EP1692467A2

EP1692467A2 - Coriolis mass flowmeter

Info

Publication number: EP1692467A2
Application number: EP04804716A
Authority: EP
Inventors: Christian Matt; Alfred Wenger; Michael Fuchs; Wolfgang Drahm
Original assignee: Endress and Hauser Flowtec AG; Flowtec AG
Current assignee: Endress and Hauser Flowtec AG
Priority date: 2003-12-12
Filing date: 2004-12-07
Publication date: 2006-08-23
Also published as: CA2547697C; WO2005057131A3; WO2005057131A9; CA2547697A1; WO2005057137A9; RU2006124841A; EP1692466A2; CA2547699A1; CA2547699C; WO2005057131A2; RU2348012C2; WO2005057137A3; WO2005057137A2; RU2339007C2; RU2006124840A

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 medium flowing in a pipeline, in particular two or more phases, 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. the mass flow rate, the density and / or the viscosity, often used such measuring devices, by means of a vibration-type transducer used in the course of the fluid-carrying pipeline, flowed through by the fluid during operation and a measuring and operating circuit connected to it, reaction forces in the fluid, such as eg. 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 sensors of the vibration type are, for example. in WO-A 03O76880, WO-A 02/37063, WO-A 01/33174, WO-A 00/57141, WO-A 99/39164, WO-A 9807009, WO-A 9516897 , WO-A 88O3261, US 2003O208325, US-B 65 13 393, US-B 65 05 519, US-A 6006 609, US-A 58 69770, US-A 57 96011, US -A 56 02 346, US-A 53 01 557, US-A 5259 250, US-A 52 18 873, US-A 50 69 074, US-A 50 29482, US-A 48 76 898, US-A 47 33 569, US-A 46 60421, US-A 45 24 610, 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.

To guide the fluid, the transducers 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 is left. In order to detect vibrations of the pipe segment, particularly on the inlet and outlet sides, the measuring sensors furthermore each have a physical-electrical sensor arrangement that reacts to movements of the pipe segment. In Coriolis mass flow meters for a medium flowing in a pipeline, the measurement of the mass flow is based, for example, on the fact that the medium flows through the measuring tube which is inserted into the pipeline and vibrates during operation is allowed to flow, whereby 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 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 US-A 41 87 721 already mentioned at the beginning mentions that the instantaneous density of the flowing medium can usually also be measured with Coriolis mass flowmeters, specifically on the basis of 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 also measured using modern Coriolis mass flowmeters, especially since they always compensate for measurement errors due to fluctuating fluid density when measuring mass flow to be drawn, 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 found, however, that in the case of inhomogeneous media, in particular two-phase or multi-phase fluids, the vibration measurement signals derived from the vibrations of the measuring tube, in particular the phase shift mentioned, despite the viscosity and Density in the individual fluid phases as well as the mass flow rate are kept practically constant and / or are taken into account accordingly, are subject to considerable fluctuations and can therefore become completely unusable for the measurement of the respective physical parameter without remedial measures. 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, outgassing and leads to foam formation. Another example of such inhomogeneous media is wet or saturated steam.

Already in US-A 45 24 610 a possible cause of this problem for the operation of vibration type sensors is indicated, namely the fact that inhomogeneities entered by the fluid in the measuring tube, such as. Gas bubbles, on attach its inner wall and can influence the vibration behavior to a significant extent. 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. In addition, 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 0 076880, US-A 5259 250, US-A 50 29482 or the US-B 65 05 519 has been discussed. While a flow or fluid conditioning prior to the actual flow measurement is proposed in WO-A 03O76880 to reduce the measurement errors associated with two-phase or multi-phase fluids, both JP-A 10-281846 and US-B 65 05 519 a correction of the flow measurement based on the vibration measurement signals, in particular the mass flow measurement, is proposed, 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 the advantage, for example, that compared to conventional Coriolis mass flow / density meters, no or only very slight changes are made to the sensor must, be it on the mechanical structure, on the excitation arrangement or the operating circuit controlling this, which are particularly adapted to the special application.

