Correcting frequency in flowtube measurements
First Claim
Patent Images
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 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 motion of the flowtube and generate a second sensor signal; and
a controller operable to;
access a frequency correction that is determined based on a characteristic curve of frequency versus phase difference;
determine an apparent frequency of the motion from the first and second signal; and
adjust the apparent frequency based on the accessed frequency correction and a phase difference between the first sensor signal and the second sensor signal, thereby obtaining a corrected frequency.
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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.
96 Citations
21 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 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 motion of the flowtube and generate a second sensor signal; and a controller operable to; access a frequency correction that is determined based on a characteristic curve of frequency versus phase difference; determine an apparent frequency of the motion from the first and second signal; and adjust the apparent frequency based on the accessed frequency correction and a phase difference between the first sensor signal and the second sensor signal, thereby obtaining a corrected frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method comprising:
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vibrating a flowtube containing a material; determine an apparent frequency of the vibration of the flowtube; access a frequency correction that is determined based on a characteristic curve of frequency versus phase difference; and adjust the apparent frequency based on the accessed frequency correction and a phase difference between the first sensor signal and the second sensor signal, thereby obtaining a corrected frequency. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. 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 an apparent frequency of vibration of a flowtube based on the first sensor signal and the second sensor signal, the flowtube containing a material; a frequency correction system operable to; access a frequency correction that is determined based on a characteristic curve of frequency versus phase difference; and adjust the apparent frequency based on the accessed frequency correction and a phase difference between the first sensor signal and the second sensor signal, thereby obtaining a corrected frequency; and a flow parameter determination system operable to determine a parameter of the material based on the corrected frequency. - View Dependent Claims (19, 20, 21)
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Specification