Abstrict A mass flow meter for flowing media, which operates according to
the Coriolis principle, has one straight Coriolis measuring tube,
several oscillation generators acting on the Coriolis measuring
tube and several sensors detecting Coriolis forces and/or Coriolis
oscillations based on Coriolis forces. The oscillation generators
are designed and arranged so that the Coriolis measuring tube oscillates
around its longitudinal axis enabling the flow of gases to be measured
with high measuring accuracy.
Claims What is claimed is:
1. A mass flow meter for flowing media, which operates according
to the Coriolis principle, with a basically straight Coriolis measuring
tube (2) having an axis, with two oscillation generators (3) offset
from one another about said axis by substantially 180.degree. and
acting on said Coriolis measuring tube (2) tangentially in the same
direction about said axis leading to an oscillation of said Coriolis
measuring tube (2) around said axis, and with at least one sensor
detecting Coriolis forces or Coriolis oscillations based on Coriolis
forces or both of them.
2. The mass flow meter in accordance with claim 1 wherein four
oscillation generators (3) are provided and the oscillation generators
(3) act on said Coriolis measuring tube (2) offset by substantially
90.degree. in the same direction tangentially.
3. A mass flow meter for flowing media, which operates according
to the Coriolis principle, with a basically straight Coriolis measuring
tube (2) having an axis, with at least one sensor detecting Coriolis
forces or Coriolis oscillations based on Coriolis forces or both
of them, wherein four oscillation generators (3) are provided, wherein
two oscillation generators (3a) are located offset with respect
to one another about said axis by substantially 180.degree. and
act on said Coriolis measuring tube (2) tangentially in the opposite
direction about said axis, and the other two oscillation generators
(3b) are offset with respect to one another about said axis by 180.degree.,
and are offset about said axis with respect to the first oscillation
generators (3a) by 90.degree., respectively, and act on said Coriolis
measuring tube 92) in the same direction radially, and the forces
exerted by the two first oscillation generators (3a) are directed
in the opposite direction to the forces exerted by the other oscillation
generators (3b).
4. The mass flow meter in accordance with any one of the claims
1 to 3 wherein said Coriolis measuring tube (2)--as viewed along
its length--has different cross-sectional shapes.
5. The mass flow meter in accordance with claim 4 wherein said
Coriolis measuring tube (2) has a circular cross-section at both
of its ends and an elliptical cross-section in the middle.
6. The mass flow meter in accordance with any one of claims 1 to
3 wherein the oscillation generators (3)--as viewed along the length
of said Coriolis measuring tube (2) --are located in the middle
of said Coriolis measuring tube (2).
7. The mass flow meter in accordance with any one of the claims
1 to 3 wherein bars (5), preferably two, three, or four bars (5),
extending--fin-like--in the longitudinal direction of said Coriolis
measuring tube (2) are provided on the inside of said Coriolis measuring
tube (2).
8. The mass flow meter in accordance with claim 7 wherein the bars
(5) are arranged so as to be distributed uniformly over the circumference
of said Coriolis measuring tube (2).
9. The mass flow meter in accordance with any one of the claims
1 to 3 wherein two sensors (4) are provided and the two sensors
(4)--viewed along the length of said Coriolis measuring tube (2)--are
arranged symmetrical to the middle of said Coriolis measuring tube
(2).
10. The mass flow meter in accordance with any one of the claims
1 to 3 wherein several sensors (4) are provided and the several
sensors--as viewed along the length of said Coriolis measuring tube
(2)--are arranged symmetrical to the middle of said Coriolis measuring
tube (2).
11. The mass flow meter in accordance with claim 10 wherein the
sensors (4) are arranged so as to be distributed uniformly over
the circumference of said Coriolis measuring tube (2).
12. The mass flow meter in accordance with any one of claims 1
to 3 wherein said Coriolis measuring tube (2) is located concentrically
within a bridge (6).