[009] However, there is a considerable disadvantage of such classifiers, among others. in the fact that, compared to conventional Coriolis mass flow meters, considerable changes in the area of measured value generation are required, especially with regard to the analog-to-digital converter used and the microprocessors. 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 a corresponding physical-mathematical model with technically relevant or comprehensible parameters is usually not explicitly available, 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 in the case of inhomogeneous, in particular multiphase, fluids. Another object is to specify a corresponding method for generating the measurement result.

To achieve this object, the invention consists in a Coriolis Mass flow meter, in particular Coriolis-Mas s flow meter / density meter, for measuring a mass flow of a two-phase or multi-phase medium flowing in a pipeline, which comprises Coriolis-Mas s flow meter:

[013] at least one measuring tube inserted into the course of the pipeline and through which the medium flows during operation,

[014] 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 excitation arrangement which sets the measuring tube into mechanical vibrations, in particular bending vibrations, during operation,

Vibration sensors for generation

A first vibration measurement signal representing inlet-side vibrations of the measuring tube and

[018] a second vibration measurement signal representing outlet-side vibrations of the measuring tube, and

[019] measurement and operating electronics, the

[020] an excitation current driving the excitation arrangement and

Provides a mass flow measurement value representing a mass flow to be measured,

[022] the measuring and operating electronics

[023]. generates a first intermediate value derived from the vibration measurement signals and corresponding to the mass flow to be measured, and generates a correction value for the first intermediate value, and

[024] determines the mass flow measured value on the basis of the first intermediate value and the correction value,

[025] wherein the measurement and operating electronics generate the correction value using at least one second intermediate value,

[026] which is derived from at least one of the vibration measurement signals and / or from the excitation current, and

[027] which represents a measure of a portion of a phase of the medium,

[028] the measuring and operating electronics

[029] 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.

[031] Furthermore, the invention consists in a method for generating a physically sical measured variable representing measured value, 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 a 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,

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

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

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

[037] correcting the intermediate value using the correction value,

Wherein the correction value is determined using the second intermediate value and using a .Table memory, in which a plurality of discrete default values five the correction value is digitally stored, in that the currently used default value for the correction value is identified on the basis of 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 supply a mass flow measurement value derived from the first and / or from the second vibration measurement signal and representing a mass flow rate of the medium.

According to a second embodiment of the Coriolis mass flow meter of the invention

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

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

[043] According to a third embodiment of the Coriolis mass flow meter of the invention, the evaluation electronics determine a memory based on the second intermediate value. address for a default value stored in the table memory and used as the 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 of an amplitude of the excitation current, an amplitude of the oscillation measurement signals, an oscillation frequency of the oscillation measurement signals, a measured density and / or the first intermediate value, determined at least for a predetermined time interval is determined.

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

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

Developing a correction value using the second measurement value.

[048] 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

Determining a second intermediate value taking into account the excitation current.

[051] According to a third embodiment of the method of the invention, the _. second intermediate value 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 a scatter of an operating parameter of the Coriolis determined for a predetermined time interval Mass flow meter, in particular an amplitude of the vibration measurement signals or an oscillation frequency of the vibration measurement signals.

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, compared to a conventional Coriolis mass flow meter, it is only necessary for the usually digital evaluation electronics minor changes, essentially limited to the firmware, are made, while no changes or only minor changes are required both for the measuring sensor and for the generation and preprocessing of the vibration measurement signals. For example, the vibration measurement signals can still be sampled with a usual sampling ratio of well below 100: 1, especially about 10: 1.

A further advantage of the invention can also be seen in the fact that, in particular also in contrast to the Coriolis mass flow meter described in US Pat. No. 65 05 519, practically the same evaluation method can always be carried out for the determination of the measured value, since the evaluation method according to the invention, even in spite of significantly changing flow conditions in the measuring tube, for example due to a temporarily two-phase or multi-phase medium and / or a medium temporarily consisting of several components, possibly also with varying concentrations of the individual phases and / or components, through a recurring selection the currently most suitable coefficient from the table memory can be adapted to the current flow conditions in a very simple manner.

