I
`
`United States Patent [191
`Kappelt et a1.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,655,089
`Apr. 7, 1987
`
`[54], MASS FLOW METER AND SIGNAL
`PROCESSING SYSTEM
`
`'
`'
`[75] Inventors: Eric G. Kappelt, Fairvrew; Frederick
`A. Ciccozzi, Erie, 130th Of Pa.
`
`4,422,338 12/ 1983 Smith ............................. .. 73/861.38
`4,438,393 3/1984 Moskalik et a1.
`324/83 D
`4,444,059 4/ 1984 Smith ............ ..
`73/861.37
`4,445,224 4/1984 lhira et a1.
`375/120
`4,491,025 1/1985 Smith et a1. .
`73/86l.38
`
`.
`
`.
`
`.
`
`173] Asslgnw 5mm‘ Meter Inc-1 Em’ Pa-
`[21] APPI- N°~= 797,98"
`Flled:
`NOV. 14,
`
`4,522,062 6/1985 Peters . . . . . .
`
`. . . . . .. 73/505
`
`4,559,833 12/1985 Sipin ............................... .. 73/861.38
`FOREIGN PATENT DOCUMENTS
`0153121 9/1983 Japan ‘
`0156813 9/1983 Japan .
`0206925 12/1983 Japan .
`Related U.S. Application Data
`0206926 ‘2/1983 Japan '
`Continuation-impart 6f Ser. NO. 742,567, Jun. 7, 1985,
`Primary Examiner—Herbert Goldstein
`abandoned.
`Ammey' Age“ 0' Fi'm-Andrew J- “menus
`[51] Int. cu .............................................. .. G01F 1/84
`[57]
`ABSTRACT
`[52] U.S. Cl. ......................................... .. 73/861318
`A Sign a1 processing system that directly dete . es the
`[58] Field of Search ....... .. 73/861.27, 861.28, 861.38
`phase difference existing between two periodic electri
`[56]
`References Cited
`cal signals and a mass ?ow meter employing the system
`U_S_ PATENT DOCUMENTS
`are provided. The system shifts together two compari
`.
`‘
`son Signals corresponding to the pen-Odie electrical
`11;.3 2,322 i
`21111111 ............................. .. 73/861.38
`signals and accumulates the shift that is necessary to
`’
`’
`{pin '
`.
`.
`3,485,098 12/1969 Sipm .
`-
`3,624,274 11/1971 Araki et al. ................... .. 307/511 x f°r°e the Phase angles °f the °°mPa?s°I1 slgnals t° be
`3,839,915 10/1974 Semi“ ,
`equal. The mass flow meter employs a moving conduit
`3,861,220 l/1975 Felsenthal, Jr. .
`through which the ?uid whose mass flow rate is to be
`3,889,186 6/1975 Larson ................... .., ...... .. 324/83 D measured ?ows and which generates Coriolis forces.
`3,927,565 12/1975 pa‘flln et al- -
`The Coriolis forces affect the motion of the moving
`3’989’931 11l1976_ph?h9s '
`_
`conduit and motion sensors provide periodic signals
`4,066,952 l/1978 Ley .1 ............................... .. 324/83 D
`.
`.
`.
`corresponding to the motion of the condmt. Under flow
`.
`.
`.
`.
`.
`.
`conditions, the Cor1ol1s forces cause the electncal s1g
`n?ls Produced by the sensors to be out of Phase with ,
`each other to an extent that depends on the magnitude
`of the mass flow rate. The system provided by the in
`vention is employed by the meter to measure the phase
`difference between the electrical signals to provide an
`‘ndlcaim °f the mass ?°w ‘ate thmugh the m°vmg
`“adult.
`
`[63]
`
`4,069,713 l/ 1978 Gussmann ...................... .. 73/861.28
`4,109,524 8/1978 Smith ‘
`I! ~
`,
`,
`,
`4,127,028 11/1978 COX et' a1. ....................... .. 73/861.38
`4,144,572 3/1979 Stamer et a1. ...........
`...... .. 364/487
`4,187,721 2/ 1930 Smith -
`4J92J84 3/1930 cm} et a1- -
`21:32:?!‘ """""""""" "
`4:381:672 5/1983 O’Connor et al.
`....... .. 73/505
`4,381,680 5/1983 Shiota .......... ..
`73/861.38
`4,400,664 8/1983 Moore ..... ..
`324/83 D
`4,420,983 12/ 1983 Langdon ........................ .. 73/861.18
`
`7 Claims, 32 Drawing Figures
`
`[- “zT _ '13:” _ "
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`DIRECTION
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`PRECISION
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`FEAK
`DETECTOR
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`|__________ ___._________. __ _____
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`