13. The mass flow meter in accordance with claim 3 wherein said
oscillation generators (3) and said at least one sensor (4) is operative
between said Coriolis measuring tube (2) and the bridge (6).
14. The mass flow meter in accordance with any one of the claims
1 to 3 wherein at least one temperature sensor is provided for
compensation of thermal influences on the measurement accuracy or
the zero point of the flow meter or both of them.
15. The mass flow meter in accordance with claim 14 wherein said
Coriolis measuring tube (2) is located concentrically within a bridge
(6) and both said Coriolis measuring tube (2) and the bridge (6)
are provided with a temperature sensor.
16. The mass flow meter in accordance with any one of claims 1
to 3 wherein said Coriolis measuring tube 92) has an elliptical,
a circular, a rectangular, or an approximately figure-eight shaped
cross-section.
17. The mass flowmeter in accordance with claim 3 wherein bars
(5), preferably two, three, or four bars (5), extending--fin-like-in
the longitudinal direction of said Coriolis measuring tube (2) are
provided on the inside of said Coriolis measuring tube (2).
18. The mass flow meter in accordance with claim 3 wherein said
Coriolis measuring tube (2) is located concentrically within a bridge
(6).
Description The invention concerns a mass flow meter for flowing media, which
operates according to the Coriolis principle, with one at least
basically straight Coriolis measuring tube, with at least one oscillation
generator acting on the Coriolis measuring tube, and with at least
one sensor detecting Coriolis forces and/or Coriolis oscillations
based on Coriolis forces.
BACKGROUND OF THE INVENTION
Mass flow meters for flowing media, which operate according to
the Coriolis principle, are known in different designs (cf. e.g.
German Patent Specification 41 24 295 and German Offenlegungsschrift
41 43 361 and the publications cited there in each case in column
1 lines 20 to 27 German Patent Specification 42 24 397 and the
publications cited there in column 1 lines 23 to 30 as well as
German Offenlegungsschrift 196 01 342) and have been increasingly
used in practice for some time.
In the case of mass flow meters for flowing media, which operate
according to the Coriolis principle, basically there are, on the
one hand, those whose Coriolis measuring tube is made at least essentially
straight, as a rule exactly straight, and, on the other hand, those
whose Coriolis measuring tube is made loop-shaped. In addition,
in the case of the mass flow meters under discussion there are,
on the one hand, those which have only one Coriolis measuring tube
and, on the other hand, those which have two Coriolis measuring
tubes. In the case of the embodiments with two Coriolis measuring
tubes, they can be hydraulically in series or parallel to one another.
Mass flow meters of the type in question, in the case of which
the Coriolis measuring tube is, or the Coriolis measuring tubes
are, made straight, with respect to their mechanical construction
are simple and can consequently be produced at relatively low cost.
In this case, it is also possible to finish or polish the inner
surfaces of the Coriolis measuring tube or Coriolis measuring tubes
well; they can be polished easily. In addition, they have a relatively
low pressure loss. In the case of mass flow meters which operate
according to the Coriolis principle, and in the case of which the
Coriolis measuring tube is made straight, or the Coriolis measuring
tubes are made straight, it can be disadvantageous that both thermally
caused expansions or stresses, as well as forces and moments acting
from outside, can lead to measurement errors and to mechanical damage,
namely stress cracks.
The experts have already dealt with the above-mentioned problems
in mass flow meters with straight Coriolis measuring tubes (cf.
in particular German Patent Specification 41 24 295 German Offenlegungsschrift
41 43 361 and German Patent Specification 42 24 379). Altogether,
a mass flow meter operating according to the Coriolis principle,
with a straight Coriolis measuring tube, which has a measurement
error of only about 0.1% (cf. the prospectus "Zulassung des
Corimass G-Gerates zum eichpflichtigen Verkehr" of the KROHNE
Me.beta.technk GmbH & Co. KG), was made successfully.
