WO2005057137A9

WO2005057137A9 - Coriolis mass flowmeter

Info

Publication number: WO2005057137A9
Application number: PCT/EP2004/053323
Authority: WO
Inventors: Christian Matt; Alfred Wenger; Michael Fuchs; Wolfgang Drahm
Original assignee: Flowtec Ag; Christian Matt; Alfred Wenger; Michael Fuchs; Wolfgang Drahm
Priority date: 2003-12-12
Filing date: 2004-12-07
Publication date: 2005-10-27
Also published as: CA2547699C; CA2547697C; EP1692466A2; EP1692467A2; RU2348012C2; WO2005057131A2; RU2339007C2; WO2005057131A3; RU2006124840A; WO2005057131A9; WO2005057137A2; WO2005057137A3; CA2547699A1; RU2006124841A; CA2547697A1

Abstract

Disclosed is a Coriolis mass flowmeter/density meter comprising at least one measuring tube (11) through which a two-phase or multiphase medium flows during operation thereof. A supporting means (12) of the Coriolis mass flowmeter/density meter is fixed to an inlet end and an outlet end of the measuring tube (11), thus clamping the same so as to allow the measuring tube (11) to vibrate. The measuring tube (11) is made to vibrate mechanically, particularly to perform bending vibrations, by means of an excitation system (13). The inventive Coriolis mass flowmeter/density meter further comprises means (141, 142) for generating test signals (xs1, xs2 ) representing vibrations at the inlet end and outlet end of the measuring tube (11). An electronic evaluation unit (2) generates an intermediate value (X'm) that is derived from the test signals (xs1, xs2) and represents a tentatively determined mass flow rate as well as a second intermediate value (X2) derived from the test signals (xs1, xs2), especially from a measured value (Xρ) which is also generated in the electronic evaluation unit (2) and represents a density of the medium, said second intermediate value (X2) representing a measure of a concentration of a phase in the medium. A corrected value (XK) for the first intermediate value (X'm) is determined using the second intermediate value (X2), said corrected value (XK ) being selected among a plurality of predefined values stored in a table memory (56) by means of the intermediate value (X2). The electronic evaluation unit (2) additionally generates a measured value (Xm) representing a mass flow rate with the aid of the intermediate value (X'm) and the corrected value (XK).

Description

Description Coriolis mass flow meter

The invention relates to a Coriolis mass flow / density meter for a flowing in a pipeline, in particular. Two or more phases, medium and a method for generating a measured value representing a mass flow.

In process measurement and automation technology for measuring physical parameters of a fluid flowing in a pipeline, such as e.g. the mass flow rate, the density and / or the viscosity, often used such measuring devices, which by means of a vibration-type measuring sensor inserted into the course of the fluid-carrying pipeline and flowed through by the fluid during operation and a measuring and operating circuit connected to it, in the fluid reaction forces, e.g. Coriolis forces corresponding to the mass flow rate, inertia forces corresponding to the density or friction forces corresponding to the viscosity, etc., and derived from these, generate the respective mass flow rate, a measurement signal representing the respective viscosity and / or the respective density of the fluid. Such vibration type sensors are e.g. in WO-A 03/076880, WO-A 02/37063, WO-A 01/33174, WO-A 00/57141, WO-A 99/39164, WO-A 98/07009, the WO-A 95/16897, WO-A 88/03261, US 2003/0208325, US-B 65 13 393, US-B 65 05 519, US-A 60 06 609, US-A 58 69,770, US-A 57 96 011, US-A 56 02 346, US-A 53 01 557, US-A 52 59250, US-A 52 18 873, US-A 50 69 074, US-A 50 29 482, US-A 48 76 898, US-A 47 33 569, US-A 46 60 421, US-A 4524 610, US-A 44 91 025, US A 41 87 721, EP-A 553 939, EP-A 1 001 254 or EP-A 1 281 938.

For guiding the fluid, the sensors each comprise at least one measuring tube held in a, for example tubular or box-shaped, support frame with a curved or straight tube segment, which vibrate to generate the above-mentioned reaction forces, driven by an electro-mechanical excitation arrangement, during operation calmly becomes. In order to detect vibrations of the pipe segment, especially on the inlet and outlet sides, the measuring sensors also each have a physical-electrical sensor arrangement which reacts to movements of the pipe segment. In Coriolis mass flowmeters for a medium flowing in a pipeline, the measurement of the mass flow is based, for example, on the fact that the medium is allowed to flow through the measuring tube which is inserted into the pipeline and vibrates during operation, as a result of which the medium experiences Coriolis forces. These in turn cause the inlet-side and outlet-side regions of the measuring tube to oscillate out of phase with one another. The size of these phase shifts serves as a measure of mass flow. The vibrations of the measuring tube are therefore detected by means of two vibration sensors of the aforementioned sensor arrangement which are spaced apart from one another along the measuring tube and converted into vibration measuring signals from whose mutual phase shift the mass flow is derived.

The initially cited US-A 41 87 721 mentions that with Coriolis mass flow meters the instantaneous density of the flowing medium can usually also be measured, based on a frequency of at least one of the vibration measurement signals supplied by the sensor arrangement. In addition, a temperature of the fluid is usually also measured directly in a suitable manner, for example by means of a temperature sensor arranged on the measuring tube. It can therefore be assumed without further ado that - even if not expressly described - the density and temperature of the medium are measured using modern Coriolis mass flowmeters, especially since they are always used in the mass flow measurement to compensate for measurement errors due to fluctuating fluid density are, cf. in particular the already mentioned WO-A 02/37063, WO-A 99/39164, US-A 56 02 346 or also WO-A 00/36379.