`U. S. Patent' Apr. 7, 1987
`
`Sheet1of24
`
`4,655,089
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`U. Patent Apr. 7, 1987
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`U. S. Patent Apr. 7, 1987
`
`Sheet3 @1424
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`4,655,089
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`////// //////////////////////////////////
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`

`U. S. Patent Apr. 7, 1987
`
`Sheet4 of24
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`4,655,089
`
`FIG.‘ 8
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`

`U. S. Patent Apr. 7, 1987
`
`'Sheet5 of24
`
`4,655,089
`
`6
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`

`U. S. Patent Apr. 1987 ‘
`
`Sheet6 of24
`
`4,655,089
`
`INTEGRATED VELOCITY SIGNA L
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`COMPARISON
`SIGNAL
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`FIG. IO
`
`7
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`

`U. S. Patent Apr. 7, 1987
`
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`4,655,089
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`U. S. Patent Apr. 7, .1987 ,
`
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`U. S. Patent Apr. 7,1987
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`U. S. Patent Apr. 7, 1987
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`Sheet 10 of24 4,655,089
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`_ US. Patent Apr. 7, 1987
`
`Sheetll of24 4,655,089
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`US. Patent 'Apr.'7,1987
`
`‘Sheet 12 of24 4,655,089
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`CHANNEL
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`US. Patent Apr. 7,1987 ‘
`
`Sheetl3 0f24 4,655,089
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`

`

`US. Patent Apr. 7, 1987
`
`Sheet 14 of24 4,655,089
`
`VOLTAGE
`
`COMIZARATO
`
`15
`
`

`

`U. S. Patent ‘Apn'll, 1987
`
`Sheet 15 0f24 4,655,089
`
`; CLOCK INT. ;
`
`I026
`
`I028
`
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`
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`INTERRUPT PRIORITIES '
`
`MASS METER: CLOCK INTERRUPT
`(MAIN LOOP)
`
`FIG. 2|
`
`16
`
`

`

`U. S. Patent Apr. 7, 1987
`
`Sheetl6 §f24 4,655,089‘
`
`I052
`
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`READ "s‘ran" /
`SWITCH
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`
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`
`FIG. 22
`
`FIG. 23
`
`17
`
`

`

`U. S. Patent Apr. 7, 1987'
`
`Sheet 17 of24 4,655,089
`
`I082
`
`ABSOLUTE
`
`"42
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`READ "woos" /'°a‘
`(SWITCH)
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`MASS METER: ABSOLUTE VALUE
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`SUBROUTINE v
`
`109a
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`FIG. 24
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`' FIG. 26
`
`18
`
`

`

`_ us. Patent Apr. 7, 1987
`
`Sheet 18 of 24
`
`4,655,089
`
`ACCELERATOR
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`FIG. 25
`
`19
`
`

`

`U. S. Patent Apr. 7, 1987
`
`Sheet 19 of 24 4,655,089
`
`.
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`s51- SNAFU J
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`MASS METER: MASS
`_— SUBROUTINE
`
`- FIG. 27
`
`20
`
`

`

`U.‘S. Patent Apr. 7, 1987
`
`*
`
`Sheet 20’of24 4,655,089
`
`"Mcounr"
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`
`21
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`

`

`US. Patent Apr. 7, 1987
`
`‘ Sheet210f24 4,655,089
`
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`22
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`