The invention and further advantageous refinements will now be explained in more detail with reference to exemplary embodiments which are shown 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 side view of a Coriolis mass flow measuring device used to generate a mass flow measurement value,

2 shows schematically, 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 measuring device from FIG. 1,

[058] FIG. 4 shows the sensor of FIG. 3 in perspective in a second side view and

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, the This is used to record a physical measured variable - here a mass flow m - of a two-phase or multi-phase medium flowing in a pipeline and into a measured value currently representing this measured variable - here the mass flow - here a mass flow measurement value X - ; the pipe m 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. To measure 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 one of outside sensor 10 attached Elektr onikgehäuse 200 provided. To detect the mass flow m, Coriolis forces are generated in the fluid flowing through by the measuring sensor 10, which is excited by the measuring device electronics 50 during operation, which are dependent on the mass flow m and which are measurable on the measuring 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, the Coriolis mass flow measurement device is also used to measure a density of the flowing medium and to determine a density measurement value X currently representing the density. Preferably, the measuring device electronics 50 is also designed such that it operates via the Coriolis mask 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 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 the vibration measuring device is provided for coupling to a fieldbus, the measuring device electronics 50, in particular programmable, has a corresponding communication interface for data communication, for example. for sending the measurement data to a higher-level programmable logic controller or a higher-level process control system, on.

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

[064] 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 predefinable nominal diameter. Elastic deformation of the measuring tube lumen 13A means here that in order to generate internal fluid forces 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 5648 616, US-A 57 96011 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, to implement the invention, instead of such a vibration-type measuring sensor, practically any of those in the prior art Corioils mass flow sensors can be used, especially one of the bending vibration type with only or at least partially vibrating, bent or straight measuring tube in a bending vibration mode. 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 154243, US-A 53 01 557, and 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 sensors 10 are, for example. WO-A 02/099363, WO-A 02/086426, WO-A 9516 897, US-A 56 02345, 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 manner on the inlet side and the outlet side with the pipeline supplying or discharging the fluid, is clamped in a rigid, in particular flexurally and torsionally rigid, support frame 14 so that it can vibrate , Instead of of the box-shaped support frame 14 shown here can of course also other suitable carrier means, such as. Pipes running parallel or coaxial to the measuring tube can be used.

The support frame 14 is fixed to the measuring tube 13 on the inlet side by means of an inlet plate 213 and from the slas side by means of an outlet plate 223, both of which are 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 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 line which runs practically parallel to a measuring tube central axis 13B virtually connecting the inlet end 1-l & 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 to the inlet plate 213, to the outlet plate 223 and to 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, a first flange 19 is formed on the inlet side of the measuring tube 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 may be formed, 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 driven during operation of the measuring 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, vibrated in the so-called useful mode and thus elastically deformed in a predeterminable manner, 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 applies in practice to those transducer arrangements in which one or more curved measuring tubes execute cantilever vibrations about a corresponding longitudinal axis connecting the respective inlet and outlet ends, or to those transducer arrangements in which one or more straight measuring tubes only have bending vibrations in a single one Execute vibration level. The excitation arrangement 16 is used to generate an excitation force F acting on the measuring tube 13 exe by converting an electrical excitation power P fed in by the measuring device electronics 50. The excitation power P serves practically exe exe only to compensate for the power component extracted from the vibration system via mechanical and fluid-internal friction. To achieve the highest possible efficiency, the excitation power P is set as precisely as possible so that exe practically the vibrations of the measuring tube 13 in the useful mode, for example. that of a fundamental resonance frequency are maintained. ,,. ^• [071] For the purpose of transmitting the excitation force F on the measuring tube 13, the exe exciter arrangement 16 as shown in Fig. 5 is shown, a rigid, electromagnetically and / or electrodynamically driven lever arrangement 15 with an on the measuring tube 13 flexural strength fixed bracket 154 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 6006 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 exciters, which are preferably electrically connected in series, for driving the lever arrangement 15 - Gerspulen 26, 36 are detachable on both sides of the measuring tube 13 below the yoke 163 on the support frame 14, in particular so that they interact with their respective armature 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 means of 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 parallel to the already mentioned measuring tube center axis 13B can, for example. through the boom 154. [073] 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 one below mentioned magnetic brake arrangement 217. 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 measuring sensor 10 of the exemplary 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, due to a torque acting on the lever arrangement 15 at the same time as the lateral deflections, a rotation about the central axis 13B of the measuring tube is forced in the measuring tube 13, so that the measuring tube 13 practically vibrates in a mixed bending vibration torsion mode serving as a useful mode. The rotation of the measuring tube 13 can be designed such that a lateral deflection of the Measuring tube 13 at the distal end of the arm 154 is either the same or opposite to the lateral deflection of the measuring tube 13. The measuring tube 13 can thus 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 into 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 6006 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 not a plane but a slightly curved surface in the vibrations spans. Furthermore, a path curve lying in this area and described by the center point of the measuring tube center axis has the smallest curvature of all the path curves described by the measuring tube center axis.