When using sensors of the type described, it has been shown, however, that with inhomogeneous media, in particular two-phase or multi-phase fluids, from the vibrations of the measuring tube derived vibration measurement signals, in particular the phase shift mentioned, despite the viscosity and density in the individual fluid phases and also the mass flow being kept practically constant and / or taken into account accordingly, are subject to considerable fluctuations and so, if necessary, for the measurement of the respective physical parameter without remedial action Measures can become completely unusable. Such inhomogeneous media can, for example, be liquids into which, as is practically unavoidable in metering or filling processes, a gas present in the pipeline, in particular air, is introduced or from which a dissolved fluid, for example carbon dioxide, is outgassed and leads to foam formation. Another example of such inhomogeneous media is wet or saturated steam. Already in US-A 4524 610 a possible cause of this

Problems for the operation of vibration type sensors are indicated, namely the fact that inhomogeneities introduced by the fluid into the measuring tube, such as gas bubbles, accumulate on its inner wall and can thus have a considerable influence on the vibration behavior. In order to circumvent the problem, it is further proposed to install the measuring sensor in such a way that the straight measuring tube runs essentially vertically and thus prevents such disturbing, in particular gaseous, inhomogeneities from accumulating. However, this is a very special and, particularly in industrial process measurement technology, only very limitedly feasible solution. On the one hand, the pipeline into which the measuring sensor is to be inserted would have to be adapted to the latter, and not vice versa, which is probably not something that the user can get across. On the other hand, as already mentioned, the measuring tubes can also be those with a curved tube shape, so that the problem cannot be solved even by adapting the installation position. It has also been shown here that the aforementioned falsifications of the measurement signal cannot be significantly reduced even when using a vertically installed, straight measuring tube. Let also the fluctuations of the measurement signal thus generated with flowing fluid cannot be prevented in this way either.

Similar causes as well as their effects on the measurement accuracy when determining the mass flow are, for example, also in JP-A 10-281846, WO-A 03/076880, US-A 52 59 250, US-A 50 29482 or US-B 65 05 519 have been discussed. While a flow or fluid conditioning prior to the actual flow measurement is proposed in WO-A 03/076880 to reduce the measurement errors associated with two-phase or multi-phase fluids, both JP-A 10-281846 and US Pat. B 65 05 519 proposes in each case a correction of the flow measurement based on the vibration measurement signals, in particular the mass flow measurement, for example using previously trained, possibly also adaptive classifiers for the vibration measurement signals. The classifiers can be designed, for example, as a Kohonen map or neural network and the correction can be based either on a few parameters measured during operation, in particular the mass flow and density, and other features derived therefrom, or also using an interval of one or more oscillation periods Carry out vibration measurement signals.

The use of such a classifier has, for example, the advantage that compared to conventional Coriolis mass flow / density meters on the sensor no or only very slight changes need to be made, be it the mechanical structure, the excitation arrangement or the operating circuit controlling it that are specially adapted to the specific application.

However, there is a considerable disadvantage of such classifiers, inter alia, that in comparison to conventional Coriolis mass flow meters, considerable changes in the area of measured value generation, especially with regard to the ones used Analog-to-digital converters and the microprocessors are required. As described in US-B 65 05 519, a sampling rate of approximately 55 kHz or more is required for sufficient accuracy for such a signal evaluation, for example when digitizing the vibration measurement signals, which may have an oscillation frequency of approximately 80 Hz. In other words, the vibration measurement signals are to be sampled with a sampling ratio of well over 600: 1. In addition, the firmware stored and executed in the digital measuring circuit is correspondingly complex.

Another disadvantage of such classifiers can be seen in the fact that they train and accordingly on the measurement conditions actually prevailing in the operation of the sensor, be it the installation situation, the fluid to be measured and its mostly variable properties or other factors influencing the measurement accuracy must be validated. Due to the high complexity of the interaction of all of these factors, the training and its validation can usually only be carried out individually on site and for each sensor, which in turn entails a considerable effort when commissioning the sensor. In addition, it has also been shown that such classification algorithms, on the one hand due to the high level of complexity, and on the other hand as a result of the fact that there is usually no corresponding physical-mathematical model with technically relevant or comprehensible parameters, classifiers have very little transparency and thus are often difficult to convey. In connection with this, considerable reservations can easily occur at the customer, whereby such acceptance problems can occur at the customer, in particular, if the classifier used is a self-adapting one, for example a neural network.

It is therefore an object of the invention to provide a corresponding Coriolis mass flow meter which measures the mass flow precisely even with inhomogeneous, in particular multiphase, fluids. A Another task is to specify a corresponding method for generating the measurement result. To achieve this object, the invention consists in one

Coriolis mass flow meter, esp. Coriolis mass flow / density meter, for measuring a mass flow of a two-phase or multi-phase medium flowing in a pipeline, which

Coriolis mass flow meter comprises: at least one measuring tube inserted in the course of the pipeline, through which the medium flows during operation, a carrier means which is fixed to an inlet-side end and an outlet-side end of the measuring tube and thus clamps it so that it can vibrate, an exciter arrangement which Measuring tube in operation in mechanical

Vibrations, especially bending vibrations, offset,

Vibration sensors for generating a first representing vibrations of the measuring tube on the inlet side

Vibration measurement signal and a second vibration measurement signal representing outlet-side vibrations of the measuring tube, as well as measurement and operating electronics which deliver an excitation current driving the excitation arrangement and a mass flow measurement value which provides one to be measured

Mass flow represents, wherein the measuring and operating electronics generates a first intermediate value derived from the vibration measurement signals, which corresponds to the mass flow to be measured, and a correction value for the first intermediate value, and the first intermediate value and the correction value

Mass flow measured value determined, the measuring and operating electronics under the correction value

Use of at least one second intermediate value generated by at least one of the vibration measurement signals and / or by

Excitation current is derived, and [0027] which represents a measure for a portion of a phase of the medium,

[0028] the measuring and operating electronics

[0029] has a table memory in which a multiplicity of discrete default values for the correction value are stored digitally, and

To determine the correction value one of the default values is used, which is read out from the table memory using the second intermediate value.

Furthermore, the invention consists in a method for generating a measured value representing a physical measured variable, in particular a mass flow measured value which represents a mass flow of a medium flowing in a pipeline, by means of a Coriolis mass flow meter, in particular Coriolis mass flow / Density meter, which method comprises the following steps:

Causing vibrations, in particular bending vibrations, of a measuring tube of the Coriolis mass flow meter through which the medium flows,

[0033] detecting the vibrations of the measuring tube and generating a first vibration measurement signal representing inlet-side vibrations and a second vibration measurement signal representing outlet-side vibrations,

Development of a first intermediate value corresponding to the physical measured variable, in particular the mass flow rate, using the two vibration measurement signals,

[0035] determining a second intermediate value, in particular using at least one of the two vibration measurement signals,

Generating a correction value for the intermediate value by means of the second intermediate value, which represents a measure for a portion of a phase of the medium, and

Correcting the intermediate value by means of the correction value,

Wherein the correction value is determined using the second intermediate value and using a table memory in which a large number of discrete default values for the correction value are digitally determined by identifying the currently used default value for the correction value based on the second intermediate value and is read from the table memory.

