Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 1 of 18 PageID #: 3880
`Case 6:12—cv—00799—JRG Document 124-8 Filed 03/07/14 Page 1 of 18 Page|D #: 3880
`
`EXHIBIT 8
`
`EXHIBIT 8
`
`
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 2 of 18 PageID #: 3881
`
`United States Patent £191
`Kalotay et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,009,109
`Apr. 23, 1991
`
`[54] FLOW TUBE DRIVE CIRCUIT HAVING A
`BURSTY OUTPUT FOR USE IN A CORIOLIS
`METER
`Inventors: Paul Kalotay, Lafayette; Robert
`Bruck, Boulder; Arnold Emc:h, Estes
`Park; Donald Martella, Louisville, all
`of Colo.
`
`[75]
`
`[73] Assignee: Micro Motion, Inc:., Boulder, Colo.
`[21] Appl. No.: 446,614
`Dee. 6, 1989
`(22] Filed:
`lat. a.s ................................................ GOlF 1/84
`[51]
`[52] u.s. a. .................................. 73/861.38; 331/154
`[58] Field of Search ............. 73/861.37, 861.38, 32 A;
`331/154, 155, 65
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,912,962 4/1990 Kawaguchi ........................ 73/32 A
`
`Primary Examiner-Herbert Goldstein
`Attorney, Agent, or Firm-Peter L. Michaelson
`
`[57]
`ABSTRACI'
`A drive circuit for providing bursts, rather than contin(cid:173)
`uously alternating amounts, of energy for use in driving
`a flow tube (conduit) in a Coriolis meter and methods
`for use in such a circuit. Specifically, the drive circuit
`provides a pre-defmed burst of energy to a drive coil
`afTued to a flow conduit at an appropriate point during
`a cycle of the oscillatory motion of the conduit in order
`to maintain the peak amplitude of the oscillatory motion
`substantially within a prescribed range. This burst can
`be applied at a pre-defmed point, illustratively the peak.
`in each cycle of the oscillatory motion with no energy
`being applied during that cycle other than when the
`pulse occurs in order to reduce the amount of electrical
`energy applied to the drive coil. Alternatively, to fur(cid:173)
`ther reduce this energy, a burst need not be applied
`during every such cycle but rather only at those pre(cid:173)
`defined points, e.g. the peaks, within those cycles where
`the velocity of the flow conduit is less than a pre(cid:173)
`defmed limit value.
`
`15 Claims, 6 Drawing Sheets
`
`100
`
`195
`
`185
`
`20
`
`26
`
`IETER
`lliCTFOHCS
`
`ANALOG & DIGITAl
`PROCESS OUTPUT SIGNALS
`
`RIGHT VELOCITY SIGNAL
`
`165R 165L
`
`MM0635546
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 3 of 18 PageID #: 3882
`
`FIG. 1
`
`20
`
`I METER
`ELECTRONICS
`
`26
`
`I
`
`I
`
`I
`
`•
`
`ANALOG & DIGITAL
`PROCESS OUTPUT SIGNALS
`
`~ • rLJ •
`~ a. n> a
`
`~
`!"'
`N
`~
`"""'
`\C
`\C
`"""'
`
`Cll =(cid:173)(!)
`
`(T) -"""' Q ...,
`
`c:7\
`
`...
`U1
`0
`0
`...
`\0
`1-l
`0
`\0
`
`195
`
`185
`
`100
`RTO SIGNAL
`lc.DRIVE SIGNAL
`lc.LEFT VELOCITY SIGNAL
`![RIGHT VELOCITY SIGNAL
`I
`?
`{
`J
`165R 165L
`
`I
`
`;,~I''-.,
`
`-,., 'w·
`·120'
`
`:5:
`:5:
`0
`0) w
`
`(}1
`(}1
`
`~ ......
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 4 of 18 PageID #: 3883
`
`I
`
`r------------, 165
`. L
`I
`LEFT
`I VELOCITY ~
`-=-
`: SENSOR
`I J
`RIGHT
`VELOCITY&:::
`SENSOR
`
`I
`
`I
`
`'
`
`FIG. 2
`
`r------------------------,
`r30
`
`I
`
`I
`
`I I .,
`
`MASS FLOW
`RATE
`CIRCUIT
`
`282
`
`I
`I
`
`40
`
`FLOW TUBE
`
`v20
`I
`I
`L---~~-:~u!~------~~~i~~!~~
`
`:
`
`I
`
`i 185
`tao i
`~~~
`-
`METER I
`L __ --;::r~~SE~~ 'U
`10
`
`:5:::
`:5:::
`0
`Q) w
`
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`()1
`~
`CXl
`
`~ •
`rJl
`•
`
`'-= a ('D = """""
`
`>
`~
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`....
