Coriolis Flowmeter Signal Processing for Precision Under Dynamic Fluid Conditions
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Solution Overview
Problem
Conventional Coriolis flowmeters face challenges in maintaining high precision and speed when measuring phase and frequency due to changes in fluid temperature, air bubble mixing, and rapid fluid state changes from gas to liquid, requiring complex computations and large memory consumption, which complicates the design and increases costs.
Innovation Solution
A signal processing method for Coriolis flowmeters that involves frequency conversion to combine flow rate signals, controlling the frequency of sum or difference frequency components to a constant value, and measuring phase from these components, using modulatable frequency signals and frequency converters to stabilize measurements, reducing computational load and improving filtering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase measurement methods (Fourier transform or digital filters) are used to measure phase and frequency, then measurement precision may be maintained under stable conditions, but computational complexity increases and measurement speed decreases when fluid temperature changes, air bubbles mix, or fluid state changes rapidly
Solution Approach 1:
The patent transforms the measurement parameters by converting variable-frequency sinusoidal signals into fixed-frequency square wave signals through zero-crossing detection. This parameter transformation allows the use of simpler digital counting methods instead of complex Fourier transforms or adaptive filters, thereby reducing computational complexity while maintaining measurement precision under dynamic fluid conditions
Solution Approach 2:
The patent replaces complex mathematical computation systems (Fourier transform, digital filtering) with a simpler electronic signal processing system based on zero-crossing detection and digital counting. This substitution uses basic electronic components and simple algorithms to achieve the same measurement function with significantly reduced computational burden
2Measurement precision
If conventional phase measurement methods are used, then measurement accuracy may be adequate under stable conditions, but measurement speed decreases due to large computational load during rapid fluid state changes
Solution Approach 1:
The patent changes the signal representation from continuous sinusoidal waves requiring complex mathematical operations to discrete square wave signals requiring only zero-crossing detection and counting. This parameter change enables real-time measurement at high speeds even during rapid fluid state transitions, as the simplified computation can be executed much faster
Solution Approach 2:
The patent uses zero-crossing detection to capture essential phase information at critical moments (when signals cross zero) rather than processing the entire continuous waveform. This approach skips unnecessary computational steps and rushes through the measurement process efficiently, achieving high measurement speed without sacrificing accuracy
3Measurement precision
If Fourier transform or digital filter methods are employed for frequency selection, then phase measurement precision may be maintained, but memory consumption increases and design becomes more complex
Solution Approach 1:
The patent extracts only the essential information needed for phase measurement (zero-crossing points) from the complete signal waveform, discarding redundant data. This extraction approach eliminates the need for large memory buffers required by Fourier transforms and digital filters, significantly reducing memory consumption while preserving measurement precision
Solution Approach 2:
The patent uses simple digital counters and basic logic circuits instead of complex computational algorithms requiring large memory resources. These simple electronic components are inexpensive and require minimal memory, providing a cost-effective solution that maintains measurement precision without the memory burden of conventional methods
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 constant precision phase and frequency measurements even with temperature changes, air bubble mixing, or fluid state changes, reducing computational complexity and cost, and providing high-speed, stable, and accurate measurements.
Implementation Method 1
When an alternate driving frequency of the flow tube is made equal to the natural frequency of the flow tube, a constant driving frequency corresponding to the density of the fluid to be measured is obtained, and hence the flow tube may be driven with small driving energy.
Implementation Method 2
When the density is to be measured using the curved-tube-type flow tube as described above, a combination of a coil and a magnet are generally used as a driving means for driving the flow tube.
Implementation Method 3
a left velocity sensor 7 for detecting a vibration velocity generated on a left side of the measurement tubes 2 and 3 vibrated by the vibrator 6, a right velocity sensor 8 for detecting a vibration velocity generated on a right side of the measurement tubes 2 and 3
Implementation Method 4
a mass flow rate is obtained from a phase difference proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes detected by two velocity sensors or acceleration sensors
Data Source
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AI summary
[Summary] [Object] To provide a signal processing apparatus with which, even when a temperature of a fluid to be measured changes, even when air bubbles are mixed into the fluid to be measured, or even when the fluid to be measured rapidly changes from gas to liquid, measurement may be always performed with constant precision and phase and density measurements may be performed with a small computing amount. [Solving Means] A signal processing apparatus for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a velocity sensor or acceleration sensor which is a vibration detection sensor, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured, includes: a transmitter (90) for transmitting a frequency signal which is modulatable; and a frequency conversion section (85) for performing frequency conversion to add (or subtract) an output frequency Fx from the transmitter (90) to (or from) an input frequency detected by the velocity sensor or acceleration sensor and shifting a frequency value obtained by the frequency conversion to a constant value.