RU2339007C2 - Coriolis acceleration mass flowmeter and method of measured value representing mass flow - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: within operation measuring tube of Coriolis acceleration flowmeter/ densimeter is driven by bending vibrational motion using exciter. Electronic unit of flowmeter develops intermediate value (X'_m) of mass flow deduced from measuring signals (x_s1, x_s2), representing input and output vibrations of measuring tube, second intermediate value (X₂) deduced from one measured operating parameter of Coriolis acceleration flowmeter: one measuring signal (x_s1, x_s2) of vibration, excitation current (i_exc) and current parameter and representing measure of medium phase portion. Using intermediate value (X₂), adjustment value (X_a) of intermediate value (X'_m) is calculated. Value (X_a) by intermediate value (X₂) is chosen from number of preset values saved in tabular memory. Using values (X'_m) and (X_a), measured value representing mass flow (X_m) is calculated.

EFFECT: higher measurement accuracy of non-uniform environments and simplified implementation.

13 cl, 5 dwg

Description

The invention relates to a Coriolis mass flow meter / densitometer for a two or more phase medium flowing in a pipeline, in particular, and also to a method for obtaining a measured value representing mass flow.

In the technique of measuring and automating processes for measuring the physical parameters of a fluid flowing in a pipeline, for example, mass flow rate, density and / or viscosity, such measuring devices are often used that, by means of a vibrating-type measuring transducer, inserted into a fluid guide pipe and connected to the measuring and operational schemes cause reaction forces in the fluid, for example, associated with the mass flow of Coriolis forces, with inertial forces associated with the density, or friction forces associated with the viscosity, etc., and produce a measurement signal representing mass flow rate, viscosity and / or density of the fluid, respectively. Such vibration-type transducers are described, for example, 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, WO-A 95/16897, WO-A 88/03261, US 2003/0208325, US-B 6513393, US-B 6505519, US-A 6006609, US-A 5869770, US-A 5796011, US-A 5602346 , US-A 5301557, US-A 5259250, US-A 5218873, US-A 5069074, US-A 5029482, US-A 4876898, US-A 4733569, US-A 4660421, US-A 4524610, US-A 4491025 , US-A 4187721, EP-A 553939, EP-A 1001254 or EP-A 1281938.

To pass the fluid, the measuring transducers include at least one measuring tube with a bent or straight segment mounted in a supporting frame, for example, tubular or box-shaped, which is forced to vibrate with an electromechanical device during operation to generate the above reaction forces excitement. To register the vibrations of the tube segment, in particular from the input and output side, the measuring transducers further comprise a physicoelectric sensor device that responds to the movements of the tube segment. In Coriolis mass flowmeters for a medium flowing in a pipeline, the measurement of mass flow is based on the fact that the medium is forced to flow through a measuring tube placed in the pipeline and vibrating during operation, as a result of which the medium experiences Coriolis forces. They, in turn, cause the input and output sections of the measuring tube to oscillate in phase with respect to each other. The magnitude of these phase shifts is a measure of mass flow. Oscillations of the measuring tube are recorded by means of two vibration sensors of the aforementioned sensor device that are spaced apart along the measuring tube and are converted into measuring oscillation signals, the mass flow rate is determined from the mutual phase shift of which.

US-A 4187721 is stated in the above source that Coriolis mass flowmeters can usually also measure the density of a flowing medium at a given moment, namely, using the frequency of at least one of the vibrational measurement signals generated by the sensor device. In addition, in most cases, the temperature of the fluid is also directly directly suitably measured, for example by means of a temperature sensor mounted on the measuring tube. Therefore, it is entirely possible to assume that - even if this is not explicitly stated - using modern Coriolis mass flowmeters, in any case, one can also measure the density and temperature of the medium, especially since they are always used to compensate for measurement errors due to density fluctuations when measuring mass flow medium, see, in particular, the already mentioned publications WO-A 02/37063, WO-A 99/39164, US-A 5602346 or WO-A 00/36379.

When using measuring transducers of the described kind, it turned out, however, that for inhomogeneous media, in particular biphasic or multiphase fluids, vibrational measuring signals obtained from the oscillations of the measuring tube, in particular also the phase shift mentioned, despite the viscosity and density of individual phases, as well as mass flow rates are practically kept constant and / or respectively also taken into account, are subject to fluctuations to a large extent and, thus, can become completely unsuitable for measurement I, if necessary, the corresponding physical parameter without supporting measures. Such inhomogeneous media can be, for example, liquids into which, as it is almost inevitable during dosing or filling processes, the existing gas in the pipeline, in particular air, is injected, or from which a dissolved fluid, such as carbon dioxide, is vented, resulting in foaming . As another example of such heterogeneous media, wet or saturated steam should be mentioned hereinafter.

Already in US-A 4,524,610, a possible cause of this problem is indicated during the operation of vibration-type transducers, namely the fact that inhomogeneities introduced by the fluid into the measuring tube, for example gas bubbles, settle on its inner wall and can thus have a significant effect on vibration characteristic. To solve the problem, it is further proposed to integrate the measuring transducer so that the direct measuring tube passes mainly vertically, thereby preventing the deposition of such interfering, in particular gaseous, inhomogeneities. This is, however, about a very special and, in particular, in the technique of measuring industrial processes, only a very conditionally implemented solution. First, in this case, the pipeline into which the measuring transducer should be integrated would have to be coordinated with it, if necessary, and not vice versa. Secondly, with measuring tubes, as already mentioned, we can talk about tubes of a curved shape, so that the problem also cannot be solved by coordinating the mounting position. In addition, it turned out that these distortions of the measuring signal cannot be significantly reduced even when using a vertically integrated direct measuring tube. In addition, fluctuations in the thus generated measuring signal in a flowing medium cannot be prevented either.

Similar reasons, as well as their influence on the accuracy of measurements in determining mass flow rate, were discussed, for example, in JP-A 10-281846, WO-A 03/076880, US-A 5259250, US-A 5029482 or US-B 6505519. while in order to reduce measurement errors associated with two or more phase fluids in WO-A 03/076880, the conditioning of the flow or the fluid preceding the actual flow measurement is proposed, in JP-A 10-281846 and US-B 6505519, preference is given to correction based on measuring oscillation signals of a flow measurement, in particular a mass flow measurement, for example p using pre-trained, if necessary also adaptive classifiers for measuring oscillation signals. Classifiers can be made, for example, in the form of Kohonen maps or a neural network and can be corrected either using the few parameters measured during operation, in particular mass flow and density, as well as other signs derived from this, or using one or several periods of oscillation of the interval of measuring oscillation signals.