According to a first embodiment of the Coriolis mass flow meter of the invention, the evaluation electronics deliver a mass flow measurement value derived from the first and / or from the second vibration measurement signal and representing a mass flow of the medium.

In a second embodiment of the Coriolis mass flow meter of the invention

The evaluation electronics supplies a density measurement value, which is derived from the first and / or the second vibration measurement signal and represents a density of the medium

The evaluation electronics determine the correction value using the density measurement value.

[0043] According to a third embodiment of the Coriolis mass flow meter of the invention, the evaluation electronics determine, based on the second intermediate value, a memory address for a default value stored in the table memory and serving as a current correction value.

According to a fourth embodiment of the Coriolis mass flow meter of the invention, the second intermediate value is based on a scatter, ascertained at least for a predetermined time interval, of an amplitude of the excitation current, an amplitude of the vibration measurement signals, an oscillation frequency of the vibration measurement signals, a measured density and / or the first intermediate value is determined.

According to a first embodiment of the method of the invention, this comprises the following further steps:

Development of a second measured value representing a density of the medium on the basis of the measurement signals and

Developing a correction value using the second measured value.

According to a second embodiment of the method of the invention, this comprises the following further steps:

Allowing an excitation current to flow through an electro-mechanical excitation arrangement mechanically coupled to the measuring tube for causing vibrations of the measuring tube, and [0050] Determining a second intermediate value taking into account the excitation current.

According to a third embodiment of the method of the invention, the second intermediate value represents at least one scatter, determined for a predetermined time interval, of a measured value determined for the medium flowing in the pipeline, in particular a measured mass flow, a measured density or a measured viscosity, and / or a scattering of an operating parameter of the Coriolis mass flow meter, in particular an amplitude of the vibration measurement signals or a vibration frequency of the vibration measurement signals, determined for a predetermined time interval.

An advantage of the invention is that the correction value for the correction of the first intermediate value, which is essentially determined in a conventional manner and temporarily represents the mass flow rate, can be determined beforehand comparatively simply but very precisely. On the other hand, the correction value can be adapted very quickly to changing conditions in the medium to be measured, in particular changing concentration ratios, since very little arithmetic operation is required to determine it. Therefore, in the Coriolis mass flow meter according to the invention, in comparison to a conventional Coriolis mass flow meter, only minor changes, essentially limited to the firmware, have to be made only in the usually digital evaluation electronics, while none or both in the measuring sensor and in the generation and preprocessing of the vibration measurement signals only minor changes are required. For example, the vibration measurement signals can still be sampled with a usual sampling ratio of well below 100: 1, in particular approximately 10: 1.

Another advantage of the invention is that, especially in contrast to the Coriolis mass flow meter described in US-B 65 05 519, always practically the same Evaluation method for the determination of the measured value can be carried out, since the evaluation method according to the invention also despite significantly changing flow conditions in the measuring tube, for example due to a temporarily two-phase or multi-phase medium and / or a medium consisting temporarily of several components, possibly also with varying concentrations of the individual phases and / or components, can be adapted to the current flow conditions in a very simple manner by recurring selection of the currently most suitable coefficients from the table memory.

The invention and further advantageous embodiments will now be explained in more detail using exemplary embodiments which are illustrated in the figures of the drawing. Identical parts are provided with the same reference symbols in all figures; if clarity requires, reference numerals already mentioned are omitted in the following figures.

1 shows a perspective view of a Coriolis mass flow measuring device used to generate a mass flow measurement,

2 schematically shows, in the manner of a block diagram, a preferred embodiment of a measuring device electronics suitable for the Coriolis mass flow measuring device from FIG. 1,

3 shows a perspective view in a first side view of an exemplary embodiment of a vibration-type measuring sensor suitable for the Coriolis mass flow meter of FIG. 1,

Fig. 4 shows the sensor of Fig. 3 in perspective in a second side view

5 shows an embodiment of an electro-mechanical excitation arrangement for the sensor of FIG. 3.

In Fig. 1, a Coriolis mass flow meter 1 is shown in perspective, which is used to record a physical quantity - here a mass flow m - of a two-phase or multi-phase medium flowing in a pipeline and into a measured quantity - to represent the mass flow - currently representative measured values - here a mass flow measured value X _m ; the pipeline is not shown for reasons of clarity. Medium can be practically any flowable substance, for example liquids, gases or vapors, in which, in addition to a main or carrier medium, inhomogeneities, i.e. undissolved portions of another medium with a consistency deviating from the carrier medium, are entered, for example solid particles carried in the liquid and / or gas bubbles bubbled into liquid. For measuring the mass flow, the Coriolis mass flow measuring device 1 comprises a measuring sensor 10 of the vibration type and, as shown in FIG. 2, measuring device electronics 50 electrically connected to the measuring sensor 10. To accommodate the measuring device electronics 50, there is also an external sensor Sensor 10 attached electronics housing 200 provided.

To measure the mass flow m, Coriolis forces are generated in the fluid flowing therethrough by means of the sensor 10, which is excited by the measuring device electronics 50 in operation, which are dependent on the mass flow m and which are measurable on the sensor 10, that is to say they can be sensed and electronically evaluated , act back. In addition to generating the mass flow measurement value X _m , the Coriolis mass flow measurement device also serves to measure a density p of the flowing medium and to determine a density measurement value Xp currently representing the density p.

Preferably, the measuring device electronics 50 is also designed such that it operates a Coriolis mass flow measuring device 1 with a higher-level measured value processing unit, for example a programmable logic controller (PLC), a personal computer and / or a workstation, via a data transmission system, For example, a fieldbus system can exchange measurement and / or other operating data. Furthermore, the measuring device electronics 50 is designed in such a way that it can be supplied by an external energy supply, for example also via the aforementioned fieldbus system. In the event that Vibration measuring device is provided for coupling to a field bus, the, in particular programmable, measuring device electronics 50 has a corresponding communication interface for data communication, for example for sending the measured data to a higher-level programmable logic controller or a higher-level process control system.

3 and 4, an embodiment of a physical-electrical transducer arrangement of the vibration type serving as a measuring sensor 10 is shown. The structure and mode of operation of such a converter arrangement is known per se to the person skilled in the art and is e.g. also described in detail in US-A 60 06 609.

