Point Symmetric Current Sensor Strain Compensation
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Solution Overview
Problem
Conventional current sensors experience measurement errors due to isotropic elongation or strain caused by temperature changes, difficulty in large current measurement, and reduced accuracy from external electric fields.
Innovation Solution
A current sensor design with a first and second half bridge circuit placed point symmetrically about the central point of a mounting substrate, utilizing magnetoresistive elements with barber pole electrode structures and compensating conductive lines to counteract magnetic fields and strain effects, ensuring balanced resistance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bridge circuit consisting of four magnetoresistive elements is placed mirror symmetrically, then the current sensor can measure current, but measurement error occurs due to isotropic elongation or strain from temperature changes
Solution Approach 1:
The patent transitions from mirror symmetric arrangement to point symmetric arrangement of the bridge circuits. This asymmetric change in symmetry type allows the bridge circuits to experience equal isotropic strain while maintaining their relative balance, thereby canceling out temperature-induced measurement errors
Solution Approach 2:
The patent introduces compensating conductive lines that act as counterweights to the magnetoresistive elements. These compensating lines experience equal strain and are arranged to counterbalance the strain effects on the measurement elements, eliminating the net effect of isotropic elongation on measurement accuracy
2Device complexity
If a conventional bridge circuit is used, then the structure is simple, but it becomes difficult to carry out large current measurement
Solution Approach 1:
The patent divides the measurement system into multiple bridge circuits (first and second bridge circuits) that are connected in parallel. Each bridge circuit handles a portion of the total current, enabling large current measurement while maintaining the simplicity of individual bridge circuit structures
3Device complexity
If no countermeasures are taken against external electric fields, then the device structure remains simple, but measurement accuracy reduces when noise sources are close
Solution Approach 1:
The patent introduces compensating conductive lines as intermediary elements between the external electric field and the magnetoresistive elements. These compensating lines act as mediators that experience the external field effects and transfer balanced strain to counterbalance the measurement elements, thereby shielding the measurement from external field interference
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 design effectively cancels out measurement errors from isotropic elongation and strain, improves accuracy by counteracting external magnetic fields, and enables precise large current measurement while minimizing noise interference.
Implementation Method 1
a first half bridge circuit placed in a first region divided by a center line of a mounting substrate, and a second half bridge circuit placed in a second region
Implementation Method 2
the first and second half bridge circuits are equally formed and placed point symmetrically about the central point of the mounting substrate
Data Source
AI summary
A current sensor that can reduce a measurement error due to isotropic elongation or strain owing to temperature and the like. A first half bridge circuit is placed in a first region divided by a center line of a mounting substrate, and a second half bridge circuit is placed in a second region, and the half bridge circuits are equally formed and placed point symmetrically about the central point of the mounting substrate. Even if elongation or strain occurs isotropically in the mounting substrate of magnetoresistive elements owing to temperature, the half bridge circuits undergo the influence of the elongation or strain equally as the bridge circuit. Thus, it can cancel the effect and reduce the measurement error due to the isotropic elongation or strain owing to temperature.