The use of such a classifier gives, for example, the advantage that, in comparison with traditional Coriolis mass flow meters / densitometers, there are no changes to be made to the transmitter or only very slight changes to be made, whether in the mechanical structure, excitation device or the operating circuit controlling it, especially adapted for special use.

A significant drawback of such classifiers is, however, including the fact that, compared with traditional Coriolis mass flowmeters, significant changes are needed in the field of obtaining measurement data, primarily with respect to the used analog-to-digital converters and microprocessors. As described in US-A 6505519, for such signal processing, for example, when digitizing measuring vibration signals, which may have a vibration frequency of about 80 Hz, a sampling frequency of about 55 kHz or more is required to achieve sufficient accuracy. In other words, the measuring oscillation signals should be discretized with a ratio of sampling frequencies much more than 600: 1. In addition, correspondingly completely dropped out is also stored in the digital measuring circuit and executed firmware.

Another drawback of such classifiers should also be seen in the fact that they are trained on the measurement conditions that actually prevail during the operation of the measuring transducer, be it the installation situation, the measured fluid and, in most cases, its changing properties or other factors affecting the measurement accuracy, and should be respectively certified. Based on the high complexity of the interaction of all these factors, training and its certification can be carried out in most cases only on site and individually for each transmitter, which also results in significant costs when commissioning the transmitter. For the rest, it turned out that such classification algorithms, on the one hand, due to their high complexity, and on the other hand, due to the fact that in most cases the corresponding physical and mathematical model with technically important or non-objectionable parameters is implicit, classifiers have very low transparency and, therefore, are often difficult to implement. Being associated with this, consumer prejudices may well arise, and such problems with consumer approval may arise, in particular, when the classifier used is also a self-adaptive, for example, neural, network.

One object of the invention is, therefore, to create an appropriate Coriolis mass flow meter that provides accurate measurement of mass flow even in heterogeneous, in particular multiphase, fluids. Another task is to create an appropriate way to obtain a measurement result.

This problem is solved, according to the invention, by means of a Coriolis mass flow meter, in particular a Coriolis mass flow meter / densitometer, for measuring the mass flow rate of two or more phase media flowing in a pipeline containing:

- at least one inserted into the pipe measuring tube, streamlined during operation of the medium;

- carrier means fixed at the input and output ends of the measuring tube and clamping it, thereby, with the possibility of vibration;

- an excitation device leading the measuring tube during operation into mechanical vibrations, in particular bending vibrations;

- vibration sensors for generating a first measuring vibration signal representing oscillations at the input of the measuring tube, and a second measuring vibration signal representing oscillations at the output of the measuring tube;

- a measuring and working electronic circuit that generates an excitation excitation device, an excitation current and a measured value of the mass flow rate, representing the measured mass flow rate,

- moreover, the measuring and working electronic circuit generates derived from the measuring oscillation signals corresponding to the measured mass flow rate of the first intermediate value and the correction value of the first intermediate value and using the first intermediate value and correction value calculates the measured value of the mass flow rate,

- moreover, the measuring and working electronic circuit generates a correction value using at least one second intermediate value, which is derived from at least one of the measuring oscillation signals and / or from the excitation current and represents a measure of the fraction of the phase of the medium,

- moreover, the measuring and working electronic circuit contains a table memory in which a plurality of discrete set values of the correction value are stored in digital form, and uses one of the set values selected from the table memory using the second intermediate value to determine the correction value.

The invention further relates to a method for producing a physical measured value, in particular a measured mass flow rate representing a mass flow rate of a medium flowing in a pipeline, by means of a Coriolis mass flow meter, in particular a Coriolis mass flow meter / densitometer, which method includes the following steps:

- excitation of vibrations, in particular bending vibrations, flowing around the medium of a Coriolis mass flow meter measuring tube;

- registration of the oscillations of the measuring tube and the generation of representing oscillations at the input of the first measuring oscillation signal and representing oscillations at the output of the second measuring oscillation signal;

- obtaining the corresponding physical measured value, in particular the mass flow rate, the first intermediate value using both measuring oscillation signals;

- determination of the second intermediate value, in particular, using at least one of both measuring oscillation signals;

- generating a correction value of the intermediate value by means of a second intermediate value representing a measure of the fraction of the phase of the medium, and

- correction of the intermediate value by means of the correction value,

- moreover, the correction value using the second intermediate value and the table memory in which a plurality of discrete set values of the correction value are stored in digital form is determined due to the fact that the currently used set value of the correction value is identified using the second intermediate value and selected from the table memory.

According to a first embodiment of a Coriolis mass flow meter according to the invention, the processing electronic circuit generates a measured mass flow value derived from the first and / or second measuring vibration signal and representing the mass flow rate of the medium.

According to a second embodiment of the Coriolis mass flow meter according to the invention, the processing electronic circuit generates a measured density value derived from the first and / or second measuring vibration signal and representing the density of the medium and determines the correction value using the measured density value.

According to a third embodiment of the Coriolis mass flow meter according to the invention, the processing electronic circuit determines the address of the set value stored in the table memory and serving as the correction value at the moment using the second intermediate value.

According to a fourth embodiment of the Coriolis mass flow meter according to the invention, the second intermediate value is obtained using the amplitude of the excitation current amplitude, the amplitude of the measurement oscillation signals, the oscillation frequency of the measurement oscillation signals, the measured density and / or the first, obtained for at least a given time interval intermediate value.

In accordance with the first variant of the method according to the invention, it includes the following steps:

- obtaining representing the density of the medium of the second measured value using the measuring signals;

- obtaining a correction value using the second measured value.

In accordance with a second embodiment of the method according to the invention, it includes the following steps:

- passing the excitation current through an electromechanical excitation device mechanically connected to the measuring tube to excite the oscillations of the measuring tube and

- determination of the second intermediate value, taking into account the excitation current. According to a third embodiment of the method according to the invention, the second intermediate value represents at least one scatter obtained for a given time interval obtained for a measured value flowing in the medium pipe, in particular a measured mass flow rate, a measured density or a measured viscosity and / or obtained for a given time interval, the spread of one working parameter of the Coriolis mass flow meter, in particular the amplitude of the measuring oscillation signals or frequency oscillations oscillation measurement signals.