For guiding the fluid to be measured, the measuring sensor 10 comprises at least one measuring tube 13 having an inlet end 11 and an outlet end 12 of predeterminable measuring tube lumen 13A which is elastically deformable in operation and of a predeterminable nominal diameter. Elastic deformation of the measuring tube lumen 13A means here that in order to generate Coriolis forces internal to the fluid and thus describing the fluid, a spatial shape and / or a spatial position of the measuring tube lumen 13A is changed cyclically, in particular periodically, within a range of elasticity of the measuring tube 13, cf. for example US-A 48 01 897, US-A 56 48 616, US-A 57 96 011 and / or US-A 60 06 609. At this point it should also be expressly pointed out that, although the sensor in the exemplary embodiment comprises only a single, straight measuring tube, in order to implement the invention instead of such a vibration-type measuring sensor, practically any of the Corioils mass flow measuring sensors described in the prior art can be used, in particular one of the bending vibration type with only or at least partially in one Bending vibration mode vibrating, curved or straight measuring tube. Particularly suitable are, for example, vibration-type sensors with two curved measuring tubes through which the medium to be measured flows, as described, for example, in EP-A 1 154 243, US-A 53 01 557, US-A 57 96 011 US-B 65 05 519 or WO-A 02/37063 are described in detail. Further suitable embodiments for such transducer arrangements serving as measuring transducers 10 are, for example, WO-A 02/099363, WO-A 02/086426, WO-A 95/16 897, US-A 56 02 345, US-A 55 57 973 or US-A 53 57 811. Titanium alloys, for example, are particularly suitable as the material for the measuring tube 13 used. Instead of titanium alloys, it is also possible to use other materials commonly used for such, in particular also for curved, measuring tubes, such as, for example, stainless steel, tantalum or zirconium, etc.

The measuring tube 13, which communicates in the usual way on the inlet side and on the outlet side with the pipeline supplying and discharging the fluid, is clamped in a rigid, in particular flexurally and torsionally rigid, support frame 14 so that it can vibrate. Instead of the box-shaped support frame 14 shown here, other suitable carrier means, such as e.g. Pipes running parallel or coaxial to the measuring tube can be used.

The support frame 14 is fixed on the measuring tube 13 on the inlet side by means of an inlet plate 213 and on the outlet side by means of an outlet plate 223, the latter both being pierced by corresponding extension pieces of the measuring tube 13. Furthermore, the support frame 14 has a first side plate 24 and a second side plate 34, which two side plates 24, 34 are each fixed to the inlet plate 213 and to the outlet plate 223 in such a way that they run practically parallel to the measuring tube 13 and are spaced apart therefrom are arranged, cf. Fig. 3. Thus, facing side surfaces of the two side plates 24, 34 are also parallel to each other. A longitudinal rod 25 is fixed to the side plates 24, 34, spaced apart from the measuring tube 13, which serves as a balancing mass which counteracts the vibrations of the measuring tube 13. The longitudinal rod 25 extends, as shown in FIG. 4, practically parallel to the entire oscillatable length of the measuring tube 13; however, this is not mandatory, the longitudinal bar 25 can of course also be made shorter, if necessary. The The support frame 14 with the two side plates 24, 34, the inlet plate 213, the outlet plate 223 and the longitudinal rod 25 thus has a longitudinal center of gravity which runs practically parallel to a measuring tube central axis 13B virtually connecting the inlet end 11 and the outlet end 12.

3 and 4 is indicated by the heads of the drawn screws that the aforementioned fixing of the side plates 24, 34 on the inlet plate 213, on the outlet plate 223 and on the longitudinal rod 25 can be done by screwing; however, other suitable types of fastening known to those skilled in the art can also be used.

In the event that the sensor 10 is to be detachably mounted with the pipeline, the measuring tube 13 has a first flange 19 formed on the inlet side and a second flange 20 on the outlet side, cf. Fig. 1; instead of the flanges 19, 20, e.g. other pipe connection pieces for detachable connection to the pipe, such as the so-called triclamp connections indicated in FIG. 3. If necessary, the measuring tube 13 can also be connected directly to the pipeline, e.g. be connected by means of welding or brazing etc.

To generate the Coriolis forces mentioned, the measuring tube 13 is vibrated during operation of the sensor 10, driven by an electro-mechanical excitation arrangement 16 coupled to the measuring tube, at a predefinable oscillation frequency, in particular a natural resonance frequency, in the so-called useful mode and thus in can be predetermined elastically deformed, the natural resonance frequency also being dependent on a density of the fluid. In the exemplary embodiment shown, the vibrating measuring tube 13 is spatially, in particular laterally, deflected from a static idle position, as is customary in such transducer arrangements of the bending vibration type. The same also applies in practice to those transducer arrangements in which one or more curved measuring tubes execute cantilever vibrations about a corresponding longitudinal axis that imaginatively connects the respective inlet and outlet ends, or also to such Transducer arrangements in which one or more straight measuring tubes only execute bending vibrations in a single vibration plane.

The excitation arrangement 16 is used to _generate an excitation force F _exc acting on the measuring tube 13 by _converting an electrical excitation power P _exc which is fed in by the measuring device electronics 50. The excitation power P _exc serves practically only to compensate for the power _component extracted from the vibration system via mechanical and fluid-internal friction. In order to achieve the _highest possible efficiency, the excitation power P _{exc is set} as precisely as possible in such a way that the vibrations of the measuring tube 13 in the useful mode, for example that of a basic resonance frequency, are maintained.

For the purpose of transferring the excitation force F _exc to the measuring tube 13, the excitation _arrangement 16, as shown in FIG. 5, has a rigid, electromagnetically and / or electrodynamically driven lever arrangement 15 with a boom 154 fixed to the measuring tube 13 and with a yoke 163. The yoke 163 is also fixed to one end of the arm 154 at a distance from the measuring tube 13, in such a way that it is arranged above the measuring tube 13 and transversely to it. A metal disk, for example, which receives the measuring tube 13 in a bore can serve as the arm 154. For further suitable designs of the lever arrangement 15, reference is made to the already mentioned US-A 60 06 609. The lever arrangement 15 is T-shaped and arranged, see. 5 shows that it acts on the measuring tube 13 approximately in the middle between the inlet and outlet ends 11, 12, as a result of which it experiences its greatest lateral deflection in the middle during operation.