`
`\0
`
`262
`
`263
`
`ftl
`
`00. =(cid:173)ftl
`....
`e,
`
`~
`
`Q'l
`
`Ul
`
`.. 0
`.. ,...,.
`
`0
`\C)
`
`0
`\C)
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 5 of 18 PageID #: 3884
`
`FIG. 3
`FLOW TUBE DRIVE CIRCUIT
`
`447 ....
`
`SYNCH
`
`~449
`
`Un.L JL LL JLLj
`
`-
`
`-
`I
`
`I
`
`435
`NEGATIVE
`EDGE
`DETECTOR
`
`REFERENCE
`LEVEL (Vu~)
`VM-'
`439
`
`I -'1
`
`•I
`
`.I
`
`POSITIVE I ~ DRIVE
`
`LEVEL
`
`_[_ 180
`
`VL r
`
`"'
`
`'
`
`40
`
`VM I "'
`
`FIG. 3A
`tORI~~ I
`DRIVE COIL
`SIGNAL
`-DRIVE
`
`:
`
`00
`•
`
`~ ..
`~ =
`......
`n> =
`......
`
`> ,
`
`!""
`~
`JH
`"""
`\C
`\C
`"""
`
`r:n g-
`
`~
`CN
`Q ....
`
`0\
`
`...
`Cll
`0
`0
`... ......
`\0
`
`0
`\0
`
`~VL
`.190' PHASEI
`
`[431
`
`SHIFT
`
`• I
`I
`LEFT
`160L I
`~f VELOCITY
`I
`SENSOR
`
`:5:::
`:5:::
`0
`Q) w
`
`()1
`()1
`.j::>.
`c.o
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 6 of 18 PageID #: 3885
`
`FIG. 4
`
`520
`
`'\
`
`I 5.5~5"\--
`
`Yin
`
`A/D
`
`c
`
`Do r-
`
`;a
`
`~1U
`
`f
`ltflUT SIGNAL
`- COtfliTIONING CIRCUIT
`
`rv
`~
`
`r
`
`160L
`·~
`i I
`...L
`
`r-
`
`~ - ENABLE ~ 54 a
`
`540
`
`GATE
`TIMER/COUNTER
`
`(
`
`OOT
`
`-
`
`~3
`
`:5:::
`:5:::
`0
`Q) w
`
`()1
`()1
`()1
`0
`
`J
`
`I 5~3
`
`555
`~
`
`530
`
`~CJ
`
`f
`
`I -
`
`fJ-P
`-- CHAtffl
`·-------..
`
`: RAM r ~535
`
`~-------·
`
`DMA
`
`c
`
`POWER
`SWITCH
`
`560
`
`TO
`
`DRI VE COIL
`'----· I
`~ I
`I --
`
`1.._""185
`
`DRIVE
`--·· ·-
`
`I
`
`I
`
`I
`I
`I
`
`~ •
`r.ll •
`
`~ a ('t) = """'
`
`>
`~
`
`~
`
`~~ ... :g ...
`
`~
`
`00
`="'
`fD a
`Q ....,
`"'
`
`...
`(II
`0
`0
`... .....