`

`‘ U. 5. Patent Apr. 7; 1937
`
`Sheet 22 of24 4,655,089
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`l238
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`23
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`

`

`US. Patent Apr.‘7,1987
`
`Sheet 23 of24 4,655,089
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`

`U. S. Patent Apr. 7, 1987
`
`.
`
`Sheet 24 of24 4,655,089
`
`ERROR SIGNAL (OUT)
`
`ZERO (IN)
`
`PERMISSIVE (IN)
`
`OUTPUT SIGNAL (TO INTERFACE 537)
`MDIR
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`

`

`1
`
`4,655,089
`
`2
`of the conduit at three selected points can be expressed
`as follows:
`
`Z(A)=ZA sin (wt)
`
`Z(D)=ZD sin (wt)
`
`Z(B)=Za sin (wt)
`
`(1)
`
`(2)
`
`(3)
`
`MASS FLOW METER AND SIGNAL PROCESSING
`SYSTEM
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`5
`
`The present application is a continuation-in-part of
`application for U.S. Ser. No. 742,567, filed June 7, 1985,
`which is now abandoned.
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to the mea-
`surement of the mass flow rate of fluids and, more par-
`ticularly, to a signal processing system for a mass flow
`meter and a mass flow meter that employs the signal
`processing system.
`DESCRIPTION OF THE PRIOR ART
`
`10
`
`15
`
`when the meter is under a no flow condition, where:
`A and B identify the two sensing points on the conduit
`at which movement sensors are located;
`D identifies the driving point of the conduit at which
`driving force is applied to the conduit to vibrate it;
`Z(A) and 2(3) represent the displacement, or position,
`of the two points A and B at time t;
`‘ Z(D) is the position or displacement of the conduit at
`the driving point D;
`24, lg and Z3 represent the maximum displacement
`from rest of points A, D and B;
`t is time in seconds; and
`w is the frequency of the driving force in radians/~
`second.
`
`20
`
`Often, the rate at which material flows through a
`supply line must be determined with the greatest possi-
`ble accuracy. For example, the actual mass or volume
`of material transferred to a buyer of the material is
`determined by a meter that measures the mass or vol-
`ume of material that flows from the seller’s reservoir of
`material to the buyer’s container. A meter that inaccu-
`rately determines the mass or volume of material that is
`transferred to the buyer will cause an adverse impact on
`the seller or the buyer. Further, the mass flow rate of
`material that is produced for human consumption is
`most desirably determined by a meter that is placed in
`the line that carries the material and that places no
`obstruction which could contaminate the material, in
`the path of the flow of the material.
`One type of mass flow meter that satisfies the require-
`ments described above employs a moving conduit that
`is placedin the line that carries fluid whose mass flow
`rate is to be measured, and is often referred to as a
`“vibratory” or “Coriolis force” meter. The concurrent ’
`movement of the fluid in the conduit and the vibration
`of the conduit itself generate forces that are exerted on
`and deform the conduit. The magnitude of the forces,
`one of which is Coriolis force, is related to the mass
`where V1 and V2 represent the voltage corresponding
`flow rate of the fluid in the conduit. Therefore, by mea-
`to movement of the vibrating conduit, and VpA and
`suring the magnitude of the force, or by measuring a
`characteristic of the conduit or its movement that is
`Vpg are the peak voltages of the electrical signals,
`affected by the force, a determination of the mass flow
`which correspond to the maximum displacement of the
`conduit at points A and B. Graphic representations of
`rate of the fluid can be made. The following U.S. pa-
`V1 and V2 are provided by FIG. 18. It should be noted
`tents disclose vibratory mass flow meters that employ
`that velocity or acceleration sensors are employed
`conduits of various shapes and signal processing sys-
`sometimes to detect conduit movement. Velocity and
`tems of various types:
`U.S. Pat. No. 3,485,098
`acceleration sensors produce signals that are expressed
`U.S. Pat. No. 4,109,524
`by appropriate derivatives of equations (7) and (8) with
`U.S. Pat. No. 4,127,028
`respect to time.
`Therefore, mass flow rate information is contained, as
`U.S. Pat. No. 4,192,184.
`U.S. Pat. No. 4,252,028
`phase information, in the argument of each of equations
`U.S. Pat. No. 4,311,054
`(7) and (8). The magnitude of the peak voltage for ve-
`U.S. Pat. No. Re. 31,450
`locity and acceleration sensors is dependent on the fre-
`U.S. Pat. No. 4,422,338
`quency of the driving force.
`U.S. Pat. No. 4,444,059
`Known vibratory mass flow meters generally use
`U..S Pat. No. 4,,491025
`either a differential amplifier technique or a time differ-
`Each meter identified above employs sensors that
`encing technique to extract mass flow rate information
`produce electrical signals that are related to the motion
`from equations (7) and (8). Employing the differential
`of the conduit at two points. The points are so chosen
`amplifier technique involves transmitting voltages V1
`that there exists a phase and time difference between the
`and V2 to a differential amplifier, which forms the dif-
`tWO signals, ideally zero, when the mass flow rate Of the 65 ference between V1 and V2 as follows;
`fluid1s zero, and a phase and time difference that varies
`from the no flow difference to an extent thatis related
`to the mass flow rate of the fluid. Generally, the motion
`
`When fluid is flowing through the conduit equations
`(1), (2) and (3) become:
`
`25
`
`Z(A)=Z,4 sin [Wt+/(M)]
`
`Z(D)=ZD sin [wt]
`
`Z(B)=ZB sin [wt—f(M)]
`
`(4)
`
`(5)
`
`(6)
`
`where f(M) represents the mathematical expression of
`angular phase difference, in terms of mass flow rate.
`Known meters often use position sensors to convert the
`motion of the vibrating conduit, at points A and B, to
`electrical signals, which can be expressed by the follow-
`ing:
`
`V1= VPA sin [wt +100]
`
`V2= VPB sin (Wt -I(M)l
`
`(7)
`
`(8)
`
`V1 - V2= VPA sin [wt +}(M)] - VPB sin [wt —}(M)]
`
`(9)
`
`30
`
`35
`
`4s
`
`50
`
`55
`
`60
`
`26
`
`26
`
`