One advantage of the invention is that the correction value for the correction obtained, mainly in the usual way, previously representing the mass flow rate of the first intermediate value, can, on the one hand, be previously determined relatively simple, but very accurately. On the other hand, the correction value can be very quickly coordinated with changing conditions in the medium being measured, in particular, changing concentration ratios, since only very few computational operations are required to determine it. Therefore, in a Coriolis mass flowmeter, in comparison with a traditional Coriolis mass flowmeter, only usually digital processing electronic circuits have to make small changes, limited mainly by the built-in software, while neither the measuring transducer nor the generation and preprocessing of measuring signals of changes in changes not required, or rather, only minor changes required. So, for example, also the measuring oscillation signals can still be sampled with the usual ratio of sampling frequencies much less than 100: 1, in particular about 10: 1.

Another advantage of the invention should be seen in that, in particular, also in contrast to the Coriolis mass flow meter described in US-B 6505519, practically the same processing method for determining the measured value can always be carried out, since the processing method according to the invention, even despite noticeably changing flow conditions in the measuring tube, for example, due to temporarily two or more phase media, if necessary also with varying concentrations of individual phases and / or components, very ostym manner can be adapted to the flow conditions at the moment due to the continuously repeated selection from a table memory, respectively the most suitable actual coefficients.

The invention and other preferred embodiments are explained in more detail with examples of its implementation, shown in the drawings. Identical parts are denoted by the same reference numerals in all figures; for clarity, the already mentioned reference positions in the following figures are omitted. The drawings show:

- figure 1: in perspective, when viewed from the side of the Coriolis mass flowmeter, which serves to generate the measured value of the mass flow rate;

- figure 2: a block diagram of a preferred embodiment of an electronic unit suitable for the Coriolis mass flowmeter of figure 1;

- figure 3: partially in section, in perspective and in the first side view, an example of execution suitable for the Coriolis mass flow meter from figure 1 of the measuring transducer of the vibration type;

- figure 4: in perspective, with a second side view, the measuring transducer of figure 3;

- figure 5: an example implementation of an electromechanical excitation device for the measuring transducer of figure 3.

In Fig. 1, in perspective, a Coriolis mass flow meter 1 is used for measuring a physical measured quantity, here the mass flow rate m flowing in the pipeline of two or more phase media, and conversion to representing this measured quantity, here is the mass flow rate, currently measured value , here, the measured value X _{m of the} mass flow rate; the pipeline is not shown for clarity. The medium can be practically any substance capable of flow, for example liquids, gases or vapors, in which inhomogeneities are contained in addition to the main or carrier medium, i.e. undissolved fractions of another medium of a different consistency from the carrier medium, for example, particles of solid substances picked up by the liquid and / or gas bubbles contained in the liquid. To measure the Coriolis mass flow rate, the mass flow meter 1 comprises a vibratory type transducer 10 and, as shown in FIG. 2, an electronic unit 50 electrically connected to the transducer 10. A housing 200 is mounted externally on the transducer 10 to accommodate the electronic unit 50.

To measure the mass flow rate m in the flowing medium by means of a measuring transducer 10 excited to vibrations during operation by the electronic unit 50, Coriolis forces are created that are dependent on the mass flow m and acting on the measuring transducer 10 with the possibility of measurement, i.e. sensor registration and electronic processing. In addition to generating the measured value X _{m of the} Coriolis mass flow rate, the mass flow meter also serves to measure the density p of the flowing medium and determine the currently representing density ρ of the measured density Xρ density.

Advantageously, the electronic unit 50 is adapted to exchange during operation of the Coriolis mass flow meter 1 via a data transmission system, for example a fieldbus system, measurement data and / or other operational data with a measurement data processing unit, for example, a programmable memory control system, a personal computer and / or workstation. In addition, the electronic unit 50 is configured to be powered from an external power source, for example, also through the aforementioned fieldbus system. If a vibration measuring device is provided for communication with the field bus, the electronic unit 50, in particular programmable, contains a corresponding communication interface for exchanging data, for example, for transmitting measurement data to a higher-level control system with programmable memory or a higher-level process control system.

Figures 3 and 4 show an exemplary embodiment of a vibration-type physical-electrical transducer device serving as a measuring transducer 10. The construction and principle of operation of such a converter device are known to the skilled person and are described in detail, for example, in US-A 6006609.

To conduct the measured fluid, the measuring transducer 10 comprises at least one measuring tube 13 having an input 11 and an output 12 ends of a given elastically deformable working width 13A and a predetermined conditional passage. The elastic deformation of the width 13A in the light means here that in order to create a fluid inherent in the fluid and thereby describe the fluid of the Coriolis forces, the spatial shape and / or spatial position of the width 13A in the light are cyclically, in particular periodically, changed within the elastic range of the measuring tube 13 in a predetermined manner (see, for example, US-A 4801897, US-A 5648616, US-A 5796011 and / or US-A 6006609. It should be strongly pointed out that, although the transmitter in this embodiment contains only one straight line measuring practically, any of the Coriolis mass flowmeters described in the prior art can be used instead of such a measuring transducer of a vibrational type, in particular a flexural-vibrational type with exclusively or at least partially vibrating in the mode of bending vibrations, curved or direct measuring Particularly suitable, for example, are vibration-type measuring transducers with two curved measuring tubes streamlined around the measuring medium, ak are described in detail, for example, in EP-A-1154243, US-A 5301557, US-A 5796011, US-A 6505519 or WO-A 02/37063. Other suitable embodiments of such serving as measuring transducer 10 converting devices are described, for example, in WO-A 02/099363, WO-A 02/086426, WO-A 95/16897, US-A 5602345, US-A 5557973 or US -A 5357811. As the material of the measuring tube 13 used, for example, titanium alloys are particularly suitable. Instead of titanium alloys, other materials commonly used for similar, in particular also curved, measuring tubes can be used, for example, stainless steel, tantalum or zirconium, etc.