`\C)
`
`0
`\C)
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 7 of 18 PageID #: 3886
`
`U.S. Patent
`
`Apr. 23, 1991
`
`Sheet 5 of 6
`
`5,009,109
`
`FIG. 5
`
`ENTER
`
`DRIVE CIRCUIT
`ROUTINE
`600
`
`610
`
`INSTRUCT TIMER/COUNTER 550 TO
`DELIVER INITIAL DRIVE PULSE (~.01 SEC)
`TO FLOW CONDUITS TO BEGIN
`OSCILLATORY MOVEMENT
`
`620
`
`INITIATE DMA TRANSFER FROM I/0 SPACE
`TO MEMORY ARRAY TO TRANSFER A REQUISITE
`NUMBER OF SAMPLES TO CHARACTERIZE ONE
`PERIOD OF FLOW CONDUIT MOTION
`
`645
`
`640
`
`PROCESS •NoN-DRIVE•
`RELATED METER FUNCTIONS
`
`690
`
`650
`
`DETERMINE MAXIMUM & MINIMUM VALUES OF SAMPLES IN ARRAY;
`CALCULATE ABSOLUTE VALUE OF PEAK, IVpeakl;and
`DETERMINE APPROXIMATE RESONANT FREQUENCY OF FLOW
`CONDUIT MOTION AND STORE FOR USE DURING NEXT
`DMA TRANSFER FROM I/0 SPACE
`
`APPLY SUITABLE LEVEL CHANGE TO
`;,..........-._..,. GATE Itf>UT OF TIMER/COUNTER
`550 TO ACTIVATE ITS PULSE
`NIDTH MODULATED
`OUTPUT
`
`675
`
`680
`
`685
`APPLY SUITABLE LEVEL CHANGE TO
`GATE INPUT OF TIMER/COUNTER 550 +----___. ______ _
`TO DEACTIVATE ITS PULSE NIDTH
`MODULATED OUTPUT
`
`MM0635551
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 8 of 18 PageID #: 3887
`
`vu
`vPEAK
`2
`FIG. JL
`vREF ---...
`
`I
`
`I
`
`I
`
`r'
`
`"
`"
`
`I
`
`DRIVE
`WINO OW
`
`. .
`
`. .
`
`r--\.
`1 ' \0
`
`I
`
`"
`
`. .
`
`t ·I\
`
`DRIVE
`WINDOW
`
`I
`• • •
`
`I
`
`.
`
`('-LEFT
`
`VELOCITY
`SENSOR
`SIGNAL
`
`t -1\ I~-
`
`- FIG. 7
`
`0 ---·----------------·---------
`TRIANGULAR
`
`HALF
`SINUSOIDAL
`
`STEPPED WITH
`DECAYING TRAILING
`EDGE
`
`HAVERSINE
`
`~
`~
`
`0 m w
`
`01
`01
`01
`1\)
`
`•
`
`~ • 00
`"'C = f"'f'-
`('D =
`
`f"'f'-
`
`>
`'1:J :s
`~
`JN
`
`~
`\C
`\C
`~
`
`00
`:r'
`ft) a
`
`Q\
`~
`Q\
`
`740
`
`(II
`
`0
`\0
`
`.. 0
`.. ... 0
`
`\0
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 9 of 18 PageID #: 3888
`
`1
`
`5,009,109
`
`FLOW TUBE DRIVE CIRCUIT HAVING A BURSTY
`OUTPUT FOR USE IN A CORIOLIS METER
`
`BACKGROUND OF THE INVENTION
`l. Field of the Invention
`The invention relates to apparatus for a drive circuit
`that provides bursts, rather than continuously alternat(cid:173)
`ing amounts, of energy for use in driving a flow tube
`(conduit) in a Coriolis meter and to methods for use in 10
`such a circuit.
`2. Description of the Prior Art
`Currently, Coriolis meters are fmding increasing use
`as an accurate way to measure the mass. flow rate and(cid:173)
`/or density of various process fluids in many applica- 15
`tions.
`Generally speaking, a Coriolis mass flow rate meter,
`such as that described in U.S. Pat. No. 4,491,025 (issued
`to J. E. Smith et al on Jan. 1, 1985), contains one or two
`parallel conduits, each typically being aU-shaped flow 20
`conduit or tube. Each flow conduit is driven to oscillate
`about an a.Xis to create a rotational frame of reference.
`For aU-shaped flow conduit, this axis can be termed
`the bending axis. As process fluid flows through each
`oscillating flow conduit, movement of the fluid pro- 25
`duces reactionary Coriolis forces that are orthogonal to
`both the velocity of the fluid and the angular velocity of
`the conduit. These reactionary Coriolis forces, though
`quite small when compared to the force at which the
`conduits are driven, nevertheless cause each conduit to 30
`twist about a torsional axis that, for a U-shaped flow
`conduit, is normal to its bending axis. The amount of
`twist imparted to each conduit is related to the mass
`flow rate of the process fluid flowing therethrough.
`This twist is frequently measured using velocity signals 35
`obtained from magnetic velocity sensors that are
`mounted to one or both of the flow conduits in order to
`provide a complete velocity proflle of the movement of
`each flow conduit with respect to either the other con(cid:173)
`duit or a fixed reference. In dual tube meters, both flow 40
`conduits are oppositely driven such that each conduit
`oscillates (vibrates) as a separate tine of a tuning fork.