`

`4,655,089
`
`3
`By using the appropriate trigonometric identities, equa-
`tion (9) becomes:
`
`V1—- V2 =( VPA — VPB) [COS/(Mush: wt+( VPA + Vpa)
`[sin f(M)]cos wt
`
`(10)
`
`By adjusting the gains associated with each position
`sensor, thereby setting VpA equal to V123, equation (1)
`reduces to:
`
`V1— V2=2VPA [sin f(M)]cos wt
`
`10
`
`(11)
`
`If the maximum value of f(M) is small, less than about
`two degrees, then sin f(M) is approximately equal to
`f(M) and equation (11) becomes:
`
`15
`
`V1— V2=2VpA/(M) cos wt
`
`(12)
`
`4
`time difference term (TB—TA) is most commonly con-
`verted to a corresponding voltage by an analog or digi-
`tal summation technique. The major disadvantage asso-
`ciated with the use of the time differencing technique is
`the dependence of the time difference on the frequency
`of vibration of the conduit, w. Variations in the density
`of the fluid flowing through the conduit and variations
`in the characteristics of the conduit due to temperature
`will cause changes in the frequency of vibration.
`Accordingly, there exists a need for a mass flow
`meter that employs Coriolis force and that does not
`depend on the frequency or the amplitude of movement
`of the conduit to measure the mass flow rate of a flow-
`ing fluid. Further, there is a need for such a mass flow
`meter that produces a digital output that can be used
`conveniently by digital computing equipment.
`SUMMARY OF THE INVENTION
`
`The present invention provides a mass flow meter
`that includes a conduit mounted at its ends to a support,
`apparatus for Vibrating the conduit, and apparatus for
`producing a pair of periodic electrical signals represen-
`tative of a characteristic of the motion of the conduit at
`two predetermined points. The flow meter includes a
`system that provides an indication of the phase differ~
`ence existing between the two periodic electrical sig-
`nals. The system includes apparatus for producing a
`measurement comparison signal from a first of the peri-
`odic electrical signals and a measurement threshold
`signal. The phase difference between the measurement
`comparison signal and the first periodic signal depends
`on the level of the measurement threshold signal rela-
`tive to the first periodic signal. The system includes
`apparatus for generating a measurement characteristic
`signal. The measurement characteristic signal is related
`to the peak amplitude of the first periodic signal. Appa-
`ratus is provided for creating a command signal, the
`nature of the command signal depending on whether
`the measurement comparison signal leads or lags a ref-
`erence signal. The reference signal can be one of many
`types. Preferably, the reference signal is the second of
`the periodic electrical signals or a signal representative
`of the motion of the conduit at a predetermined point.
`Most preferably, however, the reference signal is de-
`rived from the second periodic signal in which case the
`producing apparatus further produces a reference com-
`parison signal from the second periodic electrical signal
`and a reference threshold signal. Apparatus is provided
`for accumulating a count signal, the command signals
`determining when the level of the count signal is in-
`creased and decreased. Apparatus is provided for com-
