Signal Generator Frequency Sweep for Capacitive Measurement
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Solution Overview
Problem
Capacitive measuring devices face challenges in determining fill level and conductivity of media with transition permittivity, and existing signal generators are inefficient, requiring high energy consumption and complex components.
Innovation Solution
A dynamic signal generator using a combination of look-up tables and the CORDIC algorithm, implemented on an FPGA, allows for a wide frequency range with low power consumption and minimal components, enabling precise frequency selection and stable amplitude generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lower signal frequency is used for longer probes to avoid resonance effects, then measurement accuracy is improved, but the signal frequency becomes below optimal for shorter probes
Solution Approach 1:
The patent implements dynamic signal frequency selection by successively applying measurement signals with different discrete frequencies (frequency sweep) and automatically selecting the optimal frequency based on the probe length and medium properties. This dynamic adaptation resolves the contradiction between optimized frequency for specific probe lengths and versatility across different probe configurations.
Solution Approach 2:
The system changes the signal frequency parameter dynamically based on the measurement requirements. By sweeping through multiple discrete frequencies and selecting the optimal one, the system adapts the frequency parameter to match the specific probe length and medium characteristics, thereby maintaining measurement accuracy across varying conditions.
2Device complexity
If conventional static signal generators are used with fixed frequency, then device complexity is reduced, but the ability to handle transition permittivity media and optimize for different probe lengths is lost
Solution Approach 1:
The patent employs dynamic frequency selection through successive application of measurement signals at different discrete frequencies. The system automatically determines the optimal frequency based on probe characteristics and medium properties, enabling accurate measurement in transition permittivity media while maintaining manageable device complexity through automated frequency sweep and selection.
3Reliability
If high signal frequencies are used, then sensitivity to resonance effects is reduced, but the optimal frequency for shorter probes is exceeded
Solution Approach 1:
The system dynamically adjusts the signal frequency parameter based on the specific measurement conditions. By sweeping through multiple discrete frequencies and selecting the optimal one for each probe length and medium combination, the system achieves the right balance between resonance sensitivity and measurement accuracy without using excessively high frequencies.
4Adaptability or versatility
If frequency sweep capability is added to determine optimal frequency, then adaptability to different probe lengths and media is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent implements dynamic frequency sweep capability that successively applies measurement signals at different discrete frequencies and automatically selects the optimal frequency based on the response. This dynamic approach provides excellent adaptability to different probe lengths and media properties while managing device complexity through automated frequency selection algorithms.
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 provides a cost-effective, energy-efficient signal generator capable of generating sinusoidal signals across a broad frequency range, optimizing measuring accuracy and reducing power consumption in capacitive and vibronic measurements.
Implementation Method 1
signal generator (5) for producing periodic signals, in particular sinusoidal signals, at a variable frequency
Implementation Method 2
The fill level of the medium is determined from the capacitance of the capacitor formed by the probe electrode and the container wall or a second electrode
Implementation Method 3
capacitive measuring devices can also be used to determine and/or monitor the electrical conductivity and/or permittivity of the medium
Implementation Method 4
The guard electrode is at the same potential as the probe electrode and surrounds the probe electrode at least partially coaxially
Data Source
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AI summary
The invention relates to a signal generator for generating periodic signals for a measuring apparatus (1) in automation technology, wherein the signals have successive discrete signal frequencies which are within a predefined frequency range, having a control and/or computing unit (4), having a clock generator (6), wherein the clock generator (6) provides a constant sampling frequency which is greater than the maximum discrete signal frequency in the predefined frequency range, having a storage unit (7) in which the amplitude values of the corresponding periodic signals are or can be stored for each of the discrete signal frequencies on the basis of the sampling frequency, wherein the control and/or computing unit (4) gradually reads the stored or storable amplitude values of the discrete frequencies from the storage unit (7) at the sampling frequency of the clock generator (6) and generates the periodic signals or forwards the latter for generation, and having a static filter unit (12) with a cut-off frequency which is above the maximum signal frequency and removes the frequency components caused by sampling.