DE102020131604A1 - Measuring device for characterizing a fluid and fluidic arrangement - Google Patents

Abstract

The invention relates to a measuring device for characterizing a fluid and a fluidic arrangement with such a measuring device, the measuring device having a measuring probe with at least three rod-shaped probe elements, each of the probe elements having at least one measuring electrode with a contact surface for contacting the fluid, and the measuring device is designed to carry out a measurement cycle with a number of different measurement sequences in such a way that in each of the different measurement sequences another of the measurement electrodes or another pair of measurement electrodes is subjected to an electrical excitation signal and an electrical response signal is detected at at least one of the remaining measurement electrodes.

Description

The invention relates to a measuring device for characterizing a fluid, in which case the fluid can be, for example, a multi-phase fluid and/or can be in the form of a fluid flow, as well as a fluidic arrangement with such a measuring device. In many areas of industry and science, the characterization of fluids, especially of multiphase fluids. For example, the use of needle probes to characterize fluids and fluid flows is known from the prior art. Such needle probes have a needle-shaped measuring element, by means of which physical (eg electrical, thermal or optical) properties of the fluid volume present at the needle or probe tip at the time of measurement are determined and based on this the fluid present there is characterized. In the case of characterizing a multi-phase fluid, it can be determined, for example by means of a needle probe, based on the determined properties, which phase of the fluid is present at the needle tip at the respective measurement time. As an example, in DE 10 2012 102 870 B4 describes a needle probe for investigating multiphase flows based on the detection of optical and electrical properties of the fluid flow.

However, needle probes are not very suitable for certain measurement scenarios, in particular because they require the probe tip to be immersed in the fluid volume or phase to be characterized for reliable analysis and also only detect a small fluid volume at the probe tip. For example, needle probes are only suitable for characterizing multiphase fluids to a limited extent.

A multi-phase fluid can, for example, be a multi-phase fluid with a continuous first phase as the carrier medium and volumes of a second phase present separated therein, such volumes also being referred to as particles. The continuous first phase can be, for example, a fluid, in particular a liquid or a gas. The particles of the second phase can be, for example, solid, liquid or gaseous particles. For example, the multiphase fluid can be solid particles in a gas or in a liquid, gas bubbles in a liquid, or liquid droplets in another liquid. Such gas bubbles, droplets and solid particles are generally referred to as particles, gas bubbles and droplets are specifically referred to as fluid particles.

For such a multi-phase fluid, characterization of the particles of the second phase using needle probes is only possible to a limited extent. Because for a reliable analysis of such particles using a needle probe, the tip of the needle probe must be able to penetrate the particles, whereby the particles must not fall below a certain minimum size, which in particular allows the analysis of small and/or solid particles and the analysis of multiphase Fluids with low proportions of the particle phase is hardly possible. In addition, the measurement of particle speeds, particle sizes and/or particle shapes with needle probes is not possible or only very imprecisely.

Furthermore, the use of electrical tomography methods such as electrical impedance tomography and electrical capacitance tomography to characterize multiphase fluids, e.g. to determine the phase distribution of multiphase fluid flows, is known. For this purpose, measuring electrodes are attached to the outside of the flow channel or pipe through which the multiphase flow flows at several positions around the pipe. The measuring electrodes are placed along an outer circumference of the tube and enable the determination of the phase distribution within the flow cross-section defined by this outer circumference.

In impedance tomography, for example, an electric current is passed through different pairs of electrodes one after the other and the voltages resulting from the remaining electrodes are measured. The spatial distribution of electrical properties, for example the electrical impedance, in the flow cross-section is then reconstructed from the set of voltage measurement values obtained in this way for different active electrode pairs by solving an inverse problem. Based on the different electrical properties of the different phases of the multiphase flow, the spatial distribution of the individual phases within the flow cross section can be determined. As an example, in DE 10 2017 123 032 A1 a tomography arrangement for electrical impedance tomography is described.

In capacitance tomography, for example, a voltage signal is applied to different individual electrodes one after the other and the currents resulting from the respective remaining electrodes are measured, with the remaining electrodes being kept at a defined potential (eg ground potential). From the set of measured current values obtained in this way for different active electrodes, the spatial distribution of electrical properties, eg the electrical impedance, in the flow cross section is reconstructed by solving an inverse problem and, based on this, the spatial distribution of the individual phases of the multiphase flow within the cross-section are determined. Capacitance tomography is, for example, in EP 2 910 907 A1 described.

However, due to the position of the measuring electrodes and the long-distance propagation of the electrical field between the measuring electrodes, such arrangements for electrical tomography only allow a limited measurement quality and, for example, only a low spatial resolution. Since the measuring electrodes are provided on the outside of the wall or as part of the wall which encloses the fluid to be characterized (e.g. if the measuring electrodes are provided on the outside of the pipe through which the fluid to be characterized flows), there are e.g. between the individual Measuring electrodes correspondingly large distances, which is accompanied by a correspondingly large-scale propagation of the electric field between the electrodes, the electric field and the resulting measured values also being influenced by the proximity or contact of the electrodes to the wall or the pipe. This can have a negative effect on the measurement quality and in particular negatively influence the achievable spatial resolution, so that, for example, the achievable spatial resolution in such electrical tomography arrangements is low and is usually, for example, in the centimeter range. Therefore, such tomography arrangements are not suitable, for example, for the reliable characterization of multi-phase fluid flows with small particles (e.g. with particle sizes in the millimeter range). In addition, such electrical tomography arrangements are complex, inflexible and expensive.

The aim of the invention is to provide an uncomplicated, versatile and flexible measuring device, by means of which a fluid can be characterized with high measuring accuracy (e.g. with high spatial resolution). In addition, a fluidic arrangement with such a measuring device is to be provided.

According to one aspect of the invention, a device for characterizing a fluid is provided, the device also being referred to as a measuring device. The measuring device has a measuring probe with at least three (i.e. three or more) rod-shaped probe elements, which are also referred to as probe rods. The probe elements serve as measuring elements for acquiring measuring signals or measuring data for characterizing the fluid. The measuring probe is intended for introduction into the fluid to be characterized in such a way that when the measuring device is operated, at least the probe rods are partly or completely introduced into the fluid. However, it can also be provided that the entire measuring probe is introduced into the fluid when the measuring device is operated.

Each of the probe elements is rod-shaped and has two longitudinal ends and a longitudinal axis. The two longitudinal ends of a respective probe rod are referred to as the first and second longitudinal end or first and second longitudinal end of the probe rod. The longitudinal axis of a probe rod is an axis running along the longitudinal direction of the probe rod centrally within the latter and is also referred to as the probe rod longitudinal axis. A longitudinal section of a probe rod is a section of the probe rod extending along the longitudinal direction or longitudinal axis of the respective probe rod.

Each probe rod has at least one electrode functioning as a measuring electrode. Provision can therefore be made for each probe rod to have a single such measuring electrode or a plurality of such measuring electrodes. Each measuring electrode of a probe rod is designed and arranged in such a way that it has an outwardly exposed or uncovered surface, so that this surface - when the probe rod is introduced into the fluid to be characterized - is in direct physical contact with the fluid or the fluid contacted. The (entire) area of a measuring electrode that is exposed to the outside is also referred to as the contact area of this measuring electrode or as the measuring electrode contact area. The contact surface of each measuring electrode of a probe rod thus lies on the outer surface of this probe rod or forms part of this outer surface. The extent of the contact surface of a measuring electrode of a probe rod along the longitudinal direction of the probe rod can be less than or just as large as the extent of the measuring electrode along the longitudinal direction of the probe rod. When a probe rod is designed with a plurality of measuring electrodes, the measuring electrodes of a respective probe rod are designed and arranged in such a way that the contact surfaces of the measuring electrodes are arranged in different longitudinal sections of the respective probe rod. Different measuring electrodes of a probe rod thus have measuring electrode contact surfaces arranged in different longitudinal sections of this probe rod.

The measuring device is designed to carry out a measuring cycle with a plurality of consecutive measuring sequences by means of appropriate activation and reading of the measuring electrodes. For this purpose, the measuring device can have, for example, a correspondingly configured control and evaluation device connected to the measuring electrodes. The measuring device is designed to control the measuring electrodes in such a way that in each measuring sequence a single measuring electrode or a pair (ie two) of the measuring electrodes is acted upon by the measuring device with an electrical excitation signal, the excitation signal being in the form of an electrical voltage signal or electrical current signal. The measuring electrodes to which the excitation signal is applied serve to generate or excite an electric field in the fluid to be characterized and are also referred to as excitation electrodes or excitation electrode pairs.