5 comprises a first excitation coil 26 and an associated first permanent magnetic armature 27 and a second excitation coil 36 and an associated second permanent magnetic armature 37. The two excitation coils, which are preferably connected electrically in series, for driving the lever arrangement 15 26, 36 are on both sides of the measuring tube 13 below the yoke 163 on the support frame 14, in particular releasable, fixed in such a way that they interact with their respective associated anchors 27 and 37 during operation. If necessary, the two excitation coils 26, 36 can of course also be connected in parallel with one another. As shown in FIGS. 3 and 5, the two armatures 27, 37 are fixed to the yoke 163 so that they are spaced apart from one another in such a way that during operation of the sensor 10 the armature 27 is practically from a magnetic field of the excitation coil 26 and the armature 37 is practically from a magnetic field Exciter coil 36 passes through and is moved due to corresponding electrodynamic and / or electromagnetic force effects. The movements of the armatures 27, 37 generated by the magnetic fields of the excitation coils 26, 36 are transmitted from the yoke 163 and from the arm 154 to the measuring tube 13. These movements of the armatures 27, 37 are designed such that the yoke 163 is alternately deflected from its rest position in the direction of the side plate 24 or in the direction of the side plate 34. A corresponding axis of rotation of the lever arrangement 15 which is parallel to the already mentioned measuring tube central axis 13B can, for example, extend through the arm 154.

The support frame 14 further comprises a holder 29 for the electromechanical excitation arrangement 16, in particular detachably connected to the side plates 24, 34, in particular for holding the excitation coils 26, 36 and possibly individual components of a magnetic brake arrangement 217 mentioned below.

Finally, the measuring sensor 1 has a measuring sensor housing 100 surrounding the measuring tube and supporting frame, which protects them from harmful environmental influences. The sensor housing 100 is provided with a neck-like transition piece to which the electronics housing 200 housing the measuring device electronics 50 is fixed, cf. Fig. 1.

In the sensor 10 of the embodiment, the lateral deflections of the vibrating measuring tube 13 firmly clamped at the inlet end 11 and at the outlet end 12 simultaneously cause an elastic deformation of its measuring tube lumen 13A, which is practically formed over the entire length of the measuring tube 13. Furthermore, 13 due to a torque acting on the lever arrangement 15 at the same time as the lateral deflections at least in sections, a rotation about the measuring tube central axis 13B is forced, so that the measuring tube 13 practically oscillates in a mixed bending vibration torsion mode serving as useful mode. The rotation of the measuring tube 13 can be designed such that a lateral deflection of the end of the arm 154 spaced from the measuring tube 13 is either the same or opposite to the lateral deflection of the measuring tube 13. The measuring tube 13 can therefore execute torsional vibrations in a first bending vibration torsion mode corresponding to the same direction or in a second bending vibration torsion mode corresponding to the opposite direction. Then, in the sensor 10 according to the exemplary embodiment, the natural fundamental resonance frequency of the second bending vibration torsion mode of, for example, 900 Hz is almost twice as high as that of the first bending vibration torsion mode.

In the event that the measuring tube 13 is to perform operational vibrations only in the second bending vibration torsion mode, a magnetic brake arrangement 217 based on the eddy current principle is integrated in the excitation arrangement 16, which serves to stabilize the position of the mentioned axis of rotation. By means of the magnetic brake arrangement 217, it can thus be ensured that the measuring tube 13 always vibrates in the second bending vibration torsion mode and thus any external disturbing influences on the measuring tube 13 do not lead to a spontaneous change to another, especially not to the first, bending vibration torsion mode. Details of such a magnetic brake arrangement are described in detail in US-A 60 06 609.

At this point, it should also be mentioned that in the measuring tube 13 deflected in this way according to the second bending vibration torsion mode, the imaginary central axis 13B of the measuring tube is slightly deformed and thus spans not a plane but a slightly curved surface during the vibrations. Furthermore, one in this Surface trajectory lying from the center point of the measuring tube center axis has the smallest curvature of all trajectory curves described by the measuring tube center axis.

In order to detect the deformations of the measuring tube 13, the measuring sensor 10 further comprises a sensor arrangement 60 which, by means of at least one first sensor 17 reacting to vibrations of the measuring tube 13, generates a first, in particular analog, vibration measurement signal s1 which represents it. The sensor 17 can e.g. be formed by means of a permanent magnetic armature, which is fixed to the measuring tube 13 and interacts with a sensor coil held by the support frame 14. Particularly suitable as sensors 17 are those which, based on the electrodynamic principle, detect a speed of the deflections of the measuring tube 13. However, acceleration-measuring electrodynamic or also path-measuring resistive or optical sensors can also be used. Of course, other sensors known to the person skilled in the art and suitable for the detection of such vibrations can also be used. The sensor arrangement 60 further comprises a second sensor 18, in particular identical to the first sensor 17, by means of which it supplies a second vibration measurement signal s2, which also represents vibrations of the measuring tube 13. In this embodiment, the two sensors 17, 18 are spaced apart from one another along the measuring tube 13, in particular at an equal distance from the center of the measuring tube 13, in the measuring sensor 10 such that by means of the sensor arrangement 60 both the inlet side and the outlet side Vibrations of the measuring tube 13 are recorded locally and mapped into the corresponding vibration measurement signals s1 and s2. The first and possibly the second vibration measurement signal s1 and s2, which usually each have a signal frequency corresponding to an instantaneous vibration frequency of the measuring tube 13, are fed to the measuring device electronics 50, as shown in FIG. 2.

To vibrate the measuring tube 13, the excitation _{arrangement 16 is} adjustable by means of a likewise oscillating excitation current i _exc Amplitude and of adjustable excitation frequency f _{exc are} fed in such a way that the excitation _coils 26, 36 flow through them during operation and the magnetic fields required for moving the armatures 27, 37 are generated in a corresponding manner. The excitation current i _exc can be sinusoidal or rectangular, for example. The excitation frequency f _{exc of} the excitation current i _exc is preferably selected and set in the measuring sensor shown in the exemplary embodiment so that the laterally oscillating measuring tube 13 oscillates as exclusively as possible in the second bending vibration torsion mode.

To generate and set the excitation current i _ΘXC, the measuring _device electronics 50 comprise a corresponding driver circuit 53 which is controlled by a frequency control signal y _FM representing the excitation frequency f _{exc to be set} and by an amplitude _{control signal} y _AM representing the amplitude of the excitation current i _{exc to be set} , The driver circuit can be implemented, for example, by means of a voltage-controlled oscillator and a downstream voltage-to-current converter; Instead of an analog oscillator, for example, a numerically controlled digital oscillator can also be used to set the excitation current i _exc .

