Coriolis Mass Flow Meter Damping-Based Zero-Point Correction
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Solution Overview
Problem
Coriolis mass flow meters experience exciter-dependent and exciter-independent zero point errors due to manufacturing tolerances and asymmetries, leading to inaccuracies in mass flow measurements.
Innovation Solution
A method to determine and correct zero point errors by calculating sensitivity factors and damping values, allowing for precise determination of total zero point errors, especially in modular flow meters with replaceable measuring tube assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manufacturing tolerances are reduced to eliminate asymmetries, then zero point error decreases, but manufacturing cost and complexity increase
Solution Approach 1:
The patent changes the approach from controlling geometric parameters (manufacturing tolerances) to controlling operational parameters (damping compensation). By measuring the actual damping value during operation and using it to compensate for zero point error, the system achieves high measurement precision without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The patent replaces mechanical precision requirements with a measurement and calculation system. Instead of relying on mechanically perfect symmetry, the system uses sensors to detect damping characteristics and computationally compensates for asymmetries, substituting mechanical precision with electronic measurement and processing.
2Measurement precision
If damping compensation is implemented, then zero point error correction improves, but measurement and operating circuit complexity increases
Solution Approach 1:
The measuring and operating circuit performs multiple functions: it drives the exciter, detects sensor signals, determines mass flow, measures damping values, and compensates for zero point error. By making the circuit multi-functional, the patent avoids adding separate dedicated hardware for each function, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The system uses its own operational characteristics (damping of the measuring tube) to compensate for its own errors. The measuring tube's damping, which is affected by asymmetries, is measured and then used by the same system to correct the zero point error, creating a self-correcting mechanism that reduces the need for external calibration equipment.
3Measurement precision
If exciter positioning precision is increased, then exciter-dependent zero point error decreases, but manufacturing and assembly complexity increases
Solution Approach 1:
The patent shifts from controlling the positional parameter of the exciter to controlling the damping parameter of the measuring tube. By measuring the damping value that results from actual exciter positioning and using it for compensation, the system achieves high precision without requiring extremely precise initial positioning.
Solution Approach 2:
The system implements feedback by measuring the damping value caused by exciter positioning asymmetries and using this information to correct the zero point error. This feedback loop allows the system to automatically compensate for positioning errors without requiring manual repositioning or extremely tight positioning tolerances.
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
Enables precise and continuous correction of zero point errors, ensuring accurate mass flow measurements by accounting for exciter-dependent and exciter-independent contributions, even with changes in media properties or tube replacements.
Implementation Method 1
exciting a bending vibration mode of the measuring tube
Implementation Method 2
at least two vibration sensors for detecting vibrations of the measuring tube
Implementation Method 3
a dependence on a damping of the bending vibration mode can also be established
Data Source
AI summary
A method for determining variables influencing a total zero point error of a Coriolis mass flow meter comprises: exciting a vibration of a bending vibration mode; measuring a first total zero point error T at a flow of zero; ascertaining a first damping value D of the vibration of the bending vibration mode; measuring an exciter-independent zero point error I during a decaying vibration of the bending vibration mode at a flow of zero; ascertaining a first exciter-dependent contribution E to the first total zero point error T based on the first total zero point error T and based on the exciter-independent zero point error I; and ascertaining a sensitivity factor S for the bending vibration mode based on the first exciter-dependent contribution E to the total zero point error T and based on the first damping value D.