When the measuring device is operated, the probe rods with the measuring electrodes are introduced into the fluid, so that the measuring electrode contact surfaces are in physical contact with the fluid. The electrical excitation signal sets up an electrical field in the fluid, which depends on the spatial distribution of the electrical properties within the fluid and causes corresponding electrical response signals at the other measuring electrodes that are not exposed to the excitation signal.

The measurement cycle has several measurement sequences. In each measurement sequence, a measuring electrode or a pair of measuring electrodes (also referred to as a pair of measuring electrodes) is acted upon by an excitation signal, and in each measurement sequence at least one of the other (i.e. not acted upon by the excitation signal in the respective measurement sequence) measuring electrodes produces such a resulting electrical response signal is detected. The measuring electrodes, at which a response signal is recorded in each case, are used to record or receive an electrical signal that characterizes the electrical field within the fluid and are also referred to as receiver electrodes. In particular, provision can be made for the electrical currents or electrical voltages resulting at the receiver electrodes to be recorded as response signals. If the excitation signal is in the form of a voltage signal, the currents resulting at the receiver electrodes are preferably recorded as response signals. If the excitation signal is in the form of a current signal, the voltages resulting at the receiver electrodes are preferably recorded as response signals.

The measurement cycle has a number of different measurement sequences in such a way that in each of the number of different measurement sequences a different measuring electrode or a different pair of measuring electrodes is subjected to an excitation signal. Two measurement sequences are referred to as identical if the same measurement electrodes act as excitation electrodes and the same measurement electrodes act as receiver electrodes in the two measurement sequences. Two measurement sequences are designated as different if in the two measurement sequences at least partially different measuring electrodes act as excitation electrodes and/or at least partially different measuring electrodes act as receiver electrodes. It can be provided, for example, that the measurement cycle consists entirely of different measurement sequences such that in each measurement sequence of the measurement cycle, a different measuring electrode or a different pair of measuring electrodes is subjected to an excitation signal. However, it can also be provided that the measurement cycle has one or more identical measurement sequences. The measuring cycle has several different measuring sequences such that in each of the several different measuring sequences a different measuring electrode or another pair of measuring electrodes is subjected to an excitation signal, the measuring cycle having at least two (i.e. two or more), preferably at least three (i.e. three or more) has such different measurement sequences. In particular, it can be provided that each measuring electrode is involved in at least one of the measuring sequences of the measuring cycle, i.e. that each measuring electrode functions as an excitation electrode or as a receiving electrode in at least one measuring sequence of the measuring cycle.

The measuring cycle thus has a number of different measuring sequences such that in the different measuring sequences different individual measuring electrodes or different measuring electrode pairs are acted upon by the excitation signal, with these measuring electrodes functioning as excitation electrodes or excitation electrode pairs. An excitation signal is applied to a single measurement electrode in each measurement sequence of a measurement cycle, or an excitation signal is applied to a pair of measurement electrodes in each measurement sequence of a measurement cycle.

In each measurement sequence, a response signal is detected at one or more of the measurement electrodes not subjected to the excitation signal in the respective measurement sequence, with these measurement electrodes functioning as receiver electrodes. Provision can be made, for example, for at least one measuring electrode of each probe rod, which does not have a measuring electrode functioning as an excitation electrode in the respective measuring sequence, to function as a receiver electrode in each measuring sequence. As an alternative or in addition to this, it can be provided that in each measurement sequence only measurement electrodes of those probe rods which do not have a measurement electrode functioning as an excitation electrode in the respective measurement sequence function as receiver electrodes. The two aforementioned configurations enable, for example, the space between the probe rods to be well covered by the resulting electrical fields or a spatially extended detection of these fields, in which case an influence on the measurement by parasitic surface currents potentially occurring between different electrodes of a probe rod can also be suppressed. However, provision can also be made, for example, for at least one measuring electrode of each probe rod to function as a receiver electrode in each measurement sequence (in this case, some or all of the probe rods have at least two measuring electrodes). Furthermore, provision can be made, for example, for an electrical response signal to be detected in each measurement sequence at all measurement electrodes not subjected to the excitation signal in the respective measurement sequence, and for these electrodes to function as receiver electrodes. The two aforementioned configurations enable, for example, good coverage of the space between the probe rods by the resulting electrical fields or spatially extended detection of these fields, with rapid measurement and good time resolution also being supported due to the simultaneous detection of a large number of signals.

In each measurement sequence, one or two measuring electrodes thus function as excitation electrodes and one or more measuring electrodes as receiver electrodes. Measuring electrodes of several probe rods are involved in each measurement sequence, i.e. measuring electrodes of several probe rods are involved in each measurement sequence as excitation electrodes or receiver electrodes. The measuring device is designed in particular for carrying out the measuring sequences such that in each measuring sequence (at least) one measuring electrode of a probe rod acts as an excitation electrode and (at least) one measuring electrode of another probe rod acts as a receiver electrode. Thus, at least one excitation electrode and at least one receiver electrode of different probe rods are involved in each measurement sequence. In other words, at least two measuring electrodes of different probe rods are involved in each measuring sequence in such a way that one of the two measuring electrodes acts as an excitation electrode and the other of the two measuring electrodes acts as a receiver electrode. It can be provided, for example, that at least one measuring electrode of each probe rod is involved in each measurement sequence, in particular that at least one measuring electrode of each probe rod is involved in each measurement sequence as an excitation electrode or as a receiver electrode.

Measuring electrodes of several probe rods are preferably involved as receiver electrodes in each measurement sequence, i.e. a response signal is preferably recorded at several (i.e. two or more) measuring electrodes of different probe rods in each measurement sequence. As a result, the information content of the measurement data obtained can be increased and, for example, the spatial and temporal resolution can be improved by simultaneously covering different current or voltage tap paths. Accordingly, when using pairs of excitation electrodes, it can be provided, for example, that the measuring probe has at least three probe rods such that each probe rod has at least two measuring electrodes. Alternatively, when using pairs of excitation electrodes, it can be provided, for example, that the measuring probe has at least four probe rods such that each probe rod has at least one measuring electrode. According to one embodiment, it can generally be provided that the measuring probe has at least four probe rods such that each probe rod has at least one measuring electrode. Provision can be made, for example, for the measuring probe to have at least three or at least four probe rods in such a way that each probe rod has at least two measuring electrodes, which can improve the spatial coverage of the measurement, for example.

As explained, the measuring device is designed to carry out a measuring cycle with a plurality of consecutive measuring sequences, with an excitation signal being applied to one of the measuring electrodes or a pair of measuring electrodes in each measuring sequence and to one or more of the others (i.e. not to the excitation signal in the respective measuring sequence acted upon) measuring electrodes, a response signal is detected. Based on the excitation signals and response signals of a measurement cycle, the measuring device can be designed to characterize the spatial distribution of an electrical property within the fluid during the measurement cycle, wherein the electrical property can be electrical conductivity, electrical permittivity or electrical impedance, for example.

Due to the electrical excitation signal applied to the excitation electrodes in the form of a voltage signal or current signal, an electrical field is established in a spatial volume in the vicinity of the measuring electrodes. The electrical field causes electrical response signals in the form of current signals or voltage signals at the receiver electrodes. The electric field and thus also the response signals are dependent on and determined by the excitation signals and the spatial distribution of the electrical properties (e.g. electrical conductivity, permittivity or impedance) within the volume of space, so that based on the known excitation signals and the detected response signals by solving of an inverse problem, the spatial distribution of the electrical properties can be characterized and determined can. In particular, the electric field resulting from the excitation signals - and thus also the resulting response signals - is due to the solution of the basic equations of electrostatics for the spatial distribution α(r) within the spatial volume of an electrical property α under the general conditions of the voltages impressed by the excitation signals or currents are fully defined (where r denotes a position vector in three-dimensional space and α denotes the electrical property, where α can in particular be electrical conductivity, electrical permittivity or electrical impedance). The actual distribution α(r) can thus be characterized and determined, for example by iteratively approximating the solution or response signals calculated for an assumed spatial distribution α _mod (r) to the response signals actually measured. Accordingly, the measuring device can be designed based on the excitation signals and response signals of a measuring cycle to characterize the spatial distribution of an electrical property within the probed spatial volume during the measuring cycle. If the probe rods with the measuring electrodes are introduced into the fluid and the probed spatial volume is thus filled with the fluid, the measuring device can thus be used based on the excitation signals and response signals of a measuring cycle to characterize (e.g. determine) the spatial distribution within the fluid during the measuring cycle be formed an electrical property.

