Magneto Resistive Sensor Free Layer Shape
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Solution Overview
Problem
Magnetic speed sensors using magneto resistive sensing elements of the spin-valve type face issues with jitter in sensing signals due to sudden changes in magnetization direction, leading to inaccurate rotation speed measurements, especially when the sensor is not positioned ideally.
Innovation Solution
The implementation of a magnetic speed sensor with a high number of magneto resistive sensing elements and a free layer with a rounded, fully convex shape having an aspect ratio of at least 2, combined with a Wheatstone bridge circuit configuration, helps to reduce jitter by statistically averaging jitter effects and increasing mechanical tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small number of magneto resistive sensing elements are used, then the device complexity is reduced, but the measurement precision deteriorates due to signal jitter
Solution Approach 1:
Multiple magneto resistive sensing elements are electrically connected in a Wheatstone bridge configuration to merge their individual signals. This combining approach statistically averages out jitter effects from individual elements, significantly improving rotation speed measurement accuracy while maintaining a manageable device structure through integrated circuit design.
2Ease of operation
If the sensor is positioned far from the rotating element, then the mechanical tolerance is increased, but the measurement precision deteriorates due to weaker magnetic field signal
Solution Approach 1:
The Wheatstone bridge configuration combines signals from multiple sensing elements, providing statistical averaging that compensates for reduced magnetic field strength at larger distances. This allows the sensor to be positioned farther from the rotating element with improved tolerance while maintaining measurement precision.
3Reliability
If conventional free layer shapes are used, then the manufacturing process is simpler, but the reliability deteriorates due to sudden magnetization direction changes causing jitter
Solution Approach 1:
The free layer is designed with a rounded, fully convex shape instead of conventional rectangular or triangular geometries. This curved geometry distributes magnetization changes more uniformly, preventing sudden directional shifts that cause jitter. The rounded shape is fabricated using standard photolithography and sputtering processes, maintaining ease of manufacture while significantly improving sensing signal stability.
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 signal jitter, enhancing the accuracy of rotation speed measurements and increasing the tolerance for sensor mounting positions, making it suitable for applications requiring high precision like wheel speed sensing.
Implementation Method 1
magnetic speed sensors use a magnetic field variation caused by a rotation of the element to sense the rotational speed
Implementation Method 2
magneto resistive sensing elements of a spin-valve type
Data Source
AI summary
A magneto resistive device having a plurality of magneto resistive sensing elements. Each of the plurality of magneto resistive sensing elements has a free layer and a reference layer. The free layer has a rounded convex contour with an aspect ratio of 2 or greater. There may be one hundred or more magneto resistive sensing elements.