Current Sensor Signal Correction for External Magnetic Fields
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Solution Overview
Problem
Current measuring devices face reduced detection accuracy when non-uniform external magnetic fields from multiple sources affect magnetic sensors, as seen in Japanese Unexamined Patent Application Publication No. 2005-195427.
Innovation Solution
A current sensor with at least three magnetic field detection elements positioned differently relative to a busbar, coupled with a current detection circuit that processes signals to correct for external magnetic fields from adjacent busbars, improving detection accuracy by canceling these interfering fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are used to detect current in a busbar, then current detection is enabled, but detection accuracy is reduced when non-uniform external magnetic fields from multiple sources act on the sensors
Solution Approach 1:
The sensor divides the detection function into multiple magnetic field detection elements (at least three) positioned at different distances from the busbar. Each element detects the combined magnetic field, and the detection circuit segments the total signal into components from the target busbar and external sources based on their different spatial relationships, enabling separate processing and cancellation of interference.
Solution Approach 2:
The invention converts the harmful external magnetic field interference into a useful signal component. By detecting that external fields are present and using the differential positioning of multiple sensors, the system identifies and extracts the external field contribution, then subtracts it from the total measurement. This transforms the previously harmful interference into a cancelable component, improving overall measurement accuracy.
2Measurement precision
If additional shielding is added to block external magnetic fields, then detection accuracy improves, but manufacturing cost increases and placement freedom is reduced
Solution Approach 1:
The invention replaces the mechanical/physical shielding approach with an electronic signal processing solution. Instead of using magnetic shields or physical barriers to block external fields, the system uses multiple sensors combined with mathematical processing in the detection circuit to identify and cancel external field contributions. This substitutes a complex mechanical shielding system with a simpler electronic solution that achieves the same goal of improving measurement accuracy.
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
Enhances detection accuracy of currents flowing through busbars by effectively canceling external magnetic fields from adjacent sources, reducing manufacturing costs and increasing freedom in sensor placement without the need for additional shielding.
Implementation Method 1
at least three magnetic field detection elements configured to detect a magnetic field generated by a current flowing through a busbar
Data Source
AI summary
First, second and third magnetic detection elements are provided to detect a magnetic field generated by a current flowing through a busbar and are provided at positions different in distance in one direction with respect to the busbar. Each of the magnetic field detection elements detect, in addition to the magnetic field generated from the busbar, a magnetic field generated from each of a plurality of external magnetic field sources other than the busbar. A current detection circuit performs signal processing of performing, based on detection signals of the magnetic fields, a correction for canceling the magnetic field generated from each of the plurality of external magnetic field sources for one of the detection signals of the magnetic field, and outputting the corrected detection signal as a detection signal of the current flowing through the busbar.