Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 1 of 40 PageID #: 824
`25"‘|IIIII‘I111lflfllfllflllfilllflllflfllfllmflfllflllflfllfillIIIHIW24
`
`US007505854B2
`
`(12) United States Patent
`Henry et al.
`
`(10) Patent No.:
`
`(45) Date of Patent:
`
`US 7,505,854 B2
`*Mar. 17, 2009
`
`(54) STARTUP TECHNIQUES FOR A DIGITAL
`FLOWMETER
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`(75)
`
`Inventors: Manus P. Henry, Oxford (GB); Mayela
`E. Zamora, Oxford (GB)
`
`3,956,682 A
`
`5/1976 Van Dyck
`
`(73) Assignee:
`
`Invensys Systems, Inc., Foxboro, MA
`(US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`0 696 726 A
`
`2/1996
`
`(Continued)
`OTHER PUBLICATIONS
`
`This patent is subject to a terminal dis-
`claimer.
`
`Robert H. Wood et al., “A Phrase-locked Loop for Driving Vibrating
`Tube Densimeters,” Rev. Sci. Instrum., vol. 60, No. 3, Mar. 1989, pp.
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`
`(21) Appl.No.: 11/458,251
`
`(22)
`
`Filed:
`
`Jul. 18, 2006
`
`(65)
`
`Prior Publication Data
`
`US 2007/0027639 A1
`
`Feb. 1, 2007
`
`Related U.S. Application Data
`
`(63) Continuation of application No. 11/168,568, filed on
`Jun. 29, 2005, now Pat. No. 7,146,280, which is a
`continuation of application No. 10/402,131, filed on
`Mar. 31, 2003, now Pat. No. 6,950,760, which is a
`continuation-in-part of application No. 10/400,922,
`filed on Mar. 28, 2003, now abandoned.
`
`(60) Provisional application No. 60/368,153, filed on Mar.
`29, 2002.
`
`(51)
`
`Int. Cl.
`(2006.01)
`G06F 1/00
`(2006.01)
`G06F 19/00
`(52) U.S. Cl.
`............... .. 702/45; 73/861.12; 73/861.355;
`73/861.356
`
`(58) Field of Classification Search ........... .. 702/45—47,
`702/50, 54, 100, 104, 106, 137; 73/861.02,
`73/861.04, 861.12, 861.355, 861.356, 861.357;
`318/640; 386/34; 361/740; 340/606
`See application file for complete search history.
`
`(Continued)
`
`Primary Examiner—John H Le
`(74) Attorney, Agent, or Firm—Fish & Richardson P.C.
`
`(57)
`
`ABSTRACT
`
`Startup and operational techniques for a digital flowmeter are
`described. The techniques select an optimal mode of opera-
`tion for the digital flowmeter, depending on a current envi-
`ronment of the flowmeter. For example, during a startup
`operation of the flowmeter, the mode of operation might
`include a random sequence mode, in which filtered, random
`frequencies are applied as a drive signal to a flowtube asso-
`ciated with the digital flowmeter. Once the flowtube reaches a
`resonant mode of vibration, the digital flowmeter may tran-
`sition to a positive feedback mode, in which a sensor signal
`representing a motion of the flowtube is fed back to the
`flowtube as a drive signal, as part of a feedback loop. Once an
`oscillation of the flowtube is achieved and analyzed, a digital
`synthesis mode of operation may be implemented, in which
`the analyzed sensor signals are used to synthesize the drive
`signal. In either the positive feedback mode or the digital
`synthesis mode, the digital flowmeter may revert to a previous
`mode to regain stable and desired oscillation of the flowtube,
`such as might be required during a recovery operation asso-
`ciated with a disturbance to an operation of the digital flow-
`meter.
`
`21 Claims, 20 Drawing Sheets
`
` 215
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 2 of 40 PageID #: 825
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 2 of 40 Page|D #: 825
`
`US 7,505,854 B2
`Page 2
`
`7/2000 Cunningham et al.
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`6,505,131 B1
`1/2003 Henry et ai.
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`1/2003 Henry et ai.
`6,507,791 B2
`4/2003 Zukerwar et al.
