Measuring device, processing system and method for monitoring a gas-charged liquid

Abstract

The present invention relates to a measuring device (100) for determining the density, mass flow rate, and / or viscosity of a gas-filled liquid, comprising: an oscillator (10) having a medium conduction measuring tube (14) and two vibration modes having natural frequencies associated with the medium density; an exciter (17) for exciting the two vibration modes; at least one vibration sensor (18, 19) for detecting vibrations of the oscillator (10); and an operation and evaluation circuit (30) configured to: - apply an excitation signal to the exciter, detect the signal from the vibration sensor, and determine, based on the signal from the vibration sensor, the current values ​​of the natural frequencies of the two vibration modes of the oscillator and fluctuations of at least one natural frequency, wherein the operation and evaluation circuit is further configured to: - determine a first medium state value based on the fluctuations, wherein the operation and evaluation circuit is further configured to determine a second medium state value representing the medium based on the two natural frequencies under the assumption of microbubbles; and - output a medium state message containing the two medium state values.

Description

Technical Field

[0001] This invention relates to a measuring device for determining the density, mass flow rate, and / or viscosity of a gas-filled liquid, a processing system having such a measuring device, and a method for monitoring a gas-filled liquid. The measuring device has at least one oscillator with at least one vibratory measuring tube for conducting the medium, and has at least two vibration modes whose natural frequencies depend on the average density of the gas-filled liquid and the gas volume fraction of the gas-filled liquid. Background Technology

[0002] It is well known that density and flow rate measurements are cross-sensitive to gas filling with microbubbles due to the resonator effect. First published patent application DE 10 2015 122 661 A1 discloses a method for compensating for the effects of this cross-sensitivity, wherein the natural frequencies of two bending vibration modes are evaluated for this purpose. The result of this method is the average density value of the gas-filled liquid and the associated mass flow rate measurement.

[0003] The first published patent application, DE 10 2016 114 972 A1, discloses a method for determining the gas volume fraction of a gas-filled liquid. This method is related to the method described above, wherein, in addition to the natural frequencies of the two vibration modes, the pressure measurement of the mixture is also included in the calculation of the gas volume fraction. If the gas volume fraction and average density of the gas-filled liquid are known, the density of the liquid phase can also be calculated.

[0004] The aforementioned methods are effective to the extent that the suspended microbubbles are substantially uniformly suspended in the liquid (i.e., the medium exhibits a macroscopically homogeneous mixture). However, if larger free bubbles are present, resulting in macroscopically non-uniform spatial distribution, the methods based on the assumption of a homogeneous, compressible mixture will meet their limitations. Although the properties of macroscopically homogeneous mixtures are still recorded fairly accurately, these methods cannot truly identify gas filling within free bubbles.

[0005] The spatial non-uniform distribution of gas inclusions in a flowing medium causes temporal density fluctuations at the location of the flow measurement device, which can be detected as fluctuations in the natural frequency of the bending vibration mode. Unpublished patent applications DE 10 2018112 002.8 and DE 10 2019 003 075.3 describe measurement devices and methods that can draw conclusions about the presence of free bubbles based on frequency fluctuations. Summary of the Invention

[0006] The object of this invention is to provide a measuring device and method suitable for characterizing gas-filled liquids over a wide range of mixing ratios. A further object of this invention is to provide a processing system suitable for handling gas-filled liquids. According to the invention, this object is achieved by the measuring device, processing system, and method.

[0007] The measuring device according to the present invention includes:

[0008] An oscillator having at least one vibratory measuring tube for conducting a medium and having at least two vibration modes, the natural frequency of which depends on the average density of the gas-filled liquid and the gas volume fraction of the gas-filled liquid.

[0009] At least one exciter is used to excite two vibration modes;

[0010] At least one vibration sensor is used to detect the vibration of the oscillator; and

[0011] The operation and evaluation circuitry is configured to apply an excitation signal to the exciter, detect a signal from a vibration sensor, and determine, based on the vibration sensor signal, the current values ​​of the natural frequencies of two vibration modes of the oscillator and the fluctuation of at least one natural frequency.

