Isolated Voltage Probe with Balanced Magnetic Sensor
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Solution Overview
Problem
Existing isolated voltage probes suffer from impaired isolation mode rejection ratio (IMRR) characteristics due to unbalanced circuit configurations and ground capacitance effects, which affect measurement accuracy and noise reduction in high-voltage equipment measurements.
Innovation Solution
An isolated voltage probe design featuring a conductor with balanced resistance connections between positive and negative leads, integrated with a magnetic sensor and coaxial cable for signal transmission, and an I-V conversion circuit to minimize load effects and ground capacitance impacts, ensuring a balanced and isolated signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage probe uses a high resistance value (some MΩ) to reduce load effect, then the load effect is reduced, but the capacitance component significantly affects the voltage probe characteristics
Solution Approach 1:
The patent introduces a magnetic sensor as an intermediary between the high-resistance voltage probe circuit and the measurement system. The magnetic sensor non-contactly detects the voltage across the high resistance, converting it to a measurable signal without requiring direct electrical connection, thus eliminating the capacitance problem while maintaining the high resistance benefit
Solution Approach 2:
The patent replaces the direct electrical measurement system with a magnetic field-based measurement system. Instead of using electrical connections and capacitive components to measure voltage, the system uses a magnetic sensor to detect the magnetic field generated by the voltage-induced current, substituting electrical measurement with magnetic field measurement
2Reliability
If a voltage probe uses an unbalanced circuit configuration with high resistance, then load effect is reduced, but isolation mode rejection ratio (IMRR) characteristic is impaired
Solution Approach 1:
The patent deliberately uses an asymmetric measurement approach where the magnetic sensor is positioned to non-contactly measure the voltage across the high resistance in a specific orientation. This asymmetric magnetic measurement approach allows the system to maintain the unbalanced high-resistance circuit configuration while achieving good IMRR through the magnetic coupling mechanism that rejects common-mode signals
3Device complexity
If a voltage probe includes ground capacitance effects, then the circuit can be simplified, but measurement accuracy and noise reduction are affected
Solution Approach 1:
The magnetic sensor acts as an intermediary that isolates the measurement system from ground capacitance effects. By measuring the magnetic field rather than directly measuring voltage through capacitive coupling, the system eliminates the harmful ground capacitance while maintaining circuit simplicity
Solution Approach 2:
The patent replaces the electrical measurement path that is susceptible to ground capacitance with a magnetic field measurement path. This substitution eliminates the ground capacitance problem entirely while keeping the physical circuit configuration simple and unchanged
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 proposed solution enhances the IMRR characteristic, reducing unnecessary output signals and improving measurement accuracy by maintaining a balanced circuit configuration and eliminating ground capacitance effects, thus providing an excellent isolation mode rejection ratio.
Implementation Method 1
a magnetic sensor for measuring a magnetic field in a non-contact manner, the magnetic field being generated by a current flowing through the conductor
Data Source
AI summary
An isolated voltage probe includes: a conductor including a positive lead, a negative lead, and a resistance via which the positive lead and the negative lead are connected to each other; a magnetic sensor for measuring a magnetic field in a non-contact manner, the magnetic field being generated by a current flowing through the conductor; and a coaxial cable for transmitting a signal that is based on an output supplied from the magnetic sensor.