Asymmetric Magnetic Sensor Array for Stray Field Immune Current Measurement
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Solution Overview
Problem
Accurate current measurement through a wire is challenging, especially when the wire is not precisely positioned or when nearby current-carrying wires cause stray field interference, as existing methods like Rogowski coils are limited in direct current measurement and bulky for tight spaces.
Innovation Solution
A current measurement system using a housing with multiple magnetic sensors positioned at different distances from the center of a target measurement zone, where some sensors are tangential and others cross through the zone, reducing stray field interference and enabling accurate AC and DC measurements without precise wire positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Rogowski coil is used for AC current measurement, then the measurement does not depend on precise wire location, but the device cannot measure DC current and is too bulky for tight spaces
Solution Approach 1:
The measurement device is divided into multiple independent magnetic sensors positioned at different locations around the target measurement zone. Each sensor measures the magnetic field at its specific position, and the processor combines these segmented measurements to calculate the current, enabling both AC and DC measurement while maintaining compact size
Solution Approach 2:
The patent transitions from a single-dimensional Rogowski coil measurement to a multi-dimensional sensor array arrangement. Sensors are positioned at different radial distances and angular positions around the measurement zone, creating a two-dimensional measurement plane that provides enhanced measurement capability for both AC and DC currents while reducing bulk
2Measurement precision
If magnetic sensors are positioned close to the wire for accurate measurement, then measurement accuracy improves, but stray field interference from nearby wires increases
Solution Approach 1:
The magnetic sensors are positioned asymmetrically at different radial distances from the center of the target measurement zone rather than uniformly. This asymmetric arrangement, with some sensors closer and others farther away, allows the system to differentiate between the target wire's magnetic field and stray fields from nearby wires, reducing interference while maintaining measurement accuracy
Solution Approach 2:
The patent converts the potentially harmful stray field interference into a useful measurement signal. By positioning sensors at multiple distances and using differential measurement techniques, the system can identify and subtract stray field contributions from the total magnetic field measurement, effectively converting interference into a correctable component that improves overall measurement accuracy
3Device complexity
If sensors are positioned at a single distance from the center, then the device structure is simple, but the measurement accuracy and dynamic range are limited
Solution Approach 1:
The sensor array is segmented into multiple groups positioned at different radial distances from the center of the measurement zone. This segmentation creates multiple measurement zones with different sensitivity characteristics, allowing the system to accurately measure both small and large currents across a wider dynamic range while maintaining a relatively simple overall device structure
Solution Approach 2:
Different regions of the measurement zone have different sensor densities and configurations. Sensors positioned at different radial distances provide locally optimized measurement characteristics - closer sensors provide higher sensitivity for small currents while farther sensors reduce interference for large currents, creating local quality variations that enhance overall measurement precision across the full dynamic range
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 system provides increased accuracy and a wider dynamic range for current measurement, reducing stray field interference and allowing for accurate measurement of wires in non-ideal positions, with improved accuracy and reduced interference compared to conventional methods.
Implementation Method 1
Sensors may be positioned around an opening for a wire to measure the current flowing through the wire
Data Source
AI summary
Magnetic sensors may be positioned around an opening for a wire to measure the current flowing through the wire. A non-symmetric positioning of the sensors around the target measurement zone can enable an expanded measurement zone compared to conventional current measurement devices. Further, some sensors may be paired such that a hypothetical line connecting the sensors is tangential to the target measurement zone. Other sensors may be paired such that a hypothetical line between the sensors crosses the target measurement zone. The different pairs of the sensors can enable a reduction in the impact of stray field interference on the measurement of the current flowing through the wire.