[0012] The operation and evaluation circuitry is also configured to determine the first medium state value based on fluctuations.

[0013] The operation and evaluation circuitry is also configured to determine a second medium state value representing the gas charge under the microbubble hypothesis based on two inherent frequencies.

[0014] The operation and evaluation circuitry is also configured to output a medium status message, in which a first medium status value and a second medium status value are merged.

[0015] The specification of two media status values ​​provides system operators with a more comprehensive picture of the media status, even when the basic model of a single media status value is no longer sufficient to describe all aspects of the media status. This allows for more differentiated control over media handling.

[0016] In the development of this invention, under the assumption that free bubbles are the cause of fluctuations, the first medium state value includes a value that depends on the fraction of free bubbles in the medium. In particular, the teachings of unpublished patent applications DE 10 2018 112 002.8 and DE 10 2019 003 075.3 can be used for this purpose, which makes it possible to draw conclusions about the presence of free bubbles based on frequency fluctuations.

[0017] In the development of this invention, the second medium state value depends on the volume fraction of gas in the medium in the form of microbubbles. Details in this regard are described, for example, in DE 10 2015 122 661 A1 and DE 10 2016 114 972 A1.

[0018] In the development of this invention, under the assumption that the observed natural frequency ratio is due to the resonator effect, the second medium state value represents the volume fraction of gas in the medium in the form of microbubbles, in which the resonator effect occurs due to the vibration of the medium, which is compressible due to the microbubbles, against the measuring tube.

[0019] In this development of the invention, the operating and evaluation circuitry is configured to further determine a second medium state value as a function of a pressure measurement value, which represents the medium pressure in the measuring tube. For this purpose, the teachings of DE 102016 114 972 A1 can be used, for example.

[0020] The measuring points of the measuring device according to the invention accordingly include pressure sensors so as to provide pressure measurements to the measuring device.

[0021] In the development of this invention, in addition to the first medium state value, the medium state message also includes information about which flow state determined the first medium state value, wherein the information about the flow state includes flow measurement values ​​or ranges of flow measurement values, wherein the flow measurement values ​​particularly include flow velocity, mass flow rate, volumetric flow rate, or Reynolds number or range specifications of the aforementioned variables.

[0022] In the development of this invention, the first medium state value is normalized using a normalization function that depends on the flow measurement value.

[0023] In the development of this invention, the first medium state value is a function of fluctuations in the natural frequency, wherein the function also exhibits normalization dependent on the natural frequency.

[0024] In the development of this invention, the first medium state value includes the gas volume fraction or the range of gas volume fraction values ​​of the medium in the form of free bubbles.

[0025] The processing system according to the invention is used to process a medium containing a gas-filled liquid, wherein the processing system comprises:

[0026] At least one pipe for conducting the medium;

[0027] At least one measuring device according to the invention is installed in the pipeline;

[0028] At least one actuator for influencing the medium;

[0029] A process control system connected to a measuring device and an actuator to receive a medium state message and control the actuator, wherein the process control system includes a data memory storing at least one target value for gas charging, characterized in that the process control system is configured to control the actuator according to the medium state message in order to adjust the gas charging to the at least one target value.

[0030] In further development, actuators include temperature control devices for heating and / or cooling media, pumps, valves, ventilators, stirring devices, or mixers.

[0031] A method according to the invention for monitoring a gas-filled liquid using a measuring device for measuring the density, mass flow rate, and / or viscosity of a medium, the measuring device having at least one oscillator with at least one measuring tube for conducting the gas-filled liquid, the measuring device being particularly according to the invention, the method comprising the following steps:

[0032] Determine the natural frequencies of at least two bending vibration modes;

[0033] Determine the fluctuation at at least one inherent frequency;

[0034] The first medium state value is determined based on the fluctuation of the natural frequency;

[0035] Under the assumption of microbubbles, the second medium state value is determined based on two inherent frequencies of the gas charge representing the medium; and

[0036] The output medium status message combines the first and second medium status values. Attached Figure Description

[0037] The invention will now be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings. The drawings are as follows:

[0038] Figure 1 : A schematic diagram of an exemplary embodiment of the measuring device according to the present invention.

