Note: Descriptions are shown in the official language in which they were submitted.
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Method For Measuring A Medium Flowing In A Pipeline And Measurement
System Therefor
FIELD OF THE INVENTION
The invention relates to a method for measuring at least one physical, flow
parameter, especially a mass flow and/or a density and/or a viscosity, of a
two,
or more, phase medium flowing in a pipeline, as well as a measurement system
suited therefor.
BACKGROUND OF THE INVENTION
In process measurements and automation technology, for the highly accurate
measurement of physical parameters, such as e.g. mass flow, density and/or
viscosity, of a medium flowing in a pipeline, for example a gas and/or a
liquid,
often such inline measuring devices are used, which, by means of a
measurement pickup, or transducer, of vibration-type, through which the
medium is flowing, and a measurement and operating circuit connected thereto,
effect reaction forces in the medium, forces such as e.g. Coriolis forces
corresponding with mass flow, inertial forces corresponding with density, or
frictional forces corresponding with viscosity, etc., and produce, derived
from
these, a measurement signal representing, for the medium, mass flow, viscosity
and/or density, as the case may be. Such inline measuring devices with a
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measurement pickup of vibration-type, as well as their manner of operation,
are
known per se to those skilled in the art and are described comprehensively and
in detail e.g. in WO-A 03/095950, WO-A 03/095949, WO-A 02/37063, WO-A
01/33174, WO-A 00/57141, WO-A 99/39164, WO-A 98/07009, WO-A
95/16897, WO-A 88/03261, US 2003/0208325, US-B 6,880,410, US-B
6,691,583, US-B 6,651,513, US-B 6,513,393, US-B 6,505,519, US-A 6,006,609,
US-A 5,869,770, US-A 5,861,561, US-A 5,7 96,011, US-A 5,616,868, US-A
5,602,346, US-A 5,602,345, US-A 5,531,126, US-A 5,359,881, US-A 5,301,557,
US-A 5,253,533, US-A 5,218,873, US-A 5,069,074, US-A 4,876,898, US-A
4,733,569, US-A 4,660,421, US-A 4,524,610, US-A 4,491,025, US-A 4,187,721,
EP-A 1 291 639, EP-A 1 281 938, EP-A 1 001 254 or EP-A 553 939.
For the conveying of the flowing medium, the measurement pickups include, in
each case, at least one measuring tube with a bent and/or straight tube
segment, which is caused, during operation, to vibrate, driven by an
electromechanical exciter mechanism, for producing the above-mentioned,
reaction forces. The measuring tube is held in a support frame most often
embodied as a closed, pickup housing. For registering vibrations, especially
inlet-side and outlet-side vibrations, of the tube segment, the measurement
pickups further include, in each case, a sensor arrangement reacting to
movements of the tube segment.
In the case of Coriolis mass flow measuring devices, measurement of the mass
flow of a medium flowing in a pipeline rests, as is known, on the allowing of
the
medium to flow through the measuring tube inserted into the pipeline and
oscillating during operation, at least in part, laterally to a measuring tube
axis,
whereby Coriolis forces are induced in the medium. These forces, in turn,
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effect, that inlet end and outlet end regions of the measuring tube oscillate
shifted in phase relative to one another. The size of these phase shifts
serves,
in such case, as a measure for the mass flow rate. The oscillations of the
measuring tube are, therefore, registered by means of two oscillation sensors
of
the aforementioned sensor arrangement spaced from one another along the
measuring tube and transformed into oscillation measurement signals, from
whose phase shift with respect to one another the mass flow is derived.
Already
the initially referenced US-A 4,187,721 mentions, additionally, that also the
instantaneous density of the flowing medium is measurable by means of such
inline measuring devices, and, indeed, on the basis of a frequency of at least
one of the oscillation measurement signals delivered by the sensor
arrangement. Moreover, most often, also a temperature of the medium is
directly measured in suitable manner, for example by means of a temperature
sensor arranged on the measuring tube. Additionally, straight measuring tubes
can, when excited to torsional oscillations about a torsional oscillation axis
essentially extending parallel to, or coinciding with, the pertinent measuring
tube
longitudinal axis, effect that radial shear forces are produced in the medium
conveyed therethrough, whereby, in turn, significant oscillatory energy is
withdrawn to the torsional oscillations and dissipated in the medium. As a
result
thereof, a considerable damping of the torsional oscillations of the
oscillating
measuring tube occurs, so that, to maintain the torsional oscillations,
additional
electrical exciting power must be supplied to the measuring tube. Derived from
a correspondingly required electrical exciting power for the maintaining of
the
torsional oscillations of the measuring tube, it is possible, in manner known
to
those skilled in the art, so also to determine, at least approximately, a
viscosity
of the medium; compare, in this connection, especially also US-A 4,524,610,
US-A 5,253,533, US-A 6,006,609 or US-B 6,651,513. It is possible, therefore,
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to assume, without more, in the following that, even when not expressly
described, modern inline measuring devices with measurement pickups of
vibration-type, especially Coriolis mass flow measuring devices, can be used,
in
any case, also to measure density, viscosity and/or temperature of the medium,
especially since these variables are often drawn upon, in the case of mass
flow
measurement, in any event, for the compensating of measurement errors
arising due to fluctuating medium density and/or viscosity; compare, in this
connection, especially the already mentioned US-B 6,513,393, US-A 6,006,609,
US-A 5,602,346, WO-A 02/37063, WO-A 99/39164 or also WO-A 00/36379.
Besides such measurement pickups, or transducers, of vibration type,
frequently also inline measuring devices with magneto-inductive pickups, or
transducers, or measurement pickups, or transducers, evaluating the travel
time
of ultrasonic waves emitted in the stream direction, especially also those
working on the basis of the Doppler principle, are used in process
measurements and automation technology for inline measurements. Since the
principles of construction and manner of functioning of such magnetic-
inductive
measurement pickups are described adequately e.g. in EP-A 1 039 269, US-A
6,031,740, US-A 5,540,103, US-A 5,351,554, US-A 4,5 63 904, etc., and the
principles of construction and manner of functioning of such ultrasonic
measurement pickups are described adequately e.g. in US-B 6,397,683, US-B
6,330,831, US-B 6,293,156, US-B 6,189,389, US-A 5,531,124, US-A 5,463,905,
US-A 5,131,279, US-A 4,787,252 etc., and, moreover, are likewise sufficiently
known to those skilled in the art, a detailed explanation of these principles
of
measurement can be omitted here.
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In the use of such inline measuring devices comprising at least one measuring
tube joined into the course of the pipeline conveying the medium, it has,
however, been found, that, in the case of inhomogeneous media, especially
two, or more, phase media, the measurement signals produced therewith can
5 be subject, to a considerable degree, to non-reproducible fluctuations, even
though the medium parameters significantly influencing the measurement
signals, especially the mass flow rate, are held essentially constant;
compare, in
this connection, also the initially mentioned US-B 6,910,366, US-B 6,880,410,
US-B 6,505,519, US-B 6,311,136 or US-A 5,400,657. As a result, these
measurement signals in the case of multiphase streams of medium are
practically unusable for a highly accurate measurement of the physical flow
parameter of interest. Such inhomogeneous media can be, for example, liquids,
in which, as e.g. practically unavoidable in metering or bottling processes, a
gas
present in the pipeline, particularly air, is entrained, or from which a
dissolved
medium, e.g. carbon dioxide, outgasses and leads to foam formation. As
further examples of such inhomogeneous media, also emulsions, wet, or
saturated, steam, as well as fluids carrying solid particles can be mentioned.
Especially in the case of inline measuring devices comprising a measurement
pickup of vibration-type, such as, for example, also discussed in JP-A 10-
281846, EP-A 1 291 639, US-B 6,880,410, US-B 6,505,519, it has been found
that the oscillation measurement signals derived from the oscillations of the
measurement tube, especially also the mentioned phase shift, are, in the case
of two, or more, phase media, and in spite of keeping the mass flow rate, as
well as also viscosity and density in the separate phases of a medium,
practically constant and/or appropriately taking such into consideration,
subject
to fluctuations to a significant degree and, therefore, in given instances,
can be
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completely unusable for measuring the physical flow parameter of interest,
unless remedial measures are undertaken. Mentionable as reasons for the
measurement errors accompanying the measurement of inhomogeneous media
by means of measurement pickups of vibration-type include, for example, the
unilateral clinging or depositing of liquid-entrained, gas bubbles or solid
particles
on the measuring tube wall, and the so-called "bubble-effect", in the case of
which gas bubbles entrained in the liquid act as flow bodies for liquid volume
elements accelerated transversely to the longitudinal axis of the measuring
tube.