[078] 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 which reacts to vibrations of the measuring tube 13, generates a first, in particular analog, vibration measurement signal sl which represents it. The sensor 17 can be formed, for example, 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, it is also possible to use acceleration-measuring electrodynamic or also path-measuring resistive or optical sensors. Of course you can too other sensors known to the person skilled in the art and suitable for the detection of such vibrations can 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 in such a way that by means of the sensor arrangement 60 both inlet side and outlet side -side vibrations of the measuring tube 13 locally recorded and mapped into the corresponding vibration measurement signals sl or s2. The first and possibly the second vibration measurement signal sl or 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 allow the measuring tube 13 to vibrate, the excitation arrangement 16 is fed by means of a likewise oscillating excitation current i of adjustable amplitude and of excitation frequency f which can be set in such a way that the excitation coils 26, 36 flow through them in operation exe and in a corresponding manner required to move the armature 27, 37 magnetic fields are generated. The excitation current i can be exe, for example, sinusoidal or rectangular. The excitation frequency f of the excitation current exe i is preferably selected and set so exe in the measuring sensor shown in the exemplary embodiment 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, the measuring device exc electronics 50 comprise a corresponding driver circuit 53, which is controlled by a frequency control signal y representing the excitation frequency f to be set and by an exe FM the amplitude exc control signal y representing the amplitude of the excitation current i to be set is. The driver circuit can be implemented, for example, by means of a voltage-controlled AM-controlled oscillator and a downstream voltage-to-current converter; Instead of an analog oscillator, a numerically controlled digital oscillator can also be used to set the excitation current i. To generate the amplitude control signal y, an amplitude control circuit 51 integrated in the measuring device AM electronics 50 can be used, for example, which uses the instantaneous amplitude of at least one of the two sensor signals s, s and I 2 of a corresponding constant or variable amplitude reference value W to determine the amplitude updated control signal y; if necessary, a momentary amplitude of the excitation current i can be used to generate the amputation control signal y. exe 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. The amplitude control circuit of the latter is preferably designed such that the lateral vibrations of the measuring tube 13 are controlled to a constant amplitude, that is to say also independent of the [082] density. [083] Furthermore, the frequency control signal y can be supplied by a corresponding frequency FM control circuit 52 which, for example. updated based on at least the sensor signal s and on the basis of a frequency-representative direct voltage serving as a corresponding frequency reference value W. The frequency control circuit 52 and the driver circuit 53 are preferably connected 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 and the one to be set or the measured one Er- 1 2 excitation current i, constantly adjust the frequency control signal y to a momentary resonance FM frequency of the measuring tube 13. The construction and use of such v .. ^• phase locked loops for operating MeßrohiÄn on one of their mechanical resonance frequencies is described in detail, for example, in US-A 48 01 897. Of course, other frequency control circuits known to those skilled in the art can also be used, such as. are also described in US-A 45 24610 or US-A 48 01 897. 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 implemented 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, eg. volatile data memory RAM integrated in the signal processor DSP the meter electronics 50 are loaded. Signal processors suitable for such applications are, for example, those of the type TMS320VC33, as are marketed by Texas Instruments Inc. [086] It goes without saying that at least the sensor signal s and possibly also the sensor signal s 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 are output by the signal processor, such as, for example. convert the amplitude control signal y or AM the frequency control signal y, if necessary in a corresponding manner digital-to-analog to FM. [087] As shown in FIG. 2, the vibration measurement signals x, x are also fed to a measurement sl s2 circuit 21 of the measurement device electronics. Conventional, especially digital, measuring circuits can be used as the measuring circuit 21 for this purpose, which determine the mass flow on the basis of the vibration measuring signals x, x, cf. in this regard 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 which are known to the person skilled in the art can also be suitable Measuring circuits are used which measure phase and / or time differences between the vibration measurement signals x, x and evaluate sl s2 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 formed at least in part from the flow computer, is used in the manner known per se to the person skilled in the art based on a phase difference, which is detected between the two, possibly suitably conditioned, vibration measurement signals x, x mass flow rate to determine the correct s2 sponding measured value. 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 accurately, i.e. it must accordingly Getting corrected; 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 detected between vibration measurement signals x, x and sl s2, is therefore referred to below as a first intermediate value X '. From this first intermediate value X ', in turn, the mass flow rate becomes sufficient using the evaluation electronics 21 exactly representative mass flow measurement value X is derived. m