Mass flow meters operating according to the Coriolis principle,
which have only one straight Coriolis measuring tube, have considerable
advantages as compared with those mass flow meters which have either
two straight Coriolis measuring tubes or one loop-shaped Coriolis
measuring tube. The advantage as compared with mass flow meters
with two straight Coriolis measuring tubes in particular is to be
seen in the fact that flow separators or flow combiners, which are
required in the case of mass flow meters with two Coriolis measuring
tubes, are not needed. The advantage as compared with flow meters
with one loop-shaped Coriolis measuring tube, or with two loop-shaped
Coriolis measuring tubes, in particular is to be seen in the fact
that a straight Coriolis measuring tube can be easier to produce
than a loop-shaped Coriolis measuring tube, that the pressure drop
in the case of a straight Coriolis measuring tube is less than in
the case of a loop-shaped Coriolis measuring tube, and that a straight
Coriolis measuring tube can be cleaned better than a loop-shaped
Coriolis measuring tube.
However, mass flow meters which operate according to the Coriolis
principle and have one straight Coriolis measuring tube, also have
a physically, or mechanically, predetermined disadvantage (cf. European
Offenlegungsschrift 0 521 439).
The mass flow meters operating according to the Coriolis principle
require that the Coriolis measuring tube be put into oscillation,
and in particular by means of at least one oscillation generator;
the Coriolis forces, or the Coriolis oscillations, do indeed result
from the fact that the Coriolis measuring tube oscillates and from
the flowing of mass through the Coriolis measuring tube.
In the case of mass flow meters with two straight Coriolis measuring
tubes, or with one loop-shaped Coriolis measuring tube, or with
two loop-shaped Coriolis measuring tubes, the Coriolis measuring
tubes, or the parts of the loop-shaped Coriolis measuring tubes
causing oscillation, are designed identically and, as a rule, located
and excited into oscillation so that they oscillate opposite one
another. This has the positive consequence that the oscillating
system as a whole is not acting as such outwards. The position of
the center of mass remains constant and forces which appear are
compensated. Consequently, no forces and no oscillations are introduced
into the pipeline system in which this mass flow meter is installed,
and forces and oscillations of the pipeline system do not influence
the measurement result.
In the case of mass flow meters operating according to the Coriolis
principle, which have only one straight Coriolis measuring tube,
the positive consequence of the Coriolis measuring tubes oscillating
opposite one another, explained above, naturally does not occur.
The center of mass does not remain constant and forces which appear
are not compensated. The consequence of this is, on the one hand,
that forces and oscillations are transferred into the pipeline system
in which a mass flow meter is installed, and, on the other, that
forces and oscillations acting on the mass flow meter, derived from
the pipeline system, can influence the measurement result.
The known mass flow meters operating according to the Coriolis
principle, explained in detail previously, are indeed directly suitable
today for measuring the flow of liquids with a high measurement
accuracy, namely with a measurement accuracy of 0.1%. However, they
are not suited for the measurement of the flow of gases in the same
way. Consequently, the object of the invention is to provide a mass
flow meter of the type under consideration, which can also measure
the flow of gases with a high measurement accuracy.
SUMMARY OF THE INVENTION
The mass flow meter in accordance with the invention, which solves
the problem presented previously, is now first of all and essentially
characterized by the fact that the oscillation generator or the
oscillation generators is or are designed and arranged so that the
Coriolis measuring tube oscillates around its longitudinal axis.
On the one hand, in this way the Coriolis measuring tube can be
designed with a relatively short length and with a relatively large
diameter. This results in low production costs and a small pressure
loss. On the other hand, the oscillation of the Coriolis measuring
tube around its longitudinal axis realized in accordance with the
invention leads to the fact that the mass flow meter in accordance
with the invention is relatively insensitive to forces and oscillations
which are exerted on the mass flow meter by the pipeline system
in which such a mass flow meter is installed. Actually, the forces
and oscillations which are exerted on this mass flow meter by the
pipeline system in which a mass flow meter in accordance with the
invention is installed are those which act horizontally, vertically,
or axially, but not those which take effect as oscillations around
the longitudinal axis of the Coriolis measuring tube. Consequently,
forces and oscillations coming from outside practically do not influence
the oscillations of the Coriolis measuring tube around its longitudinal
axis, so that consequently such forces and oscillations also practically
do not influence the measurement result. This again has the consequence
that the mass flow meter in accordance with the invention can be
designed to be particularly measurement-sensitive, because external
influences practically do not influence the measurement result.
