Ultrasonic Fluid Speed Measurement with Reference-Curve Timing
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Solution Overview
Problem
Ultrasonic fluid meters face challenges in achieving accurate flow measurements over a wide range due to limitations in differential time of flight (DToF) measurement precision, especially at varying fluid temperatures.
Innovation Solution
A method involving the emission and reception of ultrasonic signals, digitization of measurement samples, and interpolation using reference samples to estimate fluid velocity, with a microcontroller-based system including a master and slave microcontroller and FPGA for precise time shift adjustments and zero crossing determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional ultrasonic measurement methods are used to measure fluid flow over a wide range, then the flow measurement range is wide (11/h to 25001/h), but the measurement precision deteriorates due to limitations in differential time of flight (DToF) measurement precision
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction factors in lookup tables before actual measurements. These correction factors are computed based on anticipated signal conditions and stored for rapid retrieval during measurement, eliminating the need for complex real-time calculations and improving both precision and measurement range.
Solution Approach 2:
The patent introduces intermediary elements including lookup tables that store pre-computed correction factors and intermediate calculation results. These intermediaries bridge the gap between raw ultrasonic measurements and final flow calculations, enabling accurate measurements across the wide flow range without requiring complex real-time processing.
2Adaptability or versatility
If the temporal measurement range is extended to cover wide flow rates, then the flow measurement capability is improved, but the measurement precision deteriorates due to the difficulty of achieving accurate DToF measurements across the entire temporal measurement range
Solution Approach 1:
The patent segments the measurement process into multiple stages: raw signal acquisition, lookup table-based correction factor retrieval, intermediate calculation, and final flow determination. This segmentation allows each stage to be optimized independently, maintaining precision across the extended temporal measurement range by applying appropriate correction methods for different measurement conditions.
Solution Approach 2:
The patent changes parameters by using lookup tables that store correction factors for different temporal ranges and flow conditions. Instead of using a single fixed measurement approach, the system adapts parameters such as correction factors and calculation methods based on the specific measurement conditions, enabling accurate measurements across the entire temporal range.
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 significantly improves the accuracy of fluid velocity and flow rate measurements by overcoming distortions and achieving precise travel time measurements, enhancing metrological performance with improved precision between 10ps and 20ps.
Implementation Method 1
an ultrasonic measurement signal is emitted into the pipe, traveling a path of defined length, the travel times taken by the ultrasonic measurement signal to travel the path of defined length from upstream to downstream are measured
Implementation Method 2
The first transducer 2a and the second transducer 2b are for example piezoelectric transducers
Data Source
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AI summary
A method for measuring a speed of a fluid, comprising the steps of: - transmitting an ultrasonic measurement signal (Se); acquiring and digitising a measurement portion (25, 26) of an ultrasonic measurement signal received (Sr, Sri, Sr2) after the ultrasonic measurement signal (Se) has travelled a path of defined length (L) to obtain measurement samples; - estimate, from the measurement samples, an amplitude of the measurement portion; - access reference samples from a reference table pre-filled and stored in a memory, the reference samples forming a reference curve which is an interpolation of the measurement samples; - produce adjusted measurement samples by multiplying the measurement samples by a ratio between an amplitude of the reference curve and the amplitude of the measurement portion; - for each adjusted measurement sample, determine a unit time delay between the adjusted measurement sample and the reference curve; - for each adjusted measurement sample, estimate a zero-crossing time of the measurement portion from the unit time delay and from the reference samples; estimate, from an average of the zero-crossing times, the time it takes the ultrasonic measurement signal to travel the path of defined length; - estimate the speed of the fluid from the travel time measurement.