The measuring tube 13, which communicates in the usual way from the input and output sides with the fluid inlet and outlet, is clamped with the possibility of oscillation in a rigid, in particular bending and torsionally rigid carrier frame 14. Instead of the box-shaped carrier frame 14 shown here, themselves, also other suitable supporting means, for example, pipes running parallel or coaxial to the measuring tube.

The carrier frame 14 is fixed to the measuring tube 13 from the input side through the input plate 213, and from the output side through the output plate 223, and the corresponding extensions of the measuring tube 13 pass through the last two. Further, the carrier frame 14 contains the first 24 and second 34 side plates, fixed on the input 213 and output 23 plates in such a way that they pass almost parallel to the measuring tube 13 at a distance from it and from each other (figure 3). Thus, the side surfaces facing each other of both side plates 24, 34 are also parallel to each other. On the side plates 24, 34 at a distance from the measuring tube 13, a longitudinal rod 25 is fixed, serving as a damping oscillation of the measuring tube 13 of the balancing mass. The longitudinal rod 25 extends, as shown in FIG. 4, almost parallel to the entire oscillating length of the measuring tube 13; this, however, is not necessary, the longitudinal shaft 25 can be made, of course, if necessary, also shorter. The supporting frame 14 with both side plates 24, 34, input 213 and output 223 plates and a longitudinal rod 25 has, thereby, a longitudinal line of gravity that runs almost parallel to the middle axis 13B of the measuring tube, imaginatively connecting the input 11 and output 12 ends.

In FIGS. 3 and 4, the heads of the screws shown indicate that said fixing of the side plates 24, 34 on the input 213 and output 223 plates and the longitudinal shaft 25 can occur by screwing; however, other suitable and well-known fastening methods may be used.

If the measuring transducer 10 should be detachably connected to the pipeline, the first flange 19 is formed on the measuring tube 13 from the input side, and the second flange 20 is formed from the output side (Fig. 1); instead of flanges 19, 20 for detachable connection with the pipeline, for example, other connecting elements can also be molded, such as, for example, Triclamp connections shown in Fig. 3. If necessary, the measuring tube 13 can also be connected directly to the pipeline, for example, by welding or soldering with refractory solder, etc.

To create the aforementioned Coriolis forces, the measuring tube 13 during operation of the measuring transducer 10, driven by an electromechanical excitation device 16 connected to the measuring tube, is forced to vibrate at a given oscillation frequency, in particular a natural resonant frequency, in the so-called useful mode, as a result of which it is given deforms elastically, and the natural resonant frequency also depends on the density of the fluid. In the illustrated embodiment, the vibrating measuring tube 13, as is the case with such transducer devices of the flexural-vibrational type, deviates spatially from the static initial position, in particular in the lateral direction. The same applies practically to such converting devices in which one or several bent measuring tubes cantilever around the corresponding longitudinal axis, imaginatively connecting the input and output ends, or to such converting devices in which one or more direct measuring tubes make only bending vibrations in a single plane.

The excitation device 16 serves to create, when the electric power P _exx introduced by the electronic unit 50 of the device is _{converted, an} excitation force F _exc acting on the measuring tube 13 is created. The excitation power P _exx serves almost exclusively to compensate for the fraction of power taken from the oscillatory system due to mechanical or inherent friction fluid. To achieve the highest possible efficiency, the excitation power P _exc is set as precisely as possible with the possibility of practically maintaining the oscillations of the measuring tube 13 in a useful mode, for example, the fundamental resonant frequency.

To transmit the excitation force F _exc to the measuring tube 13, the excitation device 16, as shown in FIG. 5, comprises a rigid linkage mechanism 15 actuated electromagnetically and / or electrodynamically with a bracket 154 flexibly rigidly fixed to the measuring tube 13 and the yoke 163. The yoke 163 is also flexurally rigidly fixed on the end of the bracket 154 that is distant from the measuring tube 13, namely, that it is located above and across the measuring tube 13. As the bracket 154 can serve, for example, a metal washer, which places the measuring tube 13 in its hole. For other suitable implementations of the linkage mechanism 15, reference should be made here to the aforementioned publication US-A 6006609. The linkage 15 is T-shaped and is arranged to act on the measuring tube 13 approximately in the middle between the input 11 and output 12 ends (FIG. 5) As a result of which, during operation, it experiences the greatest lateral deviation in the middle.

For actuating the linkage mechanism 15, the excitation device 16 comprises in FIG. 5 a first excitation coil 26 and a corresponding first permanent magnetic armature 27, as well as a second excitation coil 36 and a corresponding second permanent magnetic armature 37. Both excitation coils 26, 36, preferably electrically connected in series are fixed on both sides of the measuring tube 13 under the yoke 163 on the supporting frame 14, in particular detachable, so that when working are in interaction with their anchors 27, 37. If necessary, both excitation coils 26, 36 can be switched on, of course, also in parallel. As shown in FIGS. 3 and 5, both anchors 27, 37 are fixed on the yoke 163 at such a distance from each other that during operation of the measuring transducer 10, the armature 27 is penetrated by the almost magnetic field of the excitation coil 26, and the armature 37 is pierced by the almost magnetic field of the coil 36 excitation and moves due to the corresponding electrodynamic and / or electromagnetic force effects. The movement of the armature 27, 37 created by the magnetic fields of the coils 26, 36 is transmitted by the yoke 163 and the bracket 154 to the measuring tube 13. These movements of the armature 27, 37 are such that the yoke 163 alternately deviates from its original position either in the direction of the side plate 24 or the direction of the side plate 34. The corresponding axis of rotation of the linkage mechanism 15, parallel to the aforementioned middle axis 13B of the measuring tube, can pass, for example, through the bracket 154.

The carrier frame 14 further includes connected to the side plates 24, 34, in particular detachably, a holder 29 of the electromechanical excitation device 16, in particular for holding the excitation coils 26, 36 and, if necessary, the individual components of the magnetic brake device 217 described below.

Finally, the measuring transducer 10 comprises a housing 100 that encloses the measuring tube and the supporting frame, which protects them from harmful environmental influences. The housing 100 is equipped with a neck-shaped adapter on which the enclosure 200 enclosing the electronic unit 50 of the device is fixed (Fig. 1).

