Ultrasonic Flow Meter Temperature Compensation
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Solution Overview
Problem
Existing ultrasonic flow meters face challenges in accuracy due to the need for high timing precision and susceptibility to noise, and they require calibration to temperature, which can be difficult to maintain in field conditions.
Innovation Solution
The use of two ultrasonic transceivers that transmit and receive a continuous tone simultaneously, with automatic adjustment of the signal frequency to accommodate temperature variations, allowing for direct measurement of the mean time of flight and fluid flow rate independent of flow rate, and automatic compensation for temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high timing precision is used to detect pulse arrival time, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses periodic ultrasonic pulses instead of continuous waves, transmitting bursts of ultrasonic energy at regular intervals. This periodic transmission allows the system to measure flow by comparing arrival times of successive pulses, achieving accurate measurements with simpler timing circuits that only need to detect pulse boundaries rather than continuous phase information.
Solution Approach 2:
The patent implements continuous flow measurement by continuously transmitting ultrasonic pulses and continuously measuring their arrival times. This continuous operation allows the system to maintain accurate measurements over time without requiring complex intermittent calibration or reset mechanisms, simplifying the overall timing system while preserving measurement precision.
2Measurement precision
If high bandwidth is used to determine pulse beginning, then measurement resolution is improved, but noise susceptibility increases
Solution Approach 1:
The patent embeds multiple measurement functions within a unified ultrasonic pulse transmission system. The same transmitted pulse is used for both upstream and downstream measurements, and the arrival time detection is nested within the pulse transmission timing structure. This nesting allows accurate pulse beginning detection without requiring separate high-bandwidth detection circuits, thereby reducing noise susceptibility.
Solution Approach 2:
The patent introduces reference pulses and timing markers as intermediary signals that facilitate accurate arrival time detection without requiring direct high-bandwidth processing of the main ultrasonic signal. These intermediary timing references act as mediators that translate complex pulse beginning detection into simpler timing measurements, reducing the system's susceptibility to noise while maintaining measurement resolution.
3Measurement precision
If temperature calibration is performed, then measurement accuracy is improved, but operational complexity increases
Solution Approach 1:
The patent implements self-calibrating functionality by automatically measuring the speed of sound in the fluid through bidirectional ultrasonic pulse transmission. The system calculates temperature-dependent sound speed from the measured upstream and downstream transit times, then uses this calculated value to automatically compensate flow measurements. This self-service approach eliminates manual temperature calibration operations while maintaining high measurement accuracy.
Solution Approach 2:
The patent incorporates feedback mechanisms where the measured transit times are continuously used to update the speed of sound calculation, which in turn adjusts the flow measurement compensation. This closed-loop feedback system automatically adapts to temperature changes without requiring external calibration inputs, simplifying operation while preserving measurement precision across varying temperature conditions.
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 simplifies electronics, reduces noise susceptibility, and provides accurate measurements of fluid flow and temperature, enabling continuous operation across varying temperature conditions without the need for complex calibration.
Implementation Method 1
Each pair of ultrasonic transducers typically sends and receives an ultrasonic pulse, or series of ultrasonic pulses, back and forth
Implementation Method 2
The time of flight of each pulse, or the average time of flight of the pulses in the series of pulses, is measured
Implementation Method 3
The fluid flow causes the pulses traveling downstream (i.e., with the fluid flow) to move faster, and those traveling upstream (i.e., against the fluid flow), to move slower
Implementation Method 4
Because the speed of sound in a fluid is dependent on the temperature of the fluid, accuracy of the meter can vary with temperature if the meter is not calibrated to temperature
Data Source
AI summary
A method and apparatus utilizing a pair of ultrasonic transducers simultaneously transmitting and receiving to measure the mean time of flight of an ultrasonic signal over a given distance, and thereby the speed of sound of a fluid in a conduit at a given temperature, independent of flow rate, and the flow rate of the fluid. A signal source simultaneously drives an upstream transducer and a downstream transducer, each of which receive the signal transmitted by the other. The difference between the upstream and downstream signals takes into account the speed of sound of the fluid. The time of flight for the upstream and downstream signals can then be used to calculate the flow rate. A phase locked loop coupled to the signal source automatically adjusts for variations of the speed of sound in the fluid in response to temperature changes.