`6,551,251 B2
`5/2003 Dutton et al.
`6,564,619 B2
`9/2005 Henry et ai.
`6,950,760 B2 *
`3/2002 Dutton et al.
`2002/0033043 A1
`3/2002 Henry et ai.
`2002/0038186 A1
`9/2002 Maginnis
`2002/0133307 A1
`FOREIGN PATENT DOCUMENTS
`
`................ .. 702/45
`
`EP
`EP
`EP
`EP
`W0
`W0
`W0
`
`0 698 783
`0 702 212
`0 827 096
`0919793 A2
`WO 93/21505
`WO 00/10059
`WO 02/08703
`
`2/1996
`3/1996
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`
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`Joze Kutin et al., “Phase-locking Control of the Coriolis Meter’s
`Resonance Frequency Based on Virtual Instrumentation,” Sensors
`and Actuators A 10 (2003), pp. 86-93.
`International Search Report, Dec. 17, 2003, 7 pages.
`DeCar1o, Joseph P., “Fundamentals of Flow Measurement”, pp. 208-
`220; 1984; USA.
`J.T. Grumski et al., “Performance of a Coriolis-type Mass Flow
`Meter in the Measurement of Two-phase (air-liquid) Mixtures”,
`ASME Fluid Engineering Division Publication FED, vol. 17, pp.
`75-84, 1984.
`J. Hemp et al., “On the theory and performance of Coriolis Mass
`Flowmeters” Proceedings of the International Conference on Mass
`Flow Measurement Direct and Indirect, IBC Technical Services,
`London, Feb. 1989.
`E. Luntta et al., “Neural Network Approach to Ultrasonic Flow Mea-
`surements”, Flow Measurement and Instrumentation, vol. 10, pp.
`35-43, 1999.
`A.F. Skea, “Effects of Gas Leaks in Oil Flow on Single-Phase
`Flowmeters”, Flow Measurement and Instrumentation, vol. 10, pp.
`146-150 (1999).
`Spitzer, David A., “Industries Flow Measurement”, pp. 197-210;
`1990; USA.
`Liu, R.P, et al., “A Neural Network to Correct Mass Flow Errors
`Caused by Two Phase Flow in a Digital Coriolis Mass Flow Meter,”
`Engineering Science Department, Oxford University, Flow Measure-
`ment and Instrumentation, vol. 12, No. 1, Mar. 2001.
`Reimarm, J., “Developments in Two-Phase Mass Flow Rate Instru-
`mentation,” NATO Advanced Study Institutes Series, Series E:
`Applied Sciences, pp. 339-402, 1983.
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`18(3) dated Jul. 20, 2005 for application No. GB0512421.9.
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`* cited by examiner
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`Stadier
`
`E >
`
`>D>>>D>>>>>>>>>>>>>D>>>D>>>D>>>>>>D>D>D>D>D>D>D>D>D>D>D>D>>D>D>>D>D>>D>D>D>D>>D>D>D>U'1D>
`
`RE29,383
`4,358,822
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`4,419,898
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`5,054,326
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`5,259,250
`5,271,281
`5,295,084
`5,301,557
`5,343,764
`5,347,874
`5,400,653
`5,429,002
`5,469,748
`5,497,665
`5,497,666
`5,535,632
`5,555,190
`5,570,300
`5,578,764
`5,594,180
`5,648,616
`5,654,502
`5,687,100
`5,732,193
`5,734,112
`5,774,378
`5,804,741
`5,877,954
`5,905,206
`5,926,096
`5,969,264
`6,073,495
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 3 of 40 PageID #: 826
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 3 of 40 Page|D #: 826
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 1 of 20
`
`US 7,505,854 B2
`
`104
`
`
`Digital Transmitter
`
`104
`
`
`
`............................................................ -.
`
`............................................................ -.
