes, leading to increased costs and errors in estimating external magnetic field orientations.
Innovation Solution
The integration of an AMR sensor system with a half bridge or Wheatstone bridge configuration, where resistors have magnetoresistive segments oriented at specific tilt angles to cancel out angular errors, allowing for efficient layouts with high length-to-width ratios and reduced area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetoresistive segments with high length-to-width ratios are used, then layout efficiency is improved, but angular errors due to shape anisotropies increase
Solution Approach 1:
The magnetoresistive element is divided into multiple segments with different orientations. Each segment experiences shape anisotropy differently, and by combining their outputs, the overall angular measurement accuracy is improved while maintaining efficient layout with high length-to-width ratios.
Solution Approach 2:
Segments are deliberately oriented at asymmetric angles (e.g., 0°, 45°, 90°, 135°) relative to the external magnetic field. This asymmetric arrangement allows the system to average out the angular errors caused by shape anisotropies across different orientations.
2Measurement precision
If magnetoresistive segments with low shape anisotropy are used, then angular errors are reduced, but sensor area and cost increase
Solution Approach 1:
Instead of using a single large low-anisotropy segment, the sensor uses multiple smaller segments with high length-to-width ratios arranged in specific orientations. This segmentation achieves low effective shape anisotropy while minimizing total sensor area.
Solution Approach 2:
The solution transitions from considering only the in-plane dimensions to incorporating the orientation dimension. By arranging segments at different angles in the plane, the system achieves error cancellation without increasing the physical footprint of the sensor.
3Adaptability or versatility
If curved magnetoresistive segments are used, then angular errors are averaged over a range of orientations, but average angular error value increases
Solution Approach 1:
The curved segment approach is replaced by discrete linear segments at specific angles. This segmentation provides adaptability across orientation ranges while maintaining lower average angular error through precise angular positioning and Wheatstone bridge configuration.
Solution Approach 2:
Each magnetoresistive segment is optimized for its specific orientation with appropriate length-to-width ratios. Rather than using a uniform curved shape, each segment has locally optimized dimensions tailored to its angular position, achieving both adaptability and precision.
4Adaptability or versatility
If continuous magnetoresistive strip with multiple segments is used, then angular errors are averaged, but average angular error value increases
Solution Approach 1:
The continuous strip is divided into distinct segmented elements with specific orientations. These segments are connected through the Wheatstone bridge configuration, which provides error averaging while maintaining lower average angular error through the bridge's differential measurement capability.
Solution Approach 2:
The Wheatstone bridge acts as an intermediary that processes the signals from multiple magnetoresistive segments. It combines their outputs in a way that averages angular errors while preserving measurement accuracy, eliminating the need for continuous strip configurations.
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 effectively reduces angular errors due to shape anisotropies, achieving accuracy below 0.04 degrees for a wide range of external magnetic field orientations while maintaining a cost-effective and efficient sensor design.
Implementation Method 1
An anisotropic magnetoresistive (AMR) sensor has magnetoresistive segments which are used to detect an orientation of an external magnetic field. The external magnetic field produces magnetic moments in the magnetoresistive segments.
Data Source
AI summary
An integrated AMR sensor includes a half bridge with two resistors, a Wheatstone bridge with four resistors, or a first Wheatstone bridge with four resistors in an orthogonal configuration, and a second Wheatstone bridge with four resistors in an orthogonal configuration, oriented at 45 degrees with respect to the first Wheatstone bridge. Each resistor includes first magnetoresistive segments with current flow directions oriented at a first tilt angle with respect to a reference direction of the resistor, and second magnetoresistive segments with current flow directions oriented at a second tilt angle with respect to the reference direction. The tilt angles are selected to advantageously cancel angular errors due to shape anisotropies of the magnetoresistive segments. In another implementation, the disclosed system/method include a method for identifying tilt angles which cancel angular errors due to shape anisotropies of the magnetoresistive segments.