[0039] Figure 2 A graph of frequency fluctuations as a function of the flow rate of a liquid with free bubbles;

[0040] Figure 3 : A graph showing the frequency fluctuations of the liquid flow rate as a function of the volume fraction of free bubbles in the gas-filled liquid.

[0041] Figure 4a Flowchart of a method for determining the gas volume fraction in a gas-filled liquid;

[0042] Figure 4b Used in Figure 4aA detailed flowchart of the process for determining the sound velocity of a gas-filled liquid.

[0043] Figure 4c Used in Figure 4a A detailed flowchart of the process for calculating the gas volume fraction (GVF) of the gas-filled liquid in the method described above.

[0044] Figure 5 : A schematic diagram of an exemplary embodiment of the processing system according to the present invention;

[0045] Figure 6 : A flowchart of an exemplary embodiment of the method according to the present invention. Detailed Implementation

[0046] Figure 1 A first exemplary embodiment of the measuring device 1 according to the invention shown includes an oscillator 10 comprising a pair of vibrating measuring tubes 14 arranged in parallel and extending between an inlet flange 11 and an outlet flange 12, wherein each flange includes a flow divider or collector to which the measuring tube 14 leads. The dividers are interconnected by a rigid housing 15 such that vibrations of the dividers housing the measuring tubes are effectively suppressed within the vibration frequency range of the oscillator's bending vibration operating mode. The measuring tubes 14 are rigidly connected to an inlet node plate 20 and an outlet node plate 21, wherein the node plates define the vibration node of the oscillator 10 formed by the two measuring tubes 14, thereby largely defining the frequency of the bending vibration operating mode. The oscillator 10 is excited to vibrate by an electric actuator 17 acting between the two measuring tubes 14, wherein the vibration is detected by two vibration sensors 18, 19 capturing the relative motion of the measuring tubes 14 relative to each other. The exciter 17 is operated by an operation and evaluation circuit 30, which also captures and evaluates signals from a vibration sensor to determine the measured density value and possible mass flow rate measurements. According to the invention, the operation and evaluation circuit 30 is also configured to determine density fluctuations based on frequency fluctuations and thereby determine medium state values. Figure 1 As shown, the operation and evaluation circuitry can also include several spatially separated modules. Medium state values ​​can also be calculated in a remote computing module, to which the required raw data is transmitted wirelessly, for example.

[0047] Using a densitometer with an oscillator (which has at least one vibratory measuring tube for the conductive medium), the density-dependent natural frequency f based on the mode-specific nature of the oscillator can be determined according to the following formula. i To determine the density ρ of the medium:

[0048]

[0049] coefficient c0,i and c 1,i These are mode-specific coefficients, preferably determined for each type of measuring device or for each measuring device. Coefficient c 0,i The mass of the measuring tube is characterized by the conductive medium, while the coefficient c 1,i The time derivative of density depends on the specific stiffness of the measuring tube. Therefore, it is given as follows:

[0050]

[0051] Time derivative of density It is a suitable measure to describe density fluctuations. To determine this value, the observed frequency fluctuations of one or more vibration measurement tubes are... It must also be multiplied by the normalization factor. In this way, a basis can be created for an evaluation function that describes the inhomogeneity of the medium in the form of density fluctuations, independent of the specific type or size of the densitometer. In one embodiment of the invention, the operation and evaluation circuit 30 of the above exemplary embodiment of the measuring device according to the invention is configured to perform density fluctuations based on frequency fluctuations by utilizing the above-described normalization of the reciprocal of the cube of the pattern-specific intrinsic frequency:

[0052]

[0053] The effect of normalization can be illustrated using data from two Coriolis mass flow meters from the applicant company, namely the Promass F50 and Promass Q50, both of which also function as densitometers. Observed inherent frequency fluctuations... The difference is approximately 6.6 times when the gas is filled with 1% or 2% water medium. This is achieved using a normalization factor. After normalization, this leads to density fluctuations. The values ​​are roughly the same.

