Asymmetric Magnetic Current Sensor Stray Field Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic current sensors are sensitive to external disturbance fields and are often bulky, making them less efficient and more costly, especially when trying to measure high currents like 30 Amps, and they require precise alignment which is challenging and costly to achieve.
Innovation Solution
A magnetic current sensor design with two magnetic sensors, one positioned at a non-zero distance from the symmetry plane and the other in the symmetry plane, calculates current based on a weighted difference to compensate for sensitivity mismatch and external fields, allowing for a compact and cost-effective solution that can accurately measure high currents without requiring precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic sensor pairs are used to increase dynamic range, then measurement capability is improved, but device complexity and substrate size increase
Solution Approach 1:
The patent uses asymmetric sensor arrangement where one sensor is positioned at a distance from the conductor while the other is placed in the symmetry plane. This asymmetric configuration enables stray field rejection through differential measurement without requiring multiple sensor pairs, thereby reducing substrate size while maintaining measurement capability.
2Measurement precision
If magnetic sensors are positioned to measure magnetic field twice for doubled signal, then measurement sensitivity is improved, but sensitivity to external disturbance field increases
Solution Approach 1:
The patent converts the harmful effect of external disturbance fields into a useful feature by positioning one sensor in the symmetry plane where it measures only the stray field. This allows the differential measurement to automatically reject stray fields while maintaining sensitivity to the conductor's magnetic field, turning the previously problematic stray field sensitivity into a benefit for noise rejection.
3Measurement precision
If precise alignment of sensors is required for accurate measurement, then measurement accuracy is improved, but ease of manufacture and assembly deteriorates
Solution Approach 1:
The asymmetric positioning of sensors (one at distance, one in symmetry plane) creates a configuration that is inherently less sensitive to alignment variations. The differential measurement approach tolerates manufacturing tolerances better than symmetric arrangements, as the key requirement is maintaining the relative positional relationship rather than achieving precise absolute positioning.
4Ease of manufacture
If substrate size is reduced to lower cost, then manufacturing cost is improved, but ability to accommodate multiple sensors for high current measurement deteriorates
Solution Approach 1:
The patent extracts the function of measuring the magnetic field at two locations by using a single substrate with sensors positioned at different distances from the conductor. One sensor measures the combined field (conductor + stray) while the other in the symmetry plane measures only stray field, eliminating the need for multiple substrates or sensor pairs and reducing overall device size and cost.
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 design provides a highly insensitive and compact current sensor capable of measuring high currents while reducing the size and cost of the substrate, improving accuracy and reducing sensitivity to external disturbance fields, making it suitable for competitive markets like automotive.
Implementation Method 1
a first magnetic sensor (211) having a first axis of maximum sensitivity and adapted for providing a first value (v1), indicative of a first magnetic field component (B1) induced at said first location by the current (I) to be measured
Implementation Method 2
a second magnetic sensor (212) having a second axis of maximum sensitivity parallel to said first axis and parallel to said symmetry plane, and located at a second location (x2) situated in said symmetry plane, and adapted for providing a second value (v2), indicative of an external disturbance field (if present)
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
A current sensor device (400) for measuring an electrical current, comprising: a substrate (410) mounted relative to an electrical conductor (413) having a symmetry plane (Ω), and comprising a first and a second magnetic sensor (411, 412); the first magnetic sensor located at a first location outside the symmetry plane configured for providing a first value (v1) indicative of a first magnetic field component induced by the current; the second magnetic sensor located at a second location in the symmetry plane (Ω), and configured for providing a second value (v2) indicative of an external disturbance field; a processing circuit (610; 710) connected to the first and second magnetic sensor, and adapted for determining the current based on a difference between the first and second value (v1,v2).