Current Sensor Disturbance Field Cancellation
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Solution Overview
Problem
Current sensors using magnetic sensors face a reduction in measurement accuracy due to the influence of disturbance magnetic fields, particularly when using GMR elements, as the sensitivity in directions orthogonal to the main sensitivity axis cannot be effectively canceled out.
Innovation Solution
The use of two magnetic sensors with their main and sub-sensitivity axes oriented in specific directions relative to each other, allowing for the calculation of differences or sums of their outputs to cancel out disturbance magnetic fields, thereby maintaining measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic sensors are used to measure large current noncontact, then measurement capability is improved, but measurement precision deteriorates due to disturbance magnetic fields
Solution Approach 1:
The patent divides the measurement system into multiple magnetic sensors (first and second magnetic sensors) positioned at different locations around the current line. Each sensor independently detects the magnetic field, and the results are processed to cancel disturbance fields while preserving the measurement signal.
Solution Approach 2:
The patent converts the harmful disturbance magnetic fields into a beneficial cancellation mechanism by strategically positioning magnetic sensors so that disturbance fields appear equally or oppositely in sensor outputs. This allows the disturbance influences to be mathematically eliminated through difference or sum calculations, transforming the previously harmful factor into a tool for improving measurement precision.
2Measurement precision
If MI elements are used to cancel disturbance magnetic fields, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent uses identical or similar magnetic sensors (first and second magnetic sensors with the same or substantially the same sensitivity characteristics) positioned symmetrically around the current line. This copying approach simplifies the system compared to using complex MI elements, as the sensors can be standard components with matched characteristics rather than specialized cancellation elements.
3Reliability
If GMR elements are used instead of MI elements, then device performance is improved, but ability to cancel disturbance fields deteriorates
Solution Approach 1:
The patent applies different sensitivity axis orientations to different magnetic sensors based on their local positions relative to the current line. The first magnetic sensor has its main sensitivity axis oriented in a first direction, while the second magnetic sensor has its main sensitivity axis oriented in a second direction. This local quality differentiation enables each sensor to optimally detect magnetic fields in its specific location while maintaining the ability to cancel disturbance fields through coordinated processing.
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 significantly reduces the impact of disturbance magnetic fields, enhancing the accuracy of current measurement by ensuring that the influences of these fields are either equally or oppositely canceled, leading to improved measurement precision.
Implementation Method 1
detect an induction field generated by the measurement target current flowing through the current line
Implementation Method 2
a current sensor using a scheme in which a change in a magnetic field generated by a measurement target current is detected using magnetic sensors
Data Source
AI summary
A current sensor includes first and second magnetic sensors that are placed around a current line through which a current flows so that the current line is positioned therebetween, and that detect an induction field generated by the current. Each of the first and second magnetic sensors has a main sensitivity axis and a sub-sensitivity axis. The direction of the main sensitivity axis of each of the first and second magnetic sensors is oriented in a direction that is not orthogonal to the direction of the induction field. The directions of the main sensitivity axes of the first and second magnetic sensors are oriented in the same direction and the directions of the sub-sensitivity axes are oriented in the same direction, or the directions of the main sensitivity axes are oriented in opposite directions and the directions of the sub-sensitivity axes are oriented in opposite directions.