In the measuring transducer 10 in the exemplary embodiment, the lateral deviations of the vibrating measuring tube 13, firmly clamped at the input 11 and output 12 ends, simultaneously cause elastic deformation of its width 13A in the light, performed along almost the entire length of the measuring tube 13. Further, in the measuring tube 13 due to the acting on it through the lever mechanism 15 of the torque simultaneously with lateral deviations, at least in some areas, the twisting occurs around the middle axis 13B, so h then the measuring tube 13 oscillates practically in a mixed bending-vibrational-torsional mode serving as a useful mode. The twisting of the measuring tube 13 can be such that the lateral deviation of the end of the bracket 154, which is remote from the measuring tube 13, is either equal to or opposite to the lateral deviation of the measuring tube 13. Therefore, the measuring tube 13 can make torsional vibrations in the first, uniformly directed case, vibrational-twisting mode or in the corresponding counter-directional case of the second bending-vibrational-twisting mode. Then, the measuring transducer 10, according to the exemplary embodiment, has a natural fundamental resonant frequency in the second bending-vibrational-torsional mode, for example 900 Hz, approximately twice as high as in the first bending-vibrational-torsional mode.

If the measuring tube 13 should only oscillate in the second bending-vibrational-twisting mode during operation, a magnetic brake device 217 based on the principle of eddy currents is built into the excitation device, which serves to stabilize the position of the said axis of rotation. By means of the magnetic braking device 217, it is thereby possible to guarantee that the measuring tube 13 will always oscillate in the second bending-vibrational-twisting mode, and possible external spurious influences on the measuring tube 13 will not lead to a spontaneous transition to another, in particular not to the first bending vibrational torsion mode. Details of such a magnetic braking device are described in detail in US-A 6006609.

It should also be mentioned here that in the measuring tube 13 deviated, therefore, in the second bending-vibrational-torsional mode of the measuring tube 13, the imaginary middle axis 13B is slightly deformed and, therefore, during the oscillations describes a slightly convex surface. Further, the curve lying on this surface, described by the center of the middle axis 13B, has the smallest curvature of all the curves described by the middle axis 13B.

For detecting deformations of the measuring tube 13, the measuring transducer 10 further comprises a sensor device 60, which, through at least one vibration-sensitive measuring tube 13 of the first sensor 17, generates their first, in particular analog, measuring vibration signal s ₁ . The sensor 17 can be formed, for example, by a permanent magnetic armature, which is fixed on the measuring tube 13 and is in interaction with the sensor coil held by the supporting frame 14. Particularly suitable as sensors 17 are those which, based on the electrodynamic principle, determine the rate of deviation of the measuring tube 13. Acceleration-measuring electrodynamic or path-measuring resistive or optical sensors can also be used. Of course, other sensors known to those skilled in the art and suitable for detecting such vibrations can also be used. The sensor device 60 further comprises a second sensor 18 which is identical, in particular to the first sensor 17, by means of which it also generates a second vibration measurement signal s ₂ representing vibrations of the measuring tube 13. Both sensors 17,18 are removed from each other in this embodiment along the measuring tube 13, in particular, they are located in the measuring transducer 10 at the same distance from the middle of the measuring tube 13 with the possibility of local determination by means of a sensor device 60 of the vibrations of the measuring tube 13 from the input and output sides, and conversion into the corresponding measuring signals s ₁ , s ₂ oscillations. The first s ₁ and, if necessary, the second s ₂ measuring oscillation signals, usually having a frequency that currently corresponds to the oscillation frequency of the measuring tube 13, are fed to the electronic unit 50 of the device (figure 2).

In order to make the measuring tube 13 vibrate, the excitation device 16 is also supplied with an oscillating current i _{exc for} a given amplitude and a given excitation frequency f _exc with the possibility of its flow through the excitation coils 26, 36 during operation and creation of the necessary for the movement of the anchors 27, 37 magnetic fields. The excitation current i _exc can be, for example, sinusoidal or rectangular. The excitation frequency f _{exc of the} excitation current i _exc for the measuring transducer shown in the exemplary embodiment is chosen and set so that the lateral oscillation measuring tube 13 oscillates, if possible, exclusively in the second bending-vibrational-torsional mode.

To generate and set the excitation current i _exc , the electronic unit 50 comprises a corresponding excitation circuit 53 controlled by the frequency-setting signal representing _FM set _exc frequency f _exc and representing the set amplitude of the excitation current i _exc setting amplitude setting signal _AM . The excitation circuit can be implemented, for example, by a controlled voltage oscillator and a connected voltage-current converter; instead of an analog oscillator, for setting the excitation current i _exc , for example, a digital oscillator with numerical control can also be used.

For generating an amplitude-setting signal at _AM , for example, an amplitude control circuit 51 integrated in the electronic unit 50 can be used, which, using the amplitude at the moment, of at least one of both sensor signals s ₁ , s ₂ and using the corresponding constant or a variable amplitude reference value W ₁ updates the amplitude-setting signal of _AM ; if necessary, to generate an amplitude-setting signal at _AM, one can also draw the current amplitude i _exc of the current. Similar amplitude control circuits are also known to those skilled in the art. As an example of such an amplitude control scheme, the Coriolis mass flowmeters of the PROMASS I series should be pointed out once again. Their amplitude control circuit is preferably configured to control lateral vibrations of the measuring tube 13 to a constant, i.e. independent of density ρ, amplitude.

In addition, the frequency setting signal of _FM can be generated by the corresponding frequency control circuit 52, which updates it, for example, using at least one sensor signal s ₁ , as well as using a constant voltage serving as the corresponding reference value W ₂ frequencies and representing the frequency.

Preferably, the frequency control circuit 52 and the amplitude control circuit 51 are combined into a single phase control loop, which is known to the person skilled in the art so that, using the phase difference, measured between at least one of the sensor signals s ₁ , s ₂ and the set or measured current i _exc excitation, constantly tune the frequency-setting signal from _FM to the resonant frequency of the measuring tube 13 at the moment. The design and application of such phase-shifting loops for operating the measuring tubes at one of their mechanical resonant frequencies is described in detail, for example, in US-A 4,801,897. Of course, other frequency control circuits known to the person skilled in the art, as described, for example, in US -A 4524610 or US-A 4801897. Further, regarding the use of such frequency control circuits for measuring transducers of the described kind, reference should be made to the already mentioned series "PROMASS I". Other schemes suitable as an exciting circuit can be taken, for example, also from US-A 5869770 or US-A 6505519.