`
`
`
`105
`
`
`
`Digital Transmitter
`.\\\\\\x\\\\\.\\\‘\\\\;\\\\\\\\\\\\~u:\\\a.\~‘
`
`
`
`
`
`\\\\\\x\\\\\\\\\\V~\\\\\\\\\m\\\\\\\\\V
`
`FIG. 1B
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 4 of 40 PageID #: 827
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 4 of 40 Page|D #: 827
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 2 of 20
`
`US 7,505,854 B2
`
`Massflow
`
`Measurement
`
`200
`
`W
`
`104
`
`
`
`Digital Transmitter
`
`210
`
`215
`
`FIG. 2
`
`K 205
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 5 of 40 PageID #: 828
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 5 of 40 Page|D #: 828
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 3 of 20
`
`US 7,505,854 B2
`
`
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 6 of 40 PageID #: 829
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 6 of 40 Page|D #: 829
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 4 of 20
`
`US 7,505,854 B2
`
`-------H
`
`420
`
`400
`
`M
`
`/.104
`
`
`
`Digital Controller
`
`425
`
`450
`
`
`
`4455
`
`Flowtube
`
`FIG. 4
`
`215
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 7 of 40 PageID #: 830
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 7 of 40 PagelD #: 830
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 5 of 20
`
`US 7,505,854 B2
`
`From Codec DAC Outputs
`
`505
`
`/- 502
`
`500
`w/
`
`510
`
`Q
`
`515
`
`520
`
`Sensor Balance Term
`
`Weighted Sum
`
`Circular Buffer
`
`phase-matching delay
`
`535
`
`540
`
`Phase—Matched Output
`
`545
`
`0
`
`Drive Output
`
`560
`
`L. Drive Output
`
`R. Drive Output
`
`565
`
`550
`
`570
`
`575
`
`Drive Balance Term
`
`585
`
`Balanced
`R. Drive Output
`
`To Codec DAC Outputs
`
`F 5
`
`ProcessorBus
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 8 of 40 PageID #: 831
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 8 of 40 Page|D #: 831
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 6 of 20
`
`US 7,505,854 B2
`
` ,
`
`sensor
`signal at
`
`FIG. 6
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 9 of 40 PageID #: 832
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 9 of 40 Page|D #: 832
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 7 of 20
`
`US 7,505,854 B2
`
`From Codec ADC outputs
`
`L. Sensor Data s1
`
`704
`
`712
`
`
`
`700
`,a/
`
`710
`
`Sensor Balance Term
`
`718
`
`fs2
`
`Weighted Sum fvvs
`
`fs1
`
`Circular Buffer
`
`720
`
`__
`
`72
`
`_> Sensor signaI analysis
`
`726
`
`724
`
`Sine wave synthesis
`
`ll‘Synthesis parameters
`728
`DriveGainTerm
`I
`I
`638
`
`Coriolis or Dn'ven Mode‘?
`
`740
`
`Drive Balance Term
`
`634
`
`736
`
`L. Drive Output
`
`R. Drive Output
`
`/0
`742
`
`744
`
`Balanced
`
`R. Drive Output
`
`Processor Bus
`
`To Codec DAC inputs
`
`FIG. 7
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 10 of 40 PageID #: 833
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 10 of 40 Page|D #: 833
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 8 of 20
`
`US 7,505,854 B2
`
`
`
`signal at
`
`sensor
`
`FIG. 8
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 11 of 40 PageID #: 834
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 11 of 40 PagelD #: 834
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 9 of 20
`
`US 7,505,854 B2
`
`§i+1 §a+2
`i
`
`
`i+3
`
`i+4
`
`i+5§i+6
`
`i+7§
`
`902
`
`:
`cycle ‘
`
`906;f—910j/
`
`sensor signal
`at ADC input
`(analog)
`
`sensor signal
`at filter output
`(digital)
`
`
`
`904
`
`ADC and
`
`filter delay
`
`914
`
`drive signal
`at DAC input
`(digital)
`
`DAC delay%
`
`918
`
`K
`
`922
`
`
`
`FIG. 9
`
`drive signal
`at DAC output
`(analog)
`
`in phase with
`sensor signal at
`
`ADC input on
`cycle i+4
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 12 of 40 PageID #: 835
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 12 of 40 PagelD #: 835
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 10 of 20
`
`US 7,505,854 B2
`
`“MA
`
`1
`
`DB
`
`_
`
`_
`
`_
`
`detect zero-crossin -
`
`Input synthesis
`arameters
`
`
`wait first wait time to
`
`
`
`
`
`
`
`apply amplitude
`information
`
`Send to DAC inputs
`
`wait second wait time
`
`1012
`
`1014
`
`.
