Capacitive Level Switch Using Burst Signal for Fast Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive level sensors face challenges with long measuring times, unnecessary frequency component emissions, increased noise, and device warming due to complex signal processing and high-frequency sinusoidal signals.
Innovation Solution
The use of a burst signal that includes essential frequency components, allowing for measurement in the time domain with subsequent evaluation in the frequency domain via Discrete Fourier Transform, reduces measuring time and eliminates unnecessary frequency components, leveraging digital technology for simplified signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency sinusoidal signals are used for measurement, then measurement accuracy is maintained, but measuring time increases and device warming occurs
Solution Approach 1:
The patent applies periodic action by using a burst signal consisting of a limited number of oscillations (typically 2-5 cycles) instead of continuous sinusoidal signals. This periodic burst structure allows the measurement to be completed within a short time frame while still capturing the essential frequency information needed for accurate level detection, thereby resolving the contradiction between measurement accuracy and measuring time.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and storing reference impedance values for different liquid levels during the manufacturing or calibration phase. During actual measurement, the system only needs to compare the measured impedance against these pre-stored references using a simple lookup or comparison algorithm, rather than performing complex real-time frequency analysis. This dramatically reduces the measuring time while maintaining accuracy.
2Reliability
If complex signal processing with multiple frequency components is used, then comprehensive measurement is achieved, but noise emission increases and device warming occurs
Solution Approach 1:
The patent extracts only the essential frequency components needed for measurement by using a burst signal with a limited frequency spectrum. Instead of using continuous high-frequency signals that emit unnecessary noise, the system uses a time-limited burst that contains only the frequency range required for capacitive level sensing. This extraction of necessary components from the full spectrum reduces electromagnetic noise emission while maintaining measurement reliability.
3Measurement precision
If continuous high-frequency signals are used, then measurement accuracy is maintained, but energy consumption increases and device warming occurs
Solution Approach 1:
The patent applies periodic action by replacing continuous high-frequency signal generation with periodic burst signals. The burst signal is transmitted only during the brief measurement window (microseconds to milliseconds), followed by a quiet period where no energy is consumed for signal generation. This periodic on-off pattern dramatically reduces average power consumption while maintaining measurement accuracy through the use of sensitive impedance detection during the active burst period.
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 approach significantly reduces measuring time, minimizes noise emission, and lowers production costs while maintaining accuracy, allowing for efficient energy utilization and reduced device warming.
Implementation Method 1
a measuring electrode 3 which protrudes into the container 2 and is capacitively coupled to the device ground 4
Implementation Method 2
the essential components of the frequency range in question between the empty resonance of the system to be measured up to the resonant frequencies which are formed with the sometimes quite different liquid or pourable media
Data Source
AI summary
A capacitive limit level switch comprises a measuring electrode which protrudes into and forms an electric circuit with a container and ground. Impedance at the measuring electrode depends on the presence of a medium. The switch includes a control unit including a burst generator and a diode bridge. A switching point is determined by spectral analysis of the amplitude response at the measuring electrode. The diode bridge is connected to a controllable delay circuit. A computing unit compares the spectrum of a burst signal influenced by the medium with the spectrum of a known burst signal not influenced by the medium.