[089] It has already been discussed in the prior art that such inhomogeneities, due to the measuring principle, result primarily 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 is stated in the prior art, the correction of the intermediate value X 'can, on the one hand, be carried out using fewer, very easy-to-determine correction factors, which are easily determined by the means Coriolis mass flow meters as measured values of determined flow parameters, in particular the measured density and / or - here provisionally - measured mass flow, and / or 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 previously determined density measured value X @ and the previously determined intermediate value X 'with a computational effort which is very small in comparison to the rather complex computing methods mentioned at the outset. [090] For precise measurement of the mass flow, a corresponding correction value X is derived from the intermediate value X 'by means of the evaluation electronics 2 and the mass flow measurement value X is calculated using the correction value X to m K, the intermediate value X', especially digitally , For example, the correction of the intermediate value X 'determined practically in a conventional manner can be based on the m functional equation [091] [which is the encoded mathematical formula] (1)

[092] take place.

According to the invention, a second intermediate value X is determined to determine the currently suitable correction value X during operation, which is a measure of a percentage of a phase, for example a gas phase or a liquid phase, of the medium, in particular a percentage, or real, of the medium. represents and / or represents a deviation of the fluid to be measured from the ideal homogeneity or a degree of inhomogeneity. The correction value X is thus derived from a concentration of the inhomogeneities measured during operation or transmitted to the Coriolis mass flow measuring device. According to the invention, the evaluation electronics determine the correction value X, K on the basis of the intermediate value X, thereby practically directly that in the evaluation Electronics a clear relationship between the current intermediate value X and 2 the matching correction value X is mapped, especially programmed. For this purpose K, the evaluation electronics 2 also have a table memory 56, in which a large number of digital correction values X previously determined, for example during the calibration of the Coriolis mass flow measuring device, are stored. These K, i correction values X are directly accessed by the measuring circuit via a memory address derived by means of the second intermediate value X currently valid K, i. 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 can be, for example. can be determined in a simple manner by comparing the currently determined intermediate value X with corresponding default values for the intermediate value X entered in the table memory 2 and 2 then reading out that correction value X, that is, it is used by the evaluation electronics 2 for the further calculation, which corresponds to the default value closest to the intermediate value X 2. The use of such a table memory for determining the correction value X has the advantage, among other things, that the K correction value X is very quickly available at runtime K 2 after the calculation of the intermediate value X. In addition to the determination of the correction value X, the intermediate value X,%... K 2 can furthermore advantageously also be used, for example, to determine the degree of inhomogeneity of the fluid or measurement values derived therefrom, such as, for example. a percentage air content in the fluid or a volume, quantity or 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 of the excitation current i, which were recorded during measurements carried out on various fluids which were disturbed in a predetermined manner, it was further shown that both the excitation current i and the oscillation current exc gungsmeßsignale x, x on the one hand, in spite of essentially constant conditions, ie, for example in the case of stationary flowing liquid with constant density and viscosity and with a largely constant proportion of entrained air bubbles, can fluctuate considerably over time. On the other hand, it was also found that the excitation current i fluctuating in a practically unpredictable manner or the vibration measurement signals x, x, in particular their exe sl s2 amplitudes, each an empirical standard deviation or an empirical one Can have scatter s, which are very strongly correlated with the degree of inhomogeneity p. Accordingly, the intermediate value X is determined according to an embodiment of the invention as a function of the scattering s of the flow and / or operating parameters selected for the specific application, ie the following should apply [097] [is the coded mathematical formula] (2)

The intermediate value X 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.

