Switched-Capacitor Bandpass Filter for Oscillatory Process Variable Sensors
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Solution Overview
Problem
Existing devices for determining and monitoring process variables like fill level, density, and viscosity face challenges in achieving high-quality interference signal suppression while maintaining unadulterated signal transmission over the entire useful frequency range, leading to measurement inaccuracies and high power consumption.
Innovation Solution
The implementation of a device with a switched-capacitor bandpass filter on the output side, which adjusts its center frequency to match the excitation signal, and a second bandpass filter between the excitation signal generator and converter, both with adjustable center frequencies, ensures optimal signal transmission and effective interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a narrow-band filter is used for interference signal suppression, then interference signals are suppressed effectively, but signal transmission over the entire useful frequency range is compromised
Solution Approach 1:
The patent implements a trackable bandpass filter whose center frequency dynamically follows the excitation signal frequency. This dynamic adjustment allows the filter to maintain narrow bandwidth for interference suppression while tracking the varying useful signal frequency, resolving the contradiction between suppression effectiveness and signal transmission quality
Solution Approach 2:
The patent changes the center frequency parameter of the bandpass filter to match the excitation signal frequency. By adjusting this parameter dynamically, the filter adapts to different operating conditions while maintaining optimal interference suppression and signal transmission characteristics
2Reliability
If a wide-band filter is used for signal transmission, then signal transmission over the entire useful frequency range is maintained, but interference signal suppression is reduced
Solution Approach 1:
The trackable bandpass filter dynamically adjusts its bandwidth and center frequency to match the excitation signal characteristics. This dynamic behavior allows the filter to provide wide bandwidth when needed for signal transmission while maintaining narrow bandwidth for interference suppression, depending on the operating conditions
3Object-affected harmful factors
If traditional filtering methods are used, then interference suppression is achieved, but power consumption is high
Solution Approach 1:
The patent replaces traditional analog filtering methods with a trackable bandpass filter implemented using a switched capacitor circuit. This substitution reduces power consumption by utilizing digital switching techniques instead of continuous analog signal processing, while maintaining effective interference suppression
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 provides high-quality interference signal suppression with low power consumption, maintaining accurate and reliable signal transmission across a wide useful frequency range, reducing measurement inaccuracies and allowing for efficient determination of process variables.
Implementation Method 1
an electromechanical converter, which excites the structure to mechanical vibrations by means of an excitation signal supplied to the converter on the input side, and which converts the resulting vibrations of the structure into an electrical reception signal
Data Source
Figure 1~2
AI summary
The invention relates to a device for determining and/or monitoring at least one process variable, in particular a fill level, a density or a viscosity, of a medium (1) in a container (3), comprising a mechanically oscillatable structure (5), which protrudes into the container (3) during operation and which has at least one oscillating property that depends on the process variable, an electromechanical transducer (7), which excites the structure (5) by means of an excitation signal (S) supplied to the input side of the transducer (7) to perform mechanical oscillations and which converts the resulting oscillations of the structure (5) into an electrical received signal (E), which reproduces the oscillation, and outputs it on the output side, and an electronic system, which comprises a device connected to the input side to the transducer (7) for generating the excitation signal (19), said device comprising a first filter (23) which is connected to the output side of the transducer (7) and filters out a useful signal (N) from the received signal (E), and said device on the basis of the useful signal (N) determining and/or monitoring the process variable which has high-quality interfering signal suppression providing as unbiased as possible a signal transmission over the entire useful frequency range (?fN) of the device, wherein said transmission is brought about by the first filter (23) being a band-pass filter having adjustable center frequency (f0), and by the electronic system comprising a device (31) which sets the center frequency (f0) during operation to the frequency (fs) of the excitation signal (S).