For lessening the measurement errors accompanying two, or more, phase
media, US-B 6,880,410, for example, proposes a flow, or medium, conditioning
to precede the actual flow measurement. As another possibility for escaping
the
problems of such measurement pickups in connection with inhomogeneous
media, for example, both in JP-A 10-281846, as well as also in US-B 6,505,519,
a correction of the flow measurement, especially of the mass flow
measurement, determined from the oscillation measurement signals, is made.
The correction is based especially on the evaluation of deficits between a
highly
accurately measured, actual density of the medium and an apparent density of
the medium determined during operation using Coriolis mass flow measuring
devices. Further methods for avoiding and/or correction of measurement errors
associated with two, or more, phase media, beyond those mentioned above, are
described in US-A 2005/0081643, US-A 2005/0022611, WO-A 2005/057137 or
WO-A 2005/057131.
Alternatively or in supplementation thereof, additionally, also measurement
systems, especially diversely operating measurement systems, formed by
II
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means of a plurality of inline measuring devices and disclosed e.g. in
US-A 5,400,657, US-A 5,259,250, US-A 2005/0016292 or WO-A 03/062759,
WO-A 03/073047, WO-A 03/087735, or WO-A 04/046660, can be applied for
measuring two, or more, phase media. However, a significant disadvantage of
such,
actually quite precisely measuring, measurement systems can reside in their
increased complexity and the accompanying high installation costs, on the one
hand,
and the high servicing and maintenance costs, on the other hand. Moreover,
such
measurement systems possess, most often, a relatively high requirement for
space.
SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided a method for
measuring at
least one flow parameter of a medium flowing in a pipeline, said flow
parameter
selected from a group consisting of: a flow velocity, a mass flow, and a
volume flow,
said method comprising: causing the medium to be measured to flow through at
least
one measuring tube joined into the course of the pipeline; producing at least
one
measurement signal influenced by at least one physical parameter of the medium
in
the measuring tube, using an inline measuring device sensor arrangement
arranged
on the measuring tube and reacting to changes of the at least one physical
parameter
of the medium; registering pressures effective in the medium, in order to
repeatedly
determine a pressure difference existing in the flow medium; and using a
pressure
difference currently determined for the flowing medium and a transfer function
for
producing measured values of a first kind, which represent, following one
after the
other in time, the at least one flow parameter to be measured, said transfer
function
determining how the measured values of the first kind are generated based on
said
pressure difference currently determined for the flowing medium; using said at
least
one measurement signal produced by means of the inline measuring device for
producing a measured values of a second kind, said measured values of the
second
kind representing said physical parameter of the medium in the measuring tube,
said
physical parameter selected from a group consisting of: a flow velocity, a
mass flow
or a volume flow, a density, and a viscosity; and using at least one of said
measured
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values of the second kind for adapting said transfer function to the medium to
be
measured.
There is also provided a measuring system for measuring at least one physical,
flow
parameter of a medium flowing in a pipeline, said flow parameter selected from
a
group consisting of a flow velocity, a mass flow or a volume flow, said
measuring
system comprising: an inline measuring device for flowing media, said inline
measuring device including a flow pickup, and a measuring device electronics
electrically coupled with the flow pickup, and said flow pickup including at
least one
measuring tube inserted into the course of the pipeline conveying the medium;
and a
pressure-difference measuring device including a first pressure pickup for
registering
a first pressure existing in the medium, and a second pressure pickup for
registering
a second pressure existing in the medium, and said pressure-difference
measuring
device including measuring device electronics electrically coupled with the
pressure
pickups and electrically coupled with the measuring device electronics of the
inline
measuring device; wherein: at least one of the two measuring device
electronics is
provided to produce, on the basis of a transfer function stored therein, and
based on
the pressures registered by means of the first and second pressure pickups,
measured values of a first kind, which represent, in time following one after
the other
the at least one flow parameter of the medium to be measured, and the
measuring
device electronics of the inline measuring device is provided to produce
measured
values of a second kind, which represent, in time following one after the
other at least
one physical parameter of the medium in the at least one measuring tube, said
physical parameter selected from a group consisting of: a flow velocity, a
mass flow
or a volume flow, a density, and a viscosity; and wherein the transfer
function
determines how the measured values of the first kind are generated on the
basis of
the currently registered, first and second pressures, and the transfer
function adapted
to the medium to be measured based on at least one of the measured values of
the
second kind produced by means of the inline measuring device.
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Another aspect of the invention relates to use of such a measurement system
for
measuring at least one of: a mass flow, or volume flow, and a flow velocity of
a
multiphase medium flowing in a pipeline.
A further aspect of the invention relates to use of such a measurement system
for
performing such a method.
Embodiments of the invention may provide a method, which is suited for
measuring,
on the one hand, flow velocity, mass flow or volume flow of a medium flowing
in a
pipeline, as accurately as possible, also for the case in which the medium is
formed
of two, or more, phases, and, on the other hand, for the case, in which the
medium is
essentially of one phase, so accurately that any measurement error is
essentially
smaller than 5%, especially smaller than 1 %. Additionally, it is an object of
the
invention to provide a correspondingly suited measurement system, especially
also a
measurement system using principles of diversity, which can be constructed as
simply and/or as modularly as possible, especially by using conventional
inline
measuring devices.
An embodiment of the invention resides in a method for measuring at least one
flow
parameter, especially a flow velocity, mass flow rate or volume flow rate, of
a medium
flowing in a pipeline and which, at least at times, is of two, or
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more, phases, of which at least one phase is fluid, which method includes the
following steps:
- allowing the medium to be measured to flow through at least one measuring
tube of an inline measuring tube of an inline measuring device for flowing
media, the measuring tube being joined into the course of the pipeline and
being, especially, a measuring tube which vibrates, at least at times;
- producing at least one measurement signal influenced by at least one
physical
parameter, especially a flow velocity, a mass flow rate, a volume flow rate, a
density and/or a viscosity of the medium in the measuring tube, using a sensor
arrangement of the inline measuring device, the sensor arrangement being
arranged on the measuring tube and/or in its vicinity and reacting, at least
mediately, to changes of the at least one physical parameter of the medium;
- registering pressures effective in the medium, especially static pressures,
for
the repeated determining of a pressure difference prevailing in the flowing
medium, especially at least in part along the at least one measuring tube; and
- producing measured values of a first kind, which represent, following one
after
the other in time, and especially digitally, the at least one flow parameter
of the
medium to be measured, taking into consideration a pressure difference
currently determined for the flowing medium and applying a transfer function;
- wherein the transfer function at least determines how the measured values of
the first kind are generated using the pressure difference currently
determined
for the flowing medium; and
- wherein the transfer function is repeatedly adapted to the medium to be
measured, taking into consideration the at least one measurement signal
produced by means of the sensor arrangement of the inline measuring device.
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Furthermore, some embodiments of the invention reside in a measurement
system for measuring at least one physical flow parameter, especially a mass
and/or volume, flow and/or a flow velocity, of an, at least at times, two, or
more,
phase medium flowing in a pipeline, of which at least one phase is fluid,
which
measurement system includes:
- an inline measuring device for flowing media, which measuring device
includes a flow pickup, as well as a measuring device electronics electrically
coupled, at least at times, with the flow pickup, with the flow pickup
including at
least one measuring tube inserted into the course of the pipeline conveying
the
medium, especially a measuring tube vibrating, at least at times, during
operation; and
- a pressure-difference measuring device comprising a first pressure pickup,
especially one arranged on the inlet side of the flow pickup, for registering
a first
pressure prevailing in the medium, and a second pressure pickup, especially
one arranged on the outlet side of the flow pickup, for registering a second
pressure prevailing in the medium, as well as a measuring device electronics,
which is electrically coupled, at least at times, with the pressure pickups
and at
least at times with the measuring device electronics of the inline measuring
device;
- wherein at least one of the two measuring device electronics produces, using
a transfer function stored therein, as well as based on the pressures
registered
by means of the first and second pressure pickups, at least at times, measured
values of a first kind, which represent, following one after the other in
time,
especially digitally, the at least one flow parameter of the medium to be
measured;
- wherein the measuring device electronics of the inline measuring device
produces, at least at times, measured values of a second kind, which
represent,
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following one after the other in time, especially digitally, the at least one
parameter of the medium in the at least one measuring tube, or a measured
variable of the medium derived therefrom; and
- wherein the transfer function at least determines how the measured values of
5 the first kind are generated on the basis of the currently registered, first
and
second pressures, and, taking into consideration at least one of the measured
values of the second kind produced by the inline measuring device, is
repeatedly adapted to the medium to be measured.
10 In a first embodiment of the method of the invention, the at least one
measuring
tube vibrates, at least at times, during operation.