[099] During the operation of the Coriolis mass flow measuring device 1, the calculation of the respective scatter s for the purpose of determining the intermediate value X can be based on 2 a sampling AF of m measured values a of the selected flow parameter, for example the intermediate value X or the density measured value X§, or the selected operating parameter, for example the excitation current i or one of the vibration excitation measurement signals x, x or the like, according to the known function: sl s2

[100], where a corresponds to the mean value estimated for sampling AF. For this purpose, the individual measured values a can e.g. be stored in the volatile data memory RAM digital i. If necessary, karaidas to determine the scattering p Sampling AF eg. can also be a correspondingly stored sampling sequence of an amplitude profile of an analog measured operating parameter, for example a section of a digitized envelope of the excitation current i or one of the vibration measurement signals x, x. sl s2

[101] Studies have shown that, for a sufficiently precise estimate of the scatter, s samplings AF of only a relatively small thickness, m, eg. of approximately 100 to 1000 measured values a, are required, the individual measured values i also having to be scanned only within a very narrow scanning 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, for example. about 1 to 5 kHz is sufficient. [102] It has also been shown that the intermediate value X can be ascertained for numerous applications as a solution of simple, in particular linear or quadratic, functions with the intermediate value as an argument, so that the predetermined values to be stored for the intermediate value can be determined X a few wet measuring points, i.e. calibrated using appropriate test fluids, are sufficient to the table memory by means of simple interpolation and / or extrapolation methods between these experimentally determined support points during calibration, for example using the method of least squares, practically without further calibration measurements being able to fill up 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 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 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, using the evaluation electronics, the density measured value X§ and a predetermined or timely measured reference density value K, which is stored, for example, as a constant value when the Coriolis-Mas flowmeter is started or can be transmitted externally to the Coriolis mass flow meter during operation, a deviation 0 of the density _ of the medium from a predetermined reference density is determined. To generate the correction value X, the K deviation thus determined becomes 0 _ \ with the second intermediate value X'a based on the functional equation

[104] X = EE | X (4) K 2

[105] offset.

[106] With knowledge of the fluid to be measured, the reference density value K§ 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 a fieldbus.

[107] However, it can also be determined 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 K§ is determined using a density measurement value X also stored in the measuring device electronics, the stored density measurement value X§ representing a density of the medium, which in the case of homogeneous medium or has been measured for a medium assumed to be homogeneous. After a further development of this embodiment of the invention, the as Reference density value K stored density measurement value X is used for the subsequent correction of an intermediate value X 'm previously determined with inhomogeneous medium. This embodiment of the invention can, for example, in a particularly advantageous manner. be used in a metering or filling process in which flow conditions in the measuring tube differ considerably from one another within a batch in a short time sequence, in particular also when the measuring tube is not completely filled, and in which on the other hand primarily the totalized over an entire batch Mass flow, but ultimately the total mass of the medium actually filled is of interest. The aforementioned m used to generate the mass flow measurement value X

Functions 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, for example, advantageously. also by means of the signal processor DSP or e.g. can also be realized by means of the above-mentioned microcomputer 55. The creation and implementation of corresponding algorithms that correspond to the previously described equations or that simulate the functioning of the amplitude control circuit 51 or the frequency control circuit 52, as well as their translation into program codes that can be executed in such signal processors, is known to the person skilled in the art. is familiar and therefore requires no detailed explanation. , 4, Of course, the aforementioned equations can also be represented in whole or in part by means of corresponding, discretely constructed, analog and / or digital arithmetic circuits in the measuring device electronics 50.

