Correcting frequency in flowtube measurements
First Claim
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1. A flowmeter comprising:
- a vibratable flowtube;
a driver connected to the flowtube and operable to impart motion to the flowtube;
a first sensor connected to a first portion of the flowtube and operable to sense a frequency of the motion of the flowtube and generate a first sensor signal;
a second sensor connected to a second portion of the flowtube and operable to sense the frequency of the motion of the flowtube and generate a second sensor signal; and
a controller operable to adjust the frequency sensed by the sensors based on a phase difference between the first sensor signal and the second sensor signal, to thereby obtain a corrected frequency;
wherein the controller is operable to determine a relationship between the frequency and the phase difference, based on a plurality of frequency measurements and corresponding phase difference measurements, the relationship being determined using at least one of a linear regression and/or a quadratic fit based on the frequency measurements and phase difference measurements.
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Abstract
Techniques are described for accurately measuring a density or other parameter of a fluid traveling through a vibratable conduit, using a flowmeter. The techniques involve obtaining measurements of a frequency of vibration of the conduit, as a function of a phase difference between two sensors measuring the vibration. Using the measurements, a corrected frequency corresponding to a zero phase difference can be estimated, and this corrected frequency can be used to perform density calculations. These techniques remove an undesirable dependency between the frequency/phase difference variables.
91 Citations
17 Claims
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1. A flowmeter comprising:
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a vibratable flowtube; a driver connected to the flowtube and operable to impart motion to the flowtube; a first sensor connected to a first portion of the flowtube and operable to sense a frequency of the motion of the flowtube and generate a first sensor signal; a second sensor connected to a second portion of the flowtube and operable to sense the frequency of the motion of the flowtube and generate a second sensor signal; and a controller operable to adjust the frequency sensed by the sensors based on a phase difference between the first sensor signal and the second sensor signal, to thereby obtain a corrected frequency; wherein the controller is operable to determine a relationship between the frequency and the phase difference, based on a plurality of frequency measurements and corresponding phase difference measurements, the relationship being determined using at least one of a linear regression and/or a quadratic fit based on the frequency measurements and phase difference measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method comprising:
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determining an operational parameter associated with an operation of a flowmeter; selecting a corrected frequency corresponding to the operational parameter, the corrected frequency determined based on a phase difference between a first sensor signal and a second sensor signal, and determined based on a relationship between a plurality of measured frequency values and a plurality of measured phase differences, the relationship being determined by using at least one of a linear regression and/or a quadratic fit based on the plurality of measured frequency values and the plurality of measured phase differences, where the first sensor signal and the second signal correspond to a frequency of vibration of a flowtube associated with the flowmeter; and determining a flow parameter of a material flowing through the flowtube, based on the corrected frequency. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A flowmeter controller comprising:
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a measurement system operable to receive a first sensor signal and a second sensor signal and determine a frequency of vibration of a flowtube having a material flowing therethrough, based on the first sensor signal and the second sensor signal; a frequency correction system operable to determine a corrected frequency of the flowtube corresponding to a zero phase difference between the first sensor signal and the second sensor signal, the frequency correction system further operable to determine the corrected frequency by establishing a relationship between a plurality of frequency measurements and a plurality of phase difference measurements output by the measurement system, the relationship being determined using at least one of a linear regression and/or a quadratic fit based on the plurality of frequency measurements and the plurality of phase difference measurements; and a flow parameter determination system operable to determine a flow parameter characterizing the material, based on the corrected frequency. - View Dependent Claims (16, 17)
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Specification