[0054] Density fluctuations are implemented in a second development of the invention. Equivalent analysis. In this case, the operating and evaluation circuits are designed to determine the density fluctuations according to the following equation:

[0055]

[0056] To provide relative density fluctuations The amplitude, according to the third development design of the present invention, is used to operate and evaluate the circuit based on the following formula based on the relative frequency fluctuation. Determine the range:

[0057]

[0058] If the density of the medium at the measurement point varies only a few percentage points around a known value, but otherwise is known from the range of values, then the relative density fluctuation can be estimated from the relative frequency fluctuation using the following formula:

[0059]

[0060] Among them, a i These are constants specific to the measurement point or the medium, and optionally mode-specific constants, provided that several modes are used for density measurement. The described use of a cube power over the frequency of density fluctuations or a normalization of the frequency itself over the relative density fluctuations is advantageous, but not absolutely necessary for the implementation of this invention.

[0061] Figure 2 The diagram schematically illustrates the frequency fluctuation (df / dt) of a gas-filled liquid as a function of flow velocity V. In this case, the concentration of free bubbles is, for example, a few percent of the volume. If V = 0 or the medium is stationary, the medium in the flowmeter has a constant density. Therefore, no frequency fluctuation occurs. As flow begins, the measuring device is affected over time by the variable, locally fluctuating distribution of free bubbles in the liquid, which can be observed as density fluctuations, for example, in the form of frequency fluctuations (df / dt). Initially, the frequency fluctuation (df / dt) increases with increasing velocity. However, if the velocity increases further, the measured frequency value includes a larger amount of the average density of the medium, making the local density fluctuations less significant. Therefore, the frequency fluctuation (df / dt) decreases again.

[0062] Figure 3 A topographic representation is displayed, where frequency fluctuations df / dt are shown across flow velocity and free gas volume fraction. To create such a map, various free gas volume fractions (a) can be used for specific combinations of gas and liquid. i In each case, frequency fluctuations as a function of velocity V are captured. In this figure, the gas volume fraction a... i It increases with the increase of the exponent i, and can be, for example, the volume percentage i. After creating a sufficient database, the frequency fluctuation df / dt can be represented and modeled as, for example, the velocity V and a few concentrations a in the terrain representation chosen here. i The function, where the line fl j In each case, points with the same frequency fluctuation df / dt are connected together, where the fluctuation fl j It increases as the exponent j increases.

[0063] In measurement mode, a first state value can then be assigned to the frequency fluctuation df / dt, which is a function of the flow velocity V, generated by the instantaneous mass flow rate and the current average density of the medium. Depending on the flow velocity, for the same observed frequency fluctuation fl5, two different medium state values ​​M11 and M12 will be generated, as follows: Figure 3 As shown. The importance of the first medium state value may vary depending on the problem or measurement task at the measurement point.

[0064] On the one hand, the first medium state value can correspond to the gas volume fraction a1 or a linear function of the gas volume fraction. For example, this could be useful if the gas volume fraction a1 is a process variable to be monitored or regulated.

[0065] On the other hand, the first medium state value can also correspond to the monitoring variable exceeding the critical state; for example, all frequency fluctuations corresponding to gas volume fractions below a3 will be mapped to the first medium state value M12, while all frequency fluctuations corresponding to gas volume fractions above a3 will be mapped to the first medium state value M11, where M11 corresponds to the critical state.

[0066] The first medium status value M1 will be detected, transmitted, or signaled in an appropriate manner.

[0067] In a simpler embodiment of the invention, a tuple of frequency fluctuations and associated velocities is output as a first medium state value.

[0068] exist Figure 2 and 3 In the context of the discussion, frequency fluctuations df / dt are described. Naturally, these frequency fluctuations can be normalized to the cube of the oscillator's vibration frequency before determining the medium state value, in order to determine the first medium state value based on the density fluctuation. The same applies to the normalization described above at the vibration frequency, in order to determine the medium state value based on the relative density fluctuation. Furthermore, it is also possible to perform the normalization on mass flow rate, volumetric flow rate, or Reynolds number instead of on the flow velocity V. Figure 2 and 3 The presentation in the diagram. According to embodiments of the present invention, the operation and evaluation circuitry of the measuring device is designed to perform the required calculations.

