Hybrid Magnetometer Calibration via Gyroscope Data Caching
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Solution Overview
Problem
Hall Effect magnetometers suffer from high temperature sensitivity, leading to calibration loss and requiring user intervention for recalibration after temperature events, which affects the accuracy of magnetic field measurements in electronic devices.
Innovation Solution
An electronic device with a hybrid magnetometer featuring a Hall Effect sensor and a non-Hall Effect sensor, along with a gyroscope and temperature sensor, uses a processor to maintain a cache of data, detect temperature events, adjust magnetometer readings based on rotation data, and generate new calibration data to correct readings, thereby maintaining accurate magnetometer calibration without user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Hall Effect magnetometer is used, then cost-effectiveness and ubiquity are improved, but temperature sensitivity increases causing calibration loss
Solution Approach 1:
The patent introduces an intermediary recalibration mechanism that uses gyroscope data and magnetic field calculations to compensate for temperature-induced calibration drift in Hall Effect magnetometers, resolving the contradiction between cost-effectiveness and temperature stability
Solution Approach 2:
The system implements feedback by continuously monitoring temperature changes and automatically triggering recalibration routines when temperature events are detected, allowing the Hall Effect magnetometer to maintain accuracy despite temperature variations
2Device complexity
If Hall Effect magnetometer is used, then device complexity is reduced, but measurement precision deteriorates following temperature events
Solution Approach 1:
The patent applies preliminary action by detecting temperature events before they cause significant measurement errors and proactively triggering recalibration, thereby maintaining measurement precision without adding complex hardware
3Ease of operation
If automatic recalibration is implemented, then user intervention is eliminated, but device complexity increases
Solution Approach 1:
The patent achieves automatic recalibration by making the gyroscope serve multiple functions - both for motion tracking and for providing data to recalculate magnetometer calibration, thereby eliminating user intervention without significantly increasing overall device complexity
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 ensures continuous accurate magnetometer calibration across temperature changes, maintaining device reliability and user experience by automatically adjusting for temperature-induced calibration shifts without the need for user recalibration routines.
Implementation Method 1
Hall Effect magnetometers are commonly used. These magnetometers produce a voltage that is proportional to the applied magnetic field.
Implementation Method 2
detect a temperature event based on temperature data associated with the temperature sensor
Data Source
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AI summary
A method for calibrating a magnetometer following a temperature event is described. The magnetometer includes three sensors, including a Hall Effect sensor associated with a first sensing axis and a sensor of another type associated with a second sensing axis. The method includes: maintaining a cache of gyroscope data and magnetometer data representing magnetometer readings obtained from the magnetometer; detecting a temperature event; determining an expected magnetometer reading following the temperature event; comparing the expected magnetometer reading to a magnetometer reading obtained from the magnetometer after the temperature event to determine a calibration correction amount; compare a difference between the magnetometer reading obtained after the temperature event and the expected magnetometer reading for the second sensing axis to a threshold and, based on the comparison to the threshold, generating new calibration data for the magnetometer based on the calibration correction amount.