According to another embodiment of the invention, the amplitude control circuit 51 and the frequency control circuit 52 are implemented by a digital signal processing processor DSP provided in the electronic unit 50 and, accordingly, program codes embedded therein and flowing therein. Program codes can be stored, for example, in a non-volatile EEPROM controlling the signal processing processor and / or the microcomputer 55 controlling it, temporarily or permanently and when the DSP processor is started, loaded into the built-in, for example, volatile memory data block 50. Suitable processors for such applications Having processed the signals are, for example, processors of the type TMS320VC33, marketed by the company Texas Instrument Instrument Inc.

It goes without saying that at least the sensor signal s ₁ and, if necessary, also the sensor signal s ₂ for processing in the DSP processor must be converted by means of the corresponding A / D analog-to-digital converters) into the corresponding digital signals (see in particular EP-A 866319). If necessary, the set signals supplied by the processor, for example, the amplitude-setting signal at _AM or the frequency-setting signal at _FM , should be subjected to digital-to-analog conversion accordingly.

As shown in FIG. 2, the measurement signals x _s1 , x _{s2 of the} oscillations are then sent to the measurement circuit 21 of the block 50. As a measurement circuit 21, this can be done using traditional, in particular digital, measurement circuits that determine the mass flow rate using the measurement signals x _s1 , x _s2 oscillations (see, in particular, WO-A 02/37063, WO-A 99/39164, US-A 5648616, US-A 5069074). Of course, other measurement schemes suitable for Coriolis mass flowmeters that are known to those skilled in the art can be used that measure the phase and / or time differences between the measurement signals x _s1 , x _{s2 of the} oscillations and process them accordingly. Advantageously, the measuring circuit 21 may also be implemented by a DSP processor.

The measuring circuit 21, made at least partially as a flow meter, serves to enable the person skilled in the art to determine the measured value using the phase difference detected between the two, if necessary, pre-conditioned measuring signals x _s1 , x _s2 corresponding to the measured mass flow rate. As already mentioned, inhomogeneities in the flowing medium, such as gas bubbles and / or particles of solids carried away by liquids, can lead to the fact that this measured value, obtained in the usual way with the assumption of a homogeneous medium, will still not be exactly accurate with the actual mass flow rate, t .e. it should be adjusted accordingly; this predefined, preliminarily representing the mass flow rate, or at least the corresponding measured value, which in the simplest case can exist between the measuring signals x _s1 , x _{s2 of the} oscillations and the detected phase difference, is called, therefore, the first intermediate value X ' _m . From this first intermediate value X ′ _m, also finally, by means of the processing electronic circuit 21, the measured value X _m , which accurately represents the mass flow rate, is derived.

It has already been discussed in the prior art in this respect that such heterogeneities due to the measurement principle are mainly expressed in a change in the measured density of the flowing medium. The studies continued by the authors, however, led to the unexpected conclusion that the correction of the intermediate value X ' _m , contrary to the prior art, can be carried out, on the one hand, using a few, very easily determined correction factors that can very well be derived from those obtained by Coriolis mass flowmeters as the measured value of the flow parameters, in particular the measured density and / or measured here is the pre-mass flow rate, and / or from usually directly venno measured during operation of Coriolis mass flowmeters operating parameters, in particular the measured vibration amplitudes, vibration frequencies and / or the excitation current. On the other hand, the correction can be made using a previously obtained measured value of X _ρ density and a previously obtained intermediate value of X ' _m with calculation costs that are very small compared to the above, rather, complex calculation methods.

To accurately measure the mass flow rate by means of the processing electronic circuit 2, the corresponding correction value X _{K is} derived from the intermediate value X ' _m and the measured value X _{m of the} mass flow rate using the correction value X _{K is} calculated to the intermediate value X' _m , in particular, digitally. According to the invention, in order to determine the currently applicable correction value X _K , a second intermediate value X _{2 is} calculated during operation, representing a measure, in particular a percentage or relative, of a fraction of a phase, for example a gas phase or a liquid phase of a medium, and / or a deviation of the measured fluid from ideal uniformity or degree of heterogeneity. The correction value X _K is therefore derived from the concentration of inhomogeneities measured during operation or transferred to the Coriolis mass flowmeter.

According to the invention, the processing electronic circuit determines the correction value X _K , based on the intermediate value X ₂ , practically due to the fact that the processing electronic circuit stores, in particular, a programmed one-to-one relationship between the actual intermediate value X ₂ and the corresponding correction value X _K . For this, the processing electronic circuit 2 contains a table memory 56, which stores a lot of digital correction values X _{K, i} , previously obtained, for example, during calibration of a Coriolis mass flow meter. To these correction values X _{K, i, the} measuring circuit directly accesses through the memory address output by means of the currently valid second intermediate value X ₂ . As the table memory 56, for example, an EEPROM, i.e. FPGA (field programmable gate array) (user programmable gate array), EPROM or EEPROM. The correction value X _K can be obtained in a simple way, for example, due to the fact that the intermediate value X ₂ obtained at the moment is compared with the corresponding intermediate values X ₂ recorded in the table memory and then that correction value X is selected _{K, i} , i.e. used in the processing electronic circuit 2 for further calculation, which corresponds to the predetermined value closest to the intermediate value X ₂ . The use of such a tabular memory for determining the correction value X _K has the advantage, among other things, that the correction value X _K after calculating the intermediate value X _{2 is} very quickly available at the time of the program execution.

In addition to determining the correction value X _{K, the} intermediate value X ₂ can be further used in a preferred way, for example, to provide an optical signal about the degree of heterogeneity of the fluid or derived from this measured values, for example, the percentage of air in the fluid or volume, quantity or mass fraction particulate matter captured by the fluid, for example, in situ or at a central control room.