The probed spatial volume is also referred to as the measuring volume and comprises a spatial volume arranged between the measuring electrodes. The measuring volume can be, for example, a spatial volume arranged between the measuring electrodes or a spatial volume comprising the measuring electrodes. The measuring device can thus be designed in particular to characterize or determine the spatial distribution of the electrical property within the measuring volume.

The measuring device can be designed based on the excitation signals and response signals of a measuring cycle to characterize the spatial distribution of an electrical property within the fluid during the measuring cycle. The measuring device is accordingly designed based on the excitation signals and response signals of multiple measurement sequences (in particular multiple different measurement sequences) to characterize the spatial distribution of an electrical property within the fluid during the measurement cycle, with e.g. all excitation signals and response signals of the measurement sequences of the measurement cycle being able to enter into the characterization . The measuring device can, for example, be designed in such a way that all excitation signals and response signals of a measuring cycle (i.e. all measuring sequences of a measuring cycle) are combined into a common measurement data set and, based on this measurement data set, characterizes or determines the spatial distribution of the electrical property during the respective measurement cycle becomes. Since different current or voltage tapping paths running between the measuring electrodes and thus also between the probe rods are included in the characterization, a high-quality, spatially resolved analysis of the electrical property can be carried out with a short measurement duration.

In particular, the measuring device can be designed for electrotomographic characterization of the fluid, i.e. for characterizing the fluid by means of electrical tomography, e.g. by means of electrical impedance tomography or capacitance tomography. Accordingly, the measuring device can be a tomography device, which is designed to characterize the fluid electrotomographically based on the excitation signals and response signals of the measuring cycle. The tomography device can, for example, be designed in such a way that all excitation signals and response signals of a measurement cycle are combined into a common measurement data set and based on this measurement data set the spatial distribution of the electrical property in one or more planes during the measurement cycle is determined, these planes also called tomographic planes. The distribution of the electrical property in such a tomography plane can be visualized as a two-dimensional tomographic image. A three-dimensional image of the spatial distribution of the electrical property can be generated on the basis of the two-dimensional tomographic images assigned to a plurality of different tomographic planes. Based on different values of the electrical property, different phases of the fluid to be characterized can be identified and e.g. visualized. Accordingly, the tomography device can be designed to generate an image, e.g. a two- or three-dimensional image, of the internal structure of the fluid based on the excitation signals and response signals of a measurement cycle.

Since the measuring electrodes are provided on the probe rods, the measuring geometry is defined by the arrangement geometry of the probe rods and measuring electrodes and is therefore independent of the geometry of the wall (eg the pipe) which encloses the fluid to be characterized. In the case of the characterization of a fluid flowing through a pipe by means of the invention Measuring device, for example, the measurement geometry can be kept independent of the geometry (e.g. the diameter) of the pipe. In particular, the (maximum) distance between the individual measuring electrodes can be kept smaller than when the measuring electrodes are positioned on the wall enclosing the fluid, which makes it possible, for example, to limit the electric fields to a smaller spatial area. Since the measuring electrodes are provided on the probe rods and are introduced into the fluid to be characterized when the measuring device is operated, the measuring electrodes are in direct contact with the fluid and are not in contact with the wall enclosing the fluid, so that the electric field is not influenced by the Wall can be reduced or prevented. Characterization of the spatial distribution of the electrical property with high measurement quality—in particular with a high spatial resolution—is thereby made possible, as a result of which, for example, a characterization of multiphase fluid flows with small particles can be made possible or improved.

Since measuring electrodes of different probe rods are involved in each measurement sequence and the courses of the electric field present between different probe rods thus contribute to the measurement, the measuring device can also be used to characterize fluid volumes or particles within the measuring volume that are not in direct contact with the measuring electrodes or probe rods and are not penetrated by the probe rods. This also enables, for example, the detection of small and/or solid particles within the fluid as well as an analysis of multi-phase fluids with small proportions of one of the phases within the measuring volume. In addition, the fluid volume arranged between the measuring electrodes of the probe rods or the fluid fractions or particles flowing between the probe rods can be characterized.

Since the spatial distribution of an electrical property within the fluid can be detected by means of the measuring device, with different fluid phases being identifiable due to their different electrical properties or due to different values of the detected electrical property, the spatial distribution of different phases of the fluid can be characterized by means of the measuring device and be determined. In this way, for example, particles (solid, liquid or gaseous) of one of the phases of the fluid that are present in the fluid can be identified and their parameters can be determined. For example, the size, shape and particle density of such particles can be determined with high accuracy by means of the measuring device, whereby the flow velocities of such particles can also be determined with high accuracy based on the change in the measurement data over time (e.g. by evaluating several consecutive measurement cycles).

Due to the rod-shaped design of the probe elements, the influence of the same on the fluid to be characterized can be kept low, particularly when characterizing a flowing fluid. Due to its uncomplicated structure, the measuring device is robust and can be produced inexpensively. In addition, the measuring device does not have to be permanently installed in a fluid system to be characterized and can therefore be used in a versatile and flexible manner.

According to one embodiment, all the probe rods are of the same length, ie they all have the same length. According to a preferred embodiment, all probe rods are identical. According to a further embodiment, the measuring probe is designed in such a way that all the probe rods are arranged to run parallel to one another, ie all the probe rods are arranged in such a way that their longitudinal axes of the probe rod run parallel to one another. As an alternative or in addition to this, it can be provided that all the probe rods are each arranged with one of their two longitudinal ends in a common plane or border on a common plane (so that these longitudinal ends are coplanar). The probe rods are arranged in such a way that the longitudinal axes of the probe rod do not all run in a common plane (ie there is no plane such that all the longitudinal axes of the probe rod lie or run within this plane). Furthermore, it can be provided that all probe rods are arranged in such a way that a longitudinal end of each probe rod is arranged at a respective position along the edge of an (imaginary) common convex flat surface, these longitudinal ends preferably being arranged equidistantly. The edge of such a convex surface is given by the boundary line of this surface, the longitudinal end of a respective probe rod arranged at the edge of this surface is also referred to as its first longitudinal end. Accordingly, the probe rods can be arranged in such a way that the area or polygon formed by the straight connecting sections of each first longitudinal end of the probe rod to the two next-neighboring first longitudinal ends of the probe rod is a (flat) convex polygon. The polygon is preferably an equilateral or equiangular polygon, more preferably a regular polygon. The convex flat surface, along the edge of which the first longitudinal ends of the probe rod are arranged, can in particular be a circle or an ellipse. Accordingly, for example, it can be provided that all probe rods such are arranged such that the first longitudinal end of each probe rod is located at a respective position along the edge of a circle or an ellipse. The above embodiments enable, in particular in any combination, a characterization of the fluid with high accuracy, in particular by means of electrical tomography, in an uncomplicated manner due to the associated measurement geometries.

According to one embodiment, the measuring probe has a probe body, with the probe rods being arranged on the probe body in such a way that they protrude from the probe body. The probe body serves as a holder for holding the probe rods (and thus also the measuring electrodes) in a given geometry. Each probe rod is attached to the probe body at one of its two longitudinal ends, this longitudinal end being referred to as the first longitudinal end of the respective probe rod. When the measuring probe is configured with a probe body, each probe rod is thus attached to the probe body at its first longitudinal end, whereas the second longitudinal end of each probe rod is a free longitudinal end. According to this embodiment, it can also be provided that the measuring electrodes are designed and arranged in such a way that the contact surfaces of the measuring electrodes are each arranged at a distance from the probe body and do not reach as far as the probe body.

By arranging the measuring electrode contact surfaces at a distance from the probe body, the influence of the probe body on the electric field generated by the excitation signals can be reduced and thus a higher measuring accuracy can be made possible. In addition, when the measuring probe is inserted into a fluid flow when characterizing it, the flow is influenced by the probe body (e.g. due to the stagnation occurring there). By arranging the measuring electrode contact surfaces at a distance from the probe body, a falsification of the measurement data obtained by means of the measuring electrodes caused by this influence on the flow can be reduced or prevented.

