AMR Magnetometer with Single SET Operation
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Solution Overview
Problem
Current magnetic field sensors for mobile devices are large, costly, power-intensive, and difficult to integrate due to the need for frequent SET and RESET currents, which limits their effectiveness in mobile applications like GPS-enabled handsets.
Innovation Solution
A tri-axis magnetometer based on anisotropic magnetoresistive (AMR) technology that eliminates the RESET function and reduces SET function frequency, using a SET current to align magnetic domains and incorporating an automatic calibration system to conserve power and maintain accuracy, with a compact design and balanced sensor layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SET and RESET currents are applied frequently for every measurement, then magnetic domain orientation is maintained, but power consumption increases significantly
Solution Approach 1:
The patent implements periodic SET pulses instead of continuous or frequent SET-RESET cycles. The system applies SET pulses only when calibration is needed or when the magnetometer has been inactive for a threshold period, rather than for every measurement. This periodic approach maintains magnetic domain orientation reliability while dramatically reducing power consumption by eliminating unnecessary current applications.
Solution Approach 2:
The patent performs calibration and SET operations in advance before actual measurements are needed. By pre-aligning magnetic domains and establishing proper orientation before measurement sequences begin, the system eliminates the need for repeated SET-RESET cycles during measurement operations, thereby reducing power consumption while maintaining measurement accuracy.
2Volume of moving object
If sensor size is reduced for mobile device integration, then device portability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces mechanical alignment methods with magnetic field-based calibration. Instead of relying on precise mechanical positioning of sensor elements at 90-degree angles during manufacturing, the system uses magnetic calibration procedures to establish accurate spatial relationships between sensor axes. This substitution allows for smaller sensor footprints while maintaining measurement accuracy through software-based calibration rather than mechanical precision.
Solution Approach 2:
The patent employs calibration parameters and correction factors to compensate for manufacturing tolerances. By measuring the actual magnetic field vectors and calculating correction parameters, the system can achieve accurate three-axis measurements even when physical sensor alignment deviates from ideal 90-degree angles, thereby enabling smaller sensor designs without sacrificing precision.
3Measurement precision
If automatic calibration system is implemented, then measurement accuracy is maintained, but device complexity increases
Solution Approach 1:
The patent implements a self-calibrating magnetometer that automatically performs its own calibration without requiring external equipment or manual intervention. The system uses the Earth's magnetic field as a reference and automatically determines calibration parameters by analyzing magnetic field measurements taken during device movement. This self-service approach maintains high measurement accuracy while minimizing added complexity by eliminating the need for external calibration devices or complex manual procedures.
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 results in a low-power, compact, and cost-effective magnetic field sensor that maintains accuracy over extended periods, reducing power consumption by orders of magnitude and allowing for efficient integration into mobile devices.
Implementation Method 1
a SET current is passed through a SET coil in order to orient a respective magnetic axis of the barber pole structures. This action aligns the magnetic domain orientations of these barber pole structures into one consistent direction
Implementation Method 2
Magnetic field sensors based on anisotropic magnetoresistive (AMR) technology
Data Source
AI summary
A magnetometer with only a SET operation for initiating a magnetic orientation within a magnetic field sensor based on anisotropic magnetoresistive (AMR) technology. Within the magnetometer, the relative orientations of the respective X, Y and Z axes detectors are maintained by a package in which all detectors are mounted on a single assembly with the Z axis sensor displaced and held orthogonal to the other two sensors by potting material. Shorting bars on respective barber pole structures are provided with a geometry that allows for closer placement of adjacent barber poles to one another. The barber pole structures are deposited in a nested orientation which provides for balanced resistance legs in a Wheatstone bridge construction.