Claims

Expectations

1. Coriolis-Mas sedflußflußmesser, esp. Coriolis mass flow / density meter, for measuring a mass flow of a two- or multi-phase medium flowing in a pipeline, which Coriolis-Mas sedflußflußmesser: at least one in the course of the pipeline used measuring tube (11) which is flowed through during operation of the medium, a carrier means (12) which is fixed at an inlet-side end and an end of the measuring tube (11) on the outlet side and thus clamps it so that it can vibrate, an exciter arrangement (13) which the measuring tube (11) is set in operation in mechanical vibrations, in particular bending vibrations, vibration sensors (141, 142) for generating a first vibration measuring signal (x) representing inlet-side vibrations of the measuring tube (11) and an outlet-side sl representing vibrations of the measuring tube (11) second vibration measurement signal (x), and a measuring and operating electronics (2) which one of the Ers2 regeranordnu ng (13) driving excitation current (i) and a mass flow exc measured value (X), which represents a mass flow to be measured, m wherein the measuring and operating electronics (2) one derived from the vibration measurement signals (x, x), generates the first intermediate value (X ') with the first intermediate value (X') corresponding to the mass flow to be measured and a correction value (X) for m K, and the mass flow with the aid of the first intermediate value m (X ') and the correction value (X) -Measured value (X) determined, m K m, the measuring and operating electronics (2) generating the correction value (X) using K using at least one second intermediate value (X), which is derived from at least one of the vibration measurement signals (x, x) and / or is derived from the current s2 gerestrom (i), and which represents a measure for a portion of a phase of the exe medium, the measuring and operating electronics (2) having a table memory (56) in which a multiplicity discrete default values for the correction value (X) is stored digitally, and one of the default values is used to determine the correction value (X), which is read out from the table memory (56) using the K second intermediate value (X). 2

2. Coriolis-Mas sedflußflußmesser according to claim 1, wherein the evaluation electronics (2) a derived from the first and / or from the second vibration measurement signal (x, x), representing a density of the medium density sl s2 measured value (X ) and in which the evaluation electronics (2) rectification value (X) is determined using the density measurement value (X§). 3. Coriolis mass flow meter according to one of the preceding claims, in which the evaluation electronics (2) using the second intermediate value (X) determines a 2 memory address for a serving as a current correction value (X) default value in the table memory. 4. Coriolis mass flow meter according to one of the preceding claims, in which the second intermediate value (X) is determined on the basis of a scatter of an amplitude of the excitation current (i), an exe amplitude of the vibration measurement signals (x, x) determined at least for a predetermined 2 time interval. , an oscillation frequency of the oscillation measurement signals (x, x), a measured density and / or the first intermediate value (X ') is determined. m

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) based on the m function equation [is the encoded mathematical formula]. 6 Method for generating a measured value (X) 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 a Coriolis mass flow meter. / 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) representing inlet-side vibrations and a second vibration measurement signal (x) representing exhaust-side vibrations, developing a first intermediate value (X '), in particular corresponding to the mass flow rate, using the two vibration measurement signals (xm, x), determining a second intermediate value (X), especially using at least one of the two vibration measurement signals (x, x), generating a correction value (X) for the intermediate value (X ') by means of the second intermediate value (X), which presents a measure for a portion of a phase of the medium, and Correcting the intermediate value (X ') by means of the correction value (X), the correction value (X) using the second KK intermediate value (X) and using a table memory in which a 2 large number of discrete default values for the correction value (X ) digitally recorded K is stored, it is determined that the currently used default value for the correction value (X) is identified on the basis of the second intermediate value (XK 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), which represents a mass flow rate of the medium, on the basis of the measurement signals (x, x). sl s2

8 Method according to claim 6 or 7, further comprising the following steps: developing a second measured value (Xl) representing a density of the medium on the basis of the measurement signals (x, x) and developing a correction value (X ^π- sl s2 K) using of the second measured value (X). 9. The method according to any one of claims 6 to 8, comprising the following further steps: flowing an excitation current (i) through a with the measuring tube exe (11) mechanically coupled electro-mechanical excitation arrangement (13) for causing vibrations of the measuring tube (11), and determining a second intermediate value (X) taking into account the excitation current (i). 2 exe

10. The method as claimed in one of claims 6 to 9, in which the second intermediate value (X) has 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 one Density or a measured viscosity, and / or a scatter of an operating parameter of the Coriolis mass flow meter determined for a predetermined time interval, in particular an amplitude of the vibration measurement signals (x sl x) or a vibration frequency of the vibration measurement signals (x, x), re s2 sl s2 presents.