Fork Density Meter Signal Generation for Faster Phase Measurement
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Solution Overview
Problem
Current vibratory sensors face delays in determining fluid properties due to the incremental approach required to reach off-resonant phase differences, which is costly and inefficient in many applications.
Innovation Solution
A method of controlling a vibratory element's vibration based on phase error, involving a drive signal, filtering, and generating a synthetic time period output signal to measure and correct phase differences, thereby eliminating the need for closed-loop feedback and reducing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed-loop circuit is used to incrementally approach off-resonant phase differences, then the vibration response parameter can be determined with feedback control, but delays occur in determining fluid properties
Solution Approach 1:
The patent pre-calculates and stores the relationship between drive signal frequencies and resulting phase differences in a lookup table before measurement. During actual measurement, the system directly queries the pre-computed table to determine the drive frequency that will achieve the target off-resonant phase difference (45° or 135°), eliminating the need for incremental feedback adjustment and significantly reducing measurement delay while maintaining accuracy
2Measurement precision
If incremental adjustment is used to reach target phase differences, then the closed-loop control can achieve desired phase differences, but the process becomes costly and inefficient
Solution Approach 1:
The system pre-computes the complete mapping between drive frequencies and phase differences and stores it in a lookup table. During measurement, it directly retrieves the required drive frequency from the table based on the desired phase difference, achieving both high precision (by using pre-calculated exact values) and high efficiency (by eliminating iterative adjustment), thus resolving the contradiction between measurement precision and productivity
3Reliability
If closed-loop feedback is used to modify the vibration signal into a drive signal, then the target frequency can be achieved, but delays occur in determining vibration response parameters
Solution Approach 1:
The patent pre-calculates the relationship between drive signal frequencies and vibration response parameters (including phase differences) and stores this information in a lookup table. During actual measurement, the system directly queries the table to obtain the drive frequency that will produce the target off-resonant phase difference, eliminating the need for real-time feedback iteration and significantly reducing the delay in determining vibration response parameters while maintaining frequency control accuracy
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 improves the accuracy and speed of fluid property measurements by directly controlling vibrations to target phase differences without the delays associated with closed-loop circuits, enhancing the efficiency of vibratory flow meters.
Implementation Method 1
vibratory sensors, such as vibratory densitometers and vibratory viscometers described in WO 2012/176122 to McAnally, operate by detecting motion of a vibrating element that vibrates in the presence of a fluid to be characterized. The vibratory element has a vibration response that may have a vibration response parameter such as a resonant frequency or quality factor Q.
Implementation Method 2
The vibration response of the vibrating element is generally affected by the combined mass, stiffness, and damping characteristics of the vibrating element in combination with the fluid.
Implementation Method 3
The prior art vibratory sensor includes a driver for vibrating the vibratory element and a pickoff that creates a vibration signal in response to the vibration.
Implementation Method 4
The prior art closed-loop circuit modifies or incorporates the vibration signal or parameters of the vibration signal into the drive signal. For example, the drive signal may be an amplified, modulated, or an otherwise modified version of the received vibration signal. The received vibration signal can therefore comprise a feedback that enables the closed-loop circuit to achieve a target frequency.
Implementation Method 5
Fluid properties, such as the viscosity and density of the fluid, can be determined from the frequencies where the phase difference between the drive signal and the vibration signal is 135° and 45°. These desired phase differences, denoted as first off-resonant phase difference φ1 and second off-resonant phase difference φ2, can correspond to the half power or 3dB frequencies.
Data Source
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AI summary
A system and method of generating a synthetic time period output signal for a fork density sensor (601) which produces a consistent and low-noise output signal (705) which is identical in frequency to the frequency at which the fork density meter vibrates. Such a synthetic signal prevents any real noise from the pickoffs from propagating to the output meter and removes process noise and interference from the produced output signal.