Magnetic Field Sensor Error Correction via Hall Amplitude Feedback
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Solution Overview
Problem
Magnetic field sensors, particularly those using magnetoresistance elements, face errors such as spin-flop and anisotropy errors due to strong magnetic fields, which affect the accuracy of angle detection in applications like robotics and automotive systems.
Innovation Solution
The implementation of a magnetic field sensor system that includes a peak detect circuit, error compensation circuit with a processor, and two magnetoresistive elements with orthogonal axes of maximum sensitivity, along with a circular vertical Hall element to detect magnetic field amplitude and compensate for spin-flop errors, generates quadrature signals for precise angle calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistance elements are used to detect magnetic field angle, then the sensor can provide angular position information, but spin-flop errors occur under strong magnetic fields reducing measurement accuracy
Solution Approach 1:
A Hall effect sensor is introduced as an intermediary device to measure the amplitude of the magnetic field. This amplitude information is then used by a processor to generate correction signals that compensate for spin-flop errors in the magnetoresistance sensor output, thereby improving angle detection accuracy under strong magnetic fields.
Solution Approach 2:
The system implements feedback by using the Hall effect sensor to continuously monitor magnetic field amplitude and feed this information back to the processor. The processor then adjusts the magnetoresistance sensor output based on this feedback to correct for spin-flop errors, creating a closed-loop error compensation mechanism.
2Measurement precision
If a Hall effect sensor is added to measure magnetic field amplitude for error compensation, then spin-flop errors are reduced, but device complexity increases
Solution Approach 1:
The Hall effect sensor serves multiple functions: it detects magnetic field amplitude for error compensation, and can potentially provide additional positional information. This multi-functionality justifies the addition of the sensor by maximizing its utility while minimizing the relative impact on system complexity.
Solution Approach 2:
The patent combines multiple sensing functions (magnetoresistance for angle detection and Hall effect for amplitude detection) into a single integrated sensor system. The processor merges the outputs from both sensors to produce a corrected angle measurement, creating a unified error compensation system.
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 configuration significantly reduces spin-flop errors, improving the accuracy of magnetic field angle detection by up to 5-6 degrees at 600 Gauss, providing reliable angular position and speed measurements in various applications.
Implementation Method 1
Certain magnetic field sensors use magnetoresistance or giant-magnetoresistance elements to detect the magnetic field
Implementation Method 2
Certain magnetic field sensors use magnetoresistance or giant-magnetoresistance elements to detect the magnetic field
Implementation Method 3
A Hall effect sensor may be included to detect an amplitude of the magnetic field
Data Source
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AI summary
A magnetic field sensor includes a first magnetic field sensing element configured to produce a first signal representing a detected external magnetic field; a circular vertical hall element configured to produce a second signal representing an amplitude of the external magnetic field; and an error compensation circuit coupled to receive the first and second signal, compute an error value based on the amplitude of the external magnetic field, and apply the error value to the first signal to compensate for an error in the first signal.