In particular, it can be provided that the probe body has a flat outer surface and all probe rods are arranged or attached to the probe body in such a way that they protrude from the probe body on this flat outer surface (and thus, when the measuring device is used as intended, into the fluid to be characterized protrude). This flat outside or outer surface of the probe body is also referred to as the end face of the probe body. Accordingly, all probe rods open with their first longitudinal end on the end face of the probe body. The positions at which a respective probe rod opens out on the front face of the probe body or protrudes from the front face are also referred to as the base positions of the probe rod.

According to one embodiment, all of the probe rods are arranged on the end face of the probe body such that the probe rod base position of each probe rod is located at a respective position along the edge of a convex planar surface (with no probe rod being located inside this convex surface). Accordingly, the area or polygon formed by the straight lines connecting each probe rod base position to the two nearest adjacent probe rod base positions is a convex polygon. The polygon is preferably an equilateral or equiangular polygon, more preferably a regular polygon. For example, the convex planar surface may be arranged to be a circle or an ellipse such that all of the probe rod base positions are located at positions along the edge of a circle or an ellipse. All probe rod base positions are preferably arranged equidistantly, i.e. the distances between a respective probe rod base position and the respective next neighboring probe rod base positions are the same for all probe rod base positions. Characterization of the fluid with high accuracy is made possible in an uncomplicated manner by means of such a convex measuring geometry, in particular by means of electrical tomography.

Even when the measuring probe is designed with the probe body, it can be provided that all probe rods are designed with the same length or are even designed identically. In addition, when the measuring probe is designed with the probe body, it can also be provided that all probe rods are arranged so as to run parallel to one another. Provision can be made, for example, for all the probe rods to be arranged on the probe body in such a way that the longitudinal axes of all the probe rods run perpendicular to the end face of the probe body. According to a preferred embodiment, the measuring probe accordingly has a probe body with a flat end face, with all probe rods being of identical design and being attached to the probe body in such a way that they open into the probe body at their first longitudinal end at the end face or border on the probe body and are arranged with their probe rod longitudinal axes running perpendicularly to the end face, with the first longitudinal ends or the probe rod base positions of all probe rods as explained above along the edge of a convex surface can be arranged or can define a convex polygon.

According to one embodiment, the measuring electrodes are designed in such a way that the extension of the contact surfaces of the measuring electrodes along the longitudinal direction of the associated probe rod is at least five times the maximum cross-sectional dimension of this probe rod and a maximum of ten times the maximum cross-sectional dimension of this probe rod. Accordingly, each measuring electrode of a respective probe rod is designed in such a way that the extent of the contact surface of the measuring electrode along the longitudinal axis of the probe rod is at least as large as five times the maximum cross-sectional dimension of the probe rod and at most as large as ten times the maximum cross-sectional dimension of the probe rod. The cross-sectional dimension of a probe rod refers to the dimension of the probe rod transversely or perpendicularly to its longitudinal axis. In the case of a rotationally symmetrical probe rod with a circular cross-section or a probe rod with a rotationally symmetrical cross-sectional contour, the cross-sectional dimension of the probe rod is given, for example, by the diameter. The maximum cross-sectional dimension of a probe rod is the cross-sectional dimension at the point or longitudinal position with the largest cross-section.

Designing the contact surfaces of the measuring electrodes with such a longitudinal extent enables good spatial resolution of the measurement results obtained with a good signal-to-noise ratio at the same time. By means of contact surfaces dimensioned in this way, an electrotomographic characterization with well-defined tomography planes can also be supported, in particular with an identical configuration of all probe rods and/or alignment of all probe rods with one of their longitudinal ends on a common plane.

According to one embodiment, each probe rod has at least two measuring electrodes. Accordingly, each probe rod has at least one first measuring electrode and one second measuring electrode, each of the two measuring electrodes having a contact surface that is exposed or uncovered to the outside. The contact surface of the first measuring electrode is referred to as the first contact surface or first measuring electrode contact surface, and the contact surface of the second measuring electrode is referred to as the second contact surface or second measuring electrode contact surface. According to this embodiment, the first and the second measuring electrode of each probe rod are designed and arranged in such a way that there is a distance between the first measuring electrode contact surface and the second measuring electrode contact surface which is at least as large as the maximum cross-sectional dimension of the respective probe rod. Thus, the distance between the first and the second measuring electrode contact surface along the longitudinal direction of the respective probe rod is equal to or greater than the maximum cross-sectional dimension of the respective probe rod. The first and the second measuring electrode of each probe rod are designed and arranged in such a way that the first measuring electrode contact surface is arranged closer to the first longitudinal end of the respective probe rod than the second measuring electrode contact surface. When the measuring probe is configured with the probe body, the first measuring electrode contact surface is therefore arranged closer to the probe body than the second measuring electrode contact surface.

Characterization of the electrical property of the fluid with improved spatial coverage and spatial resolution is made possible by means of such a configuration. In addition, this design enables a tomographic characterization of the fluid in two or more different tomography planes, e.g. by using a corresponding design and arrangement of the measuring electrodes, the first measuring electrode contact surfaces of all probe rods define a first tomography plane and the second measuring electrode contact surfaces of all probe rods define a second tomography plane.

In general, it can be provided that each probe rod has n measuring electrodes, with each measuring electrode having a contact surface that is uncovered to the outside and the contact surface of the mth measuring electrode of a probe rod being referred to as the mth measuring electrode contact surface of this probe rod, and with the probe rods and measuring electrodes are designed and arranged in such a way that the mth measuring electrode contact surfaces of all probe rods are each arranged in a common plane (where n is a natural number greater than zero, ie n = 1, 2, 3, ...; and where m is a natural number greater than zero and at most equal to n and can take any value from 1 to n, ie m = 1, 2, ..., n). Accordingly, the mth measuring electrode contact surfaces of all probe rods are each arranged in such a way that they lie in a common plane, ie are intersected by a common plane. The contact surfaces of the measuring electrodes thus define n different planes, with each of the measuring electrode contact surfaces of a probe rod lying in another of these planes or being intersected by another of these planes, with these planes also being referred to as measuring planes. The plane in which the mth fair electrode contact surfaces of the probe rods are also referred to as the mth level or mth measuring level. Thus, for example, the first measuring electrode contact surfaces of all probe rods are arranged in a common first plane, the second measuring electrode contact surfaces of all probe rods are arranged in a common second plane, the third measuring electrode contact surfaces of all probe rods are arranged in a common third plane, etc. According to this embodiment the n measuring electrodes of each probe rod are preferably designed in such a way that the extent of each of the n measuring electrode contact surfaces of the respective probe rod along the longitudinal axis of this probe rod is at least five times and at most ten times greater than the maximum cross-sectional dimension of the probe rod. Furthermore, according to this embodiment, the n measuring electrodes of each probe rod are preferably designed in such a way that the distance between two adjacent measuring electrode contact surfaces of different measuring electrodes along the longitudinal axis of this probe rod is at least as large as (ie the same as or greater than) the maximum cross-sectional dimension of the respective one probe rod is. According to this embodiment, it can also preferably be provided that all probe rods are arranged with their longitudinal axes of the probe rod running parallel to one another, and that each of the n measurement planes is perpendicular to the longitudinal axes of the probe rod. Accordingly, the measuring electrodes of the probe rods are arranged in such a way that the measurement planes defined by them are perpendicular to the longitudinal axis of the probe rods. The number n of the measuring electrodes and thus also the measuring planes is preferably at least two (ie n ≥ 2), more preferably at least three (ie n ≥ 3), which in particular allows a three-dimensional characterization of the electrical property of the fluid, e.g. a three-dimensional tomography, with high measurement quality is enabled.

According to one embodiment, the measuring device is designed based on the excitation signals and response signals of a measuring cycle to characterize or determine the spatial distribution of the electrical property present within the measuring volume in each of the n measuring planes. In particular, it can be provided that the measuring device is designed based on the excitation signals and response signals of a measuring cycle for characterizing or determining the spatial distribution of the electrical property within the measuring volume in each of the n measuring planes by means of electrical tomography. It can be provided, for example, that the measuring device is designed based on the excitation signals and response signals of a measuring cycle to generate a tomographic image of each of the n planes, the tomographic image of a respective plane showing the spatial distribution of the electrical property represented or visualized.

In particular, it can be provided that each measuring cycle has n sub-cycles, each of the n sub-cycles having a plurality of different measuring sequences such that in each of the different measuring sequences of the m-th sub-cycle a different m-th measuring electrode or a different pair of the m-th measuring electrodes is acted upon by an electrical excitation signal and an electrical response signal is detected at at least one of the remaining mth measuring electrodes.