To generate the amplitude control signal y _A , for example, an amplitude control circuit 51 integrated in the measuring device electronics 50 can be used, which uses the instantaneous amplitude of at least one of the two sensor signals s ^ s ₂ and a corresponding constant or variable amplitude reference value \ N ^ the amplitude control signal y _AM updated; if necessary, a momentary amplitude of the excitation current i _exc can also be used to generate the amplitude _{control signal} y _AM . Such amplitude control circuits are also known to the person skilled in the art. As an example of such an amplitude control circuit, reference is once again made to Coriolis mass flow meters of the "PROMASS I" series. Their amplitude control circuit is preferably designed so that the lateral vibrations of the measuring tube 13 to a constant, that is, from

Density, p, independent, amplitude are controlled. Furthermore, the frequency control signal y _FM can be supplied by a corresponding frequency control circuit 52, which updates this, for example, on the basis of at least the sensor signal S _T and on the basis of a frequency-representative direct voltage serving as a corresponding frequency reference value W ₂ .

Preferably, the frequency control circuit 52 and the driver circuit 53 are interconnected to form a phase control loop, which is used in the manner known to the person skilled in the art, based on a phase difference, measured between at least one of the sensor signals s- ,, s ₂ and the one to be set or the measured excitation current i _exc , the frequency control signal y _{FM to} constantly adjust to a current resonance frequency of the measuring tube 13. The construction and use of such phase locked loops for operating measuring tubes at one of their mechanical resonance frequencies is described in detail, for example, in US Pat. No. 4,801,897. Of course, other frequency control circuits known to the person skilled in the art can also be used, as described, for example, in US Pat. No. 4,524,610 or US Pat. No. 4,801,897. With regard to the use of such frequency control circuits for sensors of the type described, reference is also made to the "PROMASS I" series already mentioned. Further circuits suitable as driver circuits can also be found, for example, in US Pat. No. 5,869,770 or also in US Pat. No. 5,505,519.

According to a further embodiment of the invention, the amplitude control circuit 51 and the frequency control circuit 52 are realized by means of a digital signal processor DSP provided in the measuring device electronics 50 and by means of program codes implemented accordingly and running therein. The program codes can, for example, be stored persistently or permanently in a non-volatile memory EEPROM of a microcomputer 55 which controls and / or monitors the signal processor and, when the signal processor DSP is started, in a volatile data memory RAM of the measuring device, for example integrated in the signal processor DSP -Electronics 50 can be loaded. Suitable for such applications Signal processors are, for example, those of the type TMS320VC33, as are offered by Texas Instruments Inc. on the market.

It goes without saying that at least the sensor signal s and possibly also the sensor signal s _{2 are} to be converted into corresponding digital signals for processing in the signal processor DSP by means of corresponding analog-to-digital converters A / D, cf. see EP-A 866 319 in particular. If necessary, control signals output by the signal processor, such as the amplitude control signal y _AM or the frequency control signal y _FM , may need to be converted in a corresponding manner from digital to analog.

As shown in FIG. 2, the vibration measurement signals x _s1 , x _{s2 are} also fed to a measuring circuit 21 of the measuring device electronics. Conventional, especially digital, measuring circuits can be used as measuring circuit 21 for this purpose, which determine the mass flow on the basis of the vibration measuring signals x _s1 , x _s2 , cf. in particular the aforementioned WO-A 02/37063, WO-A 99/39164, US-A 5648 616, US-A 50 69 074. Of course, other Coriolis mass flow meters known to those skilled in the art can also be used Measuring circuits are used which measure phase and / or time differences between the vibration measurement signals x _s1 , x _s2 and evaluate them accordingly. In an advantageous manner, the measuring circuit 21 can also be implemented by means of the signal processor DSP.

The measuring circuit 21, which is at least partially designed as a flow computer, is used in the manner known per se to the person skilled in the art on the basis of a phase difference which is detected between the two, possibly suitably conditioned, vibration measurement signals x _s1 , x _s2 to determine the measured value corresponding to the mass flow rate to be measured. As already mentioned at the beginning, inhomogeneities in the flowing medium, for example gas bubbles and / or solid particles carried in liquids, can lead to the fact that the measured value determined in a conventional manner, assuming a homogeneous medium, does not yet match the actual mass flow rate sufficiently precisely, ie it must be corrected accordingly; this previously determined, provisionally representing the mass flow rate or at least corresponding to this measured value, which in the simplest case can be the phase difference existing and detected between vibration measurement signals x _s1 , x _s2 , is therefore referred to below as a first intermediate value X ' _m . From this first intermediate value X ' _m, in turn, the electronics electronics 21 finally derives the mass flow measurement value X _{m, which} represents the mass flow rate with sufficient accuracy.

It has already been discussed in the prior art that such inhomogeneities, due to the measuring principle, primarily result in a change in the density measured by the flowing medium. Further investigations on the part of the inventors, however, led to the surprising finding that, contrary to what has been said in the prior art, the correction of the intermediate value X ' _{m can} , on the one hand, be carried out using fewer, very easy-to-determine correction factors which can easily be determined by the means Coriolis mass flow meters as measured values of flow parameters determined, in particular the measured density and / or the mass flow measured here for the time being, and / or from the operating parameters usually directly measured during operation of Coriolis mass flow meters, in particular the measured vibration amplitudes, vibration frequencies and / or the excitation current itself can be derived. On the other hand, the correction can be carried out using the predetermined density measured value Xp and the predetermined intermediate value X ' _m with a computational effort that is very small in comparison to the rather complex calculation methods mentioned at the beginning.

For precise measurement of the mass flow, a corresponding correction value X _{κ is} derived from the intermediate value X ' _m by means of the evaluation electronics 2 and the mass flow measurement value X _m using the correction value X _κ to the intermediate value X' _m , especially digitally, calculated. For example, the correction of the practically on conventionally determined intermediate value X ' _m based on the functional equation

X _m = (l + X _κ ) .χ _m (1)

Take place.

According to the invention, a second intermediate value X _{2 is} determined in operation to determine the currently suitable correction value X ₁ , which represents a measure of a, in particular percentage or realistic, proportion of a phase, for example a gas phase or a liquid phase, of the medium, and / or represents a deviation of the fluid to be measured from the ideal homogeneity or a degree of inhomogeneity. The correction value X _κ is thus derived from a concentration of the inhomogeneities measured during operation or transmitted to the Coriolis mass flow meter.

