MR Sensor Shield Layout for External Magnetic Field Error Control
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Solution Overview
Problem
Magnetic sensors using magnetoresistive effect elements (MR elements) face errors in position detection due to external magnetic fields exceeding predetermined ranges, such as leakage fields from motors or geomagnetism, leading to increased positional errors in rotational or linear displacement measurements.
Innovation Solution
Incorporating a soft magnetic body shield above and/or below the MR element, with specific size and shape configurations to attenuate external magnetic fields within the detection range, ensuring the MR element's size is physically included within the shield's perimeter, thereby reducing positional detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the MR element is exposed to external magnetic fields beyond the predetermined range (such as leakage fields from motors or geomagnetism), then the detection range is extended, but the position detection error increases significantly
Solution Approach 1:
A soft magnetic body shield is introduced as an intermediary component between the external magnetic field environment and the MR element. This shield mediates the interaction by selectively attenuating external magnetic fields (such as leakage fields from motors or geomagnetism) that would otherwise cause detection errors, while allowing the intended external magnetic fields within the predetermined range (20 to 80 mT) to reach the MR element for normal operation. The shield thus protects the MR element from harmful external magnetic influences without compromising the detection functionality.
2Measurement precision
If a soft magnetic body shield is added to attenuate external magnetic fields, then position detection accuracy is improved, but device complexity increases
Solution Approach 1:
The soft magnetic body shield's parameters (such as its size, shape, and magnetic permeability) are optimized to achieve effective magnetic field attenuation with minimal structural complexity. By carefully selecting the shield's dimensions and magnetic properties, the design achieves the desired protection against external magnetic fields while maintaining a simple overall device structure that does not significantly increase manufacturing complexity or device size.
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 solution effectively prevents an increase in positional detection errors even when external magnetic fields exceed the predetermined range, maintaining accurate rotational or linear displacement measurements by attenuating magnetic field intensity to within the detection range of 20 to 80 mT.
Implementation Method 1
a soft magnetic body shield, wherein the soft magnetic body shield(s) are positioned above and/or below the MR element(s) in a side view, and the size of the MR element is physically included within a perimeter of the soft magnetic body shield in a plan view
Implementation Method 2
a magnetoresistive effect element (MR element), which is a multilayer body having a magnetization free layer and a magnetization pinned layer, where the resistance of the MR element varies in accordance with a change of the magnetization direction of the free layer according to an external magnetic field
Data Source
AI summary
The magnetic sensor can prevent an increase of a positional detection error of a subject/object even in the case of applying an external magnetic field with a magnetic field intensity exceeding a predetermined range. A magnetic sensor is equipped with a magnetoresistive effect element (MR element) 11 that can detect an external magnetic field and a soft magnetic body shield 12. The soft magnetic body shield(s) 12 are/is positioned above and/or below the MR element 11 in a side view, and the size of the MR element 11 is physically included within a perimeter of the soft magnetic body shield 12.