In a second embodiment of the method of the invention, the method further
includes steps of producing measured values of a second kind, which represent,
on the basis of the at least one measurement signal produced by means of the
inline measuring device, following one after the other in time, the at least
one
parameter of the medium in the measuring tube or a measured variable of the
medium derived therefrom. In a first, further development of the first
embodiment of the invention, measured values of the first kind and measured
values of the second kind are produced essentially simultaneously, or, at
least,
near in time to one another. In a second, further development of the first
embodiment of the invention, measured values of the first kind and measured
values of the second kind are produced essentially asynchronously, or, at
least,
shifted in time, especially alternately. In a third, further development of
the first
embodiment of the invention, measured values of the second kind are
produced, at least timewise, when the medium is developed essentially as one
phase, or, at least, assumed to be developed as one phase.
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In a fourth, further development of the first embodiment of the invention, the
measured values of the second kind are determined at least in part, on the
basis of the registered vibrations of the measuring tube.
In a fifth, further development of the first embodiment of the invention, the
measured values of the second kind are generated, at least timewise and/or at
least in part based on an oscillation frequency of the vibrating measuring
tube,
especially an oscillation frequency determined using the at least one
measurement signal.
In a sixth, further development of the first embodiment of the invention, such
further includes steps of producing at least a first measurement signal
representing vibrations of the measuring tube, especially a measurement signal
representing inlet-side vibrations of the measuring tube, by means of a first
oscillation sensor of the sensor arrangement, and a second measurement
signal representing vibrations of the measuring tube, especially a measurement
signal representing outlet-side vibrations of the measuring tube, by means of
a
second oscillation sensor of the sensor arrangement, with the sensor
arrangement of the inline measuring device comprising at least two oscillation
sensors spaced from one another, especially in the flow direction of the
medium, and, in each case, arranged on the measuring tube and/or in its
vicinity. Especially, it is provided in the case of this further development,
that
the measured values of the second kind represent a mass flow or a volume
flow, of the medium, with the at least two measurement signals produced by
means of the sensor arrangement of the inline measuring device being used for
determining at least one of these measured values of the second kind.
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In a seventh, further development of the first embodiment of the invention,
the
measured values of the second kind are determined, as least at times and/or at
least in part, based on a phase difference existing between the first and the
second measurement signals.
In an eighth, further development of the first embodiment of the invention,
the
measured values of the second kind represent a parameter of the medium,
which corresponds essentially to the flow parameter representing the measured
values of the first kind.
In a ninth, further development of the first embodiment of the invention, the
measured values of the second kind represent a density of the medium in the
measuring tube.
In a tenth, further development of the first embodiment of the invention, the
measured values of the second kind represent a viscosity of the medium in the
measuring tube.
In a third embodiment of the method of the invention, such further includes
steps of repeatedly monitoring the flowing medium, especially using the at
least
one measurement signal produced by means of the inline measuring device.
In a fourth embodiment of the method of the invention, such further includes a
step of detecting that the medium is developed at least as two phases.
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In a fifth embodiment of the method of the invention, the inline measuring
device further includes an electrical-to-physical exciter mechanism arranged
on
the at least one measuring tube and acting, at least mediately, on the medium
conveyed therein.
In a sixth embodiment of the method of the invention, the step of producing
the
first measurement signal includes the following additional steps:
- producing, by means of the exciter mechanism of the inline measuring device,
reactions in the medium corresponding to the at least one physical parameter
of
the medium in the measuring tube; and
- registering, by means of the sensor arrangement of the inline measuring
device, reactions of the medium corresponding to the at least one physical
parameter of the medium in the measuring tube.
In a seventh embodiment of the method of the invention, the inline measuring
device involves a measurement pickup of vibration-type, and the step of
producing reactions in the medium corresponding with the at least one physical
parameter of the medium in the measuring tube includes a step of causing the
measuring tube to vibrate for producing, in the medium conveyed therein,
reaction forces, especially inertial forces, frictional forces and/or Coriolis
forces,
influenced by vibrations of the measuring tube.
In an eighth embodiment of the method of the invention, the step of
registering
reactions of the medium corresponding with the at least one physical parameter
of the medium in the measuring tube by means of the sensor arrangement
further includes a step of registering vibrations of the measuring tube.
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In a ninth embodiment of the method of the invention, the sensor arrangement
of the inline measuring device includes at least one oscillation sensor
arranged
on the measuring tube and/or in its vicinity, and the at least one measurement
signal produced by means of the sensor arrangement of the inline measuring
device represents vibrations of the measuring tube.
In a tenth embodiment of the method of the invention, the steps of registering
pressures effective in the medium include steps of registering at least one
pressure effective in the flowing medium at the inlet side of the at least one
measuring tube and/or steps of registering at least one pressure effective in
the
flowing medium at the outlet side of the at least one measuring tube.
In an eleventh embodiment of the method of the invention, at least at times,
at
least a first pressure registered at the inlet side of the measuring tube and
at
least a second pressure registered at the outlet side of the measuring tube,
especially a pressure difference in the flowing medium determined on the basis
of the first and second pressures, are/is taken into consideration in the
producing of the measured values representing the at least one, physical, flow
parameter.
In a twelfth embodiment of the method of the invention, for registering
pressures
existing in the flowing medium, at least two pressure pickups are used, of
which
a first pressure pickup is located at the inlet side of the at least one
measuring
tube and a second pressure pickup is located at the outlet side of the at
least
one measuring tube.
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In a thirteenth embodiment of the method of the invention, the steps of
registering pressures effective in the medium include steps of transmitting
pressures registered by means of the first and second pressure pickups via
pressure intermediaries to a pressure measurement cell, especially a pressure
measurement cell measuring differentially and/or capacitively.
In a fourteenth embodiment of the method of the invention, the steps of
registering pressures effective in the medium include steps of converting
pressures transmitted to the pressure measurement cell into at least one
measurement signal, which reacts to time changes of at one of the registered
changes with a corresponding change of at least one of its characteristics.
In a fifteenth embodiment of the method of the invention, the transfer
function is
a static, especially non-linear, characteristic curve function.
In a sixteenth embodiment of the method of the invention, for adapting the
transfer function to the medium to be measured, at least one coefficient
describing the transfer function is changed using the at least one measurement
signal produced by means of the sensor arrangement of the inline measuring
device.
In a seventeenth embodiment of the method of the invention, the transfer
function is a static, especially non-linear function, and, for adapting the
transfer
function to the medium to be measured, at least one coefficient describing the
transfer function is changed using at least one of the measured values of the
second kind.
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In a first embodiment of the measurement system of the invention, the flow
pickup delivers at least one measurement signal representing at least one
vibration of the at least one measuring tube.
In a second embodiment of the measurement system of the invention, the at
least one measuring tube is essentially straight.
In a third embodiment of the measurement system of the invention, the at least
one measuring tube is curved, especially U- or V-shaped.
In a fourth embodiment of the measurement system of the invention, such
further includes two measuring tubes, especially ones running essentially
parallel to one another and/or essentially of equal structures, inserted into
the
course of the pipeline.
In a fifth embodiment of the measurement system of the invention, the two
pressure pickups are connected with a pressure measurement cell, especially
one measuring differentially and/or capacitively, to form a pressure-
difference
pickup.
In a sixth embodiment of the measurement system of the invention, the
pressure-difference pickup delivers at least one measurement signal
representing a pressure difference in the flowing medium.
In a seventh embodiment of the measurement system of the measurement
system of the invention, such includes a first measuring device electronics,
as
well as a second measuring device electronics communicating, at least at
times,
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therewith, with the flow pickup being electrically coupled with the first
measuring
device electronics to form an inline measuring device, especially a Coriolis
mass
flow/density measuring device, for media flowing in pipelines, with the two
pressure pickups being electrically coupled with the second measuring device
electronics to form a pressure-difference measuring device for media flowing
in
pipelines.
A basic idea of an embodiment of the invention is to create a measurement
system with diversity, which is suited, on the one hand, to measure flow
parameters of the described kind accurately, also in the case of two, or more,
phase media, and by which, on the other hand, at least one of the measuring
devices (the pressure-difference measuring device) is recalibratable
repeatedly
during operation, using the other measuring device (here, the inline measuring
device) as master-unit. Another basic idea of an embodiment of the invention
is
to use the at least one measuring tube of the inline measuring device as a
substitute for the orifice usually applied in conventional pressure-difference
measuring devices for producing pressure drops, whereby, on the one hand, one
flow-relevant component is saved and, on the other hand, in comparison to a
serial connecting of conventional pressure-difference measuring devices with
inline measuring devices of the described kind, a lesser pressure drop is
caused
in the pipeline, or in the through-flowing medium. An embodiment of the
invention rests, in such case, especially on the recognition that pressure-
difference measuring devices are, in the case of marked multiphase-flow,
capable of measuring flow parameters of the kind considered here more
robustly and, most often, also more accurately, than, for example, Coriolis
mass
flow meters. On the other hand, it was possible to determine that the actually
lesser pressure drop via inline measuring devices of the described kind,
especially when using bent measuring tubes, can still be sufficient to enable
a
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flow measurement based thereon. This, the more so, because, for example,
modern Coriolis mass flow measuring devices now have, via their measuring
device electronics already in their standard embodiment, enormous computing
capacities.
