Impedance Limit Switch EMC Radiation Reduction
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Solution Overview
Problem
Impedance limit switches in the process industry face challenges in minimizing Electromagnetic Compatibility (EMC) radiation while maintaining measurement sensitivity, particularly in applications where excessive EMC radiation is a concern.
Innovation Solution
An adaptive electronic circuit in the impedance limit switch adjusts the amplitude of the excitation signal based on the resonance curve to reduce EMC radiation, ensuring it remains below permissible limits without compromising measurement sensitivity. This is achieved by varying the transmission signal voltage and frequency, using a control loop to identify and mitigate peak radiation regions, thereby maintaining consistent EMC levels across the frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplitude of the excitation signal is increased to improve measurement sensitivity, then the measurement precision is improved, but the EMC radiation increases
Solution Approach 1:
The patent applies dynamics by making the excitation signal amplitude variable rather than constant. The electronic circuit dynamically adjusts the amplitude of the excitation signal based on the detected resonance curve characteristics, specifically reducing amplitude when peaks are detected and maintaining higher amplitude in other frequency regions. This dynamic adaptation allows the system to maintain measurement sensitivity while minimizing EMC radiation at critical frequencies.
Solution Approach 2:
The patent implements parameter changes by modifying the amplitude parameter of the excitation signal based on frequency-dependent resonance characteristics. The electronic circuit analyzes the resonance curve and adjusts the excitation signal amplitude corresponding to different frequency regions, thereby changing the operational parameters to balance measurement precision and EMC radiation compliance.
2Object-generated harmful factors
If the amplitude of the excitation signal is reduced to decrease EMC radiation, then the EMC radiation is reduced, but the measurement sensitivity deteriorates
Solution Approach 1:
The patent applies local quality by implementing frequency-dependent amplitude control. Instead of uniformly reducing the excitation signal amplitude across all frequencies, the electronic circuit identifies specific frequency regions with resonance peaks and selectively reduces amplitude only in those localized frequency ranges. In frequency regions without resonance peaks, the amplitude remains higher, preserving measurement sensitivity where it is most needed.
3Device complexity
If a constant amplitude excitation signal is used to simplify the circuit design, then the device complexity is reduced, but the EMC radiation compliance becomes difficult to achieve
Solution Approach 1:
The patent implements feedback by creating a closed-loop control system where the electronic circuit continuously monitors the resonance curve and uses this information to adjust the excitation signal amplitude. The resonance curve detection provides feedback about the system's response at different frequencies, and this feedback is used to dynamically modify the excitation signal to comply with EMC radiation limits while maintaining measurement effectiveness.
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 solution effectively reduces EMC radiation to acceptable levels without impairing the sensitivity of the impedance measurement, ensuring compliance with limit values and maximizing interference resistance.
Implementation Method 1
determine a resonance curve of the oscillator circuit... the peak in the resonance curve can lead to an increased EMC radiation
Data Source
AI summary
An impedance limit switch is configured to determine a limit level of a medium. The switch may include a measuring probe having an oscillator circuit; and an electronic circuit configured to generate an excitation signal for the oscillator circuit. The electronic circuit is further configured to sweep a frequency of the excitation signal and determine a resonance curve of the oscillator circuit. The electronic circuit is further configured to adapt an amplitude of the excitation signal dependent upon the resonance curve in order to reduce an EMC radiation of the switch.