Accordingly, it can be provided in particular that only those measuring electrodes (as excitation electrodes and receiver electrodes) are involved in each of the sub-cycles whose contact surfaces are arranged in a common measuring plane or are intersected by a common measuring plane, with all measuring sequences of the mth sub-cycle exclusively the mth measuring electrodes of the probe rods are involved. In particular, it can be provided that in each measurement sequence of the mth partial cycle, another of the mth measuring electrodes or another pair of the mth measuring electrodes of all probe rods is acted upon by an excitation signal and at one or more of the remaining mth measuring electrodes of all Probe rods a response signal is detected. Accordingly, the contact surfaces of both the excitation electrodes and the receiver electrodes are arranged in the same measurement plane for all measurement sequences of a respective partial cycle.

The n measurement planes can function in particular as tomography planes. Provision can be made, for example, for the measuring device to be designed based on the excitation signals and response signals of the mth partial cycle to characterize or determine the spatial distribution of the electrical property within the measurement volume in the mth measurement plane by means of electrical tomography. Accordingly, the measuring device can be designed to generate a tomographic image of each of the n measuring planes based on the excitation signals and response signals of the n partial cycles.

According to one embodiment, the probe rods have additional electrodes in addition to the measuring electrodes, which are also referred to as shielding electrodes. According to this embodiment, each probe rod has at least one electrode functioning as a shielding electrode. It can be featured It can be seen that each probe rod has a single shielding electrode or multiple shielding electrodes. Each shielding electrode is constructed and arranged in such a way that it has an outwardly exposed or uncovered surface, so that this surface—when the probe rod is introduced into the fluid to be characterized—is in direct physical contact with the fluid or contacts the fluid. The (entire) surface of a shielding electrode that is exposed to the outside is also referred to as the contact surface of this shielding electrode or as the shielding electrode contact surface. The contact surface of each shielding electrode of a probe rod thus lies on the outer surface of this probe rod or forms part of this outer surface. The extent of the contact surface of a shielding electrode of a probe rod along the longitudinal direction of the probe rod can be less than or just as large as the extent of the shielding electrode along the longitudinal direction of the probe rod. If a probe rod is designed with several shielding electrodes, the shielding electrodes of a respective probe rod can be designed and arranged such that the contact surfaces of the shielding electrodes are arranged in different longitudinal sections of the respective probe rod. Accordingly, different shielding electrodes of a probe rod have shielding electrode contact surfaces arranged in different longitudinal sections of this probe rod. In addition, the measuring electrodes and the shielding electrodes of each probe rod are preferably designed and arranged in such a way that the shielding electrode contact surfaces are arranged in different longitudinal sections of the respective probe rod than the measuring electrode contact surfaces.

When the probe rods are configured with the shielding electrodes, the measuring device is designed to apply a predetermined electrical potential that is constant over time across all measurement sequences (i.e. throughout the entire measurement cycle) to the shielding electrodes, this potential also being referred to as the shielding potential. The shielding potential can be given by the ground potential, for example. Since the shielding electrodes of different probe rods are all at the same electrical potential, the field lines of the electric field caused by the excitation signals are pushed away from the probe rods and into the space between the probe rods or into the measurement volume, which means that this volume and thus the measurement volume can be reliably penetrated reliable characterization of the fluid across the entire measurement volume is also made possible.

According to one embodiment, each probe rod has a screen electrode with a screen electrode contact surface such that the screen electrode contact surface comprises a region between the measuring electrode contact surface arranged closest to the first probe rod longitudinal end and the first probe rod longitudinal end (i.e. between the closest measuring electrode contact surface arranged on the first longitudinal end of the probe rod and the first longitudinal end of the probe rod, it being possible for the shielding electrode contact surface to also include or cover the first longitudinal end). Alternatively or additionally, it can be provided that each probe rod has a shielding electrode with a shielding electrode contact surface in such a way that the shielding electrode contact surface encompasses an area between the measuring electrode contact surface arranged closest to the second longitudinal end of the probe rod and the second longitudinal end of the probe rod ( i.e. between the measuring electrode contact surface arranged closest to the second longitudinal end of the probe rod and the second longitudinal end of the probe rod, it being possible for the shield electrode contact surface to also encompass or cover the second longitudinal end). When designing a respective probe rod with several measuring electrodes, it can also be provided that each probe rod has one or more shielding electrodes such that one shielding electrode contact surface is arranged between two adjacent measuring electrode contact surfaces.

The shield electrode contact surfaces of a probe rod preferably reach as close as possible to the measuring electrode contact surfaces of the probe rod. Provision can be made, for example, for the shielding electrodes for each probe rod to be designed and arranged in such a way that the distance along the longitudinal direction of the probe rod between a respective shielding electrode contact surface and each adjacent measuring electrode contact surface is smaller than the maximum cross-sectional dimension of the respective probe rod. This supports an effective pushing of the field lines of the electrical field caused by the excitation signals into the measurement volume.

According to one embodiment, each probe rod has at least two measuring electrodes and at least one shielding electrode. Accordingly, each probe rod has at least a first measuring electrode with a first measuring electrode contact surface and a second measuring electrode with a second measuring electrode contact surface, the first measuring electrode contact surface being arranged closer to the first longitudinal end of the probe rod than the second measuring electrode contact surface, and wherein the second measuring electrode contact surface is arranged closer to the second probe rod longitudinal end than the first measuring electrode contact area. In addition, it can be provided that each probe rod has a shielding electrode with a shielding electrode contact surface such that the shielding electrode contact surface is arranged between the first measuring electrode contact surface and the second measuring electrode contact surface. Alternatively or additionally, it can be provided that each probe rod has a shielding electrode with a shielding electrode contact surface in such a way that the shielding electrode contact surface encompasses an area between the first measuring electrode contact surface and the first longitudinal end of the probe rod (i.e. that the shielding electrode contact surface is between the first measuring electrode contact surface and the first longitudinal end of the probe rod, it being possible for the shield electrode contact surface to also include or cover the first longitudinal end). Furthermore, it can be provided that each probe rod has a shielding electrode with a shielding electrode contact surface in such a way that the shielding electrode contact surface encompasses an area between the second measuring electrode contact surface and the second longitudinal end of the probe rod (i.e. that the shielding electrode contact surface between the second measuring electrodes contact surface and the second longitudinal end of the probe rod, it being possible for the shielding electrode contact surface to also include or cover the second longitudinal end). Each shielding electrode is preferably designed and arranged in such a way that the distance along the longitudinal direction of the probe rod between the associated shielding electrode contact surface and each adjacent measuring electrode contact surface is smaller than the maximum cross-sectional dimension of the respective probe rod.

The shielding electrode configurations explained enable a particularly advantageous influencing of the course of the field lines of the electric field generated by means of the excitation signals.

The measuring electrodes and the shielding electrodes are electrically conductive, e.g. by being made of electrically conductive material. The measuring electrodes and the shielding electrodes can, for example, be in the form of metallic electrodes, i.e. they can consist of metal. All measuring electrodes are electrically isolated from one another, i.e. they are not in electrically conductive contact with one another. In addition, each measuring electrode is electrically isolated from each shielding electrode. Furthermore, it can be provided that all the shielding electrodes are electrically insulated from one another.

According to one embodiment, the measuring electrodes of the probe rods are designed and arranged in such a way that the measuring electrode contact surface of each measuring electrode of a respective probe rod is rotationally symmetrical with respect to the longitudinal axis of this probe rod. Accordingly, the contact surface of the measuring electrode or each measuring electrode of each probe rod can be rotationally symmetrical with respect to the longitudinal axis of this probe rod. It can be provided, for example, that the measuring electrodes of the probe rods are designed and arranged in such a way that each measuring electrode of a respective probe rod is rotationally symmetrical with respect to the longitudinal axis of this probe rod. Accordingly, the measuring electrode or each measuring electrode of each probe rod can be rotationally symmetrical with respect to the longitudinal axis of this probe rod.