An advantage of an embodiment of the invention may, additionally, be seen also
in
the fact that the measurement system and, therefore, also the method
corresponding
therewith, can be implemented by connecting together even conventional inline
measuring devices of the described kind with conventional pressure-difference
measuring devices. In such case, it is of special advantage, when at least one
of the
measuring devices applied for the measurement system has a
programmable measuring device electronics, since, thereby, the measurement
system can be implemented by solely slight reconfiguring of the firmware,
especially the measurement signal evaluation, or the software components
concerning the measured value determination, as the case may be, and a
corresponding electric connection of the two measuring device electronics
together, be it via a superordinated field bus or directly via the measured
value
issuing and/or in-reading, signal ports of the respective measurement device
electronics. A further advantage of an embodiment of the invention could,
additionally, be seen in the fact that, for the measurement system, inline
measuring devices established in industrial measurements and automation
technology, exhibiting the most varied of measurement principles, such as e.g.
those comprising a flow measurement pickup of vibration type, as well as also
those using magneto-inductive measurement pickups or ultrasonic
measurement pickups, can be used.
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Embodiments of the invention will now be explained in the following on the
the basis of examples of embodied in the figures of the drawing; equal parts
are
provided with equal reference characters in the figures. In case helpful for
overviewability, repetition of reference characters in subsequent figures is
omitted. The figures show as follows:
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. 1 to 3 in each case, in side view, examples of embodiments of
measurement systems, each formed by means of an inline
measuring device and a pressure-difference measuring device, for
measuring at least one physical, flow parameter of a medium
flowing in a pipeline;
Fig. 4 perspectively, in a first side view, an example of an embodiment of
an inline measuring device suited for one of the measurement
systems shown in Figs. 1 to 3 and equipped with a measurement
pickup/transducer of vibation-type; and
Fig. 5 an example of an embodiment of a measuring device electronics
suited for the inline measuring device of Fig. 1, 2 or 3.
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DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
While the invention is susceptible to various modifications and alternative
forms,
exemplary embodiments thereof have been shown by way of example in the
drawings and will herein be described in detail. It should be understood,
however, that there is no intent to limit the invention to the particular
forms
diclosed, but on the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope of the
invention
as defined by the intended claims.
Figs. 1 to 3 show, in each case, an example of an embodiment for a
measurement system, especially one built modularly and/or with the principle
of
diversity, which is suited for, and provided for, very robustly measuring at
least
one physical, flow parameter, especially a mass flow rate m and/or volume flow
rate v and/or a flow velocity u, of a medium flowing in a pipeline (not shown)
and
for representing such in at least one, corresponding, measured value XM.
Especially, the measurement system is further provided for measuring one or
more of such physical, flow parameters of an, at least at times, two, or more,
phase medium. The measurement system includes, for such purpose, at least
one inline measuring device 1 for flowing media, with the inline measuring
device 1 being formed by means of a corresponding flow pickup DA, as well as
a first measuring device electronics El of the measurement system,
electrically
coupled, at least at times, therewith. Flow pickup DA includes, in such case,
at
least one measuring tube inserted into the course of the pipeline and through
which the medium to be measured is allowed to flow, at least at times, during
operation of the measurement system. The inline measuring device 1 is,
especially, provided for producing, at least at times, at least one
measurement
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signal, which is influenced by at least one physical parameter, especially a
flow
velocity, a mass flow rate m, a volume flow rate v, a density p and/or a
viscosity
n of the medium present in the measuring tube and, to such extent,
appropriately corresponds with the parameter. Serving for producing the at
least one measurement signal is, in such case, a sensor arrangement of the
inline measuring device arranged on the measuring tube and/or in its vicinity
and reacting, at least mediately, to changes of the at least one physical
parameter of the medium in a manner appropriately influencing the at least one
measurement signal.
In the example of an embodiment shown here, a Coriolis mass flow/density
and/or viscosity meter, whose flow pickup DA is embodied as a measurement
pickup of vibration-type, serves as inline measuring device. This especially
because such an inline measuring device, at least for the case in which the
medium is of two, or more, phases, is especially suited for registering the
physical parameter, especially the mass flow rate m, density p and/or
viscosity q
of the medium to be measured, highly accurately. However, in such case, also
other inline measuring devices equally established in the realm of process
automation technology can be used to register the physical parameter, devices
such as e.g. magneto-inductive flow meters, vortex flow measuring devices, or
also ultrasonic measuring devices.
Besides the inline measuring device 1 (shown here as a Coriolis mass
flow/density measuring device), the measurement system includes, further, a
pressure-difference measuring device 2, which is formed by means of a first
pressure pickup PA1 for the registering of a first, especially static,
pressure pi
existing in the medium and a second pressure pickup PA2 for the registering of
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a second, especially static, pressure P2 existing in the medium, as well as by
means of a second measuring device electronics E2, which, at least at times,
is
electrically coupled with the pressure pickups PA1, PA2 and at least at times
with
the measuring device electronics El, which is, here, primarily associated with
the inline measuring device.
In an embodiment of the invention, such as e.g. shown in Fig. 1, the first
pressure pickup PA1 is inserted into the pipeline at the inlet end of the flow
pickup DA, especially in its immediate vicinity, and the second pressure
pickup
PA2 is inserted into the pipeline at the outlet end of the flow pickup DA,
especially at its immediate vicinity. Consequently, the measurement system
thus registers by means of the first pressure pickup PA, at least one pressure
pi
effective in the flowing medium at the inlet end of the at least one measuring
tube and/or, by means of the second pressure pickup PA2, at least one pressure
P2 effective in the flowing medium at the outlet side of the at least one
measuring tube.
The pressure pickups PA1, PA2 can, as also illustrated in Fig. 1, be pressure
pickups converting the pressure on location, by means of, in each case, a
pressure measurement cell arranged directly on the pipeline, into, in each
case,
an electrical measurement signal reacting to time changes of at least one of
the
registered pressures with a corresponding change of at least one of its
properties; it is possible, however, for example, also, as shown schematically
in
Fig. 2, to use pressure pickups, which transfer the registered pressures via a
corresponding pressure intermediary, for example a correspondingly ducted, oil-
containing interface, to an, especially differentially measuring, pressure
measurement cell and/or also a plurality of pressure measurement cells
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arranged in the vicinity of the second measuring device electronics E2, which
cells then produce corresponding, electrical measurement signals for the
registered pressures. A measurement signal produced in this way would then
represent essentially directly a pressure difference in the flowing medium. A
further opportunity for implementing the pressure difference measuring device
2
is, as shown schematically in Fig. 3 and as proposed, for example, also in US-
A
2004/0254748, to register the pressures p,, P2 with, in each case, a
corresponding pressure sensor and to convert each of the locally registered
pressures already immediately on location into corresponding pressure
measured values representing the pressures pi, p2. The thus-produced
pressure measured values can then, as shown in Fig. 3, be transmitted, for
example singly, via corresponding data interfaces from the respective pressure
sensors (here, thus, essentially, in each case, from a measuring device
electronics portion E2', E2") to the measuring device electronics El. The
pressure measured values can, however, for example, also, as indicated by the
dashed line in Fig. 3, be transferred from one pressure sensor to the other
(here, thus, essentially from a measuring device electronics portion E2' to
the
other measuring device electronics portion E2") and, from there, sent to the
measuring device electronics El, as required, also as "electric" pressure
difference.
The pressure measurement cells used for the pressure pickups PA1, PA2 can
be, for example, capacitively measuring measurement cells. Of course,
however, also, as required, other pressure measurement cells converting the
pressures registered and transferred from the medium into corresponding
measurement signals can be used for the pressure pickups. Additionally, to be
referenced, in this connection, are also the pressure pickups used
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conventionally in pressure difference measuring devices of the technology of
flow measurements, especially also the construction and the connecting of
their
pressure measurement cells to the pipeline, as well as the flow-technical and
electrical interconnecting of the pressure cells.