`
`1020
`
`
`
`
`
`
`
`
`1002
`
`1006
`
`1008
`
` 1004
`
`
`
`Input sensor signal from
`
`Apply fi|ter(s) to sensor
`sinal 5
`
`Calculate weighted sum
`of sensor signals
`
`Detect zero crossing of
`weihted sum
`
`Send filtered signals to
`rocessor
`
`
`
`
`
`
`
`
`
`FIG. 10A
`
`FIG. 10B
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 13 of 40 PageID #: 836
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 13 of 40 PagelD #: 836
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 11 of 20
`
`US 7,505,854 B2
`
`Processor
`
`JLQQ
`
`99
`
`
`
`Determine zero
`
`
`crossings using
`
`interpolation
`
`
`
`
`
` Determine
`
`frequencies and
`FREQave
`
`
`
`Calculate phase
`offset
`
`Calculate
`
`
`frequency delay
`
`
`angle between
`
`
`
`
`initial values of
`sine wave
`sin/cos
`
`
`parameters
`
`Calculate and send
`
`
`
`
`second wait
`time
`
`
`
`Calculate
`
`Amplitude
`information
`
`
`
`FIG. 11
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 14 of 40 PageID #: 837
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 14 of 40 PagelD #: 837
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 12 of 20
`
`US 7,505,854 B2
`
`ADC and filter
`
`delay
`
`1202\
`
`/-415
`
`‘
`
`K1206
`
`(-450
`
`start of cycle
`offset at
`
`filter output
`1212
`
`FIG. 12
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 15 of 40 PageID #: 838
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 15 of 40 Page|D #: 838
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 13 of 20
`
`US 7,505,854 B2
`
`
`
` IIIIIIIOIIIICOIOIOI
`
`jfijjfijjjjjjj
`
`IOOIIOIIIOIOIIIIIOIII
`
`FIG. 13
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 16 of 40 PageID #: 839
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 16 of 40 Page|D #: 839
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 14 of 20
`
`US 7,505,854 B2
`
`Q
`
`60
`
`80
`
`10D
`
`120
`
`140
`
`160
`
`180
`
`220
`
`240
`
`FIG. 14B
`
`'8‘
`
`poly
`
`
`B
`fil[samples] 6
`FIG. 14C
`
`60
`
`80
`
`100
`
`120
`
`140
`
`169
`
`183
`
`2(3)
`
`220
`
`240
`
`60
`
`SO
`
`1OD
`
`120
`
`I
`140
`fiequency [Hz]
`
`1 BO
`
`200
`
`220
`
`240
`
`

`
`Case 6:12-cv-00799-JRG Document 25-4 Filed 01/31/13 Page 17 of 40 PageID #: 840
`Case 6:12—cv—OO799—JRG Document 25-4 Filed 01/31/13 Page 17 of 40 Page|D #: 840
`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 15 of 20
`
`US 7,505,854 B2
`
`1502
`
`315
`
`
`
` p rocessor
`
`
`
`
`SSFISOF
`
`signal
`
`d nve
`
`output
`signal
`
`I _
`
`1504
`
`sfinchronous
`:I
`
`1503
`
`FIG. 15
`
`

`
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`
`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 16 of 20
`
`US 7,505,854 B2
`
`zero-output
`mode
`
`
`
`Random
`
`
`
`sequence
`m°d"
`
`1604
`
`
`
`1610
`
`FIG. 16
`
`

`
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`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 17 of 20
`
`US 7,505,854 B2
`
`
`
`
`zero-value
`mode start
`
`/'
`1716
`
`Random
`
`
`
`
`SEQUENCE
`made start
`
`sample_count = 0
`
`1718
`
`sample_count = 0
`
`1702
`
`1704
`
` Yes
`
`sample_count > M?
`
`
`
`N°
`
`send zero value to
`
`DAC input
`
`1722
`
`
`
`Yes
`
`
`
`1708
`
`1710
`
`1712
`
`1714
`
`sampie_count > N?