`This "tuning fork" operation advantageously cancels
`substantially all undesirable vibrations that might other-
`wise mask the Coriolis force.
`In such a Coriolis meter, the mass flow rate of a fluid
`that moves through the meter is proportional to the
`time interval that elapses between the instant one point
`situated on a side leg of a flow conduit crosses a pre(cid:173)
`determined location, e.g. a respective mid-plane of os- 50
`cillation, until the instant a corresponding point situated
`on the opposite side leg of the same flow. conduit,
`crosses its corresponding location, e.g. its respective
`mid-plane of oscillation. For parallel dual conduit Cori(cid:173)
`olis mass flow rate meters, this interval is equal to the 55
`phase difference between the velocity signals generated
`for both flow conduits at the fundamental (resonant)
`frequency at which these flow conduits are driven. In
`addition, the resonant frequency at which each flow
`conduit oscillates depends upon the total mass of that 60
`conduit, i.e. the mass of the conduit itself, when empty,
`plus the mass of any fluid flowing therethrough. Inas(cid:173)
`much as the total mass varies as the density of the fluid
`flowing through the tube varies, the resonant frequency
`likewise varies with any changes in fluid density and as 65
`such can be used to track changes in fluid density.
`As noted above, these mass flow and density relation(cid:173)
`ships inherent in a Coriolis meter require that each flow
`
`45
`
`2
`conduit in the meter must be driven to resonantly vi(cid:173)
`brate in order for the meter to properly operate. To
`ensure that proper vibratory motion is initiated in, for
`example a dual tube Coriolis meter, and thereafter main-
`S tained during operation of the meter, the meter contains
`an appropriate drive mechanism that is mounted to both
`of the flow conduits typically between corresponding
`extremities of these conduits. Tlie drive mechanism
`fr~quently contains any one of many well known ar(cid:173)
`rangements, such as a magnet mounted to one conduit
`and a coil mounted to the other conduit in an opposing
`relationship to the magnet. A drive circuit continuously
`applies a periodic, typically sinusoidally or square
`shaped, drive voltage to the drive mechanism. Through
`interaction of the continuous alternating magnetic field
`produced by the coil in response to the periodic drive
`signal and the constant magnetic field produced by the
`magnet, both flow conduits are initially forced to vi(cid:173)
`brate in an opposing sinusoidal pattern which is thereaf(cid:173)
`ter maintained. Inasmuch as the drive circuit tightly
`synchronizes the frequency of the drive signal to essen-
`tially match the resonant frequency of the conduits,
`both flow conduits are kept in a state of opposing sub(cid:173)
`stantially resonant sinusoidal motion.
`One known drive circuit currently in use today and
`typified by that disclosed in, for example, U.S. Pat. No.
`4,777,833 (issued to B. L. Carpenter on Oct. 18,
`1988-hereinafter referred to as the '833 Carpenter
`patent-and currently owned by the present assignee)
`utilizes an analog drive circuit. Specifically, this circuit
`utilizes a synchronous analog amplifier to generate a
`continuous square wave with two analog levels that
`each equally change based upon a simultaneously oc-
`curring difference between an analog reference voltage
`and a flow conduit position signal. As the magnitude of
`this difference increases (decreases), based upon de(cid:173)
`creasing (increasing) amplitudes of the oscillatory
`movement of the flow conduits which results from, for
`example, increases (decreases) in the density in the pro(cid:173)
`cess fluid that simultaneously flows through the flow
`conduits, positive and negative drive levels produced
`by the synchronous amplifier corresponding and
`equally increase (decrease) to once again restore the
`amplitude of the oscillatory flow tube movement to its
`pro~r level. Various analog components, such as inter
`alia amplifiers, buffers, a phase shifter and an edge de(cid:173)
`tector, are used · to appropriately determine this differ(cid:173)
`ence based upon the analog reference level and one of
`the velocity sensor signals, typically a left velocity sen(cid:173)
`sor signal, produced within the meter.
`Unfortunately, analog drive circuits used in Coriolis
`meters and typified by that described in the '833 Car(cid:173)
`penter patent suffer from various drawbacks.
