In-Hole Current Measurement Using AMR Sensor Arrays
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Solution Overview
Problem
Current high-current sensors are large, heavy, and expensive due to the need for magnetic cores and step-down transformers, which also suffer from interference from adjacent conductors carrying large currents, making them inefficient for precise current measurement.
Innovation Solution
An in-hole current-measurement system using an array of Anisotropic Magnetoresistive (AMR) sensors positioned within a conductor to minimize magnetic field interference, with a signal processing unit that computes coefficients to model the magnetic field strength and reject stray fields, allowing for precise current measurement without the need for bulky magnetic cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic cores and step-down transformers are used for high-current measurement, then measurement capability for large currents is achieved, but device size, weight, and cost increase significantly
Solution Approach 1:
The patent replaces traditional magnetic core-based mechanical sensing systems with Hall effect sensors that use semiconductor physics to detect magnetic fields. This substitution eliminates the need for bulky magnetic cores and step-down transformers, achieving high-current measurement capability with dramatically reduced weight and size while maintaining measurement accuracy
Solution Approach 2:
The patent uses multiple Hall effect sensors positioned at different locations around the conductor to sample the magnetic field distribution. By combining measurements from these multiple sensor copies, the system reconstructs the total current while rejecting external magnetic interference, achieving accurate measurement without large magnetic cores
2Measurement precision
If magnetic cores and step-down transformers are used for high-current measurement, then measurement capability for large currents is achieved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex magnetic core assemblies and transformer circuits with solid-state Hall effect sensors and simple signal processing electronics. This substitution dramatically reduces device complexity while maintaining the ability to measure large currents accurately
Solution Approach 2:
The patent divides the measurement function into multiple independent Hall effect sensors positioned at different locations. Each sensor independently measures the local magnetic field, and the results are combined through signal processing to achieve the final current measurement, simplifying the overall system architecture
3Measurement precision
If traditional current sensors are used, then current measurement is achieved, but sensitivity to stray fields from adjacent conductors increases
Solution Approach 1:
The patent employs feedback signal processing where the outputs from multiple Hall effect sensors are combined in a specific manner. The signal processing unit calculates the vector sum of magnetic field measurements while using the geometric arrangement of sensors to reject common-mode stray fields from adjacent conductors, improving measurement accuracy in electrically noisy environments
Solution Approach 2:
The patent positions Hall effect sensors at specific asymmetric locations around the conductor, optimized to maximize sensitivity to the target current's magnetic field while minimizing sensitivity to stray fields from adjacent conductors. This asymmetric positioning, combined with differential signal processing, provides inherent rejection of external magnetic 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
The system enables accurate and cost-effective measurement of high currents with reduced sensitivity to stray fields and adjacent conductors, providing continuous current measurement even during transient disturbances, and is compact enough to use in sensitive applications.
Implementation Method 1
An array of Anisotropic Magnetoresistive (AMR) sensors 1302-1308 are positioned in a hole in the electrical conductor
Implementation Method 2
Measuring large currents can be done by measuring the magnetic field surrounding a conductor
Data Source
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AI summary
Apparatus and associated methods relate to an in-hole current-measurement system having three or more magnetic-field sensors and a transient-disturbance selection module configured to form an output signal from a selected subset of sensor signals while decoupling the output signals from a non-selected subset of sensor signals during a predetermined time window when a disturbance signal is expected at the non-selected set of sensor signals. In an illustrative example, a disturbance producing operation may be performed on alternating subsets of sensors while the undisturbed subset of sensors measures an electrical current in the electrical conductor. For example, each selected subset of sensors may be aligned on an axis configured to be mounted perpendicular to current flow within a hole in the electrical conductor. Some embodiments may advantageously provide continuous electrical current measurement while being uninterrupted by the predetermined transient disturbances.