According to the invention, the evaluation electronics determine the correction value X ₁ , starting from the intermediate value X ₂ , practically directly, because in the evaluation electronics a clear relationship between the current intermediate value X ₂ and the matching correction value X _{κ is} represented, in particular. is programmed. For this purpose, the evaluation electronics 2 furthermore have a table memory 56, in which a large number of digital correction values X _κ , i determined beforehand, for example during the calibration of the Coriolis mass flow rate measuring device, are stored. On these correction values X _{K |} ι is directly accessed by the measuring circuit via a memory address derived by means of the currently valid second intermediate value X ₂ . A programmable read-only memory, for example an FPGA (field programmable gate array), an EPROM or an EEPROM, can serve as the table memory 56. The correction value X _κ can be determined in a simple manner, for example, by comparing the currently determined intermediate value X ₂ with corresponding default values for the intermediate value X ₂ entered in the table memory and then reading out that correction value X _{K i} , i.e. by the evaluation electronics 2 for the further calculation is used, which corresponds to the default value closest to the intermediate value X ₂ . The use of such a table storage for the Determining the correction value X has the advantage, among other things, that the correction value XK is very quickly available at runtime after the calculation of the intermediate value X ₂ .

In addition to the determination of the correction value X ₁ , the intermediate value X ₂ can also advantageously also be used, for example, to determine the degree of inhomogeneity of the fluid or measurement values derived therefrom, such as a percentage air content in the fluid or a volume-quantity or to signal the mass fraction of solid particles carried in the fluid, for example visually perceptible on site or in a remote control room.

By evaluating a number of temporal amplitude _{profiles of} the vibration _{measurement signals} and the excitation current i _exc , which were recorded during measurements carried out on various liquids disturbed in a predetermined manner, it has also been shown that both the excitation current i _exc and the vibration _{measurement signals} x _{s1 )} x _s2, on the one hand, despite essentially constant conditions, for example in the case of a steadily flowing liquid with constant density and viscosity and with a largely constant proportion of entrained air bubbles, which can fluctuate considerably over time. On the other hand, it was also found that the excitation current i _exc, which fluctuates in a practically unpredictable manner, or the vibration _{measurement signals} x _s1 , x _s2 , especially their amplitudes, can each have an empirical standard deviation or an empirical scatter s _p , which are very strong are correlated with the degree of inhomogeneity. Accordingly, the intermediate value X _{2 is determined} according to an embodiment of the invention as a function of the scatter s _{p of} the flow and / or operating parameters selected for the specific application, that is, it should apply

X ₂ = f (s _p ) (2)

The intermediate value X ₂ can be determined both on the basis of the scatter of a single flow and / or operating parameter, for example the excitation current, and on the basis of a combination of several flow and / or operating parameters. The calculation of the respective scatter s _p for the purpose of determining the intermediate value X ₂ can be carried out during the operation of the Coriolis mass flow meter 1 using a sampling AF of m measured values a; the selected flow parameter, for example the intermediate value X _κ or the density measured value Xp, or the selected operating parameter, for example the excitation current i _exc or one of the vibration _{measurement signals} x _s1 , x _s2 or the like, according to the known function:

[0100], where a corresponds to the mean value estimated for the sampling AF. For this purpose, the individual measured values aj can be stored digitally, for example, in the volatile RAM. If necessary, the sampling AF used to determine the scatter s _{p can,} for example, also be a correspondingly stored sampling sequence of an amplitude _{profile of} an operating parameter measured in an analog manner, for example a section of a digitized envelope curve of the excitation current i _exc or one of the vibration _{measurement signals} x _s1 , x _s2 .

Investigations have shown that, for a sufficiently precise estimate of the scattering, s samples AF of only a relatively small thickness, m, e.g. of approximately 100 to 1000 measured values a "are required, the individual measured values also only having to be sampled within a very narrow sampling window or time interval of approximately 1 to 2 seconds. Accordingly, a relatively low sampling frequency would be on the order of a few kilohertz, e.g. about 1 to 5 kHz is sufficient.

It has also been shown that the intermediate value X _{κ can be determined} for numerous applications as a simple, in particular linear or quadratic, function with the intermediate value as an argument, so that some are used to determine the preset values to be stored for the intermediate value X _κ a few wet, i.e. using appropriate test fluids, calibrated measuring points are sufficient to practically without the table memory by simple interpolation and / or extrapolation methods between these support points determined experimentally during calibration, e.g. using the method of least squares to be able to fill up further calibration measurements with the remaining default values. For some applications, however, it has proven to be advantageous to calculate the default values for the intermediate value X _κ as a solution of an arctangent function or a sigmodal function. To reduce the calibration effort, the determination of the default values for the intermediate value X _{κ can} advantageously be carried out as part of a type calibration in which a few actually measured and possibly also calculated default values are adopted for Coriolis mass flow measuring devices of the same type.

According to a further embodiment of the invention, the evaluation electronics are used to store the measured density value Xp and a previously determined or timely measured reference density value Kp, which is stored, for example, as a constant value when the Coriolis mass flow meter is started up or in operation can be transmitted externally to the Coriolis mass flow meter, a deviation Δp of the density p of the medium from a predetermined reference density is determined. To generate the correction value X _κ , the deviation Δp thus determined is based on the functional equation with the second intermediate value X ₂

X _κ = Δp. X ₂ (4)

[0105] calculated.

Knowing the fluid to be measured, the reference density value Kp can be entered manually, for example on site or from a remote control room, or sent from an external density meter to the measuring device electronics, for example via fieldbus.

[0107] However, it can also be determined directly in advance for the fluid by means of the evaluation electronics 21, for example when the fluid is single-phase or at least largely homogeneous. Accordingly, according to a further embodiment of the invention, the reference density value Kp is determined using a density measurement value Xp ₀ , which is also stored in the measuring device electronics, the stored density measurement value _{Xρ ι0 representing} a density of the medium, which in the case of homogeneous medium or with the medium assumed to be homogeneous has been measured. According to a further development of this embodiment of the invention, the density measurement value Xρ ₀ stored as the reference density value Kp is used for the subsequent correction of an intermediate value X ′ _m previously determined in the case of an inhomogeneous medium. This embodiment of the invention can be used in a particularly advantageous manner, for example in a metering or filling process, in which, on the one hand, there are considerable flow conditions in the measuring tube from one another in a short time sequence, in particular even when the measuring tube is not completely filled, and in which, on the other hand, is primarily the mass flow totalized over an entire batch, but ultimately the total mass of the medium actually filled is of interest. The aforementioned functions, which serve to generate the mass flow measured value X _m , symbolized by Eq. (1) to (4) can be at least partially implemented in an evaluation stage 54 of the measuring device electronics 50. The evaluation stage 54 can advantageously also be implemented, for example, by means of the signal processor DSP or, for example, also by means of the microcomputer 55 mentioned above. The creation and implementation of corresponding algorithms which correspond to the above-described equations or which simulate the functioning of the amplitude control circuit 51 or the frequency control circuit 52, and their translation into program codes which can be carried out in such signal processors is known per se to a person skilled in the art and therefore does not require any more detailed explanation. Of course, the aforementioned equations can also be easily or completely represented in the measuring device electronics 50 by means of corresponding, discretely constructed, analog and / or digital computing circuits.