In the case of the measurement system of the invention, the two measuring
device electronics El, E2 are so coupled together, that, in the operation of
at
least one of the two measuring device electronics El, E2, correspondingly
produced measurement data can be transmitted, at least unidirectionally, to
the
other measuring device, for example in the form of measurement signals coded
in their voltage, current and/or frequency, and/or in the form of measured
values
encapsulated in digitally coded telegrams; of course, instead of this, also
data
connections communicating bidirectionally between the two measuring device
electronics El, E2 can be used. For implementing the communication
connection between the two measuring device electronics, standard interfaces
correspondingly established in the technology of industrial measurements and
automation can be used advantageously, such as e.g. line-conducted, 4-20 mA
current loops, as required also in connection with HART(R) protocols, and/or
suitable radio connections. Moreover, each of the two measuring devices, thus
the inline measuring device and the pressure-difference measuring device, is
connected via its respective measuring device electronics El, E2, at least
mediately, to an external energy, or power, supply, from which it can be fed
with
electric energy during operation. In such case, each of the two measuring
device electronics El, El can, for example, be connected separately to the
external energy supply. Alternatively, or in supplementation, however, also
one
of the two measuring device electronics El, E2 can be so connected to the
other, that it can, at least at times, obtain its electric energy therefrom.
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In an advantageous embodiment of the invention, at least one of the two
measuring device electronics El, E2 is additionally so constructed, that it
can,
during operation of the measurement system, exchange measurement and/or
other operating data, especially also the at least one measured value XM, with
a
measured value processing unit superordinated thereto, for example a
programmable logic controller (PLC), a personal computer and/or a workstation,
via a data transmission system, for example a field bus system. For this
aforementioned case, in which the measurement system is provided for
connection to a field bus or other communication system, at least the at least
one measuring device electronics connected to the communication system
includes a corresponding communication interface for a data communication,
e.g. for transmitting measurement data to the already mentioned, programmable
logic controller or a superordinated process control system. Also for this,
for
example, standard interfaces correspondingly established in the technology of
industrial measurements and automation can be used. Moreover, also the
external energy supply can be connected to the field bus system, and the
measurement system can, in the previously described manner, be supplied with
energy directly via the field bus system.
During operation, the measurement system produces, by means of at least one
of the two measuring device electronics El, E2, taking into consideration
pressures p,, p2 registered by means of the first and second pressure pickups,
at least at times, measured values X1 of the first kind, which represent,
especially digitally, following one after the other in time, the at least one
flow
parameter to be measured for the medium. For this purpose, stored in at least
one of the measuring device electronics El, E2, for example in that of the
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difference pressure measuring device, is a transfer function f(pi, p2,..),
which, at
least, determines, how the measured values X, of the first kind are generated
on the basis of the currently registered, first and second pressures pi, p2 by
means of this measuring device electronics, i.e. at least the following should
hold:
X, =f(P1,P2). (1)
The transfer function f(pi, p2,..) used for production of the measured values
of
the first kind can be, for example, a purely static, linear or non-linear,
characteristic curve function or also a dynamic transfer function taking into
consideration transient transitional processes. The transfer function f(p,,
p2,..)
can be implemented, for example, by means of an ensemble of discrete,
numerical, vertex values for a one- or multi-dimensional, characterizing field
determined initially in a corresponding calibration of the measurement system
and stored digitally in an, especially non-volatile, memory element of one of
the
measuring device electronics. The transfer function f(p1, p2,..) can, however,
also be formed by a set of coefficients describing it parametrically, where
the
coefficients are likewise determined initially during the calibration and are
stored
digitally in the memory. For the case of a linear, static, characteristic line
function, the then only two coefficients would be, for example, the known
variables, zero point and sensitivity or slope.
In an embodiment of the invention, the measurement system determines, based
on the pressures pi, p2 registered by means of the pressure-difference
measuring device, repeatedly, a pressure difference Op, which exists, at least
in
part, along the at least one measuring tube in the flowing medium. Further,
the
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measurement system produces the measured value X, of the first kind taking
into consideration a pressure difference currently determined as existing
between the two pressures p,, P2 registered for the flowing medium.
Accordingly, the measurement system determines, in the case of this
embodiment of the invention, the measured values X, of the first kind, thus,
based on the relationship:
X, = f ((AP)'), (2)
wherein the exponent lies in the region of about 0.5. For the case in which
the
physical flow parameter to be determined by means of the measurement
system is a mass flow rate m, a volume flow rate v or an average flow velocity
u,
the measured values X, of the first kind are produced, for example, based on
at
least one of the following equations:
X, = Kõ = (AP)n , (3)
X, = K, = (Ap)n (4)
X, = K,n = (Ap)n , (5)
wherein the coefficients Ku, Kv or Km mediate between the particular flow
parameter to be measured, mass flow rate m, volume flow rate v or average
flow velocity u, and a pressure difference measured by means of the two
pressures p,, P2. The coefficients Ku, Kv or Km can, in such case, be
dependent also on the instantaneous density p of the medium, and, to that
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extent, are only for media with density constants fluctuating in small degree.
For media with density fluctuating widely, the respective dependencies of the
coefficients on the density p are to be correspondingly taken into
consideration
according to the following proportionalities:
K,, - (6)
K, (7)
(8)
The aforementioned functions serving for the production of the measured
values X1 of the first kind, or the measured values X2 of the second kind, as
the
case may be, symbolized by the Equations (1) to (8), can be implemented, at
least in part, by means of a microcomputer correspondingly provided in the
second measuring device electronics. The creation and implementation of
appropriate algorithms, which correspond with, or map, the above-described
equations, as well as their conversion into executable program code, is, per
se,
within the ability of those skilled in the art and requires, therefore, at
least once
one has knowledge of the present invention, no detailed explanation. Of
course, the aforementioned equations can also be represented, without more,
completely, or partially, by means of corresponding, discretely constructed,
analog and/or digital, computing circuits in at least one of the two measuring
device electronics El, E2.
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It is further provided in the measurement system of the invention that the
measuring device electronics El of the inline measuring device 1 produces, at
least at times, measured values X2 of the second kind, which represent,
especially digitally, in time following one after the other, the at least one
parameter of the medium in the at least one measuring tube or a measurement
variable derived therefrom. The measured values X, of the first kind and the
measured values X2 of the second kind can, in such case, be produced
essentially simultaneously or, at least, near to one another in time, and, to
such
extent, can be synchronized with one another; the measured values of the first
kind and the second kind can, however, also, as required, be produced
essentially asynchronously and/or displaced in time with respect to one
another,
as required, using time stamps representing the point in time of the actual
determining. Further, the measured values X, of the first kind can represent
the
same parameter as the measured values X2 of the second kind, especially also
in the same dimension or unit of measurement.
Furthermore, in the case of the measurement system of the invention, it is
provided that the transfer function f(p1, p2,..) is adapted taking into
consideration
at least one measured value X2 of the second kind, produced by means of the
inline measuring device 1, for example, to the, in each case, current, at
least
one, physical parameter measured repeatedly for the medium to be measured
and by means of the inline measuring device, for example, the density p of the
medium and/or its mass or volume flow rate m, v. "Adapt", in this case, can
mean, for example, that, based on at least one measured value X2 of the
second kind, for example the current one, from a multitude of different
transfer
functions, of which each is implemented in the above-described manner, e.g. by
means of digitally, non-volatilely stored coefficients or digitally, non-
volatilely
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stored vertices, and of which each is matched to, in each case, at least one,
initially associated, and, to such extent, classified feature of the at least
one
parameter to be measured by means of the inline measuring device, that
transfer function is selected, which is best suited for this measured value X2
of
the second kind or a constellation of a plurality of such measured values X2
of
the second kind delivered by the inline measuring device. Adapting of the
transfer function can, however, also mean that the measured value X2 of the
second kind delivered by means of the inline measuring device represents one
of the flow parameters, mass flow rate m, volume flow rate v or average flow
velocity u, and that, using this measured value X2, as well as taking into
consideration a current density p of the medium, the, in each case, one
constant Ku, Kv or Km correspondingly intermediating between the measured
value X1 of the first kind currently to be determined and the measured value
X2
of the second kind, which instantaneously most accurately represents the
actual
parameter, is repeatedly determined and, as required, corrected.
The currently best suited, here, thus, the "adapted", or "matched", transfer
function can then finally be loaded from a non-volatile memory range, in the
form e.g. of a table memory, in one of the two measuring device electronics
El,
E2, into a volatile, working memory of the measuring device electronics E2 of
the pressure-difference measuring device 2, and, consequently, be held
available, as an updated transfer function, for the determination of the
following
measured values X, of the first kind. Advantageously, for this purpose, at
least
that one of the two measuring device electronics, which is storing the
transfer
function, is embodied as a programmable, especially also as a programmable
during operation, and, in such respect, reconfigurable, or adaptable,
measuring
device electronics. The non-volatile memory can be, for example, a
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programmable, fixed-value memory, thus an FPGA (field programmable gate
array), an EPROM or an EEPROM. The use of memory elements embodied as
table memories has, among other things, the advantage that the transfer
function is vary rapidly available during runtime, following calculation of
the
measured values X2 of the second kind. Additionally, transfer functions
entered
into the table memory can be determined on the basis of few calibration
measurements initially or even during operation of the measurement system
very accurately, e.g. based on the Eqs. (3) to (8) and using the method of
least
squares. In case required, the adapting of the transfer function to the medium
to be measured can also be achieved by transmitting the at least one
measurement signal produced by means of the sensor arrangement of the inline
measuring device 1 directly to the measuring device electronics E2 of the
pressure-difference measuring device 2 and there converting it into a
selection
signal selecting the currently best suited transfer function, for example
selecting
a coefficient describing the transfer function.
