Vibratory Meter Resonant Frequency Determination via Phase Offset
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Solution Overview
Problem
Vibratory meters, such as Coriolis mass flowmeters and densitometers, face challenges in accurately determining the resonant frequency, especially for gases, due to errors in frequency measurement affecting density calculations, and existing methods fail to account for phase differences between drive and pickoff signals, leading to inaccurate results.
Innovation Solution
A vibratory meter system that iteratively offsets the phase difference between drive and pickoff signals while sweeping the vibration frequency over a predetermined range to identify the resonant frequency, using meter electronics with a feedback loop and phase shifter to maintain closed-loop control and determine the maximum amplitude response, allowing for precise resonant frequency determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional frequency sweeping methods are used to determine resonant frequency, then the measurement process is simple, but measurement precision deteriorates due to unaccounted phase differences between drive and pickoff signals
Solution Approach 1:
The patent implements a feedback mechanism where the measured pickoff signal is phase-shifted and fed back to adjust the drive signal phase. The system continuously monitors the phase difference between drive and pickoff signals and automatically adjusts the drive phase to maintain optimal alignment, thereby eliminating phase-related measurement errors in resonant frequency determination
Solution Approach 2:
The system dynamically changes the phase parameter of the drive signal while maintaining constant frequency sweep. By varying the drive phase in relation to the pickoff signal phase, the system compensates for phase differences and achieves accurate resonant frequency measurement without being affected by phase misalignment
2Measurement precision
If phase difference compensation is implemented to improve measurement accuracy, then measurement precision improves, but device complexity increases due to additional feedback loop components
Solution Approach 1:
The phase shifter and feedback electronics are designed to serve multiple functions: they not only compensate for phase differences in resonant frequency determination but also maintain optimal phase alignment during continuous operation, enabling both accurate density measurements and efficient power consumption with the same hardware components
3Measurement precision
If resonant frequency is not accurately determined, then density calculation errors increase especially for gases, but improving measurement accuracy requires more complex procedures
Solution Approach 1:
The feedback loop continuously monitors the phase relationship between drive and pickoff signals during the frequency sweep, automatically identifying the resonant frequency point where phase alignment is optimal. This eliminates the need for complex post-processing calculations and directly provides accurate resonant frequency for density determination
Solution Approach 2:
The system performs preliminary phase alignment adjustment before final resonant frequency determination. By pre-compensating for phase differences during the frequency sweep, the system ensures that the identified resonant frequency is accurate from the start, eliminating the need for iterative corrections and improving measurement efficiency
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 method provides accurate resonant frequency measurement, reducing errors in density calculations, especially for gases, and enables efficient operation by maintaining constant power and phase alignment, enhancing the reliability of flow material quantifications.
Implementation Method 1
vibrate the one or more flow conduits of the vibratory meter using a drive signal including an initial vibration frequency
Implementation Method 2
determine a substantially maximum amplitude response in the plurality of vibration amplitudes and designate the corresponding vibration frequency as comprising the resonant frequency
Implementation Method 3
receive a pickoff sensor signal from the one or more pickoff sensors in response
Data Source
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AI summary
A vibratory meter (5) is provided, including one or more flow conduits (103), one or more pickoff sensors (105, 105'), and a driver (104). Meter electronics (20) is configured to vibrate the one or more flow conduits (103) using a drive signal including an initial vibration frequency and to receive a pickoff sensor signal from the one or more pickoff sensors (105, 105') in response, iteratively offset a phase difference between the drive signal and the pickoff sensor signal by a predetermined phase increment and measure a resulting vibrational frequency and amplitude, with the offsetting operatively sweeping the vibration frequency over a predetermined vibration frequency range and therefore generating a plurality of vibration amplitudes and a corresponding plurality of vibration frequencies, and determine a substantially maximum amplitude response in the plurality of vibration amplitudes and designate the corresponding vibration frequency as comprising the resonant frequency.