Finally, from this it follows that the mass flow meter in accordance
with the invention is also particularly suited for gasses as a flowing
medium, because, in this case, the Coriolis forces which appear
are relatively low, consequently a high measurement sensitivity
is required.
In the case of the mass flow meter in accordance with the invention,
the measuring tube, which can be made e.g. out of stainless steel,
Hastelloy, titanium, or zirconium, can be made entirely differently
with respect to its cross-section. In particular, the Coriolis measuring
tube can have an elliptical, a circular, a rectangular, therefore
also a square, or an approximately figure-eight cross-section.
In the case of the mass flow meter in accordance with the invention,
the cross-section of the Coriolis measuring tube--as viewed along
its length--does not have to be constant, therefore the Coriolis
measuring tube can--as viewed along its length--have a different
cross-section and/or cross-sectional shape. In particular, it can
be advantageous if the Coriolis measuring tube has a circular cross-section
on both of its ends and an elliptical cross-section in the middle.
In this case, the transition from the circular cross-section at
the ends to the elliptical cross-section in the middle naturally
should be continuous.
For the theory of the invention, it is significant that the oscillation
generator, or as a rule--the oscillation generators, is or are designed
and located so that the Coriolis measuring tube oscillates around
its longitudinal axis. In particular, this allows the designer a
number of possibilities for designing and locating the oscillation
generator or the oscillation generators. In particular, as known
in the prior art, electro-magnetic or piezo-electric oscillation
generators can be used. In any case, it is recommended that the
oscillation generator or the oscillation generators--as viewed along
the length of the Coriolis measuring tube--be located in the middle
of the Coriolis measuring tube, so that the oscillation of the Coriolis
measuring tube around its longitudinal axis, caused by the oscillation
generator or the oscillation generators, is symmetrical to the middle
of the Coriolis measuring tube. Naturally, the same result is obtained
when an oscillation generator or oscillation generators is provided
with a symmetrical distance to the middle of the Coriolis measuring
tube from both sides.
In the case of mass flow meters operating according to the Coriolis
principle, the usual oscillation generators, including both electromagnetic
as well as piezo-electric oscillation generators, initially generate
a back and forth motion. There are different possibilities for having
the result intended by the invention be achieved by this back and
forth motion of the oscillation generator, namely an oscillation
of the Coriolis measuring tube around its longitudinal axis. An
embodiment of the mass flow meter in accordance with the invention,
preferred in this respect, is characterized by the fact that two
oscillation generators are provided and the two oscillation generators
act on the Coriolis measuring tube preferably offset by 180.degree.
in the same direction tangentially. Instead of providing only two
oscillation generators, an even greater number of oscillation generators
can be provided, for example four oscillation generators can be
provided, the oscillation generators then acting on the Coriolis
measuring tube preferably offset by 90.degree. in the same direction
tangentially. In the same direction means here that all oscillation
generators are operative e.g. in the clockwise direction at the
same time or in the counterclockwise direction at the same time.
According to a further theory of the invention, which has a very
special significance, a preferred embodiment of the mass flow meter
in accordance with the invention is to characterized by the fact
that four oscillation generators are provided, that the oscillation
generators act on the Coriolis measuring tube preferably offset
by 90.degree., that two oscillation generators offset by 180.degree.
act on the Coriolis measuring tube in the opposite direction tangentially
and the two other oscillation generators, offset by 180.degree.
with respect to one another and in each case offset by 90.degree.