When using a certain number of temporal amplitude characteristics of the measuring oscillation signals, as well as the excitation current i _exc recorded during various measurements carried out on various liquids disturbed in a given way, it turned out further that both the excitation current i _exc and the measurement signals x _s1 , x _{s2 of} oscillations, on the one hand, despite mainly constant conditions, i.e., for example, with a steady flow of fluid with constant density and viscosity and with a substantially constant constant fraction her caught air bubbles can fluctuate depending on time to a large extent. On the other hand, however, it was also established that the oscillating hardly predictable way current i _exc excitation or measuring signals x _s1, x _s2 oscillations, particularly their amplitude, can have respectively the empirical standard deviation or empirical variation sρ, very highly correlated with degree of heterogeneity. Accordingly, the intermediate value of X ₂ , according to one embodiment of the invention, is determined as a function of the scatter s _p selected for a particular application of the flow parameters and / or operating parameters. In this case, the intermediate value of X ₂ can be obtained using the scatter of a single flow parameter and / or an operating parameter, for example, an excitation current, or by using a combination of several flow parameters and / or operating parameters.

The calculation of the corresponding spread s _p in order to determine the intermediate value of X ₂ can occur during the operation of the Coriolis mass flow meter 1 using a sample AF m of the measured values a _{i of the} selected flow parameter, for example, the intermediate value of X _K or the measured density value Xρ, or the selected operating parameter, for example excitation current i _exc or one of the measuring oscillation signals x _s1 , x _s2 :

where a corresponds to the mean value estimated for the AF sample. The individual measured values a _i can be stored for this in digital form, for example, in the volatile memory of RAM data. If necessary, the AF sample can be used to determine the spread s _p , for example, also an appropriately recorded sampling sequence of the amplitude characteristic of the operating parameter measured by analogue, for example, a segment of the digitized current envelope i _exc excitation or one of the measurement signals x _s1 , x _{s2 of the} oscillations.

Studies have shown that for a sufficiently accurate estimate of the scatter s, AF samples of only relatively low power m are required, for example, 100-1000 measured values of a _i , and individual measured values should also be sampled within a very narrow sampling window or a time interval of 1-2 seconds. Accordingly, a relatively low sampling rate of the order of several kilohertz, for example 1-5 kHz, would also be sufficient.

It turned out further that the intermediate value of X _K can be determined for numerous applications as a solution to simple, in particular linear or quadratic, functions with an intermediate value as an argument, so that several wet calibrated methods are sufficient to determine the recorded set values of the intermediate value of X _K , t .e. using appropriate control fluids, measuring points, to fill the tabular memory with the rest of the preset values using simple interpolation and / or extrapolation methods between these obtained experimentally when calibrating reference points, for example using the least squares method, with practically no further calibration measurements. For some applications, however, it turned out to be preferable to calculate the setpoints of the intermediate value X _K as a solution to the arctangent function or sigmodal function. To reduce calibration costs, the determination of the setpoints of the intermediate value X _K can be carried out in the preferred way within the framework of a typical calibration, in which several actually measured and, if necessary, also calculated setpoints are used for typical Corisol mass flowmeters.

According to another embodiment of the invention, by means of a processing electronic circuit using the measured value Xρ of the density and a predetermined or close-in-time measured value Kρ of the reference density, which can be stored, for example, as a constant value when the Coriolis mass flowmeter is put into operation or transferred to it from the outside when working, determine the deviation Δρ of the density ρ of the medium from a given reference density. To obtain the correction value X _K , the deviation Δρ thus determined is calculated with a second intermediate value X ₂ based on the equation of the function:

X _K = Δρ · X ₂

Knowing the measured fluid, the Kρ value of the reference density can be entered manually, for example, on the spot or from the central control point, or sent to the electronic unit of the device from an external density meter, for example via a field bus.

It can also be obtained directly using the processing electronic circuit 21 for the fluid in advance, for example, when the fluid is single-phase or at least substantially uniform. In accordance with this, according to another embodiment of the invention, the Kρ reference density can be obtained by using also stored in the electronic unit of the device the measured values Hρ ₀ density, the stored measured value Hρ ₀ density represents the density of the medium measured at uniform or prospective as a homogeneous medium. According to one refinement of this embodiment, the measured density value Xρ, ₀ , stored as the reference density value Kρ, is used for subsequent correction of the intermediate value X ′ _m previously obtained in an inhomogeneous medium. This embodiment of the invention can be particularly advantageously applied, for example, in a dosing or filling process, when, on the one hand, substantially different flow conditions prevail in the measuring tube within a single load in a short time sequence, in particular also when an incompletely filled measuring tube, and when, on the other hand, the mass flow mainly generalized over the entire load is of interest, in the end, the whole mass is filled second measuring tube.

The functions mentioned, which serve to obtain the measured value X _{m of} mass flow rate, can be at least partially implemented in the processing stage 54 of the electronic unit 50. The processing stage 54 can be advantageously implemented, for example, also by a DSP processor or, for example, also by the aforementioned microcomputer 55. The formation and implementation of appropriate algorithms that correspond to the above equations or simulate the principle of operation of the amplitude control circuit 51 or the hour control circuit 52 The notes and transforms performed in such a signal processor program codes skilled known and therefore require no more detailed explanation. Of course, the above equations may well be fully or partially displayed in the electronic unit 50 by means of appropriate discrete, analog and / or digital computer circuits.

Claims (13)