`First, analog drive circuits, particularly those which
`provide an alternating square shaped drive signal to the
`coil, do not permit the energy that is applied to the
`drive coil to be precisely controlled by the drive circuit
`itself at any one instant during the signal. With these
`circuits, the drive signal is merely set to alternate be(cid:173)
`tween two levels that are static within any one drive
`cycle. Precise control over the energy supplied to drive
`coil by the drive circuit itself has proven to be particu(cid:173)
`larly important in those applications, such as intended
`use of the meter particularly the mechanical Coriolis
`metering assembly itself in a hazardous environment,
`where a critical need exists to always limit this energy
`to as low a value as is realistically possible. While intrin-
`
`MM0635553
`
`

`
`Case 6:12-cv-00799-JRG Document 124-8 Filed 03/07/14 Page 10 of 18 PageID #: 3889
`
`5,009,109
`
`3
`sic safety barriers are used in these applications to limit
`the energy that would flow to the drive coil located in
`a hazardous area to below a pre-defined maximum
`amount and in doing so perform extremely well, it
`would be preferable to further limit the energy at its S
`source, if possible, i.e. drive circuit, and rely on the
`barrier as a back-up protective device rather than as a
`main mechanism for limiting the energy.
`Second, analog drive circuits generally tend to be
`complex and require a multitude of parts which adds to 10
`the manufacturing cost of the meter electronics.
`Third, discrete analog components, such as those
`used in a drive circuit, may exhibit undesirable tempera(cid:173)
`ture, aging and/or drift characteristics any one of which
`might, over time, cause the output produced by such a 15
`component to vary. These affects can be minimized to a
`certain and usually acceptable extent by using compo(cid:173)
`nents with matched temperature characteristics, appro(cid:173)
`priate temperature compensation circuits and/or suffi(cid:173)
`ciently frequent
`re-calibration. However, use of 20
`matched components further increases the cost of the
`meter electronics, while temperature compensation
`circuits often require additional components which
`increase the parts count as well as the manufacturing
`cost of the drive circuit. Re-calibration disadvanta- 25
`geously increases the costs associated with actual use of
`the meter.
`Therefore, a need exists in the art for a simple and
`inexpensive flow tube drive circuit particularly suited
`for use in a Coriolis meter that provides substantially 30
`accurate control over the amount of energy that is to be
`applied to the drive coil at any instant, has a reduced
`parts count and cost over analog drive circuits kitown
`in the art, and does not appreciably, suffer, if at all, from
`temperature, aging and/or drift affects which are com- 35
`monly associated with analog drive circuits kitown in
`the art.
`
`SUMMARY OF THE INVENTION
`An object of the present invention is to provide a 40
`drive circuit for use in a Coriolis meter that provides
`substantially accurate control over the amount of en(cid:173)
`ergy that is to be applied to the drive coil at any time.
`Another object is to provide such a drive circuit that
`generates a reduced amount of energy to the drive coil, 45
`as compared to that generated by drive circuits kitown
`in the art, but which is nevertheless sufficient to main(cid:173)
`tain the amplitude of the vibratory motion of the flow
`conduits at a desired level.
`Another object is to provide such a drive circuit that 50
`does not appreciably suffer from temperature, drift
`and/or aging affects commonly associated with analog
`drive circuits kitown in the art.
`Another object is to provide such a drive circuit that
`has a relatively low parts count and is relatively simple 55
`and inexpensive to manufacture.
`These and other objects are provided in accordance
`with the teachings of our inventive drive circuit which
`provides a pre-defmed burst of energy to a drive coil
`afflxed to a flow conduit at an appropriate point during 60
`a cycle of the oscillatory motion of the conduit in order
`to maintain the peak amplitude of the oscillatory motion
`substantially within a prescribed range. This burst can
`be applied at a pre-defmed point in each cycle of the
`oscillatory motion with no energy being applied during 65
`that cycle other than when the burst occurs in order to
`reduce the amount of electrical energy applied to the
`drive coil. Alternatively, to further reduce this energy,
`
`4
`a burst need not be applied during every such cycle but
`rather only at those pre-defined points within those
`cycles where the amplitude of the oscillatory motion of
`the flow conduit is less than a pre-defined limit value.
