Abstrict A mass flow meter in which the mass flows along a path having a
bend in one sense on one side of a pivot axis and a bend in an opposite
sense on the other side of the pivot axis. When the material flows
through the device a force is applied to part of the apparatus tending
to rotate it. A force measuring device measures the force without
the operative parts of the force measuring device moving by a significant
extent.
Claims I claim:
1. A mass flow meter comprising a flow passage through which the
material, the mass flow of which is to be measured, is constrained
to pass, the flow passage defining an inlet port, and an outlet
port, a further part of the flow passage being defined by a substantially
spherical housing that is located for pivoting about a predetermined
pivot axis, said spherical housing defining a flow path portion
having a bend in one sense and a bend in the opposite sense, said
bends being located symmetrically about said pivot axis, the flow
of material being adapted to follow said flow path portion within
the confines of said spherical housing, whereby as material flows
through the device a velocity force is applied to said spherical
housing tending to rotate said housing about said axis, and force
measuring means operatively connected to said spherical housing
for measuring the velocity force applied to said housing, said force
measuring means being of the type that can measure force with the
operative parts thereof being substantially fixed, said inlet port
and said outlet port being substantially coaxially aligned.
2. A mass flow meter according to claim 1 wherein the force measuring
means comprise a transducer.
3. A mass flow meter according to claim 2 wherein the transducer
is a gyroscopic transducer.
4. A mass flow meter according to claim 2 wherein the transducer
is an oscillating wire transducer.
5. A mass flow meter according to claim 1 wherein the housing is
formed of two identical halves which are secured together.
6. A mass flow meter according to claim 1 wherein the spherical
housing comprises an inlet connected to said inlet port and associated
with a conduit portion directing the flow into the spherical housing
in one direction, and an axially aligned outlet connected to said
outlet port and associated with a conduit portion direction the
outflow from the housing in another direction which is not aligned
with said one direction so that the material flowing through the
housing follows said flow path portion, the axis of rotation of
the housing being perpendicular to overall direction of flow of
material through the mass flow meter.
7. A mass flow meter according to claim 6 wherein the housing has
an open hollow center, said conduit portions being located at diametrically
opposed positions.
8. A mass flow meter according claim 1 including a housing defining
two chambers, one connecting with the inlet port and one connecting
with the outlet port, there being at least two flow passages interconnecting
the chamber connected to the inlet port with the chamber connecting
to the outlet port, the passages being located on opposite sides
of the axis defined by the inlet port and the outlet port, the passages
being curved in opposite senses when viewed from a side perpendicular
to the flow plane so that as material flows from the chamber connecting
to the inlet conduit to the chamber connecting to the outlet conduit
a moment is applied to the housing tending to rotate the housing,
the housing being mounted so that it can rotate at least to a limited
extend about the axis defined by the inlet and outlet ports.
9. A mass flow meter according to claim 8 wherein the housing is
formed of two identical halves which are secured together.
10. A mass flow meter according to claim 1 wherein said spherical
housing comprises an inlet conduit resiliently connected to said
housing at said inlet port for permitting some pivoting of said
housing, an outlet conduit resiliently connected to said housing
outlet port for permitting some pivoting of said housing, said inlet
and outlet conduits being axially aligned along a conduit axis which
is perpendicular to said pivot axis, said spherical housing including
a first internal stub adjacent said inlet port for deflecting fluid
in one direction in said housing and a second stub ajdacent said
outlet port for deflecting fluid in an opposite direction in said
housing, said one and opposite directions being on opposite sides
of said pivot axis and on opposite sides of said conduit axis so
that with a mass flow through said housing, forces are exerted on
said housing to tend said housing to rotate about said pivot axis
which forces are sensed by said force measuring means.
11. A mass flow meter comprising a flow passage through which the
material, the mass flow of which is to be measured, is constrained
to pass, the flow passage defining an inlet port, and an outlet
port, a further part of the flow passage being defined by a length
of conduit of substantially S shaped configuration which is mounted
for pivoting about a predetermined pivot axis within a housing,
said housing being partitioned to form two chambers, one connected
with said inlet port and the other connected with said outlet port,
said chambers being interconnected by said length of conduit, said
conduit defining a flow path portion having a bend in one sense
and a bend in the opposite sense, said bends being located symmetrically
about said pivot axis whereby as material flows through the device
a velocity force is applied to said conduit tending to rotate said
conduit about said axis, and force measuring means operatively connected
to said length of conduit for measuring the velocity force applied
to said conduit, said force measuring means being of the type that
can measure force with the operative parts thereof being substantially
fixed, said inlet port and said outlet port being substantially
coaxially aligned.
