Magnet With Opposing Magnetization For Sensor
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Solution Overview
Problem
Existing magnetic field sensors have limited sensitivity in detecting changes in magnetic fields caused by moving ferromagnetic objects, particularly gear teeth, due to the configuration of magnets with single North and South regions, which results in suboptimal detection of magnetic flux variations.
Innovation Solution
A magnetic field sensor configuration using a permanent magnet with two North and two South regions, positioned to generate opposing directions of magnetization, enhances sensitivity by positioning a magnetic field sensing element, such as a Hall element, to detect changes in magnetic flux not parallel to its surface, thereby improving detection of ferromagnetic object movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet with single North and South regions is used, then the device complexity is low, but the measurement precision of magnetic field changes is insufficient
Solution Approach 1:
The magnet is segmented into multiple magnetic regions with alternating North and South poles (at least two North regions and two South regions) arranged in a specific pattern. This segmentation creates multiple magnetic flux paths that enhance the sensitivity of detection for ferromagnetic object movement, resolving the contradiction between simple structure and high measurement precision.
Solution Approach 2:
Different regions of the magnet are assigned different magnetic polarities (North or South) to create localized magnetic field variations. The magnetic field sensing element is positioned to detect flux changes in specific local areas where the opposing magnetization directions create enhanced sensitivity gradients, improving detection precision without requiring complete system complexity.
2Measurement precision
If the magnetic field sensing element detects magnetic flux changes parallel to its surface, then the detection is simpler, but the sensor sensitivity is limited
Solution Approach 1:
The magnetic field sensing element is configured to detect magnetic flux changes in a direction not parallel to its surface, introducing a new dimensional aspect to the detection geometry. This angular or perpendicular detection orientation exploits the opposing magnetization directions of the magnet to achieve enhanced sensitivity, moving beyond conventional parallel detection limitations.
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 increases sensor sensitivity, allowing for more precise detection of magnetic field changes, particularly when a ferromagnetic tooth moves close to the sensor, leading to improved accuracy in applications like engine control and wheel speed monitoring.
Implementation Method 1
a magnet that includes two North regions and two South regions configured to generate opposing directions of magnetization to form a magnetic field
Implementation Method 2
a Hall element configured to sense magnetic flux changes not parallel to a surface of the magnetic field sensing element
Data Source
AI summary
In one aspect, a magnetic field sensor is configured to detect a ferromagnetic object. The magnetic field sensor includes a magnet that includes two North regions and two South regions configured to generate opposing directions of magnetization to form a magnetic flux. The magnetic field sensor also includes a magnetic field sensing element configured to generate an is output signal responsive to changes in the magnetic flux caused by movement of the ferromagnetic object.