`
`
`
`No
`
`generate a random
`value
`
`send value to filter
`
`send filtered value
`
`to DAC input
`
`increment
`
`sample_count by 1
`
`
`
` increment
`
`sample_count by 1
`
`1 724
`
`FIG. 17
`
`

`
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`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 18 of 20
`
`US 7,505,854 B2
`
`1 802
`
`1 804
`
`
`
`positive
`feedback
`mode sta rt
`
`In FPGA:
`
`1.3.0.11
`
`
`
`
`Get sensor signals,
`
`Filter sensor signals,
`Calculate weighted sum,
`
`
`Buffer sensor signals
`
`
`In processor?
`
`
`
`
`
`
`
`Select in-phase
`value in buffer
` Look for zero-crossings.
`180
`Coarse check for
`sinewave characteristics
`
`
`
`
`1810
`
`
`Apply gain.
`Send to DAC
`
` Calculate frequency.
`Calculate filter delay and
`"in-phase offset in buffer"
`
`
` Send "in-phase offset in
`
`buffer" to FPGA
`
`
`
`
`Fine check for sinewave
`characteristics
`
`1 826
`
`No
`
`Yes
`
`
`
`pass the checks on
`both sensors‘?
`
`random
`sequence
`
`mode
`1610
`
`
`FIG. 18
`
`

`
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`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 19 of 20
`
`US 7,505,854 B2
`
`.ImI.I.«II‘
`IIIIIIIJ
`W I
`
`
`
`Hawsensordata(’/o)
`
`
`
`Fillerompm(9.)
`
`FIG. 19A
`
`FIG. 19B
`
`I .53 _x CC 0
`
`% Synthesis
`§ Feedback
`FIG. 19D Random
`ynth
`New VaIue
`
`nckDelay5
`FIG. 19E §........,....
`
`FIG. 19F
`
`
`
`
`
`Driveoutpul(96)'1.’:O0
`
`

`
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`U.S. Patent
`
`Mar. 17, 2009
`
`Sheet 20 of 20
`
`US 7,505,854 B2
`
`310
`5
`FIG. 20A 0
`
`FIG. 203
`
`s -5
`
`If
`‘5
`
`5
`
`;
`
`-10
`
`10
`
`8
`
`FIG. 20C 3 ‘
`D 2
`
`FIG. 20D
`
`gsynthesi:
`
`>“” Handom
`—§ NowVa|0e
`
`FIG 20E 1
`
`o L
`
`? Unchanged
`
`FIG. 20F
`
`
`
`
`
`Driveoutput(%) 8o
`
`

`
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`US 7,505,854 B2
`
`1
`STARTUP TECHNIQUES FOR A DIGITAL
`FLOWMETER
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation of U.S. application Ser.
`No. 11/168,568, filed Jun. 29,2005 now U.S. Pat. No. 7,146,
`280,
`titled STARTUP AND OPERATIONAL TECH-
`NIQUES FORA DIGITAL FLOWMETER, which is a Con-
`tinuation of U.S. application Ser. No. 10/402,131, filed Mar.
`31, 2003 now U.S. Pat. No. 6,950,760, titled STARTUP AND
`OPERATIONAL TECHNIQUES FOR A DIGITAL FLOW-
`METER, which is a Continuation in Part of U.S. application
`Ser. No. 10/400,922, filed Mar. 28, 2003 now abandoned, and
`titled DRIVE TECHNIQUES FOR A DIGITAL FLOWME-
`TER, which claims priority from U.S. Provisional Applica-
`tion No. 60/368,153, filed Mar. 29, 2002, and titled ELLIP-
`TICAL FILTER FOR DIGITAL FLOWMETER, all ofwhich
`are incorporated by reference.
`
`TECHNICAL FIELD
`
`The invention relates to flowmeters.
`
`BACKGROUND
`
`Flowmeters provide information about materials being
`transferred through a conduit. For example, mass flowmeters
`provide a direct measurement of the mass of material being
`transferred through a conduit. Similarly, density flowmeters,
`or densitometers, provide a measurement of the density of
`material flowing through a conduit. Mass flowmeters also
`may provide a measurement of the density of the material.