`In accordance with the teachings of a preferred em(cid:173)
`bodiment of our invention, our inventive drive circuit
`periodically samples the left velocity sensor signal
`throughout a single cycle of this signal using a pre(cid:173)
`defmed sampling period. These samples are transferred
`on a direct memory access (DMA) basis, using a well(cid:173)
`kitown cycle stealing technique, from an input/output
`space into a memory array, both situated within random
`access memory in a microprocessor. Transferring sam(cid:173)
`pled data values in this manner does not adversely and
`appreciably affect the throughput of the microproces(cid:173)
`sor. In response to the samples occurring throughout
`this cycle of the signal, the drive circuit, specifically the
`microprocessor contained therein, determines the zero
`crossings and maximum and minimum values of this
`cycle and thereafter calculates the absolute value of the
`peak of the cycle using the maximum and minimum
`values. Using two adjacent zero crossings contained
`within the cycle, the microprocessor also determines
`the approximate . frequency of the velocity signal and
`hence the approximate resonant frequency of the flow
`conduits. Once these operations have occurred, the
`· microprocessor compares the absolute value of the peak
`against a pre-defined limit value, V ref This comparison
`determines whether the amplitude of the vibratory mo(cid:173)
`tion of the flow conduits has decayed to a sufficiently
`low value to warrant the addition of a burst of energy to
`the drive coil and therethrough to the flow conduits in
`order to appropriately restore this amplitude. Specifi(cid:173)
`cally, in the event the absolute value of the peak is less
`than the limit value, then the microprocessor illustra(cid:173)
`tively gates a timer/counter circuit to generate a burst,
`such as a pulse, having a pre-defined shape to the drive
`coil within a specific window during the remainder of
`the cycle. Alternatively, if the absolute value of the
`peak is greater than the limit value, then no such pulse
`is generated by the timer/counter and hence no burst of
`energy is applied to the drive coil. Depending upon
`various mechanical characteristics of the flow tubes and
`the rate at which the density of the process fluid flow(cid:173)
`ing therethrough changes, several, perhaps quite a num(cid:173)
`ber, of cycles of oscillatory flow tube movement may
`elapse until the absolute value of the peak decays to a
`sufficiently low value to cause the drive circuit to apply
`a burst of energy to the flow tubes. In addition, the
`microprocessor, using the approximate value of the
`frequency of the velocity signal, determines the number
`of samples that need to be obtained during the next
`DMA transfer in order to fully characterize the next
`cycle of oscillatory flow tube movement and stores this
`number for use during subsequent initiation of that
`DMA transfer.
`Furthermore, a burst of energy can also be imparted
`to the drive coil at an appropriate point outside the
`window during a cycle(s) in order to remove a fmite
`amount of vibratory energy from the flow conduits and
`thereby effectively retard the peak value of these vibra(cid:173)
`tions, when necessary.
`In accordance with a feature of our invention, the
`drive circuit can adapt its performance to changing
`operating conditions of the Coriolis meter, such as
`changes in the density of the process fluid flowing
`through the meter, while imparting relatively minimal
`amounts of energy to the drive coil that are nevertheless
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`5
`6
`tion, mass flow rate information is also provided in
`sufficient to sustain the flow tubes in resonant oscilla(cid:173)
`analog 4-20 rnA form over leads 26 for easy connection
`tory motion with a pre-defmed peak value. Specifically,
`to downstream process control and/or measurement
`the limit value can be changed, e.g. increased, when(cid:173)
`equipment.
`everthe rate of change in the absolute value of the peak
`Coriolis meter assembly 10, as shown, includes a pair
`is sufficiently high so that bursts of mechanical energy S
`of manifolds 110 and 110'; tubular member 150; a pair of
`can be rapidly added to the vibrating flow conduits,
`parallel flow conduits (tubes) 130 and 130'; drive mech(cid:173)
`such as over a larger number of successive cycles than
`anism 180; a pair of velocity sensing coils 160L and
`would otherwise occur. Adding bursts of energy in this
`160R; and a pair of permanent magnets 170L and 170R.
`fashion quickly compensates for increased attenuation
`10 Conduits 130 and 130' are substantially U-shaped and
`that occurs in the peak of the vibratory amplitude of the
`have their ends attached to conduit mounting blocks
`flow tubes, caused by large rapid increases in the fluid
`120 and 120', which are, in tum, secured to respective
`density. Moreover, whenever the absolute value of the
`manifolds 110 and 110'. Both flow conduits are free of
`peak amplitude reaches or exceeds the increased limit
`pressure sensitivejoints.