12. A mass flow according to claim 11 wherein said chambers are
partitioned by a relatively flexible membrane which assists in supporting
the said length of conduit in position.
Description This invention relates to a mass flow meter.
Whilst the mass of a material may be measured, in many circumstances,
using a weighscale or balance, such a technique cannot readily be
utilised in a situation where the material to be weighed is flowing
through a pipe.
It is common practice to determine the mass of a material flowing
through a pipe by first measuring the volume flow per unit time,
and multiplying the measured value with a value representative of
the density of the material. However, this technique is very sensitive
to variables such as pressure, viscosity, turbulence and temperature
and thus cumulative errors may arise.
Various mass flow meters have been produced previously which seek
to measure the mass of a liquid or gaseous material flowing in a
pipe directly.
One prior proposed mass flow meter imparts an angular velocity
to a previously linearly flowing fluid, and then measures the resultant
angular momentum to provide a signal that is representative of the
mass flow rate. Typically such an apparatus incorporates an impeller
comprising a suitable rotor or turbine. These mass flow meters have
the significant disadvantages of being prone to wear and damage
and of being applicable only to the measurement of flow rates in
homogenous fluids having a relatively low viscosity.
Various other proposals have been made, but at the present time
there is still a need for a mass flow meter having an accuracy of
at least 0.1% and capable of measuring bulk quantities, over a wide
range of viscosities, of homogeneous or non-homogeneous materials.
U.S. Pat. No. 3164019 discloses a mass flow measuring device
which comprises a substantially "S" shaped insert flexibly
coupled into a pipe wherein a fluid, the mass flow of which is to
be measured, is caused to flow. The flow through the "S"
shaped insert generates a torque about an axis passing through the
point of symmetry of the "S". This is measured with a
spring which resists any movement of the insert. The spring is connected
to a torque motor which is responsive to signals from a synchro
connected to a pivot which pivotally supports the insert. Thus there
is a closed loop servo which resists the torque generated in the
"S" shaped insert, maintaining the insert at a null position,
whilst measuring the torque. Since the inlet and the outlet to the
"S" shaped insert are offset, if the insert expands or
contracts, for example as a result of thermal expansion or contraction,
an error can arise.
According to this invention there is provided a mass flow meter,
said mass flow meter comprising a flow passage through which the
material, the mass flow of which is to be measured, is constrained
to pass, the flow passage defining a substantially linear inlet
port, and a substantially linear outlet port, a further port of
the flow passage being defined by an element of the apparatus that
is located for pivoting about a predetermined pivot axis, said element
defining a flow path portion having a bend in one sense and a bend
in the opposite sense, said bends being located symmetrically about
said pivot axis so that, as material flows through the device a
velocity force is applied to said element tending to rotate that
element about said axis, a force measuring means being provided
to measure the velocity force applied to said element, the force
measuring means being of the type that can measure force without
the operative parts thereof being moved by a significant extent,
the inlet port and the outlet port being substantially coaxially
aligned.
In the prior arrangement the closed loop servo is expensive to
provide, and costly to maintain. Thus in the invention preferably
the force measuring means comprise a transducer, such as a gyroscopic
transducer, or an oscillating wire transducer.
Preferably the arrangement is symmetrical about the said axis of
rotation.
Advantageously said element comprises a substantially spherical
housing, the flow being adapted to follow said flow path within
the confines of the spherical housing.
In one embodiment the spherical housing comprises an inlet associated
with a conduit portion directing the flow into the spherical housing
in one direction, and an axially aligned outlet associated with
a conduit portion directing the outflow from the housing in another
direction which is not aligned with said one direction so that the
material flowing through the housing follows said flow paths, the
axis of rotation of the housing being perpendicular to overall direction
of flow of material through the mass flow meter.
Preferably the housing has an open hollow center, said conduit
portions being located at diametrically opposed positions.
In another embodiment, the housing defines two chambers, one connecting
with the inlet port and one connecting with the outlet port, therebeing
at least two flow passages interconnecting the chamber connected
to the inlet port with the chamber connecting to the outlet port,
the passages being located on opposite sides of the axis defined
by the inlet port and the outlet port, the passages being curved
in opposite directions when viewed from the same direction so that
as material flows from the chamber connecting the inlet conduit
to the chamber connecting to the outlet conduit a moment is applied
to the housing tending to rotate the housing, the housing being
mounted so that it can rotate at least to a limited extent about
the axis defined by the inlet and outlet ports.
