Magnetic Sensor Calibration Using Multi-Orientation Rotation
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Solution Overview
Problem
Current methods for calibrating directional magnetic sensors and magnets face challenges in achieving accurate calibration, particularly in environments with unknown or variable magnetic fields, relying on unreliable assumptions or previous calibrations, and are limited to specific conditions such as zero-gauss chambers or known magnetic field orientations.
Innovation Solution
A method involving rotating the magnetic sensor or magnetic field to multiple orientations, allowing measurement of output voltages at various positions, which are then used to solve a system of equations to determine offset voltage and sensitivity vector components, enabling calibration in arbitrary magnetic fields and without relying on previous calibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a zero-gauss chamber is used to measure offset voltage, then the measurement can be performed, but the chamber may not be perfect or may be accidentally magnetized, leading to incorrect offset measurement
Solution Approach 1:
The patent introduces a known magnetic field vector as an intermediary to enable offset voltage measurement without requiring a zero-gauss chamber. By measuring the sensor output in a known magnetic field and subtracting the expected field contribution, the offset can be determined reliably without depending on the perfection of magnetic shielding
Solution Approach 2:
The patent changes the measurement parameter from requiring zero magnetic field to using a known non-zero magnetic field. This allows offset measurement to proceed by solving the sensor equation with known field values, transforming the problem from one requiring perfect shielding to one using controlled field conditions
2Ease of manufacture
If the angular position of the magnetic field vector is estimated based on geometry and material properties of the calibrating magnet, then the calibration can be performed, but substantial errors occur due to simplified models and hysteresis effects
Solution Approach 1:
The patent replaces the mechanical/geometric estimation method with a measurement-based approach. Instead of calculating angular position from magnet geometry and material properties, the system uses a second magnetic sensor to directly measure the field vector direction, substituting physical estimation with empirical measurement
Solution Approach 2:
The patent introduces a second magnetic sensor as an intermediary to measure the magnetic field vector. This intermediary device provides accurate angular position information without relying on simplified geometric models or material property assumptions of the calibrating magnet
3Reliability
If conventional calibration methods are used, then calibration can be performed in zero-gauss chambers or with known field orientations, but the methods are limited to specific conditions and cannot handle arbitrary magnetic fields
Solution Approach 1:
The patent creates a universal calibration method that works with arbitrary magnetic field vectors. By measuring the sensor output in a known magnetic field and solving for the offset and sensitivity parameters algebraically, the method becomes applicable to any field orientation and strength, not just controlled zero-gauss or aligned field conditions
Solution Approach 2:
The patent changes the calibration approach from requiring controlled field conditions to accepting arbitrary field conditions. By using a known non-zero magnetic field vector and solving the sensor equation system, the method adapts to any field orientation, transforming the calibration process from condition-specific to universally applicable
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 approach allows for more accurate and easier calibration of magnetic sensors and magnets by measuring parameters in the presence of arbitrary magnetic fields, overcoming previous limitations and improving calibration precision.
Implementation Method 1
The output voltage of a directional magnetic sensor, such as a Hall magnetic sensor, is given by the equation where V0 denotes the offset voltage of the magnetic sensor, and S·B denotes the scalar (dot) product of the sensitivity vector of the Hall sensor S and the magnetic field vector B to which the magnetic sensor is exposed.
Data Source
AI summary
A method for calibrating a magnetic sensor and/or a calibrating magnet, said sensor, when subjected to a magnetic field {right arrow over (B)} (Bx; By; Bz)T exhibiting an output voltage V governed by V=Vo+{right arrow over (S)}·{right arrow over (B)}, wherein V0 denotes an offset voltage of the magnetic sensor, and {right arrow over (S)}·{right arrow over (B)} denotes a scalar product of a sensitivity vector {right arrow over (S)}=(Sx; Sy; Sz)T of the magnetic sensor and the magnetic field vector {right arrow over (B)}, the method comprising the steps ofa. measuring a first output voltage V1 for a first orientation of the magnetic sensor relative to the magnetic field;b. rotating the magnetic sensor relative to the magnetic field to assume N−1 further orientations, wherein 2≤N∈ and each orientation is defined by a rotation matrix n, wherein n≠ for n ∈{2, . . . , N} and n≠m for n≠m∈{2, . . . , N};c. for each further orientation, measuring one further output voltage Vn, with n∈{2; . . . ; N}; andd. solving a system of N equations Vn=V0+n{right arrow over (S)})·{right arrow over (B)} with 1= for one or more of Vo, Sx, Sy, Sz, Bx, By, and/or Bz.