Digital phase locked loop signal processing for coriolis mass flow meter
First Claim
1. An improved Coriolis-type system for measuring a fluid flow rate, comprising:
- a first fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a first oscillation axis thereof;
a second fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a second oscillation axis thereof and parallel to said first oscillation axis, with said second conduit being formed so as to be physically similar to said first conduit, and further with said first and second conduits being mounted so as to be parallel to each other between their respective end portions when not in use;
driver means, responsive to a driver signal input, for oscillating said first and second conduits relative to each other about their respective oscillation axes for generating a corresponding relative oscillatory motion thereof, and for thereby causing oscillating Coriolis accelerations to act on respective fluid flows through said conduits;
respective first and second sensor means associated with said conduits for generating analog sinusoidal outputs at two respective predetermined locations in correspondence with said relative motion between said first and second conduits at said two predetermined locations;
means for digitizing said analog sinusoidal outputs and for generating corresponding first and second digitized outputs; and
means for processing said digitized outputs to estimate a fundamental frequency thereof, to estimate a phase shift between said digitized outputs, and to establish from said frequency and phase shift estimates an optimized driver signal input for said driver means, and for determining from said phase shift a corresponding mass flow rate of fluid flowing through said first and second conduits.
7 Assignments
0 Petitions
Accused Products
Abstract
A Coriolis-type fluid flow rate measuring system uses phase locked loop-based signal processing to estimate a tube vibration signal and maintain optimum tube vibrations. Analog sinusoidal sensor signals from the flow meter are digitized and processed through heterodyne mixing as part of phase locked loop tracking of the fundamental vibration or oscillation frequency. Digital signal processing is used to implement filtering and signal manipulation so as to respectively determine phase and frequency estimates for both of the two digitized signals. Frequency estimate data is used to adjust the tracker frequency mixed with the respective sensor signals. Digitally obtained phase and frequency estimate data are used to determine an optimized drive signal for continuing tube vibration. Phase estimate information for the two respective sensor signals is used to determine phase shift data, used in turn to determine a fluid flow rate through the flow meter.
-
Citations
29 Claims
-
1. An improved Coriolis-type system for measuring a fluid flow rate, comprising:
- a first fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a first oscillation axis thereof;
a second fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a second oscillation axis thereof and parallel to said first oscillation axis, with said second conduit being formed so as to be physically similar to said first conduit, and further with said first and second conduits being mounted so as to be parallel to each other between their respective end portions when not in use; driver means, responsive to a driver signal input, for oscillating said first and second conduits relative to each other about their respective oscillation axes for generating a corresponding relative oscillatory motion thereof, and for thereby causing oscillating Coriolis accelerations to act on respective fluid flows through said conduits; respective first and second sensor means associated with said conduits for generating analog sinusoidal outputs at two respective predetermined locations in correspondence with said relative motion between said first and second conduits at said two predetermined locations; means for digitizing said analog sinusoidal outputs and for generating corresponding first and second digitized outputs; and means for processing said digitized outputs to estimate a fundamental frequency thereof, to estimate a phase shift between said digitized outputs, and to establish from said frequency and phase shift estimates an optimized driver signal input for said driver means, and for determining from said phase shift a corresponding mass flow rate of fluid flowing through said first and second conduits. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a first fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a first oscillation axis thereof;
-
8. An improved method of operating a Coriolis-type system for measuring a fluid flow rate, comprising:
-
providing a first fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a first oscillation axis thereof; providing a second fluid flow conduit having respective inlet and outlet portions which are substantially coaxial with a second oscillation axis thereof and parallel to said first oscillation axis, with said second conduit being formed so as to be physically similar to said first conduit, and further with said first and second conduits being mounted so as to be parallel to each other between their respective end portions when not in use; responsive to a driver signal, oscillating said first and second conduits relative to each other about their respective oscillation axes for generating a corresponding relative oscillatory motion thereof, and for thereby causing oscillating Coriolis accelerations to act on respective fluid flows through said conduits; generating analog sinusoidal outputs at two respective predetermined locations in correspondence with said relative motion between said first and second conduits at said two predetermined locations; digitizing said analog sinusoidal outputs and generating corresponding first and second digitized outputs; processing said digitized outputs to estimate a fundamental frequency thereof, to estimate a phase shift between said digitized outputs, and to establish from said frequency and phase shift estimates an optimized driver signal and using said optimized driver signal for oscillating said conduits; and determining from said phase shift a corresponding mass flow rate of fluid flowing through said first and second conduits. - View Dependent Claims (9, 10, 11, 12, 13, 14)
-
-
15. A method of determining fluid flow rate through a Coriolis-type flow meter of the type having at least two analog sensor channels and an electromagnetically-driven vibrating-tube design, comprising the steps of:
-
digitizing the analog sensor signals; custom filtering the digitized signals for rejecting interference and noise; using phase locked loop tracking for dynamically matching the filtering operation with the time-varying sensor waveforms; processing the filtered signals for obtaining frequency and phase estimates of a drive signal for optimized tube vibrations and using such optimized drive signal for electromagnetically driving tube vibrations; and using said phase estimates to determine phase shift estimates and to determine therefrom a corresponding fluid flow rate through said flow meter. - View Dependent Claims (16, 17, 18, 19)
-
-
20. Digital signal processing apparatus for determining fluid flow through a Coriolis-type flow meter of the type having at least two analog sensor channels and an electromagnetically-driven vibrating-tube design, comprising:
-
analog-to-digital converter means for digitizing respective analog sensor signals; digital filtering means for filtering the digitized signals for rejecting interference and noise therefrom; phase locked loop means for tracking the time-varying sensor signal waveforms for dynamically matching operations of said digital filtering means thereto; means for processing the filtered signals for obtaining frequency and phase estimates therefrom and for outputting a drive signal based thereon for optimized tube vibrations; driver means, responsive to said drive signal, for electromagnetically generating tube vibrations in accordance with said drive signal; and flow rate data means for determining a corresponding fluid flow rate through the flow meter based on determining phase shift estimates from said phase estimates. - View Dependent Claims (21, 22, 23, 24)
-
-
25. Improved apparatus for operating a Coriolis-type flow meter of the type having at least two analog sensor channels and a vibrating tube design, comprising:
-
analog-to-digital converter means for digitizing respective analog sensor signals; digital signal processing means, responsive to the digitized respective sensor signals, for digitally tracking such digitized signals using a phase locked loop and for estimating from such tracking an optimized tube vibration signal; and drive means, responsive to said optimized tube vibration signal, for maintaining flow meter tube vibrations in accordance with said vibration signal, so that desired tube vibration is maintained based on digital phase locked loop tracking of the sensor signals for improved flow meter operation. - View Dependent Claims (26, 27, 28, 29)
-
Specification