Preferably the housing is formed of two identical halves which
are bolted or otherwise secured together.
In the prior art arrangement the density of the steam being metered
is measured at a point remote from the "S" shaped insert.
Where density and flow rate both fluctuate errors may arise since
it is not possible to determine the density of the particular sample
that applied any specific measured velocity force.
Advantageously means are provided to measure the density of the
contents of said element simultaneously with the measurement of
said velocity force applied to the element. Since the volume of
the element is known, and the tare mass of the element is known,
the total mass of the elements and contents may be determined, from
which the density may be directly calculated.
In a further embodiment the element comprises a length of conduit
of substantially "S" configuration, which is mounted within
a housing, the housing being partitioned to form two chambers, one
connected with the inlet and the other connected with the outlet,
the section of conduit serving to interconnect the said chambers.
Conveniently said chambers are partitioned by a relatively flexible
membrane which assists in supporting the length of conduit in position.
In order that the invention may be more readily understood, and
so that further features thereof may be appreciated, the invention
will now be described by way of example with reference to the accompanying
drawings in which:
FIG. 1 is a vertical sectional view through one embodiment of the
invention,
FIG. 2 is a top plan view with parts cut away of the embodiment
shown in FIG. 1
FIG. 3 is a vertical part sectional view corresponding to FIG.
1 but showing a modified embodiment of the invention,
FIG. 4 is a top plan view of part of the apparatus shown in FIG.
3
FIG. 5 is a side elevational view of another embodiment of the
invention,
FIG. 6 is a view taken on the line A--A of FIG. 5
FIG. 7 is a view taken on the line B--B of FIG. 5
FIG. 8 is a diagrammatic view showing the embodiment of the invention
of FIGS. 5 to 7 in use,
FIG. 9 is an end elevational view of the arrangement shown in FIG.
8
FIG. 10 is a part sectional view corresponding to FIG. 5 showing
a modified embodiment of the invention,
FIG. 11 is a view corresponding to FIG. 7 showing the modified
embodiment of FIG. 10
FIG. 12 is a vertical sectional view through yet another embodiment
of the invention,
FIG. 13 is an end elevational view of the embodiment shown in FIG.
12 and
FIG. 14 is a top plan view, with parts cut away, of the embodiment
of FIGS. 12 and 13.
The described embodiments of mass flow meters utilize transducers
to measure the force applied thereto. It is preferred that each
transducer is a transducer of the type that operates without any
significant movement of the operative parts thereof. Thus the transducer
may be considered to be a "hard" transducer having an
operative stroke that can be measured in microns (e.g. 10 microns)
as compared with a conventional "soft" transducer which
may have an operating stroke that can be measured in millimeters.
For example, the transducer may comprise an oscillating wire transducer
(in which the force applied to the transducer adjusts the tension
present in a wire which is caused to vibrate, the vibrating or resonant
or frequency of the wire being measured to determine the force applied
to the transducer) or a gyroscopic transducer (in which the force
applied to the transducer is caused to move one of the bearings
supporting a gyroscope, the subsequent precessing of the gyroscope
being indicative of the force applied).
Referring now to FIGS. 1 and 2 of the accompanying drawings in
a first embodiment of the invention an outer housing 1 is provided,
but the housing only serves the function of maintaining the inlet
conduit 2 and the outlet conduit 3 in precisely determined positions.
The inlet conduit and the outlet conduit are aligned, and are thus
co-axial. The inlet conduit 2 is connected by means of a flexible
pipe portion 4 to an inlet port 5 provided on a symmetrical spherical
inner housing 6. The inlet port 5 of the inner housing 6 is connected
to an interior stub conduit 7 which directs the flow of material
entering the inner housing 6 upwardly tangentially adjacent the
interior surface of the spherical inner housing 6.
The spherical inner housing 6 is mounted on horizontal trunions
8 for pivoting about a horizontal pivot axis 9. The housing is actually
fabricated from two identical halves 10 that are bolted together
by means of bolts 12. Thus the spherical inner housing 6 defines
an outlet port 13 which is axially aligned with the inlet port 5.