Claims

Expectations

1. 1. Coriolis mass flow meter, especially Coriolis mass flow / density meter, for measuring a mass flow of a two-phase or multi-phase medium flowing in a pipeline, which Coriolis mass flow meter comprises: at least one measuring tube inserted into the course of the pipeline ( 11), which is flowed through by the medium during operation, a carrier means (12) which is fixed at an inlet-side end and an outlet-side end of the measuring tube (11) and thus clamps it so that it can vibrate, an excitation arrangement (13) which the measuring tube (11 ) in operation in mechanical vibrations, in particular bending vibrations, vibration sensors (141, 142) for generating an inlet-side vibrations of the measuring tube (11) representing first vibration measurement signal (x _s1 ) and an outlet-side vibrations of the measuring tube (11) representing second vibration measurement signal (x _s2 ), and a measuring and operating electronics (2), the one the exciter arrangement (13) driving excitation current (i _exc ) and a mass flow measured value (X _m ), which represents a mass flow to be measured, the measuring and operating electronics (2) one derived from the vibration measurement signals (x _s1 , x _s2 ), with which mass flow to be measured corresponding to the first intermediate value (X ' _m ) and a correction value (X _κ ) for the first intermediate value (X' _m ), and based on the first intermediate value (X ' _m ) and the correction value (X _κ ) the mass flow measurement value (X _m ) is determined, the measuring and operating electronics (2) generating the correction value (X _κ ) using at least one second intermediate value (X ₂ ), which is generated by at least one of the vibration measurement signals (x _s1 , x _s2 ) and / or is derived from Erregerestrom (i _exc), and which represents a measure for a portion of a phase of the medium, wherein the measuring and operating electronics (2) has a table memory (56) in which a plurality of discrete standard values f is stored digitally r the correction value (X _κ), and uses one of the standard values for determining the correction value (X _κ) is read out using the second intermediate value (X ₂₎ from the table memory (56).

2. 2. Coriolis mass flow meter according to claim 1, wherein the Evaluation electronics (2) provides a density measurement value (Xp) derived from the first and / or second vibration measurement signal (x _s ι, x _S 2) and represents the density of the medium, and the evaluation electronics (2) provide the correction value (X _κ ) determined using the density measurement value (Xp).

3. 3. Coriolis mass flow meter according to one of the preceding claims, in which the evaluation electronics (2) uses the second intermediate value (X ₂ ) to determine a memory address for a default value serving as a current correction value (X _κ ) in the table memory.

4. 4. Coriolis mass flow meter according to one of the preceding claims, in which the second intermediate value (X ₂ ) on the basis of a scatter of an amplitude of the excitation current (i _exc ) determined at least for a predetermined time interval, an amplitude of the vibration _{measurement signals} (x _s1 , x _s2 ), an oscillation frequency of the oscillation measurement _signals (x _s1 , x _s2 ), a measured density and / or the first intermediate value (X ' _m ) is determined.

5. 5. Coriolis mass flow meter according to one of the preceding claims, in which the evaluation electronics (2) determine the mass flow measurement value (X _m ) based on the functional equation X _m = 11 + x -X _m .

6. 6. Method for generating a measured value (X _m ) representing a physical measured variable, in particular a mass flow measured value, which represents a mass flow of a medium flowing in a pipeline, by means of a Coriolis mass flow meter, in particular Coriolis mass flow / Density meter, the method comprising the following steps: causing vibrations, in particular bending vibrations, of a measuring tube (11) through which the medium flows and the Coriolis mass flow meter, detecting the vibrations of the measuring tube (11) and generating a first vibration measuring signal (x _s1 ) representing inlet-side vibrations and a second vibration measurement signal (x _s2 ) representing exhaust-side vibrations, developing a first intermediate value (X ' _m ), in particular corresponding to the mass flow, using the two vibration measurement signals (x _s1 , x _s2 ), determining a second intermediate _value (X ₂ ), esp. Using at least ens one of the two vibration _{measurement signals} (x _s1 , x _s2 ), generating a correction value (X _κ ) for the intermediate value (X ' _m ) using the second intermediate value (X ₂ ), which represents a measure for a portion of a phase of the medium, and correcting the intermediate value (X' _m ) using the correction value (X _κ ), wherein the correction value (X _κ) using the second intermediate value (X _2), and using a table memory, in which a plurality of discrete standard values for the correction value (X _κ) digitally stored, is determined by the fact that the currently to be used default value for the correction value (X _κ ) is identified on the basis of the second intermediate value (X ₂ ) and is read out from the table memory.

7. The method according to claim 6 further comprising a step of developing a mass flow measurement value serving as a measurement value (X _m ), which represents a mass flow rate of the medium, on the basis of the measurement signals (x s1> ^x s2).

8. The method as claimed in claim 6 or 7, further comprising the following steps: developing a second measured value (Xp) representing a density of the medium on the basis of the measurement signals (x _s1 , x _s2 ) and developing a correction value (X _κ ) using the second Measured value (Xp).

9. The method according to any one of claims 6 to 8, comprising the following further steps: flowing an excitation current (i _exc ) through an electro-mechanical excitation arrangement (13) mechanically coupled to the measuring tube (11) for causing vibrations of the measuring tube ( 11), and determining a second intermediate _value (X ₂ ) taking into account the excitation _current (i _exc ).

10. The method according to any one of claims 6 to 9, wherein the second intermediate value (X ₂ ) at least one scatter determined for a predetermined time interval of a measured value determined for the medium flowing in the pipeline, in particular a measured mass flow rate, a measured density or a measured viscosity and / or determined for a predetermined time interval scattering of an operating parameter of the Coriolis mass flow meter, esp. an amplitude of the oscillation measurement signals (x _s1, x _s2) or an oscillation frequency of the oscillation (x _s1, x _s2) represented.