Magnetic Sensor Offset Correction via Stored Resistance Data
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Solution Overview
Problem
Magnetic sensors face challenges in accurately measuring micro magnetic fields due to manufacturing errors that result in offset voltages, particularly when detecting geomagnetism or fields below 10 Oe, which affect precision.
Innovation Solution
A magnetic sensor configuration with a measuring section, storage section, and operating section, utilizing magnetoresistive elements with pinned and free layers and a non-magnetic intermediate layer, along with bias magnetic fields applied at specific angles, allows for the detection of resistance changes and calculation of magnetic field components, reducing the need for continuous corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If four GMR elements are used to configure a bridge circuit for detecting magnetic fields, then the detective sensitivity to magnetic field changes is improved, but manufacturing errors cause offset voltages that deteriorate measurement precision
Solution Approach 1:
The patent applies preliminary action by measuring and storing fixed data (offset voltage characteristics) during a calibration phase before actual measurement. The storage section saves the resistance values or offset voltages obtained when no detected magnetic field is applied, allowing the operating section to compensate for manufacturing variations during normal operation without requiring continuous corrections.
Solution Approach 2:
The patent implements feedback by using the stored fixed data to correct the measured resistance values in real-time. The operating section calculates corrected resistance values by subtracting the stored offset voltage (fixed data) from the measured resistance, creating a closed-loop system that continuously compensates for manufacturing errors and maintains measurement precision.
2Manufacturing precision
If the anisotropic magnetic field direction and pinned layer magnetization direction are aligned to equalize resistances, then manufacturing variations are reduced, but the structure becomes more complex and harder to manufacture
Solution Approach 1:
The patent extracts the offset voltage characteristic (fixed data) from the measurement process and stores it separately in the storage section. This allows the system to account for manufacturing variations without requiring precise alignment of magnetic fields during manufacturing. The extracted offset data is used later to correct measurements, separating the manufacturing process from the measurement process.
Solution Approach 2:
The patent changes the approach from controlling physical parameters (magnetic field alignment) to controlling data parameters (stored offset values). Instead of requiring precise angular alignment of magnetization directions during manufacturing, the system measures and stores the actual resistance values under no-field conditions, then uses these stored parameter values to correct subsequent measurements, transforming a physical alignment problem into a data processing solution.
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 enables high-precision detection of magnetic field magnitude and direction by using fixed and variable data to correct for offset voltages, improving accuracy in measuring micro magnetic fields.
Implementation Method 1
a magnetoresistive element in which a pinned layer having a magnetization pinned in a certain direction and a free layer changing its magnetization direction depending on an external magnetic field are stacked with a non-magnetic intermediate layer in between
Implementation Method 2
a magnetic field applying means for applying, to the magnetoresistive element, a bias magnetic field in a direction forming a certain relative angle against the magnetization direction of the pinned layer
Data Source
AI summary
A magnetic direction sensor can detect at higher precision the magnitude and direction of a detected magnetic field. The magnetic direction sensor has a measuring section, a storage section and an operating section. The measuring section has first and second MR elements, and detects resistance values of these elements in accordance with an attitude change of the sensor and the presence or absence of a bias magnetic field to be applied through a coil in a direction orthogonal to a magnetization direction of each pinned layer in the first and second MR elements. The storage section stores fixed data invariable in response to a detected magnetic field direction, in resistance values of these elements measured by the measuring section. The operating section calculates a detected magnetic field vector from variable data of resistance values of these elements measured by the measuring section, and fixed data stored in the storage section.