[0069] The following is for reference. Figure 4a , 4b Sections 4c describe the steps used to determine the state value of the second medium. Figure 4aThe method 400 for determining the gas volume fraction of a gas-filled liquid, as shown, begins at step 410, where the natural frequencies of the bending vibration modes f1 and f3 of the Coriolis mass flow meter are determined. For this purpose, the bending vibration modes f1 and f3 can be excited simultaneously. The desired natural frequency is determined by maximizing the ratio of vibration amplitude to mode-specific excitation power through varying the excitation frequency. Using the determined natural frequencies fi, preliminary density values ​​ρ1 and ρ3 are determined in step 420 as follows:

[0070]

[0071] Among them, c 0i c 1i and c 2i It depends on the coefficients of the pattern.

[0072] Refer to the following Figure 4b In step 430, which is further described, the sound velocity of the gas-filled liquid and an optional correction term for density measurement are determined. Then, in step 440, as further described below, based on... Figure 4c The gas volume fraction is calculated using the speed of sound.

[0073] like Figure 4b As shown, step 430 of determining the correction term first includes, in step 431, calculating the ratio V of the initial density values, for example, dividing the initial density values ​​ρ1 and ρ3 to obtain V:=ρ1 / ρ3.

[0074] Subsequently, in step 432, the value of the sound velocity c is determined at the natural frequencies f1 and f2 of the measured bending vibration mode, which results in a ratio V of the initial density values ​​observed in the following equation:

[0075]

[0076] Where r is approximately 0.84, b = 1, and g is a fractional factor relating the speed of sound and resonant frequency to the measuring tube, which can be, for example, 10 m. -1 The value of the sound velocity that satisfies the above equation is the sound velocity of a liquid filled with gas.

[0077] Based on a given value of the speed of sound, Figure 4b In step 433 of the method, the mode-specific correction term K for the resonator effect can be calculated according to the following formula. i :

[0078]

[0079] Mixing density value ρ for resonator effect correction mix-coriolis The final calculation is as follows:

[0080]

[0081] Mass flow measurement used to calculate the correction for the effect of resonator effect. Corresponding mass flow rate correction item It can be calculated in step 434 as follows:

[0082]

[0083] Therefore, the mass flow measurement value corrected for the effect of the resonator effect The result is:

[0084]

[0085] in this case, This is a preliminary mass flow rate measurement, obtained by multiplying the calibration factor of the measuring sensor by the phase angle between the first bending vibration mode and the Coriolis mode.

[0086] The following will explain how the gas volume fraction and liquid density in the form of microbubbles can be determined.

[0087] According to Sorokin, the velocity of sound in a gas-filled liquid has the following known relationship with other parameters:

[0088]

[0089] In this case, α is the gas volume fraction (or gas void fraction GVF), and c g It is the speed of sound of a pure gas, c l ρ is the speed of sound in a pure liquid, γ is the adiabatic coefficient of the gas, p is the current pressure of the liquid filled with gas, and ρ is the velocity of sound in a pure liquid. l It is the density of a liquid filled with gas.

[0090] In fact, within the pressure range where gas charging is a confounding variable, and within 10... 3 kg / m 3 At fluid densities on the order of , the sum in parentheses on the right side of the equation is essentially determined by a third sum. The expression above therefore simplifies to:

[0091]

[0092] Therefore, the gas volume fraction α can be estimated as a function of the other parameters in the equation. If we consider the liquid density ρ... l The density ρ of the Coriolis mixture, determined by dividing by the liquid volume fraction, is... mix-coriolis If the quotient, i.e. (1-α), is set, the result is as follows:

[0093]

[0094] Therefore, such as Figure 4c As shown, in step 441, the pressure value of the liquid filled with gas that dominates in the measuring tube when measuring natural frequencies f1 and f3 is determined, and then the speed of sound c is determined based on this.

