Coriolis Flowmeter Zero-Offset Calibration via Eigenvector Phase Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coriolis flowmeters face challenges in accurately calibrating zero-flow offset due to environmental and piping system changes, leading to errors in mass flow rate measurements, as the offset is not constant and can vary over time, especially during long periods of no-flow conditions.
Innovation Solution
The method involves exciting a vibration mode of the flow tube using two drivers with amplitude modulated signals that are out of phase, measuring the relative phase between pickoffs, and determining the relative phase of right and left eigenvectors to distinguish between zero-offset and flow-induced phase changes, allowing for continuous calibration of zero-offset without stopping the flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero-flow offset is corrected by measuring during no-flow conditions and subtracting from subsequent measurements, then measurement accuracy is improved under stable conditions, but measurement precision deteriorates when environmental or piping changes occur during flow
Solution Approach 1:
The system performs preliminary measurement of the zero-flow offset during no-flow conditions, then uses this pre-measured offset to correct subsequent flow measurements. This preliminary action allows the system to compensate for environmental and piping changes without requiring continuous no-flow calibration periods.
Solution Approach 2:
The system continuously monitors flow conditions and dynamically adjusts the zero-offset correction based on real-time measurements. By comparing measured phase differences against the pre-determined zero-offset, the system provides continuous feedback correction to maintain measurement accuracy despite environmental variations.
2Device complexity
If calibration is performed only during no-flow conditions, then device complexity is reduced, but productivity deteriorates due to long periods between calibrations during normal operations
Solution Approach 1:
The system performs a preliminary zero-offset calibration during initial no-flow conditions, then uses this pre-established baseline to enable continuous correction during flow operations, eliminating the need for frequent recalibration and maintaining high productivity.
Solution Approach 2:
The zero-offset correction mechanism operates continuously during flow conditions without interruption, allowing the flowmeter to maintain accurate measurements throughout normal operations without requiring periodic shutdowns for recalibration.
3Measurement precision
If left eigenvectors are used to diagonalize non-symmetric system matrices, then measurement precision is improved by distinguishing zero-offset from flow effects, but device complexity increases
Solution Approach 1:
The system replaces traditional mechanical calibration methods with mathematical eigenvector analysis. By using left and right eigenvectors to diagonalize the system matrices, the system can computationally distinguish between zero-offset and flow-induced phase changes, achieving high measurement precision through software-based solutions rather than complex hardware modifications.
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 and continuous calibration of zero-flow offset, reducing measurement errors by distinguishing between non-proportional damping and flow effects, thereby improving the precision of mass flow rate measurements.
Implementation Method 1
vibrating a fluid-carrying tube(s) in a sinusoidal motion
Implementation Method 2
C is a general damping matrix which may have a symmetric component due to damping and a skew symmetric component due to Coriolis force
Data Source
AI summary
A method and apparatus for a flowmeter (5) is provided. The method comprises the steps of placing a material in a flow tube (130, 130′) while exciting a vibration mode of the flow tube (130, 130′). Exciting the vibration mode of the flow tube (130, 130′) comprises the steps of periodically driving a first driver (180L) with a first signal and periodically driving a second driver (180R) with a second signal, wherein the second driver (180R) is driven essentially in phase with the first driver (180L), but wherein the first driver's (180L) drive amplitude modulated signal reaches a maximum amplitude when the second driver's (180R) drive modulated signal reaches a minimal amplitude, and the first driver's (180L) drive amplitude modulated signal reaches a minimum amplitude when the second driver's (180R) drive amplitude modulated signal reaches a maximum amplitude. The method also comprises the steps of measuring the relative phase between a first pickoff (170L) and a second pickoff (170R) and determining a relative phase of a right eigenvector for the flow tube (130, 130′).