Dual Magnetic Current Sensing With Integrated Tamper Detection
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Solution Overview
Problem
Existing contactless current sensors are vulnerable to tampering by external magnetic fields, which can cause measurement errors or damage, and existing tamper detection methods add bulk and expense.
Innovation Solution
A dual differential contactless current sensor system that uses a pair of magnetic sensors to measure electrical current and detect external magnetic fields, integrating tamper detection without additional components by processing sensor outputs to generate a tamper alarm signal when the external field exceeds a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional magnetic sensors are added to detect tampering, then tamper detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies multi-functionality by enabling the existing dual magnetic sensors to serve both their original purpose of measuring electrical current and the additional purpose of detecting tampering magnetic fields. The sensor pair processes two types of signals: differential signals for current measurement and common-mode signals for tamper detection, eliminating the need for separate dedicated tamper sensors.
Solution Approach 2:
The system uses its own existing sensors to detect tampering conditions. The magnetic sensors that normally measure current are also utilized to detect external tampering fields, making the system self-diagnostic without requiring external monitoring devices or additional sensors.
2Measurement precision
If a shunt wire is added to the electrical path for current measurement, then measurement accuracy is improved, but power loss increases
Solution Approach 1:
The patent replaces the mechanical/shunt-based current measurement method with a magnetic field-based contactless sensing method. Instead of inserting a physical shunt wire that creates resistive power loss, the system uses magnetic sensors to non-contactually detect the magnetic field generated by the current, eliminating the energy loss associated with shunt insertion.
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 provides accurate current measurement while detecting tampering with minimal added circuitry, reducing cost and complexity, and allows for tamper-resistant operation.
Implementation Method 1
the electrical current in the conductor induces complementary magnetic fields in the pair of sensors
Implementation Method 2
detecting any external magnetic field, also called a tampering signal herein, based on the same signals from the same sensors
Data Source
AI summary
A dual differential contactless current sensor uses a pair of magnetic sensors placed adjacent to a conductor, such as a metallic trace on a printed circuit board, which is conducting electrical current. The ability to detect and measure a tampering magnetic field in such a sensor is provided by a circuit that sums the outputs of the pair of magnetic sensors. The circuit can output an alarm signal, such as a programmable one-bit alarm that indicates when the external magnetic field exceeds a programmed threshold, or an analog voltage proportional to the external field. The alarm signal can be polled by additional circuitry that indicates to the stakeholders that a party is attempting to alter the power measurement.