`Coriolis-type mass flowmeters are based on the Coriolis
`effect, in which material flowing through a rotating conduit
`becomes a radially travelling mass that is affected by a Corio-
`lis force and therefore experiences an acceleration. Many
`Coriolis-type mass flowmeters induce a Coriolis force by
`sinusoidally oscillating a conduit about a pivot axis orthogo-
`nal to the length of the conduit. In such mass flowmeters, the
`Coriolis reaction force experienced by the traveling fluid
`mass is transferred to the conduit itself and is manifested as a
`deflection or offset of the conduit in the direction of the
`
`Coriolis force vector in the plane of rotation.
`Energy is supplied to the conduit by a driving mechanism
`that applies a periodic force to oscillate the conduit. One type
`of driving mechanism is an electromechanical driver that
`imparts a force proportional to an applied current. In an
`oscillating flowmeter, the applied current is periodic, and is
`generally sinusoidal. The period of the input current may be
`chosen so that the motion of the conduit matches a resonant
`
`mode ofvibration ofthe conduit, which generally reduces the
`energy needed to sustain oscillation. An oscillating flowmeter
`may use a feedback loop in which a sensor signal that carries
`instantaneous frequency and phase information related to
`oscillation of the conduit is amplified and fed back to the
`conduit using the electromechanical driver. Other types of
`driving mechanisms, such as an electromechanical driver that
`imparts a force proportional to an applied voltage, also may
`be used.
`
`flowmeters are essentially analog
`Many conventional
`devices in which a sensor signal frequency and phase infor-
`mation are amplified, for example by an analog op-amp,
`before being fed back into the electromechanical driver. In
`such flowmeters,
`there may be little or no phase delay
`between the signal(s) being sensed at the conduit and the
`
`2
`
`driving signal being applied to the conduit at the other end of
`the feedback loop. Such analog flowmeters may be prone to
`the introduction of high harmonics of a desired oscillation
`frequency, particularly during start-up operations when an
`estimated drive signal is applied to the conduit to begin the
`feedback loop described above. Moreover, analog flowmeters
`may be prone to gain saturation of the op amp, which may
`occur during “two-phase flow” through the conduit (e.g., an
`air pocket or entrained air in a flow of liquid) and which can
`lead to a damping effect on the conduit, or a stalling of the
`entire oscillation process. Finally, analog flowmeters may be
`prone to typical shortcomings of analog circuitry, e.g., rela-
`tively low precision and high noise measurements.
`In contrast to analog flowmeters, digital flowmeters also
`exist. For example, U.S. Pat. No. 6,311,136 and U.S. Pat. No.
`6,507,791, which are hereby incorporated by reference, dis-
`close the use of a digital flowmeter and related technology.
`Such digital flowmeters may have various advantages over
`analog flowmeters; for example, they may be more precise in
`their measurements, with less noise, and may be capable of
`enabling a wide range of positive and negative gains at the
`driver circuitry. Such digital flowmeters are thus advanta-
`geous in a variety of settings. For example, U.S. Pat. No.
`6,505,519 discloses the use ofa wide gain range, and/or the
`use of negative gain, to prevent stalling and to more accu-
`rately exercise control of the flowtube, even during diflicult
`conditions such as two-phase flow.
`
`SUMMARY
`
`According to one general aspect, a digital flowmeter is
`operating in a random sequence mode, where the random
`sequence mode is characterized by a first drive signal that
`includes randomly-generated values and that causes a vibra-
`tion of a flowtube. The digital flowmeter also is operated in a
`positive feedback mode, where the positive feedback mode is
`characterized by a sensor signal that corresponds to the vibra-
`tion and that is used as a second drive signal for maintaining
`the vibration. The digital flowmeter also is operated in a
`digital synthesis mode, where the digital synthesis mode is
`characterized by a synthesis of a third drive signal for main-
`taining the vibration.
`Implementations may include one or more ofthe following
`features. For example, the digital flowmeter may be transi-
`tioned between two or more of the random sequence mode,
`the positive feedback mode, and the digital synthesis mode.