`value, the limit value can be appropriately decreased to
`15 With the side legs of conduits 130 and 130' fixedly
`a normal value in order to reduce the rate at which
`attached to conduit mounting blocks 120 and 120' and
`mechanical energy wil.l be imparted to the vibrating
`these blocks, in tum, fixedly attached to manifolds 110
`flow conduits.
`and 110', as shown in FIG. 1, a continuous closed fluid
`BRIEF DESCRIPTION OF THE DRAWINGS
`path is provided through Coriolis meter assembly 10.
`The teachings of the present invention may be clearly 20 Specifically, when meter 10 is connected, via inlet end
`understood by considering the following detailed de-
`101 and outlet end 101', into a conduit system (not
`shown) which carries the fluid that is being measured,
`scription in conjunction with the accompanying draw-
`ings, in which:
`fluid enters the meter through an orifice in inlet end 101
`FIG. 1 is an overall diagram of Coriolis mass flow
`of manifold 110 and is conducted through a passageway
`rate metering system 5;
`25 therein having a gradually changing cross-section to
`FIG. 2 depicts a block diagram of meter electronics
`conduit mounting block 120. There, the fluid is divided
`20 shown in FIG. 1;
`and routed through flow conduits 130 and 130'. Upon
`FIG. 3 is a block diagram of a prior art embodiment
`exiting flow conduits 130 and 130', the fluid is recom-
`of flow tube drive circuit 40;
`bined in a single stream within conduit mounting block
`FIG. 3A depicts various waveforms associated with 30 120' and is thereafter routed to manifold 110'. Within
`manifold 110', the fluid flows through a passageway
`drive circuit 40 shown in FIG. 3;
`FIG. 4 is a block diagram of a preferred embodiment
`having a similar gradually changing cross-section to
`of drive circuit 40 constructed in accordance with the
`that of manifold 110-as shown by dotted lines 105-to
`teachings of our present invention;
`an orifice in outlet end 101'. At end 101' the fluid reen-
`FIG. 5 depicts a flowchart of drive circuit routine 35 ters the conduit system. Tubular member 150 does not
`600 executed by microprocessor 530 shown in FIG. 4 to
`conduct any fluid. Instead, this member serves to axially
`generate a drive signal in accordance with the teachings
`align manifolds 110 and 110' and maintain the spacing
`of our invention;
`therebetween by a pre-determined amount so that these
`FIG. 6 is a waveform depicting two illustrative cy-
`manifolds will readily receive mounting blocks 120 and
`cles of the left velocity signal and the temporal relation- 40 120' and flow conduits 130 and 130'.
`ship between this velocity signal and the occurrence of
`U-shaped flow conduits 130 and 130' are selected and
`drive signal bursts produced by our inventive drive
`appropriately mounted to the conduit mounting blocks
`so as to have substantially the same moments of inertia
`circuit; and
`FIG. 7 depicts various illustrative waveforms each of
`and spring constants about bending axes W-W and
`which can be used to produce a drive signal burst.
`45 W'-W', respectively. These bending axes are perpen-
`To facilitate understanding, identical reference nu-
`dicularly oriented to the side legs of the U-shaped flow
`merals have been used, where appropriate, to designate
`conduits and are located near respective conduit mount-
`identical elements that are common to the figures.
`ing blocks 120 and 120'. The U-shaped flow conduits
`extend outwardly from the mounting blocks in an essen(cid:173)
`DETAILED DESCRIPTION
`SO tially parallel fashion and have substantially equal mo-
`ments of inertia and equal spring constants about their
`After reading the following description, those skilled
`respective bending axes. Inasmuch as the spring con-
`in the art will readily appreciate that our inventive drive
`stant of the conduits changes with temperature, resistive
`circuit can be utilized with nearly any Coriolis meter
`temperature detector (RTD) 190 (typically a platinum
`regardless of whether that meter is measuring mass flow
`rate, density or other parameter(s) of a process fluid. 55 RTD device) is mounted to one of the flow conduits,
`Nevertheless, for purposes of brevity, the inventive
`here conduit 130', to continuously measure the tempera-
`drive circuit will be discussed in the context of a meter
`ture of the conduit. The temperature of the conduit and
`that specifically measures mass flow rate.
`hence the voltage appearing across the RTD, for a
`FIG. 1 shows an overall diagram of Coriolis mass
`given current passing therethrough, will be governed
`flow rate metering system 5.