[0095] Adiabatic coefficient γ = c p / c v = (f+2) / f, where f is the number of molecular degrees of freedom for the gas, for example, 1.4 for nitrogen and dry air at room temperature, and 1.3 for methane. The corresponding adiabatic coefficient can be used depending on which gas or gas mixture is expected. Based on these variables, the gas volume fraction α is then calculated in step 442.

[0096] like Figure 4a As shown, in step 450, by mixing density ρ mix-coriolis The liquid density ρ of the gas-filled liquid can be calculated using the following formula, based on the gas volume fraction α. liquidGVF Value:

[0097] ρ liquidGVF =ρ mix-coriolis / (1-α)

[0098] The liquid density is of interest, for example, because it is able to estimate the component fraction of a liquid comprising a solution or homogeneous mixture of two components with different densities.

[0099] The gas volume fraction α and the mixed density ρ of a gas-filled liquid mix-coriolis Or liquid density ρ liquidGVF These parameters can be output as a second media status value. Alternatively, several of these parameters can be output as other media status values, wherein the user can select which parameter(s) to output as a second or other media status value. The operation and evaluation circuitry is preferably configured to allow the user to freely select the parameters to be output along with the media status message.

[0100] The processing system 500 according to the present invention Figure 5The example shown is for the production and filling of viscous media, such as liquid adhesives or mustard 530. The processing system 500 includes a reactor vessel 510 and a series of actuators, namely, two inlet pumps 514, 516 for supplying the media components, a filling pump 518, a low-vacuum pump 522 connected to the upper opening of the reactor vessel 510, a stirrer 524 for mixing the components, and a temperature control device 526. Furthermore, the processing system 500 includes: a Coriolis mass flow rate and density measuring device 540 according to the invention; and a pressure sensor 550, which is arranged upstream of the Coriolis mass flow rate and density measuring device 540 to determine a pressure measurement representing the medium in the Coriolis mass flow rate and density measuring device 540. Finally, the processing system 500 includes a conveyor system 560 for supplying and removing containers 570 to be filled.

[0101] During system operation, various phenomena may occur that can lead to gas filling in medium 530, which can impair product quality.

[0102] First, if the filling level of the mixture 530 in reactor vessel 510 is too low and if the residual gas charge is too high, agitator 524 can agitate the macroscopic free bubbles into a liquid phase. Similarly, if the reactor vessel is excessively emptied, pump 518 can draw in bubbles.

[0103] Secondly, microbubbles may be generated during the reaction or when mixing the components, suspended in the liquid phase. To remove these microbubbles, the space 532 above the mixture 530 in reactor 510 can be evacuated using a low-vacuum pump 522. The viscosity of the mixture 530 can be reduced using a temperature control device 526. Furthermore, the mixture 530 can be circulated using a stirrer to promote the removal of microbubbles.

[0104] The Coriolis mass flow rate and density measurement device 540 according to the invention is configured to detect and distinguish between two types of gas charge. A first media state value indicates the presence of free bubbles at frequency fluctuations observable upon addition of media 530. In contrast, the first media state value is "invisible" for uniformly distributed microbubbles because they do not cause frequency fluctuations. Depending on the embodiment, the second media state value may have: a mixed density value, which, due to deviations from a reference density of the liquid phase, already indicates a gas charge with microbubbles; or an exact value of the gas volume fraction. However, due to the underlying model, the second media state value cannot adequately describe the fraction of free bubbles. Nevertheless, the combination of these two state values ​​provides a comprehensive description of the media state related to the gas charge, which the system operator can take into account in process control by operating actuators to make the gas charge correspond to a target value range.

[0105] exist Figure 6In an exemplary embodiment of the method 600 according to the present invention, the inherent frequencies of two bending vibration modes of an oscillator are detected in a first step 610. The oscillator has a measuring tube for vibration density or a flow meter for conducting medium.

[0106] Subsequently, for at least one of the inherent frequencies, the frequency fluctuation is determined in the second step 620, which enables the determination of the first medium state value in the third step 630, as described above. Figure 2 and 3 The medium state value specifically describes, or is related to, the volume fraction of free bubbles in the liquid.

