Magnetic Sensor Stray Field Rejection via Calibration
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Solution Overview
Problem
Magnetic sensors face challenges in achieving improved stray field rejection and reduced variability due to manufacturing variations and environmental interference, leading to measurement errors and increased costs associated with larger, bulkier magnets and stringent assembly requirements.
Innovation Solution
A field sensor device comprising a reference field sensor and calibrated field sensors, where the calibrated sensors are adjusted to match the reference sensor signal through an adjustable current, allowing for improved accuracy and precision by minimizing stray field influence and accounting for manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple redundant sensors are employed and their sensed values are averaged, then measurement variability is reduced, but device complexity and cost increase
Solution Approach 1:
The sensor system is segmented into multiple identical sensor elements that can be independently manufactured and then combined in a modular array configuration. Each sensor element processes its own signal independently, and the results are combined through simple averaging, reducing variability without requiring complex integrated processing circuits.
Solution Approach 2:
Multiple identical sensor elements are merged into a single functional unit where their outputs are combined through simple arithmetic averaging. This merging approach reduces measurement variability while maintaining low complexity by avoiding the need for complex individual sensor designs or sophisticated signal processing electronics.
2Measurement precision
If sensors are calibrated or re-calibrated to ensure measurements conform to external standards, then measurement accuracy is improved, but cost and difficulty increase
Solution Approach 1:
All necessary calibration and adjustment operations are performed during the manufacturing process before the sensor array is deployed. Identical calibration procedures are applied to all sensor elements during production, ensuring they start with consistent baseline characteristics. This preliminary calibration eliminates the need for complex field calibration procedures later.
Solution Approach 2:
The system uses adjustable gain and offset parameters for each sensor element that can be programmed during manufacturing to compensate for individual variations. By changing these electrical parameters during the manufacturing process, accurate calibration is achieved without requiring complex mechanical adjustment procedures or expensive equipment.
3Object-affected harmful factors
If magnets with stronger magnetization are employed or the magnet is brought closer to the sensor, then stray field rejection is improved, but size, weight, and assembly complexity increase
Solution Approach 1:
The magnetic field sensing function is segmented into multiple identical sensor elements arranged in an array, rather than relying on a single high-performance sensor or strong magnet. This segmentation allows the use of weaker magnets with relaxed tolerance requirements while achieving the same overall performance through the combined output of multiple elements.
Solution Approach 2:
Instead of using a single magnet operating at the limit of its capabilities with stringent tolerance requirements, the system uses multiple magnets or a distributed magnetic field configuration where each element operates with relaxed tolerances. The cumulative effect of multiple partial contributions achieves the desired stray field rejection without requiring any single component to meet excessive specifications.
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 provides field sensor devices with enhanced accuracy, precision, and reduced variability, effectively addressing stray field rejection and measurement errors while maintaining a compact and cost-effective design.
Implementation Method 1
Magnetic sensors can incorporate Hall-effect sensors that generate an output voltage proportional to an applied magnetic field
Implementation Method 2
magneto-resistive materials whose electrical resistance changes in response to an external magnetic field
Data Source
AI summary
The present invention relates to a field-sensor device comprising a reference field sensor providing a reference sensor signal in response to a field, a calibrated field sensor providing a calibrated sensor signal in response to the field, a reference circuit connected to the reference field sensor and adapted to receive a reference signal, and an adjustable circuit connected to the calibrated field sensor and adapted to receive a calibrated signal. When the adjustable circuit is adjusted with the calibrated signal, said calibrated signal being different from the reference signal, the calibrated field sensor provides a calibrated sensor signal substantially equal to the reference sensor signal. The field sensor device is arranged to be exposed, when in a calibration mode, to a uniform calibration field and, when in operational mode, to an operational field being a field gradient.