with respect to the first two oscillation generators, act on the
Coriolis measuring tube in the same direction radially, and that
the forces exerted by the two first oscillation generators are directed
in the opposite direction to the forces exerted by the other two
oscillation generators. The result of this is that, at any moment,
on the one hand the sum of the forces exerted by the oscillation
generators on the Coriolis measuring tube--and naturally also the
sum of all reaction forces--is zero, that, on the other hand, the
position of the center of mass of the Coriolis measuring tube--and
that, in addition to this, the position of the center of mass of
the mass flow meter in accordance with the invention as a whole--remains
constant. The extremely important consequence of this is that the
mass flow meter so designed is free of the disadvantages described
initially, which actually are characteristic of mass flow meters
which operate according to the Coriolis principle and have only
one straight Coriolis measuring tube.
According to a further theory of the invention, which again acquires
considerable special significance, a special embodiment of the mass
flow meter in accordance with the invention is characterized by
the fact that bars, preferably two, three, or four bars, under certain
circumstances even more bars, extending--like fins--in the longitudinal
direction of the Coriolis measuring tube, are provided on the inside
of the Coriolis measuring tube, the bars being arranged so that
they are distributed preferably regularly over the circumference
of the Coriolis measuring tube. The Coriolis forces which appear
act on the bars provided on the inside of the Coriolis measuring
tube and thus on the Coriolis measuring tube.
In the case of all embodiments of mass flow meters in accordance
with the invention described until now, the designer has extensive
freedom with respect to the configuration and arrangement of the
sensors. The sensors can, as known in the prior art, also be designed
like the oscillation generators, e.g. electro-magnetically or piezo-electrically.
Moreover, it is recommended that two sensors be provided and that
the two sensors --as viewed along the length of the Coriolis measuring
tube--be arranged symmetrical to the middle of the Coriolis measuring
tube. Naturally there is also the possibility of providing more
than two sensors, namely--as viewed along the length of the Coriolis
measuring tube--in each case providing several sensors symmetrical
to the middle of the Coriolis measuring tube and arranging the sensors
so that they are distributed uniformly over the circumference of
the Coriolis measuring tube.
Previously it was stated that the mass flow meter under consideration
has a straight Coriolis measuring tube, at least one oscillation
generator acting on the Coriolis measuring tube, and at least one
sensor detecting Coriolis forces and/or Coriolis oscillations based
on Coriolis forces. As known in the prior art, in the case of the
mass flow meter in accordance with the invention, the Coriolis measuring
tube can also be located concentrically within a bridge preferably
made circular-cylindrical. In this case, it is recommended that
the oscillation generator or the oscillation generators and the
sensor or the sensors be located between the Coriolis measuring
tube and the bridge so that the oscillation generator or the oscillation
generators and the sensor or the sensors are operative between the
Coriolis measuring tube and the bridge.
Finally, it is recommended that at least one temperature sensor
for compensation of thermal influences on the measurement accuracy
and/or the zero point, as known in the prior art, also be provided
in the case of the mass flow meter in accordance with the invention
If the mass flow meter in accordance with the invention, has a bridge
holding the Coriolis measuring tube as described previously, it
is recommended that both the Coriolis measuring tube as well as
the bridge be provided with a temperature sensor.
In particular there are now a number of possibilities for designing
and developing the mass flow meter in accordance with the invention.
For these, refer to the dependent claims on the one hand, and the
description of preferred embodiments in connection with the drawings
on the other hand .
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIGS. 1a to 1c show a graphic representation for the general explanation
of the teaching of the invention,
FIG. 2 shows a preferred embodiment of a Coriolis measuring tube
belonging to a mass flow meter in accordance with the invention,
FIG. 3 shows a longitudinal section through a first embodiment
of a mass flow meter in accordance with the invention,
FIG. 4 shows a longitudinal section through a second embodiment
of a mass flow meter in accordance with the invention,
FIG. 5 shows a cross-section through a preferred embodiment of
a mass flow meter in accordance with the invention,
FIG. 6 shows a graphic representation for explaining a further
embodiment of the invention,
FIG. 7 shows a graphic representation for explaining the Coriolis
forces appearing in the case of the embodiment of the invention
in accordance with FIG. 6
FIG. 8 shows a graphic representation corresponding to FIG. 7
FIG. 9 shows a graphic representation--corresponding to FIGS. 1
and 6--for explaining a further embodiment of a mass flow meter
in accordance with the invention,
FIG. 10 shows a cross-section through differently designed embodiments
of a further embodiment of a mass flow meter in accordance with
the invention,
FIG. 11 shows a perspective representation of a flow meter in FIG.
