Hybrid Hall-MR Magnetometer Self-Calibration for Wide Dynamic Range
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Solution Overview
Problem
Existing magnetometers face challenges in achieving high dynamic range, sensitivity, and low noise, particularly in detecting low DC and AC magnetic fields, especially in the presence of large DC fields, with Hall sensors having high noise and lower sensitivity, and MR sensors saturating at low fields and exhibiting hysteresis.
Innovation Solution
A hybrid magnetometer integrating a monolithically integrated 3-axis Hall sensor with an ASIC and a 3-axis MR sensor in a single IC package, allowing for a sensing operation mode with the Hall sensor off and MR sensor active for high precision, and a self-calibration mode where both sensors are on, with the MR sensor bias error calibrated using the Hall sensor reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Hall sensor is used for magnetic field detection, then high dynamic range is achieved, but sensitivity and noise performance deteriorate
Solution Approach 1:
The patent combines Hall sensor and MR sensor into a hybrid magnetometer system. The Hall sensor provides high dynamic range for large magnetic fields while the MR sensor provides high sensitivity for small magnetic fields. The system merges the outputs of both sensors through a summation node to achieve both high dynamic range and high sensitivity simultaneously.
2Measurement precision
If MR sensor is used for magnetic field detection, then high sensitivity is achieved, but saturation at low fields and hysteresis occur
Solution Approach 1:
The Hall sensor acts as an intermediary to compensate for MR sensor limitations. The Hall sensor's linear response and lack of saturation provide a reference signal that compensates for the MR sensor's saturation and hysteresis effects. The compensation circuit uses the Hall sensor output to correct the MR sensor output, eliminating saturation and hysteresis errors.
3Measurement precision
If both Hall sensor and MR sensor are integrated, then high dynamic range and high sensitivity are achieved, but device complexity increases
Solution Approach 1:
The patent divides the magnetometer into distinct functional modules: Hall sensor module, MR sensor module, and signal processing module. Each sensor type is independently integrated and then combined through modular signal processing. This segmentation allows independent optimization of each sensor while managing overall system complexity through structured integration.
4Measurement precision
If self-calibration mode is implemented, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The system implements periodic self-calibration rather than continuous calibration. The calibration mode is activated at specific intervals or under specific conditions (e.g., when device is stationary or during initialization), while normal operation uses the calibrated parameters. This periodic action reduces power consumption compared to continuous calibration while maintaining measurement accuracy.
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 hybrid sensor achieves ultra-low absolute offset shift, providing high sensitivity and low noise for detecting low and high DC magnetic fields and AC fields, reducing dependence on software calibration for accurate device headings and enabling magnetic tracking and navigation applications.
Implementation Method 1
Hall-effect sensors (hereinafter, 'Hall sensor') detect the presence and magnitude of a magnetic field using the Hall effect. The Hall effect is when a magnetic field is applied at right angles to the current flow in a thin film where an electric field is generated
Implementation Method 2
Magnetoresistive (MR) sensors also detect the presence and magnitude of a magnetic field. The MR sensor, however, operates based on the principal that the electrical resistance in a ferromagnetic thin film alloy is changed through an external magnetic field
Data Source
AI summary
A hybrid Hall/MR magnetometer with self-calibration includes a circuit coupled to a magnetometer and configured to determine whether the magnetometer is to operate in a sensing operation mode or a self-calibration operation mode. The magnetometer comprises a Hall sensor and MR sensor coupled to the circuit. In accordance with determining a sensing operation mode, the Hall sensor is turned off and the MR sensor is turned on; and an external magnetic field is measured using the MR sensor. The magnetic field measurement is calibrated using a MR sensor bias error determined in a self-calibration operation mode of the sensor.