1. Coriolis mass flow meter, in particular Coriolis mass flow meter / densitometer, for measuring the mass flow rate of two or more phase media flowing in the pipeline, containing at least one measuring tube (13) inserted into the pipeline, flowing during operation, carrying a frame (14) fixed on the input and output ends of the measuring tube (13) and clamping it with the possibility of vibration of the excitation device (16), configured to bring the measuring tube (13) when operating in mechanical vibrations in particular, bending vibrations, vibration sensors (17, 18) for generating a first measuring signal (X _s1 ) of oscillations representing oscillations at the input of the measuring tube (13), and a second measuring signal (X _s2 ) of oscillations representing oscillations at the output of the measuring tube (13), an electronic unit (50), which is configured to generate an excitation current excitation device (16) of the excitation current (i _exc ) and a measured mass flow rate value (X _m ) representing the measured mass flow rate, wherein the electronic block to (50) is configured to generate oscillations derived from the measurement signals (x _s1 , x _s2 ) corresponding to the measured mass flow rate of the first intermediate value (X ' _m ) and the correction value (X _K ) of the first intermediate value (X' _m ) and the ability to determine using the first intermediate value (X ' _m ) and the correction value (X _K ) the measured value (X _m ) of the mass flow rate, and the electronic unit (50) is configured to generate a correction value (X _K ) using at least at least one second intermediate value (X ₂ ), which is derived from at least one measured parameter: the operating parameter of the Coriolis mass flow meter - at least one of the measuring signals (x _s1 , x _s2 ) of the oscillations, current (i _exc ) excitation and flow parameter and represents a measure of the fraction of the phase of the medium, and the electronic unit (50) contains a table memory (56), which digitally stores a lot of discrete set values of the correction value (X _K ), and to determine the correction value (X _K ) ispo zuet one of the predetermined values selected from the table memory (56) using the second intermediate value (X _2). 2. The flow meter according to claim 1, characterized in that the electronic unit (50) is configured to generate a measured density value (Xρ) derived from the first or second measurement signal (x _s1 , x _s2 ) of the oscillations and representing the density of the medium, and which electronic unit (50) is configured to determine a correction value (X _K ) using the measured density value (Xρ). 3. The flow meter according to claim 1 or 2, characterized in that the electronic unit (50) is configured to determine by means of a second intermediate value (X ₂ ) the address for a given value in the table memory, currently serving as the correction value (X _K ) 4. The flow meter according to claim 1 or 2, characterized in that the second intermediate value (X ₂ ) is obtained using the obtained at least for a given time interval of the spread of the current amplitude (i _exc ) of the excitation, the amplitude of the measuring signals (x _s1 , x _s2 ) oscillations, the oscillation frequency of the measuring signals (x _s1 , x _s2 ) oscillations, the measured density and / or the first intermediate value (X ' _m ). 5. The flow meter according to claim 4, characterized in that the second intermediate value (X ₂ ) is obtained using the amplitude of the measurement signals (x _s1 , x _s2 ) obtained at least for a given time interval of the spread of the current amplitude (i _exc ) ) oscillations, the oscillation frequency of the measuring signals (x _s1 , x _s2 ) of the oscillations, the measured density and / or the first intermediate value (X ' _m ), and the electronic unit (50) is configured to determine the address for the second intermediate value (X ₂ ) for setpoint in table the memory currently serving as the correction value (X _K ). 6. The flow meter according to claim 1, characterized in that the electronic unit (50) is configured to generate a measured density value (Xρ) derived from the second measurement signal (x _s2 ) of the oscillations and representing the density of the medium; moreover, the electronic unit (50) is configured to determine a correction value (X _K ) using the measured density value (Xρ). 7. A method of obtaining a physical value of a measured value (X _m ), in particular a measured mass flow rate representing a mass flow rate of a medium flowing in a pipe, by a Coriolis mass flow meter, in particular a Coriolis mass flow meter / densitometer, comprising the following steps: vibrations, in particular bending vibrations, flow around the medium of the measuring tube (13) of the Coriolis mass flow meter, registration of oscillations of the measuring tube (13) and rolling back the representative oscillation at the input of the first measuring signal (x _s1 ) of the oscillations and representing the oscillation at the output of the second measuring signal (x _s2 ) of the oscillations, obtaining the corresponding, in particular mass flow, first intermediate value (X ' _m ) using both measuring signals (x _s1 , x _s2 ) of oscillations, determination of the second intermediate value (X ₂ ), in particular using at least one of both measuring signals (x _s1 , x _s2 ) of oscillations, generating a correction value (X _K ) an intermediate value (X ′ _m ) by means of a second intermediate value (X ₂ ) representing a measure of the phase fraction of the medium, as well as a correction of the intermediate value (X ′ _m ) by means of a correction value (X _K ), the correction value (X _K ) s using the second intermediate value (X ₂ ) and the table memory in which a plurality of discrete set values of the correction value (X _K ) are stored in digital form, it is determined that the currently used set value of the correction value (X _K ) are identified using the second intermediate value (X ₂ ) and selected from the table memory. 8. The method according to claim 7, characterized in that it comprises the following steps: obtaining a measured value representing the density of the medium (Xρ) using measuring signals (x _s1 , x _s2 ) and obtaining a correction value (X _K ) using the measured value (Xρ ) 9. The method according to claim 7, characterized in that it includes the following steps: passing an excitation current (i _exc ) through an excitation device (16) mechanically connected to the measuring tube (13) to excite the oscillations of the measuring tube (13) and determining a second intermediate value (X ₂ ) taking into account the excitation current (i _exc ). 10. The method according to claim 7, characterized in that the second intermediate value (X ₂ ) represents at least one scatter of at least one measured parameter obtained for a given time interval: in particular, the first intermediate value (X ' _m ), the density or measured viscosity, and the operating parameter of the Coriolis mass flowmeter, in particular the amplitude of the measurement signals (x _s1 , x _s2 ) of the oscillations or the oscillation frequency of the measurement signals (x _s1 , x _s2 ) of the oscillations. 11. The method according to claim 7, characterized in that it includes the following steps: passing an excitation current (i _exc ) through an excitation device (16) mechanically connected to the measuring tube (13) to excite the oscillations of the measuring tube (13) and determining a second intermediate value (X ₂ ) taking into account the excitation current (i _exc ), obtaining a measured value representing the density of the medium (Xρ) using the measuring signals (x _s1 , x _s2 ) and obtaining a correction value (X _K ) using the measured value (Xρ). 12. The method according to claim 7, characterized in that it includes the following steps: obtaining representing the density of the medium of the measured value (Xρ) using the measuring signals (x _s1 , x _s2 ;) and obtaining the correction value (X _K ) using the measured value ( Hρ), wherein a second intermediate value (X ₂₎ is obtained for a predetermined time interval variation, at least one of the measured parameters: flow, in particular the first intermediate value (X _'m), the measured density or viscosity, and the working parameter k riolisova mass flow meter, in particular the amplitudes of the measurement signals (x _s1, x _s2) the oscillation frequency or oscillation measurement signals (x _s1, x _s2) oscillations. 13. The method according to claim 7, comprising the following steps: passing the excitation current (i _exc ) through a drive device (16) mechanically connected to the measuring tube (13) to excite the oscillations of the measuring tube (13); determination of a second intermediate value (X ₂ ) taking into account the excitation current (i _exc ); obtaining a measured value representing the density of the medium (Xρ) using a second measurement signal (x _s2 ); and obtaining a correction value (X _K ) using the measured value (Xρ).

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