The information exchange between the two measuring device electronics El,
E2 required for the adapting of the transfer function can, in such case, occur
via
the already mentioned, data connections of the measurement system, using the
communication interfaces correspondingly provided in the measuring device
electronics El, E2.
As already indicated, the inline measuring device includes, in the example of
an
embodiment shown here, a measurement pickup of vibration-type, through
which medium to be measured flows during operation, and which serves for
producing in a through-flowing medium such mechanical reaction forces,
especially Coriolis forces dependent on mass flow rate, inertial forces
ii
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dependent on the density of the medium and/or frictional forces dependent on
the viscosity of the medium, which react measurably, especially sensorially
registerably, on the measurement pickup. On the basis of these reaction forces
describing the medium, it is thus possible, in manner known to those skilled
in
the art, to measure mass flow, density and/or viscosity of the medium. To that
extent, the mechanical construction of the measurement system corresponds
essentially to that of the measurement system shown in US-A 5,359,881.
Fig. 4 shows, schematically, an example of an embodiment of a physical-to-
electrical transducer arrangement serving as a measurement pickup 10 of
vibration-type. The mechanical construction and manner of functioning of such
a transducer arrangement is known, per se, to those skilled in the art and
described in detail e.g. also in US-B 6,860,158, US-A 5,796,011 or US-A
5,359,881. It is to be noted, additionally, here, that, for implementation of
the
invention, instead of a measurement pickup according to the example of an
embodiment shown here, practically any of the measurement pickups known
already to those skilled in the art for Coriolis mass flow/density measuring
devices, especially also one of the bending oscillation types with a bent or
straight measuring tube vibrating exclusively or at least partly in a bending
oscillation mode, can be used. Other suited forms of embodiment for such
transducer arrangements serving as measurement pickup 10 are described
comprehensively and- in detail e.g. in US-B 6,691,583, US-B 6,308,580, US-A
5,301,557, US-A 5,357,811, US-A 5,557,973, US-A 5,602,345, US-A 5,648,616,.
WO-A 03/095949 or WO-A 03/095950. Moreover, also e.g. magneto-inductive
pickups or also ultrasonic measurement pickups known to those skilled in the
art can be used.
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For the conveying of the fluid to be measured, the measurement pickup
includes, here, a single, curved measuring tube 10, which is connected via an
inlet tube piece 11 opening on the inlet end and an outlet tube piece 12
opening
on the outlet end, to the pipeline or also possible carrier tubes of the
aforementioned pressure pickup. Inlet and outlet tube pieces 11, 12 are, as
much as possible, aligned with one another as well as with an imagined,
longitudinal axis Al of the measurement pickup. Moreover, measuring tube,
inlet and outlet tube pieces 11, 12 are advantageously embodied as one piece,
so that e.g. a single, tubular stock can serve for their manufacture; in case
required, measuring tube 10, as well as the inlet and outlet tube pieces 11,
12
can, however, be manufactured also by means of separate, subsequently joined
stock, which is e.g. welded together. For manufacturing measuring tube 10, it
is
possible, in such case, to use practically any of the materials usual for such
measurement transducers, such as e.g. steel, Hastelloy, titanium, zirconium,
tantalum, etc. It is to be noted here that, instead of the measurement pickup
shown in the example of an embodiment, with a single curved, here, more U- or
V-shaped, measuring tube, the measurement pickup serving for implementation
of the invention can, as well, be selected from a large number of vibration-
type
measurement pickups known from the state of the art. Especially suited, for
example, are also vibration-type measurement pickups including two straight or
bent measuring tubes, for example extending essentially parallel to, and/or
essentially equal in construction to, one another, through which the medium to
be measured flows in parallel, such as are described, for example, also in US-
A
5,602,345, or also such with a single, straight, measuring tube; compare, in
this
regard, for example, also US-B 6,840,109 or US-B 6,006,609 .
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For the case, in which the measurement pickup is to be releasably mounted
with the pipeline, first and second flanges 13, 14 can be formed in the usual
manner on the inlet and outlet tube pieces 11, 12, respectively; in case
required,
the inlet and outlet tube pieces 11, 12 can also be connected directly with
the
pipeline, e.g. by means of welding or brazing.
Further provided affixed to the inlet and outlet tube pieces 11, 12 is, as
shown
schematically in Fig. 4, a housing 100 accommodating the measuring tube 10.
Compared with the measuring tube, the housing is constructed to have greater
bending and torsional stiffness. Besides the oscillatable holding of the
measuring tube, the measurement pickup housing 100 also serves for housing
the measuring tube 10, as well as possible other components of the
measurement pickup and for protecting these, thus, from harmful environmental
influences and/or for damping possible sound emissions of the measurement
pickup to the outside. Beyond this, the measurement pickup housing 100
serves also as support for an electronics housing, which houses the measuring
device electronics 50. For this purpose, measurement pickup housing 100 is
provided with a necklike transition-piece, to which the electronics housing
200 is
appropriately affixed. Instead of the more box-shaped transducer housing 100
shown here, it is, of course, also possible to use other suitable housing
shapes
matched to the particular shape of the actually used, measuring tube, such as
e.g. tubular structures extending coaxially with the measuring tube.
As shown in Fig. 4, the measurement pickup of the example of an embodiment
further includes a counteroscillator 20 for the measuring tube 10.
Counteroscillator 20 is oscillatably affixed by means of an inlet-side, first
coupler
31 to an inlet end of the measuring tube 10 and by means of an outlet-side,
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second coupler 32, especially one formed identically to coupler 31, to an
outlet
end of the measuring tube 10. Serving as coupler 31 can be, in such case, e.g.
one, or, as also shown in Fig. 4, two node-plates, which are secured in
appropriate manner, in each case, to the measuring tube 10 and the
counteroscillator 20 on the inlet side; analogously thereto, also the coupler
32
can be realized by means of node-plates secured to the measuring tube 10 and
the counteroscillator 20 on the outlet side. The here likewise tubular
counteroscillator 20 is spaced from the measuring tube 10 and arranged in the
measurement transducer essentially parallel thereto. Measuring tube 10 and
counteroscillator 20 can, in such case, be so embodied that they may have,
with
outer spatial forms as identical as possible, equal, or at least mutually
similar,
especially mutually proportional, mass distributions. It can, however, be of
advantage to shape the counteroscillator 20 non-identically to the measuring
tube 10; e.g. the counteroscillator 20 can also, if required, be arranged to
extend in the measurement transducer coaxially with the measuring tube 10.
For producing the above-mentioned reaction forces in the fluid, the measuring
tube 13 is, during operation of the measurement pickup 10, caused to vibrate,
driven by an electromechanical exciter mechanism 40 coupled with the
measuring tube 10, at a predeterminable exciter frequency fexc, especially a
natural resonance frequency, in the so-called wanted mode and is,
consequently, elastically deformed in predeterminable manner. In the present
example of an embodiment, the measuring tube 10, as usual in the case of
vibration-type measurement transducers of such character, is so excited in the
wanted mode to cantilever oscillations, that it executes, at least in part,
cantilever-type, bending oscillations, moving with a pendulum-like motion
about
an imagined longitudinal axis essentially aligned with the inlet tube piece 11
and
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the outlet tube piece 12 of the measurement pickup. Simultaneously, the
counteroscillator 20 is also excited to cantilever oscillations, and, indeed,
such
that it, at least in the case of medium at rest, oscillates essentially in the
same
form, and yet with opposite phase, compared with the measuring tube 10
oscillating in the wanted mode. In other words, measuring tube 10 and
counteroscillator 20 move, thus, in the manner of oscillating tuning-fork
tines.
For the case, in which the medium is flowing at such time and, consequently,
the mass flow rate m is different from zero, Coriolis forces are induced by
means of the medium flowing through the measuring tube 10 while oscillating in
the wanted mode. These, in turn, react on the measuring tube 10 and effect, in
manner known to those skilled in the art, additional, sensorially registerable
deformations of the measuring tube 10. These deformations are superimposed
on the bending oscillations of the wanted mode in the form of a so-called
Coriolis mode. The instantaneous character of the deformations of the
measuring tube 10 is, in such case, especially as regards their amplitudes,
also
dependent on the instantaneous mass flow rate m and is registered by means
of a corresponding sensor arrangement arranged on the measuring tube. In the
present example of an embodiment, the Coriolis mode is, as usual in the case
of such measurement transducers, developed as an antisymmetric, twist mode,
in which the measuring tube 10 also executes rotary oscillations about an
imagined normal axis A2 directed perpendicular to the longitudinal axis Al.