The outlet port is associated with a stub conduit 14 located on
the interior of the spherical inner housing 6 this stub conduit
extending downwardly substantially tangentially with the interior
of the lower part of the spherical inner housing 6. The stub conduits
7 and 14 are diametrically opposed.
The outlet port 13 of the spherical inner housing 6 is connected
by a flexible pipe portion 15 to the outlet conduit 3 of the entire
flow meter.
A force measuring transducer 16 is provided, of the type described
above and a connecting rod 17 extends between part of the inner
housing 6 and the transducer 16 so that any force tending to rotate
the inner housing 6 about the axis defined by the trunnions may
be detected by the transducer 16.
It is to be noted that flow dividing webs 18 may be provided on
the interior of the housing associated with the stub conduits 7
14. In FIG. 2 the open mouths of the stub conduits 7 14 are shown
in phantom and the webs 18 are also illustrated in a similar manner.
It is to be appreciated that the described embodiment of the invention
is substantially symmetrical. This will reduce any measurement errors
that might be caused by temperature variations, vibrations or the
like.
In practive, as the housing 6 may be hot or cold, the transducer
is thermally insulated from the housing, for example by providing
a thermal break in the connecting rod. Temperature compensation
may be achieved by providing a connecting rod having a selected
coefficient of expansion such that as the configuration of the housing
is changed, due to expansion or contraction upon a change in ambient
temperature, a precisely compensating change occurs in the configuration
of the connecting rod. The connecting rod may conveniently be formed
from metals having different coefficients of expansion.
When a flow of material is introduced to the described apparatus
through the inlet conduit 2 the material flows through the flexible
pipe portion 4 through the inlet port 5 of the inner spherical
housing 6 and is then constrained to flow upwardly through the short
stub pipe 7. The flow of material then must turn downwardly, and
this downturning of the flow occurs at a point spaced above the
rotational axis 9 defined by the trunnions 8. When the material
has flowed downwardly it subsequently again turns to flow upwardly
through the stub conduit 14 to the outlet port 13. This upward turning
is effected at a position below the pivoting axis 9 defined by the
trunnions 8. The flow then leaves the described apparatus through
the outlet ports 13 and the outlet conduit 3. Since the flow is
constrained to change its direction of flow twice in opposite senses
or directions on opposite sides of the pivot axis 9 a resultant
rotational force is applied to the inner housing 6. This force is
dependent on the velocity of flow, and thus termed a velocity force.
However, the force is also dependant on the mass flow rate. This
velocity force is measured by the transducer 16. Since the transducer
is of the "hard" type as described above, the inner housing
6 does not actually rotate to any significant extent, but nevertheless
the velocity force tending to rotate the inner housing can be measured
accurately.
It is to be noted that the material flowing through the described
device is first constrained to change direction in one sense and
is then constrained to change direction in the other sense, the
points at which the change of direction of flow is effected being
located in a symmetrical way on opposite sides of an axis of rotation,
the resultant velocity force tending to rotate the housing about
that axis subsequently being measured. The velocity force that tends
to rotate the housing is generated since when any material flowing
through the housing turns a corner, a force is applied to the housing
which is dependent upon the density i.e. the mass of the material
flowing through the conduit, and the square of the velocity. Since
the material changes direction first in one sense and then in the
opposite sense, and since the changes of direction are located on
opposite sides of the axis 9 defined by the trunnions 8 the resultant
force causes a moment about the horizontal axis 9 and this force
tends to cause the housing to rotate about the horizontal axis 9.
However, since the connectio rod 17 extends between the housing
and the transducer 16 this rotation of the housing is resisted,
and thus the housing remains subtantially stationary. However, the
velocity force tending to rotate the housing can be measured by
the transducer 16 this force being indicative of the density or
mass of material flowing through the conduit.
FIGS. 3 and 4 illustrate an alternative embodiment of the invention
which operates on the same principle as the embodiment illustrated
in FIG. 2. It will be observed that this embodiment of the invention
incorporates a spherical housing 20 which corresponds to the spherical
housing 6 of the first described embodiment of the invention. Instead
of being mounted by means of flexible pipe portions, the housing
20 is mounted in position by means of an inlet pipe 21 and an outlet
pipe 22 the inlet and outlet pipes being mounted, by means of appropriate
"O" rings 23 23 in inlet and outlet apertures formed
in the spherical housing 20. The inlets are associated with short
stub pipes 24 24 corresponding to the stub pipes of the first
described embodiment. The pipes 21 22 are mounted by means of further
"O" rings (only one of which, 25 is shown) in a housing
26. The arrangement is such that the spherical housing 20 is pivotally
mounted for rotation about an axis 27 and can rotate slightly about
that axis due to the freedom of movement provided to the spherical
housing 20 by virtue of the way it is mounted in position by means
of the pipes 21 22 and the associated "O" rings.
