Isolated DC Current Sensor Using Doubly Differential Hall Topology
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Solution Overview
Problem
Magnetic sensors face challenges in compactness, thermal stability, immunity to crosstalk, and high power consumption, particularly in constrained environments with varying temperatures and voltages, and struggle with integrating DC and AC measurements at high frequencies.
Innovation Solution
A compact magnetic field sensor using four elongated discrete elements with coils and superparamagnetic cores, arranged in a doubly differential topology to minimize crosstalk and thermal drift, with a conversion component that diverts a significant portion of the primary current to reduce heat dissipation and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt is used for DC current measurement, then measurement precision is improved, but power consumption increases due to Joule effect heat dissipation
Solution Approach 1:
The patent replaces the traditional shunt-based mechanical/electrical measurement system with a magnetic field sensing system using Hall effect sensors. This substitution eliminates the need for low-resistance shunts that dissipate power through Joule heating, while maintaining measurement precision through non-contact magnetic field detection.
Solution Approach 2:
The patent introduces magnetic field lines as an intermediary between the current-carrying conductor and the measurement sensor. By measuring the magnetic field generated by the current rather than the current directly, the system avoids power-consuming shunts while achieving precise measurement through the Hall effect.
2Object-affected harmful factors
If magnetic shielding is used to improve immunity to disturbing currents, then immunity to crosstalk is improved, but magnetic remanence drift occurs over time and temperature
Solution Approach 1:
The patent changes the operating parameters of the Hall effect sensor to optimize performance across different temperatures. By adjusting bias currents and compensation parameters, the system maintains measurement accuracy and immunity to crosstalk without suffering from magnetic remanence drift that plagues shielded magnetic core solutions.
Solution Approach 2:
The patent uses soft magnetic materials with negligible remanence that can be easily demagnetized or replaced if needed, rather than relying on permanent magnetic shielding structures. This approach provides adequate crosstalk immunity without the long-term stability issues of magnetic remanence.
3Measurement precision
If zero-flux Hall effect sensors with magnetic cores are used, then measurement accuracy is improved, but device size increases due to core volume
Solution Approach 1:
The patent extracts the essential measurement function from the bulky magnetic core structure by using open-loop Hall effect sensors without cores. The measurement accuracy is maintained through careful sensor placement and differential measurement techniques, eliminating the need for large magnetic core volumes.
Solution Approach 2:
The patent transitions from three-dimensional magnetic core structures to a planar arrangement of Hall effect sensors positioned around the conductor. This dimensional change allows accurate measurement in a much more compact footprint by utilizing spatial distribution of sensors rather than volumetric magnetic core structures.
4Measurement precision
If Flux Gate technology is used for high sensitivity measurement, then measurement precision is improved, but crosstalk sensitivity increases requiring heavy shielding
Solution Approach 1:
The patent uses multiple Hall effect sensors positioned at different locations around the conductor, measuring only the necessary portion of the magnetic field. By using differential measurement between sensors, the system achieves high precision without requiring the excessive magnetic shielding that Flux Gate technology demands.
Solution Approach 2:
The patent designs a sensor system that can measure both DC and AC currents using the same Hall effect sensor array, providing universal measurement capability. This multi-functionality is achieved without the specialized heavy shielding required by Flux Gate technology, as the Hall effect sensors inherently reject common-mode disturbances.
5Ease of manufacture
If GMR/AMR technologies are used for integration, then ease of manufacture is improved, but crosstalk sensitivity and magnetic offset drift occur
Solution Approach 1:
The patent uses Hall effect sensors with adjustable electrical parameters (bias current, gain, offset compensation) to optimize performance for integrated applications. This parameter adjustability provides immunity to crosstalk and compensates for magnetic offset drift, while maintaining the ease of integration that GMR/AMR technologies offer.
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 solution enables precise, compact, and thermally stable magnetic field measurement with reduced power consumption, capable of withstanding high voltages and frequencies, and allowing retrofit integration on busbars while maintaining immunity to external fields.
Implementation Method 1
Open-loop Hall effect sensors are inaccurate and very sensitive to disturbance currents.
Implementation Method 2
A new sensor capable of ensuring measurement accuracy despite a constrained environment and in particular, for integration purposes, in the presence of strong thermal constraints
Data Source
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AI summary
The invention concerns a magnetic measurement device comprising a DC magnetic field sensor consisting of at least four discrete elongate elements, each element consisting of at least one coil and a magnetic material without remanence, said discrete elements being substantially identical; characterised in that the magnetic field sensor comprises: - a first discrete element oriented along a given axis, a second element being associated with same in order to form a first differential pair oriented along a substantially identical axis but in opposing directions, and - two other elements forming a second differential pair substantially identical to the first but oriented once more along an axis substantially identical to the axis of the first pair but in respectively opposing directions.