10 and
FIG. 12 shows a graphic representation for explaining the embodiment
of a mass flow meter in accordance with the invention which is shown
in FIGS. 10 and 11.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The mass flow meter for flowing media in accordance with the invention,
in particular for gasses, is one which operates in accordance with
the Coriolis principle. In the first place, as a rule, but not functionally
necessarily, a housing 1 indicated only in FIGS. 3 and 4 belongs
to the mass flow meter in accordance with the invention. An at least
essentially, as a rule and in the embodiment shown exactly, straight
Coriolis measuring tube 2 at least one oscillation generator 3
acting on the Coriolis measuring tube 2 and at least one sensor
4 as a rule two sensors 4 detecting Coriolis forces and/or Coriolis
oscillations caused by Coriolis forces are functionally necessary
for the mass flow meter in accordance with the invention.
In accordance with the invention, the oscillation generators 3
in the first place are designed and arranged so that the Coriolis
measuring tube 2 oscillates around its longitudinal axis.
In particular, it can be deduced from FIGS. 1 5 and 6 that the
Coriolis measuring tube 2 can have an elliptical cross-section.
In the embodiment shown in FIG. 9 the Coriolis measuring tube 2
has an approximately figure eight-shaped cross-section. As FIG.
9 shows, this is not a strictly figure eight-shaped cross-section
here. The cross-section shown here also can be called a double-circular
cross-section, two circular partial cross-sections being connected
with one another by means of a neck-like middle part. For the embodiment
to which FIGS. 10 11 and 12 refer, it is the case that the Coriolis
measuring tube 2 has a circular cross-section.
Moreover, it can be deduced from FIGS. 2 and 4 that the Coriolis
measuring tube 2 --as viewed along its length--can have different
cross-sections or different cross-sectional shapes. In both embodiments,
the Coriolis measuring tube 2 has a circular cross-section on both
of its ends and an elliptical cross-section in the middle, in which
case, as FIG. 2 shows in particular, the transition is continuous
from the circular cross-section on both ends to the elliptical cross-section
in the middle.
In FIG. 1a, the arrows indicate that the Coriolis measuring tube
2 oscillates around its longitudinal axis, on the one hand counterclockwise,
on the other hand clockwise. The entry side end of the Coriolis
measuring tube 2 is on the left, the middle of the Coriolis measuring
tube 2 is in the middle, and the exit side end of the Coriolis measuring
tube 2 is shown on the right. This obtains also for FIGS. 1b and
1c.
In FIG. 1b, the arrows indicate how the emerging Coriolis forces
act in the case of a medium flowing through the Coriolis measuring
tube 2. The effects on the exit side end of the Coriolis measuring
tube 2 are opposed to the effects on the entry side end of the Coriolis
measuring tube 2. Coriolis forces do not appear in the middle of
the Coriolis measuring tube 2.
The arrows in FIG. 1c, show, on the one hand, the oscillation of
the Coriolis measuring tube 2 around its longitudinal axis, and,
on the other hand, the effects of the Coriolis forces which appear.
Two oscillation generators 3 are provided for the embodiments of
mass flow meters in according with the invention to which FIGS.
3 4 and 5 refer, and the two oscillation generators 3 act on the
Coriolis measuring tube 2 offset by 180.degree. in the same direction
tangentially. There is also the possibility of providing more than
two oscillation generators 3 for example four oscillation generators
3 which then act on the Coriolis measuring tube 2 offset by 90.degree.
in the same direction tangentially.
