Coriolis Flow Meter Electronics Phase Detection
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Solution Overview
Problem
Existing Coriolis mass flow meters face challenges in accurately and quickly determining phase differences during two-phase flows and rapid frequency transitions, leading to errors in mass flow rate and density measurements due to the reliance on slow and error-prone reference signal methods.
Innovation Solution
The implementation of a method using a Hilbert transform and quadrature demodulation to determine phase differences between sensor signals, allowing for faster and more accurate frequency and phase determination, reducing processing time and increasing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an independent reference signal is used to determine pickoff signal frequency, then frequency determination can be performed, but the process becomes slow and error-prone, producing low frequency AC signals that complicate measurements
Solution Approach 1:
The patent replaces the mechanical reference signal method with a digital signal processing approach using Hilbert transform and quadrature demodulation. This substitution eliminates the need for physical reference signals and associated timing issues, achieving both speed and accuracy in frequency determination through mathematical transformation of the sensor signals.
2Reliability
If a notch filter is used to track pickoff sensor frequency, then frequency determination works under quiescent conditions, but the measurement suffers during two-phase flows and rapid frequency transitions when the pickoff signal moves outside filter bandwidth
Solution Approach 1:
The patent implements a dynamic frequency tracking method using Hilbert transform that automatically adapts to changing flow conditions. Unlike the static notch filter with fixed bandwidth, the Hilbert transform approach continuously calculates instantaneous frequency, enabling reliable measurement during two-phase flows and rapid frequency transitions without requiring the signal to remain within a predetermined bandwidth.
3Measurement precision
If demodulation is performed at a determined frequency, then phase difference can be calculated, but errors in frequency determination compound errors in phase and flow characteristic measurements
Solution Approach 1:
The patent replaces the sequential process of frequency determination followed by demodulation with a unified quadrature demodulation approach based on Hilbert transform. This method simultaneously extracts both frequency and phase information from the sensor signals, eliminating the error propagation that occurs when frequency errors feed into subsequent phase and flow characteristic calculations.
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 enables phase difference determination 40 times faster than prior art, with improved accuracy and reliability, effectively addressing the limitations of existing methods in handling two-phase flows and rapid frequency changes.
Implementation Method 1
generating a Hilbert transform of the sensor signal, which comprises a 90 degree phase shift of the sensor signal
Implementation Method 2
As a material begins to flow through the flow tube, Coriolis accelerations cause each point along the flow tube to have a different phase with respect to other points along the flow tube
Data Source
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AI summary
Meter electronics (20) for processing sensor signals in a flow meter is provided according to an embodiment of the invention. The meter electronics (20) includes an interface (201) for receiving a first sensor signal and a second sensor signal and a processing system (203) in communication with the interface (201) and configured to receive the first sensor signal and the second sensor signal, generate a ninety degree phase shift from the first sensor signal, and compute a frequency from the first sensor signal and the ninety degree phase shift. The processing system (203) is further configured to generate sine and cosine signals using the frequency, and quadrature demodulate the first sensor signal and the second sensor signal using the sine and cosine signals in order to determine the phase difference.