Current Sensor Shielding for Accurate Failure Detection
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Solution Overview
Problem
Current sensors face issues with accurate failure determination under the influence of external magnetic fields, particularly when detecting small currents, due to differing signal-to-noise ratios between magnetic detection units, leading to erroneous failure determinations and a need for miniaturization.
Innovation Solution
A current sensor design featuring a current path surrounded by an electromagnetic shield with first and second magnetic detection units positioned to maintain similar signal-to-noise ratios, where the second unit is closer to the current path than the first, and amplifiers to match their outputs, ensuring accurate failure detection regardless of external magnetic field strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic detection units are disposed on the top and bottom surfaces of a substrate with adjusted sensitivity, then failure determination can be performed, but the S/N ratio differs between units causing erroneous failure determination under strong external magnetic fields
Solution Approach 1:
The patent converts the harmful effect of external magnetic fields into a beneficial configuration by strategically positioning magnetic detection units at locations where the external magnetic field influence is naturally balanced. By placing units at opposite sides of the current path with equal distances, the external magnetic field affects both units equally, allowing their outputs to be compared for failure detection without being misled by external interference.
Solution Approach 2:
The patent creates an equipotential arrangement regarding external magnetic field exposure by positioning both magnetic detection units at equal distances from the current path. This ensures that both units experience the same external magnetic field conditions, making their S/N ratios consistent and enabling reliable failure determination through output comparison.
2Volume of moving object
If the sensor is miniaturized, then compactness is improved, but maintaining accurate failure determination under external magnetic fields becomes more difficult
Solution Approach 1:
The patent transitions from a planar substrate arrangement to a three-dimensional spatial configuration by positioning magnetic detection units on opposite sides of the current path. This dimensional change allows both units to be equidistant from the current path while maintaining a compact overall structure, enabling accurate failure determination without increasing sensor volume.
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 enables accurate failure determination of each magnetic detection unit even under strong external magnetic fields and allows for miniaturization of the current sensor while maintaining high detection accuracy.
Implementation Method 1
an electromagnetic shield configured to surround a periphery of the current path
Implementation Method 2
first and second magnetic detection units configured to face the current path
Data Source
AI summary
First and second magnetic detection units are disposed at positions where an S/N ratio, which is a ratio between the strength of a magnetic field generated by a current to be measured flowing through a current path and the strength of an external magnetic field, is the same. A processing unit determines a normal operation state in a case where the detection signal of the first magnetic detection unit and the detection signal of the second magnetic detection unit approximately match each other. The processing unit determines that either one of the first and second magnetic detection units has failed in a case where the detection signals do not match each other.