In the case of the embodiment of a mass flow meter in accordance
with the invention to which FIGS. 6 7 and 8 refer, a further embodiment
of the invention is realized, which acquires very special significance.
Four oscillation generators 3a, 3a, 3b, 3b are provided for this
embodiment, the oscillation generators acting on the Coriolis measuring
tube being offset by 90.degree.. Two oscillation generators 3a located
offset with respect one another by 180.degree. act on the Coriolis
measuring tube in the opposite direction tangentially, and the two
other oscillation generators 3b offset by 180.degree. with respect
to one another and with respect to the first two oscillation generators
3a in each case by 90.degree., act on the Coriolis measuring tube
2 in the same direction radially. The forces exerted by the first
two oscillation generators 3a are directed in the opposite direction
to the forces exerted by the other two oscillation generators 3b.
In this way, it is achieved that, at any moment, on the one hand
the sum of the forces exerted by the oscillation generators 3a and
3b on the Coriolis measuring tube 2--and naturally also the sum
of all reaction forces--is zero, and that, on the other hand, the
position of the center of mass of the Coriolis measuring tube and
that, in addition to this, the position of the center of mass of
the mass flow meter in accordance with the invention as a whole-remains
constant. The pronounced positive consequence of this is that the
mass flow meter thus designed is free of the disadvantages described
initially, which are actually characteristic of mass flow meters
which operate according to the Coriolis principle and have only
one straight Coriolis measuring tube 2.
The arrows in FIGS. 7 and 8 show how the Coriolis forces act on
the Coriolis measuring tube 2 when the oscillation generators 3a
and 3b act on the Coriolis measuring tube 2 as is shown in FIG.
6.
If only for the sake of accuracy, it is to be noted that the deformations
of the Coriolis measuring tube 2 appearing because of the oscillation
generators 3a and 3b, on the one hand, and those appearing as a
result of the Coriolis forces, on the other hand, are shown very
exaggerated.
FIGS. 10 11 and 12 show an embodiment of a mass flow meter in
accordance with the invention which is additionally characterized
by the fact that bars 5 extending--like fins--in the longitudinal
direction of the Coriolis measuring tube 2 namely three bars 5
in the left part of FIG. 10 four bars 5 in the right-hand part
of FIG. 10 and two bars 5 in the middle part of FIG. 10 as well
in FIGS. 11 and 12 are provided on the inside of the Coriolis measuring
tube 2. In this case, the bars 5 as FIGS. 10 11 and 12 show,
are arranged so as to be distributed uniformly over the circumference
of the Coriolis measuring tube 2. The Coriolis forces which appear,
as indicated in FIG. 12 act on the bars 5 provided on the inside
of the Coriolis measuring tube 2 and thus on the Coriolis measuring
tube 2.
The designer has extensive freedom with respect to the sensors
4 provided in the case of the mass flow meters in accordance with
the invention, and indeed both with respect to the design as well
as with respect to the arrangement of the sensors 4. In particular,
as is known in the prior art, e.g electromagnetic or piezo-electric
sensors 4 as well as oscillation generators 3 can be used.
FIGS. 3 and 4 show that in each case four sensors 4 are provided.
The sensors 4--as viewed along the length of the Coriolis measuring
tube--are located symmetrical to the middle of the Coriolis measuring
tube, moreover uniformly over the circumference of the Coriolis
measuring tube 2.
FIGS. 3 and 4 show embodiments of mass flow meters in accordance
with the invention whose Coriolis measuring tube 2 is located concentrically
within a circular-cylindrically designed bridge 6. In the case of
this embodiment then, in each case, the oscillation generators 3
and the sensors 4 are operative between the Coriolis measuring tube
2 and the bridge 6.
Finally, in accordance with the invention, at least one temperature
sensor 7 (FIG. 4) can be provided for compensation of thermal influences
on the measuring accuracy and/or the zero point. Preferably, both
the Coriolis measuring tube 2 and the bridge 6 are provided with
a temperature sensor. |