`60 by the temperature of the fluid passing through the flow
`As shown, system 5 consists of two basic compo-
`conduit. The temperature dependent voltage appearing
`nents: Coriolis meter assembly 10 and meter electronics
`across the RTD is used, in a well known method, by
`20. Meter assembly 10 measures the mass flow rate of a
`meter electronics 20 to appropriately compensate the
`desired process fluid. Meter electronics 20, connected
`value of the spring constant for any changes in conduit
`to meter assembly 10 via leads 100, illustratively pro- 65 temperature. The RTD is connected to meter electron-
`ics 20 by lead 195.
`vides mass flow rate and totalized mass flow informa-
`tion. Mass flow rate information is provided over leads
`Both of these flow conduits are sinusoidally driven in
`26 in frequency form and in scaled pulse form. In addi-
`opposite directions about their respective bending axes
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`5,009,109
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`7
`and at essentially their common resonant frequency. In
`this manner, both flow conduits will vibrate in the same
`manner as do the tines of a tuning fork. Drive mecha(cid:173)
`nism 180 supplies the sinusoidal oscillatory driving
`forces to conduits 130 and 130'. This drive mechanism S
`can consist of any one of many well known arrange(cid:173)
`ments, such as a magnet mounted to illustratively flow
`conduit 130' and an opposing coil mounted to illustra~
`tively flow conduit 130 and through which an alternat(cid:173)
`ing current is passed, for sinusoidally vibrating both 10
`flow conduits at a common frequency. A suitable con(cid:173)
`tinuous alternating drive signal is applied by meter elec(cid:173)
`tronics 20, via lead 185, to drive mechanism 180.
`With fluid flowing through both conduits wJille these
`conduits are sinusoidally driven in opposing directions, 15
`Coriolis forces will be generated along adjacent side
`legs of each of flow conduits 130 and 130' but in oppo(cid:173)
`site directions, i.e. the Coriolis force generated in side
`leg 131 will oppose that generated in side leg 131'. This
`phenomenon occurs because although the fluid flows 20
`through the flow conduits in essentially the same paral-
`lel direction, the angular velocity vectors for the oscil(cid:173)
`lating (vibrating) flow conduits are situated in opposite
`though essentially parallel directions. Accordingly,
`during one-half of the oscillation cycle of both flow 25
`conduits, side legs 131 and 131' will be twisted closer
`together than the minimum distance occurring between
`these legs produced by just the oscillatory movement of
`the conduits generated by drive mechanism 180. During
`the next half-cycle, the generated Coriolis forces will 30
`twist the side legs 131 and 131' further apart than the
`maximum distance occurring between these legs pro(cid:173)
`duced by just the oscillatory movement of the conduits
`generated by drive mechanism 180.
`During oscillation of the flow conduits, the adjacent 35
`side legs, which are forced closer together than their
`counterpart side legs, will reach the end point of their
`travel, where their velocity crosses zero, before their
`counterparts do. The time interval which elapses from
`the instant one pair of adjacent side legs reaches their 40
`end point of travel to the instant the counterpart pair of
`side legs, i.e. those forced further apart, reach their
`respective end point is proportional to the total mass
`flow rate of the fluid flowing through meter assembly
`10. The reader is referred to U.S. Pat. No. 4,491,025 45
`(issued to J. E. Smith et. al. on Jan. 1, 1985) for a more
`detailed discussion of the principles of operation of
`parallel path Coriolis flow meters than that just pres(cid:173)
`ented.
`To measure the time interval, ~t, coils 160L and 160R so
`are attached to either one of conduits 130 and 130' near
`their free ends and permanent magnets 170L and 170R
`are also attached near the free ends of the other one of
`the conduits. Magnets 170L and 170R are disposed so as
`to have coils 160L and 160R located in the volume of SS
`space that surrounds the respective permanent magnets
`and in which the magnetic flux fields are essentially
`uniform. With this configuration, the electrical signal
`outputs generated by coils 160L and 160R provide a
`velocity profile of the complete travel of the conduit 60
`and can be processed, through any one of a number of
`well known methods, to determine the time interval
`and, in turn, the mass flow rate of the fluid passing
`through the meter. In particular, coils 160L and 160R
`produce. the left and right velocity signals that appear 65
`on leads 165L and 165R, respectively.
`As noted, meter electronics 20 accepts as input the
`R TD signal appearing on lead 195, and left and right
`
`8
`velocity signals appearing on leads 165L and 165R, re(cid:173)
`spectively. Meter electronic