As can be seen more clearly from FIG. 4 one of the trunnions 28
by means of which the spherical chamber 20 is mounted for rotation
about the axis 27 is actually inserted through an aperture formed
in a lever 29. One end, 30 of the lever 29 is pivotally connected
by means of a pivot pin 31 to one wall of the housing 26. The other
end 32 of the lever is adapted to provide a force to a density force
sensing transducer 33. It will be seen that the mass of the spherical
housing 20 will tend to cause the trunnion 28 to move downwardly,
thus causing lever 29 to pivot in a downward manner about the pivotal
connectio 31 thus forcing the end 32 of the lever downwardly on
to the force sensing transducer 33. The density force sensing transducer
can thus provide an output signal representative of the mass of
(or density of the contents of) the spherical housing 20. Of course,
the effective mass of the spherical housing 20 will depend upon
the weight of material present within the housing at any point in
time, and since the volume of the housing is known the output from
the transducer 33 may be calibrated in mass or in density. Consequently
it will be appreciated that the embodiment described in FIGS. 3
and 4 can provide an indication of the mass of, and density of,
material flowing through the chamber 20. Of course, a velocity transducer
corresponding to the transducer 16 will be provided to measure the
rotational force applied to the spherical chamber 20 by means of
the material flowing therethrough, and thus the apparatus shown
in FIGS. 3 and 4 can provide detailed information concerning the
density, and the mass flow rate, of material flowing through the
spherical chamber 20.
It is to be understood that the embodiment of FIGS. 3 and 4 measures
the density of a sample being measured and the turning force generated
by that sample simultaneously. This provides a more accurate result
than obtainable with prior proposed devices in which the density
of a flowing stream is measured at one point, and a turning moment
generated by the velocity force of the stream is measured at another
point.
It is to be noted that the material flowing through the described
device is first constrained to change direction in one sense and
is then constrained to change direction in the other sense, the
points at which the change of direction of flow is effected being
located in a symmetrical way on opposite sides of an axis of rotation,
the resultant force tending to rotate the housing about that axis
subsequently being measured.
FIGS. 5 to 9 illustrate another embodiment of the invention.
An outer housing 40 of square form, contains an inner housing
41 the exterior of which is of generally spherical configuration.
The outer housing 41 is formed of two identical halves 42 43 which
are bolted together by bolts 44 passing through coaligned apertures
in protruding flanges formed on the housing halve 42 43.
The housing half 42 defines an inlet port 45 which passes through
one exterior wall of the housing 40 and the housing half 41 defines
an outlet port 4 axially aligned to the inlet port 45 which passes
through the other side of the housing.
The inner housing 41 is mounted for rotation about the axis defined
by the inlet port 45 and the outlet port 46. Part of the periphery
of the housing is connected by means of an appropriate connecting
rod 47 to a transducer 48 of the "hard" type as described
above.
The two housing parts 42 43 define respective chambers 49 50
which are substantially sealed from each other. However, two flow
passages are provided which interconnect the chambers 49 50. As
can be seen most clearly in FIG. 6 one communication passage is
located adjacent the top of the inner housing 41 and is located
adjacent the shell of the housing. A channel 51 that forms the flow
passage is configured to be of a substantially "U" configuration,
the two arms of the "U" being parallel with and on either
side of the central partition which separates the chambers 49 and
50. It will be appreciated that a flow of material passing through
the "U" shaped channel will impart a force F' to the housing
as indicated by the arrow 52. Another identical channel 53 is located
on the opposite side of the pivot axis defined by the inlet port
45 and the outlet port 46 and comprises a similar configured "U"
channel, but having (when viewed in plan), the opposite sense. Thus
the force F', indicated by the arrow 54 exerted on the housing when
material flows through the flow meter cooperates with the force
indicated by the arrow 52 to create a moment, proportional to the
velocity force, tending to rotate the inner housing 41 about the
pivot axis defined by the inlet port 45 and the outlet port 46.
The force actually applied to the inner housing is measured by
the transducer 48 which is of the "hard" typd, as described
above. Thus, whilst the force applied to the housing is measured,
the housing does not actually rotate to any significant extent.