[0107] In step 640, a second medium state value is determined based on two natural frequencies and, if applicable, pressure measurements. This second medium state value may specifically include the mixture density or gas volume fraction. (Combined with the above...) Figure 4a The section to C describes the details in this regard.

[0108] In step 650, a medium status message is output, in which two medium status values ​​are included. Optionally, in step 660, the process can then be controlled based on the medium status message to adjust the gas filling in the liquid to the target value.

Claims

1. A measuring device (100) for determining the density, mass flow rate, and / or viscosity of a gas-filled liquid, comprising: At least one oscillator (10) having at least one vibratory measuring tube (14) for conducting medium and having at least two vibration modes, the natural frequencies of which depend on the average density of the gas-filled liquid and the gas volume fraction of the gas-filled liquid. At least one exciter (17) is used to excite two vibration modes; At least one vibration sensor (18, 19) is provided for detecting the vibration of the oscillator (10); as well as An operation and evaluation circuit (30) is configured to apply an excitation signal to the exciter to detect a signal from the vibration sensor, and to determine, based on the signal from the vibration sensor, the current value of the natural frequencies of two vibration modes of the oscillator and a fluctuation of at least one of the natural frequencies. The operation and evaluation circuit is further configured to determine a first medium state value based on the fluctuation. The operation and evaluation circuit is further configured to determine a second medium state value representing the gas charge of the medium under the microbubble hypothesis based on the two inherent frequencies. The operation and evaluation circuit is further configured to output a media status message, wherein the first media status value and the second media status value are merged into the media status message. Wherein, under the assumption that free bubbles are the cause of fluctuations, the first medium state value includes a value that depends on the fraction of free bubbles in the medium. Wherein, under the assumption that the observed ratio of natural frequencies is due to a resonator effect, the second medium state value depends on the volume fraction of gas in the form of microbubbles in the medium, in which the resonator effect causes the compressible medium due to the microbubbles to vibrate against the measuring tube. The first medium state value is normalized using a normalization function that depends on the flow measurement value. In addition to the first medium state value, the medium state message also includes information about which flow state is used to determine the first medium state value. The information about the flow state includes a flow measurement value or a range of values ​​for the flow measurement value. The flow measurement value includes flow velocity, mass flow rate, volumetric flow rate, or Reynolds number, or a range of flow velocity, mass flow rate, volumetric flow rate, or Reynolds number.

2. The measuring device according to claim 1, wherein, The operation and evaluation circuit is configured to further determine a second medium state value as a function of the pressure value representing the medium pressure in the measuring tube.

3. The measuring device according to claim 1, wherein, The first medium state value is a function of the fluctuation of the inherent frequency, wherein the function also exhibits normalization dependent on the inherent frequency.

4. The measuring device according to claim 1, wherein, The first medium state value includes the gas volume fraction of the medium in the form of free bubbles or the range of values ​​for the gas volume fraction.

5. A processing system for processing a medium containing a gas-filled liquid, wherein, The processing system includes: At least one conduit for conducting the medium; At least one measuring device according to any one of claims 1-4, wherein the at least one measuring device is installed in the pipeline; At least one actuator for influencing the medium; A process control system connected to the measuring device and the actuator to receive the medium state message and control the actuator, wherein the process control system includes a data memory storing at least one target value for gas charging, characterized in that the process control system is configured to control the actuator according to the medium state message to adjust the gas charging to the at least one target value.

6. The processing system for processing media according to claim 5, wherein, The actuator includes a temperature control device, a pump, a valve, a ventilator, or a mixer.

7. A method for monitoring a gas-filled liquid using a measuring device according to any one of claims 1 to 4, said measuring device having at least one oscillator, said oscillator having at least one measuring tube for conducting the gas-filled liquid, wherein, The method includes the following steps: Determine the natural frequencies of at least two bending vibration modes; Determine the fluctuation of at least one of the inherent frequencies; The first medium state value is determined based on the fluctuation of the inherent frequency; Under the assumption of microbubbles, a second medium state value is determined based on two inherent frequencies representing the gas charge of the medium; and Output a media status message in which the first media status value and the second media status value are merged.

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