Magnetic Field Sensor with Dual Transducers for Saturation Correction
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Solution Overview
Problem
Magnetic sensors, particularly those with anisotropic magnetoresistive (AMR) elements, experience non-linearity and saturation issues at high magnetic field strengths, leading to distortion of output signals and reduced sensitivity, which affects their ability to accurately detect external magnetic fields across a wide dynamic range.
Innovation Solution
The magnetic field sensor employs a dual-transducer configuration, comprising a primary transducer with a half-bridge arrangement and a secondary transducer with a folded bridge, where the secondary transducer has a higher saturation threshold, allowing for correction of non-linearities in the primary transducer's output by determining the angle of the external field, thereby maintaining signal accuracy across varying field strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single AMR transducer is used to detect external magnetic fields, then the device complexity is low, but measurement precision deteriorates at high field strengths due to saturation and non-linearity
Solution Approach 1:
The sensor is divided into two separate transducers: a primary transducer that is highly sensitive to external magnetic fields and a secondary transducer that serves as a reference. This segmentation allows the primary transducer to detect weak fields with high precision while the secondary transducer provides reference data for correction, resolving the contradiction between measurement precision and device complexity by distributing functions across multiple components.
Solution Approach 2:
The patent changes the operating parameters of the two transducers by applying different bias fields and configuring them with different saturation thresholds. The primary transducer operates in a high-sensitivity regime with lower saturation threshold, while the secondary transducer operates in a stable regime with higher saturation threshold. This parameter differentiation enables the system to maintain measurement precision across varying field strengths without excessive complexity.
2Measurement precision
If the primary transducer operates at high sensitivity to detect small external fields, then measurement precision for weak fields is improved, but reliability deteriorates at high field strengths due to saturation
Solution Approach 1:
The system implements feedback by using the output signal from the secondary transducer to correct the output signal from the primary transducer. The processing circuit continuously monitors the secondary transducer's reference output and applies correction algorithms to the primary transducer's measurement output, ensuring reliability across the full dynamic range while maintaining high sensitivity for weak field detection.
Solution Approach 2:
The secondary transducer acts as an intermediary reference element that mediates between the primary transducer's high-sensitivity measurements and the actual magnetic field conditions. By introducing this intermediate reference component, the system can detect small fields with high precision while using the secondary transducer's stable output to correct reliability issues at high field strengths.
3Measurement precision
If a dual-transducer configuration is implemented with different saturation thresholds, then measurement precision is maintained across wide dynamic range, but device complexity increases
Solution Approach 1:
The patent merges the primary and secondary transducers into a single integrated sensor assembly with shared biasing circuits and combined signal processing. By combining the two transducers and their processing circuits into one unified device, the system maintains measurement precision across the wide dynamic range while minimizing the increase in device complexity through integrated design.
4Measurement precision
If the primary transducer uses a half-bridge arrangement for high sensitivity, then measurement precision for weak fields is improved, but reliability deteriorates due to non-linearity at high field strengths
Solution Approach 1:
The patent changes the bias field parameters applied to the primary and secondary transducers. The primary transducer receives a bias field optimized for high sensitivity and linearity in the weak field range, while the secondary transducer receives a different bias field that ensures stable operation and linear response across the full dynamic range. This parameter differentiation resolves the contradiction between sensitivity and linearity by optimizing each transducer for its specific function.
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 effectively corrects for non-linearity and saturation issues, ensuring accurate detection of external magnetic fields and reducing errors in speed and position sensing applications, even at high field strengths, by using the secondary transducer's output to refine the primary transducer's signal.
Implementation Method 1
Magnetic sensors comprising anisotropic magnetoresistive (AMR) elements tend to become non-linear in response to a field that is above a saturation threshold
Implementation Method 2
AMR based speed sensors are a specific type of magnetic sensor, which may be provided with a permanent magnet, producing a bias field
Implementation Method 3
The external magnetic field may be associated with teeth or permanent magnets of an encoder wheel
Data Source
Figure 1~2b
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Figure 5~6
AI summary
A magnetic field sensor (120) is disclosed for providing an output signal (174) in response to an external magnetic field (Hy). The sensor (120) comprises a primary magnetic field transducer (130) for producing a primary signal (131) in response to the external magnetic field (Hy) and having a first magnetic field saturation characteristic; a secondary magnetic field transducer (140) for producing a secondary signal (141) in response to the external magnetic field ( Hy ) and having a second magnetic field saturation characteristic. The first magnetic field saturation characteristic is different from the second magnetic field saturation characteristic. The sensor (120) is configured to use the secondary signal (140) to correct for errors in the output signal (174) arising from saturation of the primary transducer (130).