Single Pick-Off Flow Device Using Dual Frequency Vibration
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Solution Overview
Problem
Vibrating densitometers with a single drive and single pick-off are unable to detect the presence, direction, or mass flow rate of a substance within the conduit, requiring multiple pick-offs to achieve these measurements.
Innovation Solution
A flow device with a single conduit, a pick-off, and electronics that generate and apply two distinct signals to the drive, allowing the measurement of time shifts between these signals to determine flow characteristics, including presence, direction, and mass flow rate, while maintaining phase lock for density determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive and single pick-off are used in a vibrating densitometer, then the device complexity is reduced, but the ability to detect flow characteristics (presence, direction, mass flow rate) is lost
Solution Approach 1:
The patent applies parameter changes by utilizing different vibration frequencies (resonance and non-resonance) to extract different measurements. The single pick-off measures time shift at non-resonance frequencies to detect flow characteristics while maintaining density measurement capability at resonance frequencies, thereby achieving flow detection without adding hardware complexity.
2Adaptability or versatility
If multiple pick-offs are used to detect flow characteristics, then the flow detection capability is improved, but the device complexity increases
Solution Approach 1:
The single pick-off is designed to perform multiple functions: measuring density (at resonance frequency) and detecting flow characteristics (at non-resonance frequencies). This multi-functionality eliminates the need for separate pick-offs for different measurements, reducing device complexity while maintaining comprehensive flow detection capability.
Solution Approach 2:
The system changes the vibration frequency parameter to differentiate between density measurement and flow detection modes. By operating at resonance frequencies for density and non-resonance frequencies for flow detection, the single pick-off can distinguish between different measurement types and extract appropriate information without hardware additions.
3Measurement precision
If the pick-off frequency is phase-locked to the drive frequency, then the density measurement accuracy is maintained, but the flow detection capability is reduced
Solution Approach 1:
The system employs periodic action by alternating between resonance frequency excitation (for density measurement with phase-lock) and non-resonance frequency excitation (for flow detection). This periodic switching between different operational modes allows the single pick-off to maintain density measurement precision while periodically acquiring flow detection data.
Solution Approach 2:
The system dynamically changes the drive frequency parameter between resonance and non-resonance values. At resonance frequencies, phase-lock is maintained for accurate density measurement; at non-resonance frequencies, the system measures time shift for flow detection. This parameter switching enables both functions with a single pick-off.
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 the detection of flow presence, direction, and mass flow rate using a single pick-off and drive, enhancing the capability of vibrating flow devices without additional hardware, while maintaining accurate density measurement.
Implementation Method 1
The particular resonance frequency at which the one or more conduits vibrates is partially determined by the density of the substance within the one or more vibrating conduits
Implementation Method 2
A pick-off detects the frequency of vibration of the one or more conduits and generates a sinusoidal pick-off signal representative of the motion of the flow tube
Implementation Method 3
the time shift between the frequency of vibration induced by the driver and the frequency of vibration detected by the pick-off may be used
Data Source
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AI summary
The present invention relates to flow devices that measure a characteristic of a flowing substance and methods for operating flow devices. In one embodiment, a drive (40) is provided that receives a first signal (55) for vibrating at least one conduit (20) at a resonance frequency and a second signal (56) for vibrating the at least one conduit (20) at a frequency that is different than the resonance frequency. In another embodiment, a drive (140) is provided that alternates between receiving a drive signal (155) to vibrate at least one conduit (120) at a resonance frequency and providing a pick-off signal (145) for measuring motion of the at least one conduit (120). In another embodiment, one or more electronics (50, 150) are provided that determine a mode of vibration of at least one conduit (20, 120) and compare the determined mode of vibration to one or more reference modes of vibration to determine whether a substance is flowing within the at least one conduit (20, 120). The principals of the present invention may be used to determine whether a substance is flowing within a conduit (20), the direction which a substance is flowing within a conduit (20), and the mass flow rate of a substance flowing within a conduit (20). Furthermore, the principals of the present invention may be used to determine whether a pick-off (30) and another pick-off (30) are functioning properly on a flow device.