According to a further embodiment, the shielding electrodes are designed and arranged in such a way that the shielding electrode contact surface of each shielding electrode of a respective probe rod is rotationally symmetrical with respect to the longitudinal axis of this probe rod. Accordingly, the contact surface of the shielding electrode or each shielding electrode of each probe rod can be rotationally symmetrical with respect to the longitudinal axis of this probe rod. It can be provided, for example, that the shielding electrodes of the probe rods are designed and arranged in such a way that each shielding electrode of a respective probe rod is rotationally symmetrical with respect to the longitudinal axis of this probe rod. Accordingly, the shielding electrode or each shielding electrode of each probe rod can be rotationally symmetrical with respect to the longitudinal axis of this probe rod.

According to one embodiment, the probe rods are designed in such a way that the outer surface of each probe rod is rotationally symmetrical with respect to the longitudinal axis of the respective probe rod. The outer surface of a probe rod designates the outwardly exposed surface of this probe rod which—when the probe rod is introduced into the fluid to be characterized—is in (physical) contact with the fluid. When the measuring probe is designed with a probe body and probe rods protruding from it, the outer surface of a respective probe rod is the outer surface of the probe rod lying outside of the probe body. The outer surface of a probe rod is also referred to as the outer surface of the probe rod. Provision can also be made, for example, for each probe rod to be rotationally symmetrical with respect to its longitudinal axis.

The geometry or the course of the field lines of the electric fields, which are associated with the aforementioned rotationally symmetrical configurations of the probe rods or parts of the probe rods (in particular the measuring electrodes and/or shielding electrodes), enables a simple evaluation of the data obtained by means of the measuring device and enables a high, uncomplicated measurement quality.

According to one embodiment, each probe rod has an inner element made of electrically insulating material, with the measuring electrode or each measuring electrode of a respective probe rod being applied to the (outer) lateral surface of the inner element, with the outer surface of a respective measuring electrode that is exposed or uncovered to the outside being the contact surface of this measuring electrode. According to this embodiment, each measuring electrode of a respective probe rod is attached to the inner element in a longitudinal section of the inner element of the probe rod, ie attached to the outer surface of the inner element. If the probe rods are designed with several measuring electrodes, the measuring electrodes of a respective probe rod are applied to the inner element of the probe rod in different, spaced longitudinal sections of the same, so that different measuring electrodes of a respective probe rod are arranged at a distance from one another (and thus also the contact surfaces of different measuring electrodes of a of each probe rod are each arranged at a distance from one another).

If the probe rods are designed with shielding electrodes, according to this embodiment it can also be provided that each shielding electrode of a respective probe rod is applied to the (outer) lateral surface of the inner element, with the outer surface of a respective shielding electrode that is exposed or uncovered to the outside forming the contact surface of this shielding electrode . Accordingly, each shield electrode of a respective probe rod is applied to the inner element in a longitudinal section of the inner element of the probe rod, i.e. applied to the outer surface of the inner element. If the probe rods are designed with a plurality of shielding electrodes, the shielding electrodes of a respective probe rod are applied to the inner element of the probe rod in different longitudinal sections spaced apart from one another, so that different shielding electrodes of a respective probe rod are each arranged at a distance from one another (and thus also the contact surfaces of different shielding electrodes of a respective probe rod are each arranged at a distance from each other). In addition, the shielding electrodes of a respective probe rod are applied to the inner element in different longitudinal sections than the measuring electrodes of this probe rod, so that the shielding electrodes and measuring electrodes of a respective probe rod are each arranged at a distance from one another.

The inner element of a respective probe rod can in particular be designed in the form of a rod. The inner element of a respective probe rod is preferably designed to be rotationally symmetrical with respect to the longitudinal axis of the probe rod (the longitudinal axis of the probe rod being at the same time the longitudinal axis of the inner element). The inner element can be, for example, a rod or a tube, in particular a rod that is rotationally symmetrical with respect to its longitudinal axis or a tube that is rotationally symmetrical with respect to its longitudinal axis. According to this embodiment, the measuring electrodes and/or the shielding electrodes of each probe rod are preferably designed to be rotationally symmetrical with respect to the longitudinal axis of the respective probe rod.

According to another embodiment, each probe rod has a coaxial arrangement which alternately consists of electrically conductive and electrically insulating elements which are arranged coaxially with respect to the longitudinal axis of the respective probe rod and are also referred to as coaxial elements. The electrically conductive elements are made of electrically conductive material (eg metal), the electrically isolating elements are made of electrically isolating material (eg an electrically isolating ceramic). According to this embodiment, each probe rod has a rod-shaped central element (also referred to as a central element) and one or more hollow-cylindrical elements arranged coaxially thereto (also referred to as hollow-cylindrical elements). The central element is thus successively surrounded by one or more hollow-cylindrical elements, the central element being encased at least in sections by a hollow-cylindrical element. It can be provided, for example, that the central element is encased at least in sections by a first hollow cylinder element, the first hollow cylinder element is encased at least in sections by a second hollow cylinder element, the second hollow cylinder element is encased at least in sections by a third hollow cylinder element etc. The central element and the hollow cylinder elements of a respective probe rod are rotationally symmetrical with respect to the longitudinal axis of the probe rod. The coaxial arrangement consists alternately of electrically conductive and electrically insulating elements, i.e. along the radial direction or along the direction running transversely to the longitudinal axis of the probe rod, an electrically conductive and an electrically insulating coaxial element are arranged alternately, with the central element being either electrically conductive or electrically can be isolating. It can be provided, for example, that the central element is electrically conductive, the first hollow cylinder element is electrically insulating, the second hollow cylinder element is electrically conductive, the third hollow cylinder element is electrically insulating, etc. Alternatively, For example, provision can be made for the central element to be electrically insulating, the first hollow cylinder element to be electrically conductive, the second hollow cylinder element to be electrically insulating, the third hollow cylinder element to be electrically conductive, etc.

The coaxial elements of a respective probe rod are offset from one another along the longitudinal axis of the probe rod in such a way that each of the electrically conductive elements is exposed to the outside in a different longitudinal section of the respective probe rod. Provision can also be made for the coaxial elements to be offset from one another along the longitudinal axis of the probe rod in such a way that each of the coaxial elements (i.e. both each of the electrically conductive elements and each of the electrically insulating elements) projects outwards in a different longitudinal section of the respective probe rod exposed. This can be realized, for example, by each of the coaxial elements having a predetermined length and at least the electrically conductive coaxial elements (i.e. either only the electrically conductive coaxial elements or all coaxial elements) having decreasing lengths along the radial direction from inside to outside.

According to the present embodiment, each of the measuring electrodes and (if provided) each of the shielding electrodes of a respective probe rod is formed by one of the electrically conductive coaxial elements, the electrodes being electrically isolated from one another by means of the electrically insulating coaxial elements. The number of electrically conductive coaxial elements thus corresponds to the sum of the number of measuring electrodes and the number of shielding electrodes. The coaxial arrangement thus has one or more electrically conductive coaxial elements that act as measuring electrodes. In addition to this, the coaxial arrangement has a number of electrically conductive coaxial elements corresponding to the number of shielding electrodes. Since the coaxial elements are offset from one another along the respective longitudinal axis of the probe rod in such a way that each of the electrically conductive elements is exposed to the outside in a different longitudinal section of the respective probe rod, each of the electrodes formed by these elements is exposed in a corresponding longitudinal section. The contact surface of a respective electrode is formed by the section of this electrode that is exposed to the outside.

According to one embodiment, the measuring device has electrical lines for electrically contacting the measuring electrodes and (if provided) shielding electrodes, by means of which the measuring electrodes acting as excitation electrodes can be supplied with the electrical excitation signals, which can be picked off at the measuring electrodes acting as receiver electrodes resulting in electrical response signals. and the shielding electrodes can be charged with the shielding potential. Provision can be made, for example, for the measuring device to have a separate electrical line for electrically contacting each measuring electrode and optionally also for each shielding electrode, with the electrical line contacting the respective electrode at its first end and being connected at its second end, e.g. to the control and evaluation device of the measuring device is connected. In particular, the measuring probe can be designed in such a way that the electrical lines provided for electrically contacting the measuring electrodes and/or shielding electrodes of a respective probe rod are arranged in such a way that they enter the same at one (e.g. the first) longitudinal end of the probe rod and from there inside the Probe rod are arranged to run up to the respective electrode. When designing the measuring probe with the probe body, it can also be provided that the electrical lines are arranged in such a way that each line from the point of its exit from the respective probe rod inside the probe body or through the inside of the probe body and e.g. to the control - Is arranged running out and evaluation device. By arranging the electrical lines in the interior of the probe rods and, if applicable, the probe body and thus not being in physical or electrical contact with the fluid, physical and electrical influencing of the measurement results through the lines can be reliably prevented.

