Ultrasonic Flow Meter Phase Offset Ambiguity Resolution
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Solution Overview
Problem
Ultrasonic flow meters face challenges in accurately determining transit time differences and flow rates over large ranges due to phase offset ambiguities, requiring complex control electronics and reduced measurement accuracy with low-frequency signals.
Innovation Solution
The method involves determining phase offsets for different vibration modes of the measuring wave in the side wall, selectively exciting and measuring Lamb waves to eliminate ambiguity, and using a prognosis value to select the appropriate vibration mode based on expected fluid flow, allowing for accurate transit time determination across broader ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-shift-based transit-time measurement is used, then measurement accuracy is improved, but the measuring range is limited due to phase offset ambiguities
Solution Approach 1:
The patent applies periodic action by using multiple vibration modes with different frequencies. Each vibration mode provides periodic phase measurements, and by combining measurements from multiple periods (different vibration modes), the system resolves the phase ambiguity that limits the measuring range while maintaining high measurement accuracy.
2Adaptability or versatility
If ultrasonic waves with low frequencies are used to extend measuring range, then adaptability is improved, but measurement accuracy is reduced
Solution Approach 1:
The patent segments the measurement process by using multiple vibration modes with different frequencies. Instead of using a single low-frequency wave that compromises accuracy, the system divides the measurement into multiple frequency components, each contributing to resolving the overall transit time with high precision while extending the measurable range.
Solution Approach 2:
The patent changes the frequency parameter by utilizing multiple vibration modes with different frequencies. This allows the system to adapt the measurement frequency based on the expected flow conditions, maintaining high accuracy across a wide measuring range by selecting appropriate frequency combinations.
3Adaptability or versatility
If sequential excitation with ultrasonic signals of different frequencies is used, then measuring range is extended, but device complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the natural resonant frequencies of the measuring tube itself. The measuring tube's structural characteristics provide the different vibration modes, eliminating the need for complex external frequency generation and control systems. The system leverages the tube's inherent properties to provide multiple measurement frequencies.
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 high-accuracy phase-offset-based propagation time measurement over large ranges with reduced complexity, enhancing measurement accuracy and extending the measuring range without compromising precision.
Implementation Method 1
This is known, for example, from publication WO 2010/034713 A2 or from DE 10 2017 008776 A1. Especially over relatively short measurement distances, a time-of-flight difference can be determined with high accuracy by evaluating the phase difference between received signals for the two propagation directions.
Implementation Method 2
the first vibration transducer for a first measuring direction to excite a measuring wave guided in the side wall and the second vibration transducer for a second measuring direction to excite a measuring wave guided in the side wall
Implementation Method 3
a first phase offset between the received signals detected for the first and the second measuring direction is determined. The first phase shift for a first vibration mode of the side wall is determined
Data Source
Figure 1~2
Figure 3
AI summary
Method for determining a fluid quantity by means of a measuring device (1) comprising a measuring tube (3) and a first and second vibration transducer (5, 6), wherein the control device (2) controls the first vibration transducer (5) for a first measuring direction to excite a measuring wave guided in the side wall (9) and the second vibration transducer (6) for a second measuring direction to excite a measuring wave guided in the side wall (9), wherein the excited measuring waves are guided directly in the side wall (9) or indirectly via the fluid to the respective other vibration transducer (5, 6) and are recorded there to determine a respective received signal, wherein a first phase offset between the received signals recorded for the first and the second measuring direction is determined, wherein the first phase offset is determined for a first vibration mode of the side wall (9).