Radar Level Gauge Impedance Switching for Conducted EMC Control
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Solution Overview
Problem
Radar level gauge systems face challenges in meeting electromagnetic compatibility (EMC) requirements due to conducted disturbances, which are difficult to filter effectively and costly to address with conventional galvanic isolation, especially in explosion-prone environments.
Innovation Solution
A radar level gauge system with a control connection that switches between low- and high-impedance modes, using an internal energy storage to disconnect measurement connections during measurements, thereby preventing conducted disturbances from reaching the measurement module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filtering is added at the wired connection to handle conducted disturbances, then electromagnetic immunity is improved, but the effectiveness is limited due to Ex requirements restricting energy storing components
Solution Approach 1:
The patent extracts the energy storage function from the communication module and places it in a separate measurement module. This separation allows the communication module to maintain low output impedance for communication while the measurement module can use the stored energy for measurements without being constrained by Ex requirements on energy storing components in communication circuits.
Solution Approach 2:
The patent introduces an energy storage component (capacitor) as an intermediary between the communication module and measurement module. This intermediary stores energy during communication phases and releases it during measurement phases, allowing the measurement module to operate with high impedance without affecting the communication module's low impedance operation.
2Reliability
If galvanic isolation is introduced to handle conducted disturbances, then electromagnetic immunity is improved, but cost and complexity increase significantly
Solution Approach 1:
The patent makes the output impedance of the communication module dynamic by switching between low impedance during communication and high impedance during measurement. This dynamic impedance switching eliminates the need for galvanic isolation while maintaining electromagnetic immunity, as the measurement module is effectively isolated during measurements through high impedance state.
Solution Approach 2:
The patent changes the impedance parameter of the communication module output based on operational phase. During communication, low impedance is used for signal integrity; during measurement, high impedance is used to prevent conducted disturbances. This parameter change approach replaces the need for complex galvanic isolation.
3Loss of energy
If the measurement connection maintains low impedance to minimize power losses, then energy efficiency is improved, but conducted disturbances can reach the measurement module
Solution Approach 1:
The patent uses periodic switching of the measurement connection impedance. During communication phases, the connection maintains low impedance for efficient energy transfer. During measurement phases, the connection switches to high impedance to block conducted disturbances. This periodic action resolves the contradiction between energy efficiency and disturbance rejection.
Solution Approach 2:
The patent performs preliminary energy storage in the energy storage component during communication phases before measurements are taken. This preliminary action ensures that the measurement module has sufficient energy stored to operate with high impedance during measurements without causing power losses, while simultaneously blocking conducted disturbances.
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 achieves improved EMC properties at a lower cost and complexity by minimizing power losses and suppressing conducted disturbances, ensuring accurate measurements.
Implementation Method 1
an energy storage arranged to be charged by the measurement connection and to provide power to the power supply for performing a measurement by the measurement module
Implementation Method 2
a switch arranged between the communication module and the energy storage, the switch being controllable to break the measurement connection between the communication module and the energy storage during a measurement
Data Source
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AI summary
Radar level gauge system (200) comprising: a communication module (202) configured to be connected to an external communication device; a measurement module (204) configured to generate, transmit and receive a measurement signal; a control connection (206) configured to connect the communication module to the measurement module, the control connection being configured to be in a high-impedance mode at least during a measurement by the measurement module; a power supply (208) configured to provide power to the measurement module; an energy storage (210) coupled to the power supply; a measurement connection (212) connecting the communication module to the energy storage, wherein the energy storage is arranged to be charged by the measurement connection and configured to provide power to the power supply for performing a measurement by the measurement module; and a switch (214) arranged between the communication module and the energy storage, the switch being controllable to break the measurement connection between the communication module and the energy storage during a measurement by the measurement module.