Magnetic Field Sensor Calibration for Current Probes
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Solution Overview
Problem
Magnetic field sensors used as current probes are sensitive to placement and alignment, and suffer from interference from nearby current-carrying conductors, making calibration and crosstalk issues challenging, especially when applied to practical scenarios like printed circuit boards.
Innovation Solution
A calibration method for magnetic field sensors that involves injecting a known current into the conductor under test, measuring the resultant magnetic field, and calculating a calibration factor to accurately measure unknown currents without encasing or encircling the conductor, using multiple sensors and advanced signal processing techniques to mitigate crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor is used as a current probe, then current measurement is enabled, but the measurement is sensitive to placement and alignment
Solution Approach 1:
The patent segments the magnetic field measurement into multiple discrete sensor positions arranged in an array. By measuring at multiple locations and combining the data through mathematical processing, the system achieves accurate current measurement without requiring precise placement or alignment of a single sensor, thus resolving the contradiction between measurement precision and ease of operation.
2Measurement precision
If a magnetic field sensor is used as a current probe, then current measurement is enabled, but interference from nearby current-carrying conductors occurs
Solution Approach 1:
The patent uses multiple segmented sensors positioned at different locations to measure magnetic fields from various conductors. By segmenting the measurement into multiple spatial components, the system can distinguish and separate the magnetic field contributions from different current-carrying conductors through mathematical processing, thereby reducing crosstalk interference while maintaining measurement accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the measured magnetic field data from multiple sensors is processed to calculate calibration factors and compensate for interference from nearby conductors. This feedback loop allows the system to identify and subtract crosstalk components, improving measurement accuracy by actively counteracting the harmful interference effects.
3Measurement precision
If conventional calibration methods using Rogowski coils or Faraday-effect probes are used, then current measurement accuracy is improved, but the probe must encircle the conductor which is impractical for PCB applications
Solution Approach 1:
The patent extracts the calibration function from traditional encircling probe methods and implements it using discrete magnetic field sensors positioned near the conductor without encirclement. By taking out the calibration requirement from the physical encirclement constraint and replacing it with mathematical calibration based on measured field data, the system achieves accurate calibration suitable for PCB applications where encirclement is impractical.
Solution Approach 2:
The patent replaces the mechanical encirclement requirement with a mathematical field integration approach. Instead of mechanically wrapping a probe around the conductor, the system uses multiple magnetic field sensors to sample the field and computationally integrate the measurements to derive accurate current values, substituting a mechanical system with a mathematical one that is much more practical for PCB applications.
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 allows for precise measurement of electrical currents without the need to encircle the conductor, reducing practical limitations and interference, and provides accurate calibration factors for reliable current measurement.
Implementation Method 1
Electrical current creates a magnetic field encircling the current in a circuit, so a magnetic field (H-field) sensor can be used as a form of current probe
Data Source
AI summary
A test and measurement instrument for measuring a current in a device under test, comprising an input configured to receive signals from a magnetic field probe; and one or more processors configured to measure, from a signal from the magnetic field probe, a magnetic field generated by a current-carrying conductor of the device under test based on a known current, determine a calibration factor based on the known current and the magnetic field, and generate a calibrated measurement of an unknown current in the current-carrying conductor using a magnetic field generated by the current-carrying conductor based on the unknown current and the calibration factor.