`bining a signal corresponding to the count signal and
`the measurement characteristic signal to produce the
`measurement threshold signal.
`The present invention further provides a mass flow
`meter having a conduit mounted at its ends to a support
`an apparatus for vibrating the conduit. Apparatus is
`provided for producing a pair of periodic electrical
`signals representative of a characteristic of the motion
`of the conduit at two predetermined points. The meter
`includes a system that provides an indication of the
`phase difference between the periodic electrical signals.
`The system includes apparatus for receiving the peri-
`odic signals and producing a comparison signal from at
`least a first of the periodic electrical signals. Apparatus
`is provided for shifting the comparison signal to de-
`crease to a predetermined magnitude the phase differ-
`ence between the comparison signal and a reference
`
`20
`
`25
`
`30
`
`35
`
`There are several disadvantages associated with the use
`of the differential amplifier technique. First, the output
`of the differential amplifier is in analog form, which
`makes interfacing with digital equipment a problem.
`Second, a vibratory mass flow meter that employs the
`differential amplifier technique will introduce at least
`some inaccuracy into equation (12) if it produces a value
`for f(M) that exceeds about 3 degrees. Further, the
`value of the difference between V1 and V2 and, hence,
`the calculated mass flow rate, is dependent on the am-
`plitude of vibration of the vibrating conduit and to the
`; gain constants of the position sensors.
`Employing the time differencing technique involves
`the use of a pair of voltage comparators A and B of the
`type shown in FIG. 19. Comparator A receives at its
`noninverting terminal input voltage V1 and at its invert-
`ing terminal the threshold voltage VTA. Comparator B
`receives at its noninverting terminal input voltage V2
`and at its inverting terminal the threshold voltage VTA.
`Each comparator produces a high signal when the input
`voltage exceeds the threshold voltage and a low signal
`when the threshold voltage exceeds the input voltage.
`The electrical signals V1 and V2 produced by the mo-
`tion sensors and the threshold voltages VTA and V73 are
`shown in FIG. 20(0). The signals, Cx and Cy, that are
`produced by comparators A and B are shown in FIG.
`20(b). The time differencing technique measures the
`difference in time between the occurrence of a pair of 45
`edges for each cycle of Q, and Cy, as is shown in FIG.
`20(b). When using the time differencing technique,
`equations (7) and (8) become:
`
`..
`
`'
`
`j
`
`-
`
`V1 = VTA= VPA sin [W(TA)+f(M)]
`
`V2= VTB= VPB sin [W(TB)—](M)]
`
`(13)
`
`50
`
`(14)
`
`where TA represents the times at which V1 is equal to
`VTA, and T}; represents the times at which V2 is equal to
`VTB. Solving for TA and TB yields:
`
`55
`
`TA=[(aI'CSin VTA/VPAVW-flM/W]
`
`TB=[(arcsin VTB/VPB)/W+flM)/WI
`
`Taking the difference between TA and TB yields:
`
`TR— TA = 2f(M)/w+ [(aIcsin VTB/VPB)+(81'CSin
`VTA/VPA)l/W
`
`(15)
`
`(16)
`
`60
`
`(17)
`
`65
`
`Equation (17) shows that the time difference (TB—TA)
`is directly proportional to a time term, f(M)/w, and a
`constant divided by the frequency of vibration, w. The
`
`27
`
`27
`
`

