Impedance Limit Switch Adaptive Frequency Wobble
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Solution Overview
Problem
Impedance limit switches used for level measurement are prone to incorrect determination due to interference from jammers, such as conveyor belts or pumps, which can shift the resonance curve and lead to incorrect coverage states.
Innovation Solution
The impedance limit switch employs a wobble generator to vary frequency within a defined range, measures impedance at multiple points, and uses a quality criterion based on frequency safety and error margins to determine reliable coverage, potentially re-measuring if criteria are not met to ensure accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance limit switch measures resonance frequency to determine coverage, then measurement precision is improved, but reliability deteriorates due to interference from jammers that shift the resonance curve
Solution Approach 1:
The patent applies dynamics by making the evaluation criteria adaptive rather than fixed. The system dynamically adjusts the frequency window and evaluation parameters based on the measured resonance curve characteristics, allowing the measurement system to adapt to varying interference conditions and maintain reliability despite jammer-induced shifts in the resonance frequency
Solution Approach 2:
The patent changes parameters by introducing multiple evaluation parameters including frequency window adjustment, impedance threshold adaptation, and quality factor analysis. These parameter changes allow the system to distinguish between genuine coverage changes and interference-induced variations, thereby maintaining measurement precision and reliability simultaneously
2Reliability
If frequency is varied to measure impedance at multiple points, then reliability is improved, but measurement precision may deteriorate due to interference signals
Solution Approach 1:
The patent implements feedback by continuously monitoring the measured impedance values and resonance curve characteristics, then using this information to adjust the frequency window and evaluation criteria for subsequent measurements. This feedback mechanism allows the system to learn from interference patterns and improve its ability to distinguish genuine coverage changes from interference signals
Solution Approach 2:
The patent applies preliminary action by performing a preliminary measurement scan to identify the actual resonance frequency and characteristics before conducting the final coverage determination. This preliminary action allows the system to establish baseline parameters and adjust its measurement strategy accordingly, improving both reliability and precision
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 method significantly improves the reliability of determining coverage by minimizing interference effects, providing a robust yes/no decision or measurement quality assessment, even under jamming conditions.
Implementation Method 1
A measuring capacitance is formed between the measuring electrode and the reference electrode, which forms a series resonant circuit with a discrete inductance
Implementation Method 2
A measuring capacitance is formed between the measuring electrode and the reference electrode
Implementation Method 3
The impedance of the resonant circuit changes depending on the frequency. This can be illustrated, for example, by a curve in which the magnitude of the impedance (y-axis) is plotted against the frequency (x-axis). This curve is sometimes called the 'impedance curve.' The curve shows a minimum at the resonant frequency of the resonant circuit.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The invention relates to devices and methods for level measurement or limit level determination, in particular an impedance limit switch based on an electrical resonant circuit that determines the coverage with a fill material (120). The impedance limit switch (100) comprises a measuring probe (200), a variable frequency generator (300), and an analysis unit (400). The determination is carried out in the following steps: measuring the impedance of the measuring probe (200) in a range from a first to a second frequency with first reference points (641) in a first time interval (631); determining a plurality of local minima (650) of the measured impedance of the measuring probe (200) and determining a quality criterion. If the quality criterion for the measurement is not met, measuring the impedance of the measuring probe (200) with second reference points (642) in a second time interval (632).If the quality criterion for the measurement is met, determine whether the global minimum (652) is above or below the cutoff frequency for the impedance in air (670), from which the coverage can be determined.