Coriolis Flowmeter Digital Signal Processing Phase Deviation
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Solution Overview
Problem
Coriolis mass flowmeters face accuracy issues due to phase deviation caused by delay in converting analog signals to digital signals using Δ∑ AD converters, leading to lowered vibration control and measurement accuracy.
Innovation Solution
A Coriolis mass flowmeter employing Δ∑ modulators to convert sensor signals into pulse density signals, followed by LPFs to generate multi-bit signals, which are used to control the amplification factor for precise resonance excitation, reducing component count and board area while maintaining high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a highly accurate Δ∑ AD converter IC is used to convert sensor signals to digital signals, then measurement precision is improved, but phase deviation occurs due to delay in the LPF conversion process, which lowers vibration control accuracy and measurement accuracy
Solution Approach 1:
The patent applies preliminary action by performing Δ∑ modulation on the sensor signals before they are processed by the LPF. This preliminary modulation creates pulse density signals that can be processed with minimal delay, allowing the excitation signal to be generated in advance of the traditional analog-to-digital conversion process, thereby eliminating phase deviation while maintaining high measurement precision
Solution Approach 2:
The patent replaces the traditional mechanical/analog signal conversion process with a digital signal processing approach. By using Δ∑ modulators to convert analog sensor signals to digital pulse density signals, and then processing these digital signals through LPFs and other digital circuits, the system eliminates the phase deviation inherent in analog-to-digital conversion while maintaining high accuracy in both measurement and vibration control
2Manufacturing precision
If an analog excitation circuit is used to control the amplitude of resonance vibration, then vibration control accuracy is improved, but the number of components increases, board area increases, and cost increases
Solution Approach 1:
The patent replaces the complex analog excitation circuit with a digital signal processing system. Instead of using analog amplifiers, filters, and oscillators to control vibration amplitude, the system uses digital circuits including Δ∑ modulators, LPFs, multipliers, and digital-to-analog converters. This substitution dramatically reduces the number of physical components, board area, and cost while maintaining or improving vibration control accuracy through precise digital control of the excitation signal parameters
Solution Approach 2:
The patent changes the fundamental parameters of signal representation from analog voltage levels to digital pulse density codes. By manipulating the digital representation of the excitation signal through software-controlled digital circuits, the system achieves precise control of vibration amplitude without requiring complex analog component assemblies. The digital approach allows for flexible parameter adjustment through software rather than hardware changes
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
The solution enables high-accuracy, stable excitation with minimal delay, reducing component costs and allowing for efficient excitation of measurement tubes with varying diameters, while minimizing the influence of air bubbles and external vibrations.
Implementation Method 1
a measurement tube which generates when the measurement tube which is fixed at both ends is vibrated as a fluid flows through it
Implementation Method 2
a resonance circuit configured to generate an excitation signal on the basis of at least one of the output signals of the two sensors
Implementation Method 3
an exciter configured to excite the measurement tube using an amplified excitation signal
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
First and second ΔΣ modulators convert output signals of two sensors into pulse density signals. First and second LPFs convert the pulse density signals into multi-bit signals. A signal computing module calculates a mass flow rate based on the multi-bit signals. A resonance circuit generates an excitation signal based on the output signals of the sensors. A drive output module amplifies the excitation signal. An exciter excites the measurement tube using an amplified excitation signal. A multiplier amplifies one of the pulse density signals to generate a multi-bit signal. An amplification factor controller controls an amplification factor of the multiplier based on the multi-bit signal. A third ΔΣ modulator converts an amplified signal into a pulse density signal. A DAC generates the excitation signal based on the pulse density signal.