In an embodiment of the invention, the exciter-, or also wanted-, mode
frequency fexc is so tuned, that it corresponds as accurately as possible to a
natural eigenfrequency of the measuring tub 10, especially a lowest natural
eigenfrequency, so that the measuring tube 10 deflects in bending essentially
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according to a natural form of eigenoscillation. In the case of use of a
measuring tube made of high-grade steel, especially stainless, high-grade
steel,
having a nominal diameter of 29 mm, a wall thickness of about 1.5 mm, a
stretched length of about 420 mm and a bridge length of 305 mm, measured
from inlet end to outlet end, the lowest resonance frequency of the same would
amount, for example, in the case of a density of zero, to about 490 Hz. Since
the natural eigenfrequencies of such bending oscillation modes of measuring
tubes depend, to a considerable degree, also on the density p of the medium,
it
is also possible, without more, to measure also the density p, in addition to
the
mass flow rate m.
For producing vibrations of the measuring tube 10, the measurement pickup
includes, additionally, as already mentioned, an electrical-to-physical, here,
electrodynamic, exciter mechanism 40 arranged on the at least one measuring
tube and acting, at least mediately, on the medium conveyed therein. This
serves for converting an electrical exciter energy Eexc, e.g. having a
controlled
current and/or a controlled voltage, fed from a measurement and operating
electronics 50 of the measuring device electronics El into an exciter force
Fexc
acting, e.g. in pulse form or harmonically, on the measuring tube 10 and
deflecting such in the above-described manner. Fig. 5 shows a corresponding
example of an embodiment of the mentioned measuring and operating
electronics 50. Driver circuits suited for the adjusting of the exciter energy
Eexc
are shown e.g. in US-A 4,777,833, US-A 4,801,897, 4,879,911 or US-A
5,009,109. The exciter force Fexc can, as usual in the case of measurement
transducers of such type, be embodied bidirectionally or unidirectionally and
can
be adjusted in manner known to those skilled in the art, e.g. by means of a
current-, and/or voltage-, control circuit with respect to its amplitude, and
e.g. by
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means of a phase control circuit with respect to its frequency. The exciter
mechanism 40 can be e.g. a simple plunger coil, or solenoid, arrangement, with
a cylindrical exciter coil secured to the counteroscillator 20 and flowed
through
during operation by a corresponding exciter current, and a permanent magnet
armature plunging at least partially into the exciter coil and affixed
externally,
especially at the halfway point of the measuring tube 10, on the measuring
tube
10. Additionally capable of serving as exciter mechanism 40 is e.g. an
electromagnet.
For detecting and registering vibrations, especially bending oscillations, of
the
measuring tube 10, the measurement pickup includes, additionally, a sensor
arrangement 50. The sensor arrangement 50 can be practically any of the
sensor arrangements usually used for such kinds of measurement transducers
for registering the movements of the measuring tube 10, especially its
movements on its inlet, and outlet, sides, and for converting such into
corresponding oscillation signals delivered by the sensor arrangement. Thus,
the sensor arrangement 50 can, e.g. in the manner known to those skilled in
the
art, be formed by means of a first sensor arranged on the inlet side of the
measuring tube 10 and by means of a second sensor arranged on the outlet
side of the measuring tube 10. Examples of sensors, in such case, for
measuring the oscillations are relatively measuring, electrodynamic, velocity
sensors or, however, also electrodynamic path-measuring sensors, or
acceleration sensors. Instead of electrodynamic sensor arrangements,
additionally sensor arrangements measuring by means of resistive or
piezoelectric strain gages, or optoelectronic sensor arrangements can serve
for
detecting the oscillations of the measuring tube 10. In case required, it is,
moreover, possible to apply, in manner known to those skilled in the art,
still
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other sensors needed for the measuring and/or for the operation of the
measurement transducer, such as e.g. additional oscillation sensors arranged
on the counteroscillator 20 and/or on the transducer housing 100 (compare, in
this connection, also US-A 5,736,653) or e.g. also temperature sensors
arranged on the measuring tube 10, on the counteroscillator 20 and/or on the
transducer housing 100 (compare, in this connection, also US-A 4,768,384 or
WO-A 00/102816).
For causing the measuring tube 10 to vibrate, the exciter mechanism 40 is, as
already mentioned, fed by means of a likewise oscillating, especially
multifrequent, exciter current ieXC of adjustable amplitude and adjustable
exciter
frequency feXC in such a manner that the exciter coils (here, just one) are
flowed
through by the exciter current and, in corresponding manner, the magnetic
fields
needed for moving the corresponding armature are produced. The exciter
current ieXC can be e.g. harmonic, multifrequent or also rectangular. The
lateral
oscillation, exciter frequency fexcL of exciter current ieXC required for
maintaining
the oscillations of the measuring tube 10 can, in the case of the measurement
pickup shown in the example of an embodiment, be so selected and tuned, that
the laterally oscillating measuring tube 10 oscillates essentially in a
bending
oscillation, fundamental mode with a single oscillation antinode. For
producing
and tuning the exciter current iexCi the measuring and operating electronics
50
includes, as shown in Fig. 5, a corresponding driver circuit 53, which is
controlled by a frequency adjusting signal yFM representing the exciter
frequency
feXC to be set, and by an amplitude adjusting signal YAM representing the
amplitude to be set for the exciter current ieXC. The driver circuit 53 can be
realized e.g. by means of a voltage-controlled oscillator and a voltage-to-
current
converter connected downstream thereof; instead of an analog oscillator,
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however, also e.g. a numerically controlled, digital oscillator can be used
for
tuning the instantaneous exciter current ieXC. For producing the amplitude
adjusting signal YAM, an amplitude control circuit 51 integrated into the
measuring and operating electronics 50 can serve, which updates the amplitude
adjusting signal YAM on the basis of the instantaneous amplitudes of at least
one
of the two oscillation measurement signals sl, s2, measured at the
instantaneous lateral oscillation frequency, as well as on the basis of
corresponding, constant or variable, amplitude reference values for the
oscillations W; if required, also instantaneous amplitudes of the exciter
current
ieXC can be brought-in for generating the amplitude adjustment signal YAM;
compare Fig. 5. Construction and manner of operation of such amplitude
control circuits are likewise known to those skilled in the art. For an
example of
such amplitude control circuits, reference is made to measuring transmitters
of
the series "PROMASS 80", such as are available from the assignee, for
example in connection with measurement pickups of the series "PROMASS F"
or "PROMASS H". Their amplitude control circuit is advantageously so
embodied, that the lateral oscillations of the measuring tube 10 are
controlled to
a constant amplitude, thus an amplitude also independent of the density, p.
The frequency control circuit 52 and the driver circuit 53 can be embodied
e.g.
as a phase-locked loop (PLL), which is used, in manner known to those skilled
in the art, on the basis of a phase difference measured between at least one
of
the oscillation measurement signals s1, s2 and the exciter current ieXC to be
set,
or the instantaneously measured exciter current iexCi for adjusting the
frequency
adjusting signal YFM continually to the instantaneous eigenfrequencies of the
measuring tube 10. The construction and use of such phase-locked loops for
driving measuring tubes at one of their mechanical eigenfrequencies is
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described in detail e.g. in US-A 4,801,897. Of course, also other frequency
control circuits known to those skilled in the art can be used, such as
proposed
e.g. also in US-A 4,524,610 or US-A 4,801,897. Additionally, reference to made
to the already mentioned, measuring transmitters of the series "PROMASS 80"
with respect to an application of such frequency control circuits for
measurement pickups of vibration type. Other circuits suited as driver
circuits
can also be taken, for example, from US-A 5,869,770 or US-A 6,505,519.
In a further embodiment of the invention, the amplitude control circuit 51 and
the
frequency control circuit 52 are realized, as shown schematically in Fig. 5,
by
means of a digital signal processor DSP provided in the measuring and
operating electronics 50 and by means of program code correspondingly
implemented in such and running therein. The program code can be stored
persistently or, however, also permanently, e.g. in a non-volatile memory
EEPROM of a microcomputer 55 controlling and/or monitoring the signal
processor, and loaded into a volatile data memory RAM of the measuring and
operating electronics 50, e.g. RAM integrated in the signal processor DSP,
upon
startup of the signal processor. Signal processors suited for such
applications
are e.g. those of type TMS320VC33 available from the firm Texas Instruments T
Inc.. Of course, the oscillation measurement signals sl, s2 must be converted
into corresponding digital signals by means of corresponding analog-to-digital
converters A/D for a processing in the signal processor DSP; compare, in this
connection, especially EP-A 866 319. In case required, adjusting signals
issued
by the signal processor, such as e.g. the amplitude adjustment signal YAML or
the frequency adjustment signal YFM, are to be converted in corresponding
manner, from digital to analog.
