Magnetic Sensor Current Measurement with Differential Interference Cancellation
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Solution Overview
Problem
Accurate remote measurement of current through a wire is challenging, especially when other current-carrying wires are nearby, as existing methods like Rogowski coils cannot measure direct current and can be bulky for tight spaces.
Innovation Solution
An apparatus with magnetic sensors and a processor that generates a differential signal to determine the location and magnitude of current flowing through a wire, using Hall Effect or AMR sensors to cancel common mode interference and measure both AC and DC currents, regardless of wire placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Rogowski coil is used for AC current measurement, then the measurement does not depend on precise wire location, but the device cannot measure DC current and is too bulky for tight spaces
Solution Approach 1:
The device divides the sensing function into multiple discrete magnetic sensors positioned at specific locations around the opening, rather than using a single large Rogowski coil. This segmentation allows for a compact form factor while maintaining measurement capabilities through differential signal processing of readings from multiple sensor elements.
Solution Approach 2:
The invention replaces the mechanical Rogowski coil structure with an electronic sensing system using magnetic sensors and differential signal processing. This substitution enables both AC and DC current measurement capabilities in a compact configuration that does not rely on the precise placement of wires within a large coil structure.
2Measurement precision
If magnetic sensors are positioned close to the wire for accurate measurement, then measurement precision improves, but interference from nearby current-carrying wires increases
Solution Approach 1:
The invention extracts and eliminates the common mode interference signal by using differential measurement. The differential signal processing removes the unwanted magnetic field contributions from nearby current-carrying wires, isolating only the signal from the wire of interest while maintaining close sensor-to-wire positioning for accurate measurement.
Solution Approach 2:
The magnetic sensors are positioned asymmetrically on opposing sides of the opening at specific locations where they can detect the magnetic field from the wire of interest. This asymmetric positioning, combined with differential processing, allows the system to distinguish the target wire's field from interfering fields of nearby wires.
3Adaptability or versatility
If the wire placement position varies, then adaptability to different installations is improved, but measurement precision deteriorates due to location-dependent signal strength
Solution Approach 1:
The device is designed with a universal sensing approach that functions regardless of where the wire is positioned within the opening. The multiple magnetic sensors and differential signal processing create a measurement system that is insensitive to the exact wire location, allowing the same device to accurately measure current for wires of various thicknesses and positions without requiring precise placement.
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
Enables precise and accurate current measurement in tight spaces without mechanical parts, accommodating various wire thicknesses and reducing interference from nearby wires, allowing for both AC and DC measurements.
Implementation Method 1
using Hall Effect or AMR sensors to cancel common mode interference and measure both AC and DC currents
Implementation Method 2
using Hall Effect or AMR sensors to cancel common mode interference and measure both AC and DC currents
Implementation Method 3
two magnetic sensors within the housing positioned on opposing sides of the opening in the first dimension... generate a differential signal indicative of a difference between outputs of the two magnetic sensors
Data Source
AI summary
In an embodiment, a body of apparatus includes an opening, such as a V-shaped jaw, that deterministically locates a position of a wire in at least one dimension when the wire is placed in the opening. The apparatus also includes a plurality of sensors. At least one differential signal can be generated from signals from magnetic sensors, such as anisotropic magnetoresistance (AMR) sensors, of the plurality of sensors to cancel out common mode interference. An additional sensor of the plurality of sensors provides an output from which the location of the wire in another dimension is determined. The current flowing through the wire can be derived from at least the at least one differential signal and the location of the wire the other dimension.