Magnetic Field Sensor Using MR Elements for Distance Detection
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Solution Overview
Problem
Magnetic sensors face limitations such as excessive size, inadequate sensitivity, dynamic range, cost, and reliability, particularly in measuring magnetic field strength over distance and immunity to stray fields.
Innovation Solution
The development of a magnetic field sensor using magnetic field sensing elements coupled in a differential bridge configuration, with a processing module to determine distance from the magnet based on flux line divergence, enhancing sensitivity and immunity to stray fields over a larger air gap range by employing MR or GMR elements and a specific bridge arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic sensors are used to measure magnetic field strength over distance, then the sensor can detect the magnetic field, but the sensitivity is inadequate and the sensor suffers from excessive size
Solution Approach 1:
The sensor is divided into multiple magnetoresistive elements (L1, L2, R1, R2) arranged in a bridge configuration, with each element contributing to the overall measurement. This segmentation allows for differential measurement that enhances sensitivity while maintaining a compact form factor.
Solution Approach 2:
The invention transitions from measuring only magnetic field strength to measuring flux line divergence by adding spatial dimension considerations. The bridge configuration measures differences in magnetic field orientation across multiple elements, enabling distance measurement through divergence detection rather than just field intensity.
2Reliability
If conventional sensors are used to measure magnetic field over air gap, then the measurement can be performed, but the immunity to stray fields is inadequate
Solution Approach 1:
The bridge configuration uses asymmetric positioning of magnetoresistive elements relative to the magnet, with elements L1 and L2 on one side and R1 and R2 on the other side. This asymmetric arrangement creates differential measurement that naturally rejects common-mode stray fields while preserving sensitivity to the target magnetic field divergence.
Solution Approach 2:
Instead of trying to shield against stray fields directly, the invention inverts the approach by using the bridge configuration to measure the difference between opposing sides of the magnet. Stray fields affect both sides equally and cancel out in the differential measurement, while the actual magnetic field divergence creates asymmetric signals that are amplified.
3Adaptability or versatility
If conventional sensors are used, then the sensor structure is simple, but the dynamic range is inadequate
Solution Approach 1:
The bridge configuration of magnetoresistive elements serves multiple functions simultaneously: it measures magnetic field divergence, determines distance from the magnet, provides immunity to stray fields, and maintains sensitivity across a wide dynamic range. This multi-functionality is achieved through the interconnected bridge structure where each element contributes to multiple measurement aspects.
4Reliability
If conventional magnetic sensors are used, then the cost is controlled, but the reliability is inadequate
Solution Approach 1:
The invention merges multiple magnetoresistive elements into a single bridge configuration that functions as one integrated sensing unit. This combining approach improves reliability through redundant measurement paths and differential signaling while keeping the overall device complexity manageable through systematic arrangement of the elements.
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 enhanced sensitivity and immunity to stray fields, with output signals being substantially linear for a given airgap range, improving the accuracy and reliability of magnetic field measurements.
Implementation Method 1
magnetic field sensing elements coupled in a differential bridge... the magnetic field sensing elements comprise MR elements
Implementation Method 2
the magnetic field sensing elements comprise GMR elements
Implementation Method 3
the magnetic field sensing elements comprise Hall elements
Data Source
AI summary
Methods and apparatus for s sensor having magnetic field sensing elements coupled in a differential bridge and a signal processor configured to receive signals from the bridge to determine a distance from the magnetic field sensing elements to a magnet from flux line divergence of magnetic flux generated by the magnet.