Magnetic Sensor Offset Reduction via Refresh Field Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic sensors face challenges in accurately measuring micro magnetic fields, such as geomagnetism, due to manufacturing errors that result in offset voltages, which are amplified when detecting weak fields, leading to reduced precision.
Innovation Solution
The magnetic sensor employs a stacked structure with pinned and free layers, where the relative angles between the magnetization directions of these layers are aligned through rotational and parallel shift operations, and a refresh magnetic field is applied to stabilize the anisotropic magnetic fields, ensuring coincident configurations and minimizing offset outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing methods are used to create GMR elements, then production is simpler and faster, but manufacturing errors cause variations in the angle between anisotropic magnetic field direction and pinned layer magnetization direction, leading to offset voltage
Solution Approach 1:
The patent applies preliminary action by introducing a refresh magnetic field application step before measurement to reset and align the magnetization directions of free layers. This preliminary alignment action compensates for manufacturing errors in angle alignment, ensuring that all GMR elements start from a consistent initial state, thereby reducing offset voltage without requiring higher manufacturing precision
Solution Approach 2:
The patent changes the magnetic field parameter by applying a refresh magnetic field with sufficient strength to saturate the free layers and align their magnetization directions. This parameter change (applying external magnetic field) overrides the manufacturing errors in angle alignment, allowing all GMR elements to operate from a standardized initial condition regardless of manufacturing variations
2Measurement precision
If the anisotropic magnetic field direction and pinned layer magnetization direction are not perfectly aligned, then manufacturing is easier, but offset voltage is generated that reduces measurement precision of weak magnetic fields
Solution Approach 1:
The refresh magnetic field application serves as a preliminary action that resets the magnetization state of free layers before each measurement cycle. This preliminary alignment compensates for misalignment between anisotropic magnetic field direction and pinned layer magnetization direction, enabling high-precision measurement of weak magnetic fields without requiring difficult manufacturing alignment
Solution Approach 2:
The patent converts the harmful effect of manufacturing misalignment into a benefit by using the refresh magnetic field to systematically realign all elements to a known reference state. The manufacturing imperfections are acknowledged but rendered irrelevant through the refresh operation, which establishes a consistent initial condition for all GMR elements regardless of their manufactured angles
3Measurement precision
If four GMR elements are used in a bridge circuit to detect magnetic fields, then detection sensitivity is improved, but any resistance mismatch between elements generates offset voltage that reduces precision
Solution Approach 1:
The refresh magnetic field application is applied to all four GMR elements before measurement to ensure they all start from the same magnetization state. This preliminary action equalizes their resistance values in the initial condition, eliminating offset voltage in the bridge circuit and ensuring reliable differential output precision
Solution Approach 2:
The refresh magnetic field creates an equipotential initial state for all GMR elements by aligning their magnetization directions to a common reference. This ensures that all elements have equal resistance before measurement, making the bridge circuit balanced and eliminating offset voltage, thereby improving both precision and reliability
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 approach allows for higher-precision detection of magnetic fields by reducing offset voltages and stabilizing the output, enabling accurate measurement of even extremely weak magnetic fields like geomagnetism.
Implementation Method 1
giant magneto-resistive elements exhibiting higher detective sensitivity to a change in a magnetic field
Implementation Method 2
the magnitude and direction of an exchange bias field to be generated between the pinned layer and the free layer
Implementation Method 3
generating an anisotropic magnetic field in a different direction from the magnetization direction of the pinned layer
Data Source
AI summary
First and second MR elements are provided with a plurality of element patterns each having a stacked structure. The stacked structure includes a free layer changing its magnetization direction depending on an external magnetic field, an intermediate layer generating no specific magnetization direction, and a pinned layer having magnetization pinned in a certain direction. The first and the second MR elements have a rotationally symmetrical relationship with each other around a central axis parallel to the directions of anisotropic magnetic fields of the free layer. In the initial condition, the resistance of the first MR element and the resistance of the second MR element are equal to each other. The resistances of the first and the second MR elements exhibit changes in opposite directions in accordance with a magnetic field to be detected. This provides a magnetic sensor permitting higher-precision detection of the magnetic field to be detected.