Level Gauge Impedance Matching for Resonant Probe Cable Length
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Solution Overview
Problem
Existing level gauges and fill limit switches face interference issues due to line resonances caused by long extension cables between the electronic components and the resonant probe, limiting the distance between the sensor and the electronic components, especially at high temperatures or when the probe needs to be positioned below the container lid.
Innovation Solution
A level gauge design with a connecting element comprising two separate conductors, where the impedance of each conductor is adjusted to minimize reflection factors at the input of the signal generator and detector, preventing interference and allowing longer cable lengths, up to a fourth of the wavelength of the resonance frequency, while maintaining high resonance frequencies above 10 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a long extension cable is used to connect the electronic components to the probe, then the probe can be positioned further from the electronic components (e.g., below container lid or in high temperature areas), but line resonances occur on the connecting conductor that interfere with the probe resonances and reduce measurement accuracy
Solution Approach 1:
The patent applies impedance matching to transform the harmful line resonances into beneficial effects. By adjusting the impedance of the connecting conductors to match the characteristic impedance (typically 50 ohms), the reflections that cause line resonances are minimized. This converts the potentially harmful long cable into a controlled transmission line that can be made electrically transparent through proper impedance matching, allowing the cable to transmit signals without creating interfering resonances.
Solution Approach 2:
The patent changes the electrical parameters of the connecting conductors by adjusting their impedance characteristics. Specifically, the impedance of the connecting conductors is optimized to match the source and load impedances, which changes the electrical behavior of the cable from a resonant structure to a controlled transmission line. This parameter adjustment allows the system to operate with longer cables while maintaining measurement accuracy.
2Reliability
If the resonance frequency of the probe is increased above 10 MHz to improve functional safety and reduce interference from media adherence, then the wavelength decreases and the maximum acceptable cable length becomes shorter due to line resonance constraints
Solution Approach 1:
The patent changes the electrical parameters of the connecting conductors by adjusting their impedance characteristics. Specifically, the impedance of the connecting conductors is optimized to match the source and load impedances, which changes the electrical behavior of the cable from a resonant structure to a controlled transmission line. This parameter adjustment allows the system to operate with longer cables while maintaining measurement accuracy.
Solution Approach 2:
The patent applies impedance matching to transform the harmful line resonances into beneficial effects. By adjusting the impedance of the connecting conductors to match the characteristic impedance (typically 50 ohms), the reflections that cause line resonances are minimized. This converts the potentially harmful long cable into a controlled transmission line that can be made electrically transparent through proper impedance matching, allowing the cable to transmit signals without creating interfering resonances.
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 design minimizes signal interference and allows for longer cable lengths between the electronic components and the probe, enhancing the accuracy and reliability of fill level detection by preventing line resonances from affecting the measurement, thus enabling more flexible and accurate level gauge operation.
Implementation Method 1
The resonance frequency of the resonance circuit characterizes here the size of the capacity to be measured
Implementation Method 2
The excitation of an electric resonance circuit requires the feeding of an alternating power signal via an alternating power generator
Implementation Method 3
Another principle for a fill level switch comprises the use of a conductor resonance. A conductor embodied as an oblong probe generates reflections of an electric alternating voltage supplied, from which a standing voltage oscillation forms on the probe
Implementation Method 4
a connecting element, which electrically connects the electronic with the resonance measuring probe
Data Source
AI summary
A level gauge with a control and evaluation electronic comprising a signal generator for generating an alternating voltage, a signal detector for detecting a reflected voltage, a resonant measuring probe, and a connecting element, which connects the evaluating electronic electrically to the measuring probe, with the connecting element comprising a first connecting conductor, which connects the signal generator to the measuring probe, and a second connecting conductor which connects the measuring probe to the signal detector.