Magnetoresistance Sensor with Temperature-Compensating Bias Layer
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Solution Overview
Problem
Magnetoresistance effect type magnetic sensors face decreased sensitivity due to temperature increases, requiring temperature compensation, but existing solutions necessitate additional temperature sensors, increasing device size and installation labor.
Innovation Solution
A sensor element with a longitudinal bias magnetic field that mimics the temperature characteristics of the magnetic film, suppressing the magnetoresistance effect and canceling out temperature-induced sensitivity changes, allowing for autonomous temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature compensation circuit with additional temperature sensors is used, then temperature compensation accuracy is improved, but device size and installation complexity increase
Solution Approach 1:
The patent combines the temperature compensation function with the magnetic sensor element itself by integrating a longitudinal bias magnetic field generation layer that exhibits temperature-dependent magnetic field changes. This merging eliminates the need for separate temperature sensors and compensation circuits, thereby maintaining temperature compensation accuracy while reducing device size and installation complexity.
Solution Approach 2:
The magnetic sensor element performs self-temperature compensation through its own longitudinal bias magnetic field generation layer, which automatically adjusts the bias magnetic field strength according to temperature changes. This self-service mechanism eliminates the need for external temperature sensing and compensation circuits, resolving the contradiction between compensation accuracy and device complexity.
2Difficulty of detecting and measuring
If magnetoresistance effect type magnetic sensor is used, then magnetic field detection capability is improved, but sensitivity decreases with temperature increase
Solution Approach 1:
The patent changes the parameter of longitudinal bias magnetic field strength dynamically with temperature by incorporating a longitudinal bias magnetic field generation layer with specific temperature characteristics. As temperature increases, the layer's magnetic field strength decreases, which compensates for the magnetoresistance effect's temperature-dependent sensitivity degradation, thereby maintaining reliable magnetic field detection capability across temperature ranges.
Solution Approach 2:
The magnetic sensor element uses a composite structure combining magnetic film layers with a longitudinal bias magnetic field generation layer that has complementary temperature characteristics. This composite material approach allows the sensor to maintain both high magnetic field detection capability and temperature-stable sensitivity by leveraging the interacting properties of different material layers.
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
Maintains sensitivity accuracy under harsh temperature changes, simplifying installation and reducing device size, while enabling reliable operation in varying temperature environments.
Implementation Method 1
the longitudinal bias magnetic field addition magnet 20 has a temperature characteristic similarly to the magnetic film 12, and acts such that the longitudinal bias magnetic field decreases with the rise in temperature
Implementation Method 2
a magnetic sensor utilizing the magnetoresistance effect is particularly referred to as a magnetoresistance effect type magnetic sensor. The magnetoresistance effect type magnetic sensor detects the magnitude of a measurement-target magnetic field
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3
AI summary
A magnetoresistance effect type magnetic sensor has a problem in that the increase in the surrounding temperature decreases the magnetic characteristic of a magnetic film itself and thereby decreases the sensitivity of the sensor. A sensor element includes: a magnetic film having magnetoresistance effect; a pair of electrodes for applying an electric current to the magnetic film, the pair of electrodes being opposed across the magnetic film; a longitudinal bias magnetic field addition magnet to generate a first bias magnetic field in an opposing direction of the electrodes; and a lateral bias magnetic field addition magnet to generate a second bias magnetic field in an orthogonal direction to the longitudinal bias magnetic field addition magnet, in which a temperature characteristic of the longitudinal bias magnetic field addition magnet is higher than a temperature characteristic of the lateral bias magnetic field addition magnet.