Referring now to FIGS. 10 and 11 a further embodiment of the invention
is shown which corresponds broadly to the embodiment of FIGS. 5
to 9 although it will be noted that the spherical chamber 61 of
the embodiment shown in FIGS. 10 and 11 is of a slightly different
design to the spherical chamber 41 of the embodiment of FIGS. 5
to 9. Howver, the differences are not sufficient to warrant detailed
description at this stage. It will be noted that, in the embodiment
illustrated in FIGS. 10 to 11 the housing 61 carries a protruding
arm 62 adapted to engage a force sensing transducer 63 which corresponds
to the transducer 48 of the embodiment of FIGS. 5 to 9. It will
be noted that the spherical housing 61 is mounted in position by
means of three rollers 64 65 66 to permit the housing 61 to rotate
about the axis defined by the inlet pipe 67 and the outlet pipe
68 which are connected appropriately to the housing 61.
It will be observed that the lowermost roller 66 is mounted on
a force measuring transducer 67 which is of the "hard"
type described above. The transducer 67 is thus adapted to provide
an output signal representative of the mass of the chamber 61 and
the contents thereof. It will be appreciated, therefore, that the
embodiments shown in FIGS. 10 and 11 may be used not only to measure
the mass flow rate of material passing through the chamber 61 but
may also be used to measure the instantaneous mass present within
the chamber 61 thus enabling the density of the material to be
calculated. The embodiment of FIGS. 3 and 4 may also be used in
this way.
It will be observed that in all the previously described embodiments
of the invention, the inlet and outlet conduits are axially co-aligned,
and this serves to minimise any errors that may be introduced to
the apparatus if, for example, the pressure (and thus in some cases
the density) of material entering on one side of the mass flow meter
is less than the pressure of the material leaving the other side
of the mass flow meter. Also, the coalignment of the inlet and outlet
ports reduces the risk of any errors arising due to temperature
differentials present in the apparatus. If the inlet and outlet
were not aligned, but were offset, if the temperature of the apparatus
varies, due to thermal expansion and contraction, an error would
be introduced. However, with the inlet and outlet coaligned thermal
expansion and contraction of the components of the mass flow meter
does not cause the inlet and the outlet to be misaligned.
Referring now to FIGS. 12 to 14 a further embodiment of the invention
is disclosed. In this embodiment of the invention an outer housing
70 is provided, but this outer housing is optional. The outer housing
contains an inner housing 71 of generally rectangular configuration
which defines an axial inlet port 72 and, at the opposite end thereof
an axial outlet port 73. The inlet and outlet ports are co-aligned,
as in the earlier described embodiments of the invention. The housing
is actually formed of two identical elements 74 75 which are connected
together by means of bolts 76 passing through appropriate flanges
provided on the elements 74 75. A slightly resilient diaphragm
77 is provided which is trapped between the housing halves and which
serves to divide the interior of the housing into two separate chambers,
namely a first chamber 78 communicating with the inlet port 72 and
a second chamber 79 communicating with the outlet port 73. A substantially
"S" sectioned length of conduit 80 is sealingly mounted
on the diaphragm 77 and is also mounted for rotation about an axle
81 which can be seen most clearly in FIG. 14. One end of the axle
81 is connected to a lever 82 the end of which is connected by
means of a connecting rod 83 to a transducer 84 of the "hard"
type as described above. A baffle 85 may be provided within the
chamber 78 coaligned with the inlet port 72 if desired.
A material, the mass flow of which is to be measured, may be introduced
to the described apparatus through the inlet port 72. The material
will then flow through the "S" shaped channel defined
by the "S" configured section of conduit 80 which is symmetrical
relative to the axis 81 of rotation thereof. The material flowing
through the conduit 80 is thus constrained to change direction in
one sense on one side of the pivot axle 81 and to change direction
in the opposite sense on the other side of the pivot axle 81. Thus
the section of conduit 80 has a moment of force applied thereto,
proportional to the velocity force, tending to rotate the section
of conduit 80 about the axle 81. This rotational force is measured
by means of the transducer 84. Since the transducer 84 is a "hard"
transducer the conduit 80 does not actually rotate to any significant
extent, but nevertheless the force tending to rotate the conduit
is still measured. This force is representative of the mass flow.
In all the above described embodiments the force measuring transducer
or transducers may be connected to an appropriately programmed microprocessor
or computer which will provide an output indication of the value
of the specific parameter being measured.
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