According to one embodiment, the electrical excitation signal is an electrical current signal, this embodiment being particularly suitable and intended for characterizing electrically conductive fluids. Accordingly, the measuring device can be provided and designed, for example, to characterize an electrically conductive fluid. According to this embodiment, the measuring device for controlling the measuring electrodes for carrying out a measuring cycle with several different measuring sequences is designed in such a way that in each of the different measuring sequences a different pair of measuring electrodes is subjected to an electrical excitation signal in the form of an electric current and thus acts as a pair of excitation electrodes. The electric current functioning as an excitation signal flows between the two excitation electrodes of the respective excitation electrode pair, ie from one of the two excitation electrodes to the other of the two excitation electrodes of the excitation electrode pair. According to this embodiment, therefore, in particular in each trade fair frequency of the measurement cycle, the excitation signal is applied to a pair of measuring electrodes and thus acts as an excitation electrode pair. The same current signal is preferably applied to the respective pair of excitation electrodes in all measurement sequences of the measurement cycle, ie identical current signals are used as excitation signals in all measurement sequences.

In particular, it can be provided that the excitation signal is a time-constant electrical current. Accordingly, the measuring device for driving the measuring electrodes is designed in such a way that in each measuring sequence the respective excitation electrode pair is supplied with a time-invariable electric current for the duration of the measuring sequence, with the respective excitation electrode pair preferably being supplied with the same time-invariant current in all measuring sequences of the measuring cycle . Accordingly, it can be provided that the measuring device or its electronic measuring system drives a precisely defined electric current through different pairs of measuring electrodes at short time intervals one after the other.

For a current-carrying excitation electrode pair, according to the laws of electrostatics, an electric field is established in the fluid to be characterized, which is obtained by solving the basic equation of electrostatics ∇ ■ (σ(r)∇φ(r)) = 0 under the boundary conditions of the Currents flowing through the excitation electrodes are defined, where r denotes a position vector of three-dimensional space, φ(r) denotes the position-dependent electrical potential, and σ(r) denotes the position-dependent electrical conductivity of the fluid. The current density distribution j(r) in the fluid to be characterized is defined by the electric field or potential via j(r) = σ(r)∇φ(r), where j(r) is the location-dependent current density vector. The electrical field (or the electrical potential) and the current density distribution are clearly determined by the conductivity distribution σ(r) determined by the fluid and by the currents at the excitation electrodes defined as boundary conditions. As a result of the development of the electrical field, corresponding electrical potentials result at the measuring electrodes that are not acted upon by the excitation signal, which can be measured as electrical voltages. According to the present embodiment, provision can therefore be made in particular for each response signal to be an electrical voltage signal, with a response signal in the form of an electrical voltage or an electrical voltage signal being generated in each of the measurement sequences at one or more of the measuring electrodes not subjected to the excitation signal in the respective measurement sequence is detected, these electrodes acting as receiver electrodes in the respective measurement sequence. Accordingly, the electrical potentials resulting at the receiver electrodes can be detected in the form of electrical voltages.

Provision can be made, for example, to determine the absolute voltage present at a respective receiver electrode with respect to ground potential. Accordingly, the measuring device can, for example, be designed in such a way that it detects the electrical voltage between the ground potential and the respective receiver electrode as a response signal (i.e. the electrical potential difference between the ground potential and the electrical potential present at the respective receiver electrode).

Alternatively, provision can be made, for example, to determine the electrical voltage present between the two receiver electrodes of such a receiver electrode pair for selected pairs of receiver electrodes. Accordingly, the measuring device can be designed, for example, in such a way that it detects the electrical voltage present between the two receiver electrodes of the respective pair as a response signal in each measurement sequence for one or more receiver electrode pairs. The voltage or potential difference between the two receiver electrodes of a pair of receiver electrodes is also referred to as differential voltage.

The voltages detected at the receiver electrodes are completely determined by the spatial distribution of the electrical conductivity α(r) and the excitation electrode currents, so that based on the excitation signals in the form of electrical currents and the response signals in the form of electrical voltages, the spatial distribution of the electrical conductivity α(r) can be determined. Accordingly, the measuring device can, for example, be designed to characterize or determine the spatial distribution of an electrical property in such a way that the electrical property is the electrical conductivity. The optimal configurations for the selection of the excitation electrode pairs and receiver electrodes or receiver electrode pairs can be determined, for example, by means of simulations and/or experiments.

Based on the excitation signals and response signals of a measurement cycle, the spatial distribution of the electrical conductivity σ(r) within the measurement volume can be determined, with different phases of the fluid to be characterized being able to be identified using different values of the electrical conductivity. Thus, the measuring device For example, the device can be designed in such a way that it determines how many different phases the fluid to be characterized has and—if the presence of several different phases is determined—in which structure they are present. If, for example, the fluid to be characterized has a continuous first phase with particles of a second phase separated therein, the first phase having a different electrical conductivity than the second phase, then the measuring device can be used to identify, locate and characterize the particles of the second phase be designed with the characteristic conductivity. In particular, the electrical potential φ(r) and the current density distribution depend on the position, size, shape and electrical properties of such particles in the fluid, with a movement of such particles also leading to a change in the potential distribution and the current density distribution over time. Thus, parameters such as location or positioning, size and shape of such particles can be determined, for example by solving an inverse problem, for example on the basis of the spatial distribution of the electrical conductivity determined for a predetermined measurement cycle. In addition, the movement or speed of such particles can be determined, for example, on the basis of the spatial distributions determined for a plurality of measurement cycles that follow one another in terms of time and on the basis of their change over time. Thus, the measuring device can be designed in particular to determine the location or positioning, size, shape and/or movement speed of such particles, for example by means of the algorithm explained below.

According to this embodiment, it can be provided in particular that the measuring device is designed based on the excitation signals present as current signals and the response signals present as voltage signals for characterizing the fluid by means of impedance tomography. Accordingly, the measuring device can be a tomography device for characterizing a fluid by means of impedance tomography, wherein the tomography device is designed based on the excitation signals present as current signals and the response signals present as voltage signals of a measurement cycle for characterizing the internal structure of the fluid (present during the measurement cycle) by means of impedance tomography ( e.g. to generate a tomographic image of the fluid by means of impedance tomography), whereby e.g. based on the excitation signals present as current signals and the response signals present as voltage signals, the impedance between different pairs of measuring electrodes can be determined and based on the determined impedances the material distribution or phase distribution can be determined using an image reconstruction algorithm and can be visualized.

If the probe rods are designed with one or more shielding electrodes, it can also be provided according to the embodiment explained above (according to which the excitation signals are present in the form of current signals) that the shielding electrodes of the measuring device are switched to a time-constant electrical Potential can be switched, e.g. to ground potential.

According to another embodiment, the electrical excitation signal is an electrical voltage signal, this embodiment being particularly suitable and intended for characterizing electrically non-conductive fluids. Accordingly, the measuring device can be provided and designed, for example, to characterize an electrically non-conductive (or electrically insulating) fluid. According to this embodiment, the measuring device for controlling the measuring electrodes for carrying out a measuring cycle with several different measuring sequences is designed in such a way that in each of the different measuring sequences a single different measuring electrode or another pair of measuring electrodes is subjected to an electrical excitation signal in the form of an electrical voltage signal and is thus used as an excitation electrode or acts as a pair of excitation electrodes. The same voltage signal is preferably applied to the respective excitation electrode or the respective pair of excitation electrodes in all measurement sequences of the measurement cycle, i.e. identical voltage signals are used as excitation signals in all measurement sequences.

In particular, it can be provided that the excitation signal is a time-varying voltage signal. Accordingly, the measuring device for driving the measuring electrodes is designed in such a way that in each measuring sequence the respective excitation electrode or the respective excitation electrode pair is subjected to a voltage signal that varies over time during the duration of the measuring sequence. The time-varying excitation signal is preferably an AC voltage signal, but other time-varying voltages can also act as excitation signals, such as voltage pulses or voltage jumps. Accordingly, it can be provided that the measuring device or its measuring electronics apply a time-varying voltage signal to one of the measuring electrodes or a pair of measuring electrodes one after the other at short time intervals.