`

`4,655,089
`
`6
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`5
`signal. Apparatus is provided for monitoring and accu-
`mulating the angle through which the comparison sig-
`nal is shifted to reduce the phase difference to the pre-
`determined magnitude, Accordingly, the accumulated
`angle provides an indication of the phase difference
`between the periodic electrical signals when the phase
`difference between the comparison and reference sig-
`nals reaches the predetermined magnitude.
`Preferably, the meter can compensate for mechanical
`and electrical noise occurring at zero flow to eliminate
`any offsets that would otherwise exist in the meter. Also
`preferably, the compensation is accomplished using a
`two-step procedure. First, a coarse adjustment is made
`followed by a fine adjustment of the system.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`
`
`The following detailed description of the preferred
`embodiments can be understood better if reference is
`made to the accompanying drawings, in which:
`FIG. 1 is a side view of the sensing assembly of a
`preferred embodiment of the present invention, with
`the central body partially cut away;
`FIG. 2 is a front view of the sensing assembly shown
`in FIG. 1;
`FIG. 3 is a bottom view of the sensing assembly
`shown in FIG. 1;
`FIG. 4 is a section view of the sensing assembly ‘
`shown in FIG. 1, taken along the line IV—IV;
`FIG. 5 is a sectional view of the assembly shown in
`FIG. 2 taken along the line V—V;
`.
`FIG. 6 is a sectional view of the assembly shown in
`FIG. 2 taken along the line VI—VI;
`FIG. 7 is a sectional view of a sensor and drive assem-
`bly of the assembly shown in FIG. 1;
`FIG. 8 is an isometric view of the assembly shown in
`FIG. 1;
`FIG. 9 is a block diagram representation of the pre-
`ferred signal processing system provided by the present
`invention;
`FIG. 10 shows in graphic form the periodic and
`threshold signals received by and the comparison signal
`produced by the precision comparator;
`FIGS. 11 through 15 present schematic representa-
`tions of the details of circuits, that are particularly use-
`ful for implementing the system shown in FIG. 9;
`FIG. 16 presents in schematic form the details of an
`LVDT drive circuit;
`FIG. 17 presents in schematic form the details of an
`LVDT demodulator;
`FIG. 18 is a graphic representation of the periodic
`electrical signals produced by the motion sensors of a
`vibratory mass flow meter;
`FIG. 19 is a diagrammatic representation of a pair of
`voltage comparators used with the time differencing
`technique of the prior art;
`FIG. 20 shows, the periodic electrical signals pro-
`duced by the position sensors of and the threshold sig-
`nals produced by known systems employing the time
`differencing technique and the signals produced by the
`voltage comparators shown in FIG. 19;
`FIGS. 21 through 30 are flow chart representations
`of a program that is particularly suitable for operating
`microprocessor 1000;
`FIG. 31 shows a portion of a system including micro-
`processor 1000; and
`FIG. 32 is a block diagram representation of micro-
`processor 1000.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`The present invention provides a meter for measuring
`the mass flow rate of a fluid and a signal processing
`system that is particularly useful with mass flow meters.
`The preferred mass flow meter includes, generally, a