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As shown in Fig. 5, the measurement signals sj, s2 delivered by the sensor
arrangement and, as required, first suitably conditioned, are fed,
additionally, to
a corresponding measuring circuit 54 of the measuring and operating
electronics 50, which serves for producing, on the basis of at least one of
the
measurement signals s1, s2 and/or on the basis of the exciter current iexCi
the at
least one measured value of the second kind X2. In an embodiment of the
invention, the measuring circuit 54 is at least in part embodied as a flow
calculator and serves, in manner known per se to those skilled in the art, for
determining a measured value X2 of the second type serving, here, as mass
flow measured value Xm, on the basis of a phase difference detected between
the oscillation measurement signals si, s2 generated in the case of a
measuring
tube 10 laterally oscillating, at least in part, and representing, as
accurately as
possible, the mass flow rate m to be measured. Measuring circuit 21 can, in
such case, be one of the measuring circuits, especially digital, already used
in
conventional Coriolis mass flow measuring devices for determining mass flow
rate on the basis of the oscillation measurement signals si, s2; compare, in
this
connection, especially the initially mentioned WO-A 02/37063, WO-A 99/39164,
US-A 5,648,616, US-A 5,069,074. Of course, also other measuring circuits
known to those skilled in the art as suitable for Coriolis mass flow measuring
devices can be used, which measure and correspondingly evaluate the phase
and/or time differences between oscillation measurement signals of the
described kind. Furthermore, the measuring circuit 54 can also serve for
generating, derived from an oscillation frequency of the at least one,
vibrating
measuring tube 11, which frequency is measured for example on the basis of at
least one of the oscillation measurement signals sj, s2, a measured value X2
of
the second kind usable as density measured value Xp and instantaneously
representing a density p of the medium, or of a phase of the medium.
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Alternatively or in supplementation, the measuring circuit can also serve for
producing a measured value X2 of the second kind usable as viscosity
measured value Xn and instantaneously representing a viscosity n of the
medium, or of a phase of the medium. It is clear, without more, for those
skilled
in art, that the inline measuring device can determine the individual measured
values X2 for the different measured variables m, p, n both, in each case, in
a
common measurement cycle, thus with an equal update rate, or also with
different update rates. For example, a highly accurate measurement of the
most often considerably varying mass flow rate m usually requires a very high
sampling and update rate, while, in comparison therewith, the, over a longer
period of time, most often, less changeable density p and/or viscosity n of
the
medium can be updated, as required, at greater time intervals. Furthermore, it
is possible, without more, to assume, that currently determined measured
values X2 can be intermediately stored in the measuring device electronics El
and so be kept for subsequent uses. In advantageous manner, the measuring
circuit 54 can, furthermore, be implemented, at least partially, also by means
of
the mentioned signal processor DSP.
Since the flow measurement pickup 10 shown here is essentially a multivariable
measurement pickup, with which can be detected, in alternation, or also
simultaneously, e.g. the mass flow rate, m, on the basis of the two sensor
signals s1, s2, and/or the density, p, on the basis of the oscillation
frequency feXc
and/or the viscosity, q, of the fluid on the basis of the exciter current
iexc, it is
possible within the framework of the present invention to think of the
oscillation
measurement signals sj, s2 delivered by the sensor arrangement, and the
exciter current iexc, separately or also in combination, as "measurement
signals".
Equally, corresponding measured voltages of the devices used, as required,
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instead of the Coriolis mass flow meter, such as voltages measured in the
cases of magneto-inductive flow meters, vortex flow measuring devices or also
ultrasonic flow measuring devices, can be measurement signals. It is also to
be
noted, that, for the case in which a magneto-inductive flow pickup serves as
measurement pickup, instead of the above-discussed exciter arrangement, a
coil arrangement can be used, in manner known to those skilled in the art, as
exciter mechanism, which, flowed through by an exciter current, couples a
magnetic field into the fluid in the measuring tube. In corresponding manner,
then, a voltage sensing, electrode arrangement serves as the sensor
arrangement for out-coupling a measurement voltage induced in the fluid by
means of the above-mentioned, magnetic field. For the case, in which an
ultrasonic flow pickup serves as measurement pickup, an ultrasonic transducer
is used as exciter mechanism, actuated by a corresponding exciter signal, in
the
manner known to those skilled in the art, for coupling ultrasonic waves into
the
fluid in the measuring tube. Likewise, usually also an ultrasonic transducer
serves as sensor arrangement, for coupling the ultrasonic waves out of the
fluid
and converting them into a corresponding, measured voltage.
As already mentioned, the measuring system is especially provided for
measuring the at least one flow parameter of the medium flowing in the
pipeline
also then, when such is developed as two or more phases. The medium can, in
this case, be practically any streaming, or at least flowable, substance
having at
least one fluid phase, for example, an oil-water-gas mixture, or another
liquid-
gas mixture, a solid-entraining liquid, an aerosol, a spray, a powder, or the
like.
However, in an embodiment of the invention, it is provided that the measured
value X2 of the second kind delivered by the inline measuring device is
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predominantly only generated, or at least only issued as a valid, measured
value, when the medium is essentially developed as one phase or at least can
be assumed to be one phase. As initially mentioned, the development of first
and second phases in the flowing medium, for example gas bubbles and/or
solid particles entrained in liquids can lead to increased measurement errors,
especially in the case of inline measuring devices using a vibration-type
measurement pickup, especially in the case of determining the mass flow rate
m. Already discussed in the state of the art with reference thereto is the
fact
that this can immediately affect the phase difference measured between the two
oscillation measurement signals s,, s2, as well as affecting the oscillation
amplitude or the oscillation frequency of each of the two oscillation
measurement signals, or the exciter current, as the case may be, thus
practically every one of the operating parameters usually measured in the case
of measuring device of the described kind. This is true, indeed, especially,
as
explained also in US-B 6,880,410 or US-B 6,505,519, for the operating
parameters determined in the case of laterally oscillating measuring tube; it
can,
however, also not always be excluded for those operating parameters measured
in the case of torsionally oscillating measuring tube; compare, in this
connection, US-A 4,524,610. Therefore, it is additionally provided that the
flowing medium, especially internally in the measuring system itself, is
repeatedly monitored concerning whether it can still be considered to be
developed essentially as one phase, or whether it is developed now at least as
two phases. The detection can occur, in such case, for example using the at
least one measurement signal produced by means of the inline measuring
device; compare, in this connection, also US-B 6,910,366 or US-B 6,505,519.
For the case, in which the medium is recognized as being at least two-phase,
it
is further provided that the measured value X, of the first kind is issued as
the
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measured value XM of the measurement system instantaneously representing
the flow parameter to be measured. The measurement system is, thus,
operated in a first operating mode, in the case of which the measured value XM
varies practically only as a function of the registered pressures pi, p2, or
the
pressure-difference Ap derived therefrom. The at least one measurement
signal produced by means of the inline measuring device can, in this first
operating mode, serve especially for repeatedly monitoring the flowing medium
concerning whether, or to what degree, it is developed as two, or more,
phases.
Additionally, it is provided in a further embodiment of the invention that the
measured value X2 of the first kind is issued as the measured value XM of the
measurement system instantaneously representing the flow parameter to be
measured, at least for the case, in which the medium is viewed as essentially
one phase. The measurement system is, then, thus, operated in a second
operating mode, in the case of which the measured value XM, because of the
above-mentioned, high measurement accuracy, varies practically exclusively, or
at least in predominant measure, as a function of the at least one measurement
signal produced by means of the inline measuring device 1. The at least one
measurement signal produced by means of the inline measuring device can, in
this second mode of operation, as already mentioned, additionally also serve
for
repeatedly monitoring the flowing medium concerning whether it is still
developed essentially as one phase. In case required, for the purpose of
decreasing the total electrical power consumption of the measurement system,
in at least one of the two aforementioned operating modes, the then, in each
case, not needed measurement pickup and/or the then, in each case, not
needed measuring device electronics can be clocked at a lower rate, or, as
required, set into a suitable ready-mode. For example, thus, in the first
operating mode, the flow pickup DA and/or the measuring device electronics
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El, or, in the second operating mode, at least one of the two pressure pickups
PA1, PA2 and/or the measuring device electronics E2 can be turned off.
While the invention has been illustrated and described in detail in the
drawings
and forgoing description, such illustration and description is to be
considered as
exemplary not restrictive in character, it being understood that only
exemplary
embodiments have been shown and described.
