Current Comparator Accuracy via Bipolar Core Saturation
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Solution Overview
Problem
Current current comparator systems face challenges in achieving parts per billion accuracy due to factors like interruptions during measurements and manufacturing variations in toroids, leading to residual flux and offsets.
Innovation Solution
A method involving a current comparator design with a bi-polar current profile to saturate and null the magnetic field within the magnetic core, using a digital to analog converter, current tracking amplifiers, and load resistors to iteratively cycle the current through negative and positive cycles, effectively addressing residual flux and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current comparator systems are used, then measurement capability is provided, but residual flux and offsets prevent parts per billion accuracy
Solution Approach 1:
The patent applies preliminary action by implementing a degaussing sequence that saturates the magnetic core in both positive and negative directions before measurements are taken. This preliminary saturation process eliminates residual flux and hysteresis effects that would otherwise compromise measurement accuracy at parts per billion levels.
Solution Approach 2:
The patent implements periodic action through iterative cycling of bi-polar current through the magnetic core. By repeatedly saturating the core in alternating positive and negative directions, the system progressively reduces residual flux to negligible levels, enabling high-precision measurements.
2Ease of operation
If measurement cycles are interrupted, then operational flexibility is improved, but residual flux generates offsets reducing accuracy
Solution Approach 1:
The system performs preliminary degaussing cycles after interruptions to restore the magnetic core to a flux-free state before resuming measurements. This ensures that operational flexibility does not compromise measurement accuracy by eliminating residual flux generated during interruptions.
Solution Approach 2:
The patent employs feedback mechanisms that monitor measurement conditions and automatically initiate degaussing sequences when interruptions are detected. This feedback control ensures the magnetic core is properly conditioned before measurements resume, maintaining parts per billion accuracy despite operational interruptions.
3Ease of manufacture
If manufacturing variations in toroids occur, then device complexity is reduced, but residual flux increases causing offsets
Solution Approach 1:
The patent converts the harmful effect of manufacturing variations that cause residual flux into a beneficial process by implementing controlled saturation cycles. These cycles deliberately drive the magnetic core to saturation in both directions, systematically eliminating residual flux from whatever source, thereby transforming manufacturing imperfections into manageable conditions that enable high-precision measurements.
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 approach enhances the accuracy of current comparator systems to parts per billion by effectively nullifying magnetic field offsets and improving measurement precision.
Implementation Method 1
generating a first predetermined current profile to initially saturate a magnetic core of the current comparator and subsequently iteratively cycle the current through negative and positive cycles to null the magnetic field within the magnetic core
Implementation Method 2
null the magnetic field within the magnetic core
Implementation Method 3
selectively coupling the first winding of the current comparator to ground via the load resistor
Data Source
AI summary
Precision AC and DC voltage, current, phase, power and energy measurements and calibrations with current ranges from 1 uA to 20 kA and voltage ranges from 1V to 1000 kV are now performed with accuracies of better than one part per million. Continued demand for improved accuracy has led the inventors to address remnant magetization within the current comparators that form the basis of the measuring process within many of the measurement instruments providing the precision AC and DC measurements and calibrations. Accordingly, the inventors present current comparator and measurement system architectures together with control protocols to provide for correction of this remnant magnetization.