Vibrating Tube Sensor Density Correction Using Multi-Mode Frequencies
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Solution Overview
Problem
Existing methods for determining mass flow and density of gases using vibronic sensors face cross-sensitivities to the speed of sound and compressibility, requiring complex setups and multiple sensors to compensate for these factors effectively.
Innovation Solution
A method that calculates a correction term using natural frequencies of different vibration modes to correct for the influence of gas oscillations, allowing for simpler and more robust compensation of cross-sensitivities by determining a corrected mass flow rate and density, which involves calculating a mode-specific correction term based on the speed of sound and natural frequencies of the gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors and complex exciter structures are used to compensate for cross-sensitivities to speed of sound and compressibility, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by utilizing the natural frequencies of different vibration modes (f1, f2, f3) as measurement parameters to determine speed of sound and compressibility. Instead of adding more sensors, the invention changes the approach by using frequency ratio relationships between different modes to calculate correction terms, thereby maintaining measurement precision while avoiding increased device complexity
Solution Approach 2:
The patent replaces the need for multiple physical sensors with a computational approach. By using the ratio of natural frequencies from different vibration modes and applying mathematical correction terms, the invention substitutes mechanical/sensor-based compensation with a calculation-based system that determines speed of sound and compressibility effects
2Measurement precision
If radial mode vibrations are used for compressibility compensation, then measurement precision is improved, but the number of sensors and exciter structure complexity increase
Solution Approach 1:
The patent applies universality by using the same measuring tube and exciter structure to generate multiple vibration modes (f1, f2, f3) that serve different functions. The first mode (f1) provides primary mass flow measurement, while the second (f2) and third (f3) modes are used for determining speed of sound and compressibility corrections, allowing one structure to perform multiple measurement functions
Solution Approach 2:
The patent uses the relationship between different vibration modes as a computational model to represent compressibility effects. Instead of physically measuring radial mode vibrations with additional sensors, the invention creates a mathematical model that copies the compressibility information through frequency ratio relationships, eliminating the need for extra sensors and complex exciters
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 enables accurate compensation of cross-sensitivities with fewer sensors and a simpler exciter structure, reducing errors and improving the precision of mass flow and density measurements.
Implementation Method 1
the measuring tube can be excited to oscillate between the two fixing devices
Implementation Method 2
determining natural frequencies of the measuring tube in at least three different vibration modes, in particular in a first bending vibration mode with the natural frequency f1, in a second bending vibration mode with the natural frequency f2 and in a third bending vibration mode with the natural frequency f3
Implementation Method 3
The determination of the density of a medium based on the oscillation frequency of a vibronic sensor
Implementation Method 4
determining a value for the speed of sound in the gas... the resonant frequency of the oscillating gas depends on its speed of sound
Data Source
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AI summary
The invention relates to a method for ascertaining a physical parameter of a gas using a measuring sensor with at least one measuring tube for conducting the medium, wherein flexural vibrations of different modes with different natural frequencies can be excited in the measuring tube. The method has the following steps: ascertaining the natural frequency of the f1 mode and the f3 mode (110); ascertaining previous density values (120) for the gas being conducted in the measuring tube on the basis of the natural frequencies of the f1 mode and the f3 mode; and ascertaining a value for the speed of sound of the gas conducted in the measuring tube and/or at least one correction term (130) and/or density error, which is dependent on the speed of sound and the natural frequency of a mode, for the previous density value, which has been ascertained on the basis of the natural frequency of the mode, in order to determine a corrected density measurement value (140) and/or a correction term for a previous mass flow rate value in order to determine a corrected mass flow rate measurement value on the basis of the first previous density value, the second previous density value, the natural frequency of the f1 mode, and the natural frequency of the f3 mode.