Multipole Current Sensing for Stable Magnetic Field Measurement
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Solution Overview
Problem
Current sensor devices for determining electrical current in conductors suffer from long-term instability due to mechanical displacement, misalignment of components, and susceptibility to external magnetic fields, leading to inaccurate measurements.
Innovation Solution
A method and sensor device using magnetic sensor elements with a predefined reference point and multipole expansion to determine current, which compensates for relative position changes and external interference, eliminating the need for magnetic cores and shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are placed nearby to sense the magnetic field generated by current, then current measurement is enabled, but long-term stability deteriorates due to mechanical displacement and misalignment of components
Solution Approach 1:
The patent divides the sensor system into multiple magnetic sensors arranged in a specific geometric pattern around the conductor. Each sensor measures the magnetic field at its specific location, and the evaluation unit processes these individual measurements separately before combining them through mathematical evaluation to determine the current, thereby maintaining measurement accuracy despite individual sensor displacements.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct magnetic field measurement at a single point to measuring magnetic field components at multiple points and evaluating them through mathematical relationships. The evaluation unit uses the geometric arrangement and magnetic field component relationships to calculate current, making the measurement immune to individual sensor position variations.
2Measurement precision
If magnetic sensors are used to detect the magnetic field, then current determination is achieved, but susceptibility to external magnetic fields increases, reducing measurement accuracy
Solution Approach 1:
The patent extracts only the relevant magnetic field information by using multiple sensors to measure magnetic field components and applying mathematical evaluation to isolate the current-generated field from external interference. The geometric arrangement and evaluation method selectively process the useful signal while rejecting external field components.
Solution Approach 2:
The evaluation unit continuously processes the magnetic field measurements from all sensors and adjusts the current determination based on the combined information. This mathematical evaluation acts as a feedback mechanism that compensates for external field interference by analyzing the spatial pattern of magnetic field components across multiple sensor locations.
3Reliability
If multiple magnetic sensors are arranged around the conductor, then measurement robustness improves, but device complexity increases
Solution Approach 1:
The patent makes each magnetic sensor serve multiple functions: each sensor measures the magnetic field at its location, contributes to determining current magnitude, helps identify external field interference, and provides spatial information for geometric evaluation. This multi-functionality reduces the need for additional specialized components, offsetting the complexity of having multiple sensors.
Solution Approach 2:
The patent combines the functions of multiple magnetic sensors and their evaluation into a unified measurement system. The evaluation unit integrates measurements from all sensors through mathematical processing, merging individual sensor data into a single current determination. This combining approach simplifies the overall system architecture despite the presence of multiple sensors.
4Measurement precision
If calibration is performed to ensure accurate measurement, then initial measurement precision is achieved, but long-term stability deteriorates due to component displacement and electronic drift
Solution Approach 1:
The patent performs preliminary calibration by determining geometric relationships between sensors and the conductor during manufacturing or initial setup. These geometric parameters are stored and used during operation, eliminating the need for repeated calibration. The preliminary action of establishing geometric relationships ensures long-term stability without requiring subsequent adjustments.
Solution Approach 2:
The evaluation unit continuously uses the stored geometric information and real-time magnetic field measurements to self-correct for any drift or displacement. The system automatically maintains measurement accuracy by processing current sensor data through the pre-established geometric model, without requiring external calibration interventions.
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 method and device provide robust, accurate, and reliable current measurements with improved long-term stability and reduced susceptibility to external fields and component misalignment, while simplifying manufacturing and implementation.
Implementation Method 1
An electric current flowing in a conductor produces a magnetic field. The current in the conductor may be determined by magnetic sensors placed nearby and sensing the related magnetic field generated by the current. The current measurement is based on the principles of Maxwell's equations, which provide that the magnitude of the magnetic field generated by the flow of current in the conductor is inversely proportional to a distance from the center of the conductor to the point of measurement, and proportional to the current flowing in the conductor.
Data Source
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AI summary
Method for determining a current (Imeas) flowing in a conductor (11), comprising: providing a number of magnetic sensor elements (HEj), sensitive to a magnetic field (B) generated by the current (Imeas), at respective sensor locations (dj) relative to a predetermined reference point; outputting sensor signals (sj(t)) indicative of a characteristic of the magnetic field at the respective sensor locations; receiving the sensor signals by a processing circuit (12); mapping the received sensor signals to an output value (xk|k) indicative of the current; and outputting the output value, wherein the mapping comprises using a multipole expansion of the magnetic field generated by the current, the multipole expansion comprising a predetermined number (Mm) of predetermined multipole components (ma) and respectively associated predetermined multipole coefficients (ca); further a current sensor device (10, 15, 16) and a current measuring system (30, 31, 32).