Coriolis Flowmeter Digital Signal Processing Phase Measurement
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Solution Overview
Problem
Conventional Coriolis mass flowmeters face challenges in achieving precise phase difference measurements between upstream and downstream coil signals due to environmental condition fluctuations and component changes, leading to measurement inaccuracies and increased flow rate measurement interruption times.
Innovation Solution
The implementation of a digital signal processing system with time division switching of upstream and downstream coil signals, allowing for continuous flow rate measurement without interrupting zero point compensation, using multiple signal paths and reference signals to correct for phase differences and environmental effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional synchronous sampling method is used for phase difference measurement, then measurement precision is maintained, but device complexity increases due to requirement of special A/D converter and flow rate measurement must be interrupted for zero point compensation
Solution Approach 1:
The patent divides the signal processing into two separate time-division paths: one for flow rate measurement (phase difference detection) and another for zero point compensation. By sequentially alternating between these two functions using a switching mechanism, the system eliminates the need for complex synchronous sampling hardware while maintaining measurement precision through temporal separation of operations.
Solution Approach 2:
The system implements periodic alternation between flow rate measurement mode and zero point compensation mode. A switching circuit periodically connects different signal paths to the A/D converter based on the current operational phase, enabling both functions to share the same hardware resources without interference, thus simplifying the device while preserving accuracy.
2Measurement precision
If flow rate measurement is interrupted for zero point compensation, then measurement accuracy is improved, but productivity decreases due to measurement interruption time
Solution Approach 1:
The patent enables continuous operation by implementing overlapping time-division multiplexing where flow rate measurement and zero point compensation are performed in rapid succession rather than completely interrupting one for the other. The switching between modes is so fast that the overall measurement process appears continuous, eliminating dead time while still performing necessary calibration.
Solution Approach 2:
The system performs zero point compensation measurements in advance during intervals between flow rate measurements, preparing correction data before it is needed. This preliminary action ensures that when flow rate measurement resumes, the correction factors are already available, maintaining accuracy without causing interruptions.
3Device complexity
If environmental condition fluctuations are not compensated, then device complexity is reduced, but measurement precision deteriorates due to phase difference errors
Solution Approach 1:
The system uses itself to compensate for environmental effects by measuring its own zero point drift through the dedicated compensation path. By periodically measuring the phase difference when no fluid is flowing (or with symmetric flow conditions), the system self-calibrates to account for temperature changes, component aging, and environmental fluctuations, maintaining precision without adding external reference systems.
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 enhances measurement stability and accuracy by reducing measurement interruption times and error components, enabling precise flow rate calculations with a general-purpose A/D converter, thus improving the overall performance and cost-effectiveness of the Coriolis mass flowmeter.
Implementation Method 1
the tube 15 is vibrated in a primary mode indicated by signs M1 and M2 in FIG. 13, for example. The primary mode refers to a vibration state appearing only in portions where nodes of vibration are fixed and supported by the support members 16 and 17. When a fluid flows into the tube 15 in such a vibration state, the tube 15 vibrates in a secondary mode indicated by signs M3 and M4 in the figure, for example.
Implementation Method 2
The upstream sensor 62 is placed on the right side of the support member 16 and in the proximity of the tube 15, detects vibration of the upstream fluid, and outputs an upstream coil signal S1 (pickup signal) to the converter 75.
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
There is provided a Coriolis mass flowmeter. The flowmeter is configured to vibrate a pipe line through which a fluid flows and measure a mass flow rate of the fluid flowing through the pipe line, based on a phase difference between an upstream vibration signal and a downstream vibration signal, wherein the upstream vibration signal is detected in an upstream side of the pipe line, and the downstream vibration signal is detected in a downstream side of the pipe line.