`In operating the digital flowmeter in the random sequence
`mode,
`the randomly-generated values may be filtered to
`remove frequency components above a pre-determined cut-
`off level, where the pre-determined cut-off level may be
`selected based on a range of potential resonance frequencies
`associated with the flowtube. Alternatively in operating the
`digital flowmeter in the random sequence mode, the ran-
`domly-generated values may be filtered to remove frequency
`components above a first pre-determined cut-off level and
`below a second pre-determined cut-off level.
`The digital flowmeter also may be operated in a zero-
`output mode, the zero -output mode characterized by having a
`zero-value drive signal. In this case, operating the digital
`flowmeter in the random sequence mode may include detect-
`ing a pre-determined condition, and initiating operation ofthe
`zero-output mode, based on the predetermined condition.
`In operating the digital flowmeter in the zero -output mode,
`the fact that a pre-determined amount oftime has passed may
`be detected, and operation of the digital flowmeter may be
`transitioned into the positive feedback mode. Further, detect-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`
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`
`US 7,505,854 B2
`
`3
`ing the pre-determined condition may include detecting an
`end of a predetermined time period.
`In operating the digital flowmeter in the positive feedback
`mode, a first pre-determined condition may be detected, and
`operation of the digital synthesis mode may be initiated,
`based on the first pre-determined condition. In this case, in
`detecting the first pre-determined condition, a signal wave-
`form may be detected within the sensor signal, it may be
`determined that the signal waveform has a pre-determined
`characteristic, such as sinewave characteristics, and operation
`ofthe digital flowmeter may be transitioned from the positive
`feedback mode into the digital synthesis mode.
`Further, an instability associated with the operation of the
`digital flowmeter may be detected in the digital synthesis
`mode, and operation of the digital flowmeter may be transi-
`tioned from the digital synthesis mode into the positive feed-
`back mode, in response to detecting the instability. Alterna-
`tively, an instability associated with the operation of the
`digital flowmeter in the digital synthesis mode may be
`detected, and operation of the digital flowmeter may be tran-
`sitioned from the digital synthesis mode into the random
`sequence mode, in response to detecting the instability.
`In operating the digital flowmeter in the positive feedback
`mode, a second predetermined condition may be detected,
`and operation of the flowmeter may be transitioned from the
`positive feedback mode into the random sequence mode,
`based on the second pre-determined condition. In this case,
`detecting the second predetermined condition may include
`detecting an instability in an operation of the flowmeter.
`In operating the digital flowmeter in the positive feedback
`mode, an initial sensor signal may filtered to obtain the sensor
`signal. The sensor signal may be a digital signal, and operat-
`ing the digital flowmeter in the positive feedback mode may
`include converting an analog sensor signal into the sensor
`signal.
`In operating the digital flowmeter in the positive feedback
`mode, the sensor signal may be buffered to obtain a buffered
`sensor signal, and values may be selected from the buffered
`sensor signal to use as the second drive signal so as to com-
`pensate for a delay associated with the second drive signal,
`where the delay is associated with a digital element associ-
`ated with the flowmeter.
`
`In operating the digital flowmeter in the digital synthesis
`mode, an initial sensor signal may be filtered to obtain the
`sensor signal. Also, the synthesis ofthe third drive signal may
`be based on an analysis of the sensor signal.
`According to another general aspect, a digital flowmeter
`includes a vibratable flowtube, a sensor connected to the
`flowtube and operable to sense information about a motion of
`the flowtube, a driver connected to the flowtube and operable
`to impart energy to the flowtube, a filter system, a random-
`value generator operable to generate random-frequency sig-
`nals, and a control and measurement system operable to apply
`the filter system to the random-frequency signals and supply
`filtered, random-frequency signals to the driver for applica-
`tion to the flowtube of a first drive signal during a first mode,
`and further operable to transition the digital flowmeter into a
`second mode characterized by a second drive signal.
`Implementations may include one or more ofthe following
`features. For example, the control and measurement system
`may be operable to transition the digital flowmeter from the
`second mode to the first mode, in response to detecting a
`system disturbance associated with the digital flowmeter.