`sensing assembly, which produces a pair of electrical
`signals containing mass flow rate information, and a
`signal processing system that extracts the mass flow rate
`information from the signals produced by the sensing
`assembly.
`FIGS. 1 through 8 show the sensing assembly 10 of
`the preferred meter of the present invention. Sensing
`assembly 10 is of the type disclosed and claimed in
`application for US. Letters Patent Ser. No. 655,305,
`filed Sept. 26, 1984, which is owned by the assignee
`hereof. However, a sensing assembly having any suit~
`able conduit of any known shape can be used with the
`system provided by the present invention. Sensing as-
`sembly 10 includes a conduit 12 that defines conduit
`sections 18 and 20. Conduit section 18 defines an inlet 14
`and an outlet 16. Conduit section 20 defines an inlet 33
`and an outlet 35. A central body 11 defines a manifold
`section 22 that joins together and provides fluid com-
`munication between inlets 14 and 33 and the supply line
`(not shown) by means of a passage 61. Outlet manifold
`section 24 joins together and provides fluid communica-
`tion between the supplyvline and outlets 16 and 35 by
`means of a passage 51. Manifold 22 defines an inlet 13
`which can be placed in fluid communication with the
`supply line using a circular flange 15 and an outlet 25
`through which fluid flows to reach conduit 12. Mani-
`fold 24 defines an inlet 49, which receives fluid from
`conduit 12 and an outlet 17 which can be placed in fluid
`communication with the supply line using circular
`flange 19. Flanges 15 and 19 define passages 21 and 23,
`respectively, that are adapted to receive fluid from the
`supply line, and bolt holes 57 and 59, respectively,
`which are adapted to receive the bolts (not shown) that
`secure the supply line to conduit 12. Passage 61 of mani-
`fold 22 is circular at inlet 13 to facilitate fluid flow from
`the supply line into manifold 22. Passage 61 is oval at
`outlet 25 of manifold 22 to facilitate the division of the
`fluid into two streams, each of which flows through a
`conduit section 18 or 20. A one-piece oval input casting
`27 is sized to mate with outlet 25 of manifold 22. Casting
`27 defines two passages 29 and 31, each of which is
`aligned with an inlet 14 or 33. Casting 27 is welded to
`outlet 25 of manifold 22 and to inlets 14 and 33 of con-
`duit sections 18 and 20. Accordingly, casting 27 oper-
`ates to split the fluid flowing through outlet 25 into two
`streams and to direct those streams through conduit
`sections 18 and 20. Passage 51 of manifold 24 has a
`circular cross section at outlet 17 to facilitate fluid flow
`between outlet 17 and the supply line. Passage 51 has an
`oval cross section at inlet 49 to facilitate fluid flow
`between conduit sections 18 and 20 and inlet 49. An
`oval outlet casting 53 defines a pair of openings 63 and
`65, which are adapted to receive outlets 16 and 35 of
`, conduit sections 18 and 20, respectively. An oval isola-
`tor 37 defines a passage 39 that receives conduit section
`18 and a passage 41 that receives conduit section 20. An
`oval isolator 43 defines a pair of passages 45 and 47 that
`receive outlets l6 and 35 of conduit sections 18 and 20,
`respectively. Isolators 37 and 43 operate to limit vibra-
`tion of conduit sections 18 and 20 to those portions
`located between isolators 37 and 43. Walls 58 and 60 of
`
`28
`
`28
`
`

