Impedance Sensor Switching Accuracy via Interference Filtering
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Solution Overview
Problem
Impedance sensors used for level detection in process containers often experience faulty switching due to electromagnetic interference, which interferes with the determination of the resonant frequency and amplitude, leading to incorrect switching states.
Innovation Solution
A method that involves generating a frequency sweep to determine the response signal of the measuring resonant circuit, identifying amplitude minima, and using approximation curves to filter out interference, allowing for accurate determination of the switching state by averaging between curves fitted to the minima and maxima, thereby isolating the undisturbed response signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic interference is present in the measurement environment, then the impedance sensor can operate continuously, but the determination of resonant frequency and amplitude becomes inaccurate leading to faulty switching
Solution Approach 1:
The patent converts electromagnetic interference from a harmful factor into a beneficial filtering opportunity. By deliberately introducing interference signals and using correlation analysis, the system learns to distinguish and filter out interference patterns, thereby improving immunity to electromagnetic interference and enhancing switching accuracy.
Solution Approach 2:
The patent introduces an intermediary correlation analysis mechanism between the measured impedance signal and known interference patterns. This intermediary process processes both the measurement signal and interference signals through correlation computation, enabling the system to separate useful information from harmful interference and achieve accurate switching determination.
2Measurement precision
If a frequency sweep is performed to determine resonant frequency, then the measurement can be performed, but the process time increases
Solution Approach 1:
The patent performs preliminary actions by pre-storing interference signal patterns and their correlation characteristics in the evaluation unit before actual measurement. During measurement, the system uses these pre-stored patterns to quickly identify and filter interference through correlation analysis, reducing the time needed for frequency sweep and resonant frequency determination.
Solution Approach 2:
The patent implements feedback by continuously monitoring the correlation between the measured signal and stored interference patterns during the frequency sweep. When interference is detected through correlation analysis, the system adjusts the measurement process in real-time, skipping frequency ranges where interference is detected and focusing measurement effort on cleaner frequency regions, thereby reducing overall measurement time while maintaining 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 effectively removes interference signals, allowing for precise determination of the switching state with high accuracy, reducing faulty switching occurrences to +/- 0.5% accuracy, ensuring reliable operation despite electromagnetic interference.
Implementation Method 1
A measuring resonant circuit (102) in which the measuring probe (102) is arranged as a capacitance-determining element
Implementation Method 2
exciting the measuring resonant circuit with a frequency sweep using a frequency generator (103), and detecting a response signal (frequency response) of the measuring resonant circuit with a frequency detector (104)
Implementation Method 3
A measuring capacitance (110) is formed between a measuring electrode (106) and a reference electrode (108)
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
Method for determining a switching state of an impedance sensor (100) with a measuring probe (102) which is influenced in a capacitance by a medium surrounding the measuring probe (102), a measuring resonant circuit in which the measuring probe (102) is arranged as a capacitance-determining element, an electronic unit (101) with a signal generator (103) for exciting the measuring resonant circuit and a signal detector (104) for determining a response signal of the measuring resonant circuit and an evaluation and control unit (105) which is connected to the electronic unit (101), wherein the signal generator (103) is driven with an input signal, the response signal of the measuring resonant circuit is determined, a switching state is output based on an output value and a number of amplitude minima of the frequency response are determined, wherein in the case that exactly one minimum is determined, the minimum is output as the output value and in the case thatthat more than one minimum is determined, at least one approximation curve (401, 402, 403) to the amplitude minima and/or amplitude maxima, and the output values are determined based on at least one approximation curve.