`The second mode may be a zero-output mode in which the
`second drive signal has a magnitude of substantially zero, and
`the control and measurement system may transition the digi-
`tal flowmeter from the first mode to the second mode after a
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`
`pre-determined amount of time. In this case, the control and
`measurement system may be further operable to transition the
`digital flowmeter from the second mode into a third mode, the
`third mode being a positive feedback mode characterized by
`a third drive signal that includes components of a sensor
`signal detected by the sensor and fed back to the driver.
`Further, the control and measurement system may be fur-
`ther operable to transition the digital flowmeter from the third
`mode back into the first mode, in response to detecting a
`system disturbance associated with the digital flowmeter.
`Also, the control and measurement system may be further
`operable to transition the digital flowmeter from the third
`mode into a fourth mode, the fourth mode being characterized
`by a drive signal that is synthesized by the control and mea-
`surement system based on an analysis of the sensor signal. In
`this case, the filter system may be operable to filter an initial
`sensor signal to obtain the sensor signal, which may be a
`digital signal.
`The control and measurement system may initiate transi-
`tion from the third mode to the fourth mode in response to a
`pre-determined event, which may include detection of sin-
`ewave components within the sensor signal.
`The control and measurement system may be further oper-
`able to transition the digital flowmeter from the fourth mode
`to the third mode, upon detecting a system disturbance asso-
`ciated with the digital flowmeter. The control and measure-
`ment system may be further operable to transition the digital
`flowmeter from the fourth mode to the first mode, upon
`detecting a system disturbance associated with the digital
`flowmeter.
`
`The second mode may be a positive feedback mode in
`which the second drive signal includes components of a sen-
`sor signal detected by the sensor and fed back to the driver.
`Also, the second mode may be a digital synthesis mode in
`which the second drive signal is synthesized based on an
`analysis of a sensor signal detected by the sensor. The filter
`system is operable to filter the random-frequency signals to
`include a pre-determined range of frequencies within the
`filtered, random-frequency signals.
`According to another general aspect, a flowmeter may
`include a vibratable flowtube, a sensor connected to the flow-
`tube and operable to sense information about a motion of the
`flowtube by way of a sensor signal, a driver connected to the
`flowtube and operable to impart energy to the flowtube by
`way of a drive signal, and a digital transmitter operable to
`select and implement, from among a plurality of operational
`modes, an operational mode determined to be best-suited for
`a current operational environment of the digital flowmeter.
`Implementations may include one or more ofthe following
`features. For example, the plurality ofoperational modes may
`include a random- sequence mode to generate the drive signal,
`in which the digital transmitter generates random frequen-
`cies, filters the random frequencies to obtain filtered random
`frequencies and delivers the filtered random frequencies to
`the driver. In this case, the digital transmitter may be filter the
`random frequencies to retain frequencies within a pre-deter-
`mined frequency range. The random- sequence mode may be
`selected and implemented during a startup operation of the
`flowmeter.
`
`The plurality of operational modes includes a zero-output
`mode, in which a magnitude of the drive signal is substan-
`tially zero. The plurality of operational modes may include a
`positive feedback mode, in which a sensor signal is processed
`and supplied to the driver. The plurality of operational modes
`may include a digital synthesis mode, in which the drive
`signal is digitally synthesized, based on an analysis of the
`sensor signal.
`
`

`
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`US 7,505,854 B2
`
`5
`The details of one or more implementations are set forth in
`the accompanying drawings and the description below. Other
`features will be apparent from the description and drawings,
`and from the claims.
`
`DESCRIPTION OF DRAWINGS
`
`FIG. 1A is an illustration of a digital flowmeterusing a bent
`flowtube.
`
`FIG. 1B is an illustration of a digital flowmeter using a
`straight flowtube.
`FIG. 2 is a block diagram of an operation of a digital
`flowmeter.
`
`FIG. 3 is a block diagram of the digital transmitter of FIG.
`
`2.
`
`FIG. 4 is a block diagram of a digital flowmeter.
`FIG. 5 is a flowchart illustrating a positive feedback mode
`of operation of the system of FIG. 4.
`FIG. 6 is a timing diagram i