`

`4,655,089
`
`7
`body 11 define rectangular openings 62 and 64, respec-
`tively, which receive conduit sections 18 and 20 and
`facilitate assembly of assembly 10. A pair of housings 66
`and 68 (shown in phantom in FIG. 1 and 8) can be
`secured to channels 70, 72, 74 and 76 to provide a cover
`for central body 11.
`Sensing assembly 10 is adapted to be installed in the
`supply line that carries the fluid whose mass flow rate is
`to be measured. The line is broken to form a fluid exit
`
`and fluid reentry for the line. Inlet 13 of sensing assem-
`bly 10 is placed in fluid communication with the line
`exit using flange 15, and outlet 17 is placed in fluid
`communication with the line reentry using flange 19.
`Accordingly, fluid flowing through the line will exit the
`line at the line exit to enter the sensing assembly at its
`inlet 13. After flowing through passage 61 of manifold
`22 the fluid will be split into two streams of generally
`equal mass flow rates by casting 27. The two streams
`enter and flow through conduit sections 18 and 20.
`After the streams enter casting 53 and manifold 24, the
`two streams are united. The joined stream travels
`through passage 51 and leaves the sensing assembly at
`outlet 17 to reenter the line at the line reentry.
`Sensor assembly 10 includes a conduit drive assembly
`26 and a pair of velocity sensors 28 and 30. Position or
`acceleration sensors, or any other type of motion sen-
`sor, could be used in place of velocity sensors 28 and 80.
`Conduit drive assembly 26 exerts force against conduit
`., sections 18 and 20 along axis Z—Z’. The direction in
`‘ which assembly 26 exerts force against sections 18 and
`20 periodically is reversed to cause sections 18 and 20 to
`vibrate. The direction in which assembly 26 exerts force
`on section 18 is always opposite to that in which assem-
`bly 26 exerts force on section 20.
`As can be seen in FIG. 7, each of sensors 28 and 30
`and conduit drive assembly 26 includes a cylindrical
`* permanent magnet 48 that is secured to a magnet holder
`50. Permanent magnet 48 is adapted to be received by
`the passage 52 formed by cylindrical electrical coil 54.
`Magnet holder 50 is mounted to section 20 and coil 54
`is secured to conduit section 18 in any suitable fashion.
`~ Accordingly, movement of conduit sections 18 and 20
`relative to each other will cause movement of magnets
`48 within passages 52 of sensors 28 and 30. Movement
`of magnet 48 within the coil 54 of a velocity sensor 28
`or 30 generates a voltage (of the type shown in FIGS.
`10 and 18) that is proportional to the velocity at which
`conduit sections 18 and 20 are moving relative to each
`other. Conduit drive assembly 26 also comprises a per-
`manent magnet 48 that is secured to a magnet holder 50
`and an electrical coil 54 that defines a passage 52. Mag-
`net holder 50 of assembly 26 is secured to conduit sec-
`tion 20 and coil 54 is secured to conduit section 18. A
`sinusoidal voltage is applied to coil 54 of assembly 26,
`which causes oscillatory movement of coil 54 and base
`50 relative to each other to cause conduit sections 18
`and 20 to vibrate. Accordingly, applying a sinusoidal
`voltage to coil 54 of conduit drive assembly 26 causes
`conduit sections 18 and 20 to vibrate and causes sensors
`28 and .30 to produce sinusoidal voltage signals that are
`proportional to the velocity at which the sections of the
`conduit to which they are mounted are moving.
`If the mass flow rate of fluid travelling through sec-
`tions 18 and 20 is zero, the sinusoidal signals produced
`by velocity sensors 28 and 30, ideally, will be in phase
`with each other. However, fluid flowing through con-
`duit sections 18 and 20 will coact with vibrating conduit
`sections 18 and 20 to produce Coriolis forces that are
`
`‘
`
`
`
`8
`exerted on conduit sections 18 and 20. Detailed discus-
`sions of the generation of Coriolis forces in a vibrating
`conduit and the effect of those forces on the motion of
`the conduit can be found in the art identified in the
`section hereinabove entitled Description of the Prior
`Art. The generated Coriolis forces cause the oscillating
`sections of conduit sections 18 and 20 to be out of phase
`with each other. Therefore, when fluid is flowing
`through conduit 12 and conduit drive assembly 26 is
`vibrating conduit sections 18 and 20, velocity sensors 28
`and 30 will produce signals, of the type shown in FIG.
`18 and designated V1 and V2, that are shifted from each
`other. The magnitude of the phase shift is related to the
`magnitude of the Coriolis forces generated by the vi~
`brating conduit and, hence, to the magnitude of the rate
`of mass flow through conduit 12.
`The preferred signal processing system 100 provided
`by the present invention is shown in FIG. 9. System 100
`receives the sinusoidal signa