Hall Sensor Yoke for Current Measurement Shielding
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Solution Overview
Problem
Current current measuring devices are limited in measuring ranges, suitable only for small currents up to 20A, and lack effective shielding against external magnetic interference fields.
Innovation Solution
A current measurement device featuring a magnetic field sensor with a high permeability yoke that encloses the current conductor, amplifies the magnetic field, and shields against external interference, allowing measurement of currents from 0 to 200A or 300A with optional overload capacity and enhanced shielding through a U-shaped additional shield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor with an integrated current conductor is used, then the device can measure currents, but it is only suitable for measuring relatively small currents of up to 20A and external magnetic interference fields are hardly shielded
Solution Approach 1:
The device is divided into separate components: the current conductor is external and can be chosen independently, while the magnetic field sensor and yoke form a separate measuring unit. This segmentation allows the same sensor to be used with different conductor types and configurations, enabling measurement across multiple current ranges (0-20A, 0-200A, 0-300A) and providing shielding capability without limiting the measuring range
Solution Approach 2:
A yoke made of magnetic material with high permeability is introduced as an intermediary component between the current conductor and the magnetic field sensor. The yoke serves dual functions: it concentrates and amplifies the magnetic field generated by the current for accurate measurement, and it shields the sensor from external magnetic interference fields, thereby resolving the contradiction between measurement capability and shielding effectiveness
2Object-affected harmful factors
If the yoke is expanded in the direction to be shielded to increase shielding factor, then shielding against external magnetic interference fields improves, but the gain factor for magnetic field amplification decreases
Solution Approach 1:
The yoke is designed with non-uniform geometry: it has a larger cross-sectional area in the regions where shielding is needed and a smaller cross-sectional area in the region where magnetic field concentration is needed. Specifically, the yoke extends further in the direction to be shielded (providing shielding) while maintaining a compact dimension perpendicular to the conductor (providing field amplification). This local variation in geometry allows both shielding and amplification functions to be optimized simultaneously
Solution Approach 2:
The yoke geometry is optimized by considering multiple dimensions independently: the dimension parallel to the conductor provides shielding through extended coverage, while the dimension perpendicular to the conductor provides field amplification through concentrated flux paths. By optimizing each dimension separately rather than uniformly scaling the yoke, both shielding factor and gain factor are maximized
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 device effectively measures currents in various ranges with improved shielding, maintaining sensitivity to the magnetic field generated by the current while rejecting external interference, and can handle brief overload currents up to 1000A.
Implementation Method 1
a magnetic field sensor with a Hall element integrated in a semiconductor chip
Implementation Method 2
The yoke and the two magnetic field concentrators form a magnetic amplifier that amplifies the magnetic field generated by the current
Implementation Method 3
a yoke made of a magnetic material with high permeability, which surrounds the current conductor in the measuring area
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A current measuring device comprises a magnetic field sensor (2) for measuring the magnetic field generated by a current I flowing through a conductor and a yoke (3) made of a material with high magnetic permeability. The magnetic field sensor (2) preferably has a semiconductor chip with at least one Hall element and an electronic circuit for operating the Hall element. On a top side of the semiconductor chip, two magnetic field concentrators separated by an air gap are arranged such that the Hall element is permeated by magnetic field lines that originate from the first magnetic field concentrator near the air gap and impinge on the second magnetic field concentrator near the air gap.The yoke (3) consists of an elongated piece of sheet metal or a laminate of sheet metal with two ends (10, 11), which has been bent into a shape in which the end faces (12, 13) of the ends (10, 11) of the yoke (3) are opposite each other and separated by an air gap (14). The ends (10, 11) of the yoke (3) are tapered, such that the width of the ends (10, 11) of the yoke (3) is less than the width of the yoke (3).