It can be provided, for example, that in each measurement sequence a different (single) measurement electrode is subjected to an electrical voltage signal, wherein the voltage signal can in particular be a voltage signal that varies over time (during the measurement sequence), preferably an AC voltage signal. Accordingly, in each measurement sequence, a voltage signal is applied to the respective excitation electrode or an electrical voltage potential is applied to the excitation electrode, wherein the voltage potential can be a voltage potential that changes over time (during the measurement sequence), preferably an AC voltage potential.

Alternatively, it can be provided, for example, that in each measurement sequence a different pair of excitation electrodes is subjected to an electrical voltage signal, i.e. an electrical voltage is applied between the two excitation electrodes of the respective pair of excitation electrodes, which acts as an excitation signal. The excitation signal can in particular be an electrical voltage which varies over time (during the measurement sequence) between the two excitation electrodes, in particular an alternating voltage

According to the present embodiment, in each measurement sequence, the measuring electrodes not acted upon by the excitation signal or voltage signal in the respective measurement sequence are also acted upon by the measuring device with a predetermined electrical potential that does not change over time (i.e. is constant over time), this potential also being referred to as the reference potential. In particular, it can be provided that the measuring electrodes not functioning as excitation electrodes are subjected to the same reference potential in all measurement sequences or during the entire measurement cycle, i.e. that the reference potential is identical for all measurement sequences. In particular, it can be provided that the reference potential is identical to the shielding potential and/or is given by the ground potential.

Due to the excitation voltage, according to the laws of electrostatics, an electric field is created in the fluid to be characterized, which is determined by solving the basic equation of electrostatics ∇ • (ε(r)∇φ(r)) = 0 under the boundary conditions at the excitation electrodes applied electrical voltages or potentials is defined, where r denotes a location vector of the three-dimensional space, φ(r) denotes the location-dependent electrical potential, and ε(r) denotes the location-dependent permittivity of the fluid. The current density distribution j(r) in the fluid to be characterized is defined by the electric field or potential via j(r) = ε(r)∇φ(r), where j(r) is the location-dependent current density vector. It should be noted that if the fluid to be characterized is a non-conductive or weakly electrically conductive fluid, the current density is mainly represented by displacement currents. As a result of the development of the electric field, corresponding electric currents result at the measuring electrodes not subjected to the excitation signal, which currents can be measured and can function as response signals. According to the present embodiment, provision can accordingly be made in particular for each response signal to be an electrical current signal, with a response signal in the form of an electrical current or an electrical current signal being generated in each of the measurement sequences at one or more of the measuring electrodes not subjected to the excitation signal in the respective measurement sequence is detected, these electrodes acting as receiver electrodes in the respective measurement sequence.

The currents detected at the receiver electrodes are completely determined by the spatial distribution of the permittivity ε(r) and the excitation voltage signals, so that the spatial distribution of the permittivity ε( r) can be determined. Accordingly, the measuring device can be designed, for example, to characterize or determine the spatial distribution of an electrical property in such a way that the electrical property is the permittivity. Based on the excitation signals and response signals of a measurement cycle, the spatial distribution of the permittivity ε(r) within the measurement volume can be determined, with different phases of the fluid to be characterized being able to be identified using different values of the permittivity. The measuring device can thus be designed, for example, in such a way that it determines how many different phases the fluid to be characterized has and—if the presence of a plurality of different phases is determined—in which structure they are present. If, for example, the fluid to be characterized has a continuous first phase with particles of a second phase separated therein, the first phase having a different permittivity than the second phase, then the measuring device for identifying, locating and characterizing the particles of the second phase can use the characteristic permittivity. In particular, the electrical potential and the current density distribution are dependent on the position, size and shape as well as the electrical properties of such particles located in the fluid Potential distribution and the current density distribution leads. Thus, parameters such as location or positioning, size and shape of such particles can be determined, for example by solving an inverse problem, for example on the basis of the spatial distribution of the permittivity determined for a predetermined measurement cycle. In addition, the movement or speed of such particles can be determined, for example, on the basis of the spatial distributions determined for a plurality of measurement cycles that follow one another in terms of time and on the basis of their change over time. Thus, the measuring device can be designed in particular to determine the location or positioning, size, shape and/or movement speed of such particles, for example by means of the algorithm explained below.

According to this embodiment, it can be provided in particular that the measuring device is designed based on the excitation signals present as voltage signals and the response signals present as current signals for characterizing the fluid by means of capacitance tomography. Accordingly, the measuring device can be a tomography device for characterizing a fluid using capacitance tomography, the tomography device being designed based on the excitation signals present as voltage signals and the response signals present as current signals of a measurement cycle for characterizing the internal structure of the fluid (present during the measurement cycle) using capacitance tomography ( e.g. to generate a tomographic image of the fluid by means of capacitance tomography), whereby e.g. based on the excitation signals available as voltage signals and the response signals available as current signals, the capacitance between different pairs of measuring electrodes can be determined and based on the determined capacities using an image reconstruction algorithm the material distribution or phase distribution can be determined and can be visualized.

However, it can also be provided to determine the impedance between different measuring electrode pairs based on the excitation signals present as voltage signals and the response signals present as current signals and to determine and visualize the material distribution or phase distribution based on the determined impedances using an image reconstruction algorithm.

If the probe rods are configured with one or more shielding electrodes, it can also be provided according to the embodiment explained above (according to which the excitation signals are present in the form of voltage signals) that the shielding electrodes are set to a time-constant electrical Potential can be switched, e.g. to ground potential.

If the measurement cycle contains _NA measurement sequences and _NE response signals are recorded at _NE receiver electrodes or pairs of receiver electrodes in each measurement sequence, the result of a measurement cycle is a measurement data set with _NA × _NE values, with each excitation signal being assigned _NE response signals.

If the excitation signals are in the form of voltage signals and the response signals are in the form of current signals, an electrical parameter can be calculated from a respective excitation signal and a respective associated current signal response, e.g. the amplitude damping, the phase shift or the complex impedance, so that the result is a measurement data set with N _A × N _E values of the respective characteristic value. Parameters of the fluid and any particles present therein can be determined from this measurement data set, for example by solving an inverse problem, for example by means of the algorithm explained below.

As explained, the spatial distribution of the electrical properties of the fluid can be characterized and determined based on the excitation signals and the response signals by solving an inverse problem, with particles arranged in the fluid also being able to be identified and characterized. An algorithm for solving the inverse problem is explained below by way of example, by means of which particles that are in the fluid to be characterized can be identified and characterized on the basis of the measurement data obtained by means of the measuring device.

näherungsweise zu lösen. Aus dem derart ermittelten Partikelwerte-Vektor x können anhand der entsprechenden Partikelparameter z.B. die Lage- und Formparameter direkt ermittelt werden. Partikelgeschwindigkeiten können ermittelt werden, indem die für mehrere aufeinanderfolgende Messungen bzw. Messzyklen vorliegenden Schwerpunktkoordinaten ermittelt werden und deren Ableitung nach der Zeit gebildet wird. Befinden sich mehrere Partikel gleichzeitig innerhalb des Messvolumens, kann es zu Ungenauigkeiten bei der approximativen Lösung des inversen Problems kommen. Deshalb kann bei hohen Partikeldichten vorgesehen sein, das Verfahren zu einer vollständigen elektrischen Tomographie auszuweiten. Eine vollständige elektrische Tomographie kann auch in anderen Fällen vorgesehen sein, z.B. wenn die innere Struktur des zu charakterisierenden Fluids unbekannt ist und z.B. überhaupt nicht bekannt ist, ob sich in dem Fluid Partikel befinden.In the present case, N _A denotes the number of measurement sequences in a measurement cycle, with N _E also denoting the number of response signals detected in each measurement sequence. Thus, in the corresponding measurement cycle, an excitation signal is applied to N _A excitation electrodes or excitation electrode pairs in succession, with a response signal being detected at N _E receiver electrodes or receiver electrode pairs. The N _E response signals recorded for N _A excitation signals are combined in a measured value vector m, which then contains N _A ×N _E values. The measured value vector m ₀ designates the measured value vector for the case, acting as a reference, in which there are no particles in the fluid in the measured volume. A respective particle is characterized by specific parameters _{x 1} ten, diameter and other shape parameters, and where x = [x ₁ , x ₂ ... x _M ] ^T denotes the vector of the particle values. If there is a particle with a set of parameters x ₁ . . . x _M in the fluid between the measuring electrodes or in the measuring volume, the electric field changes and a measured value vector m ₁ is obtained. Since the presence of the particle causes a change in the measured values in the form m ₁ - m ₀ , there is a functional relationship between the particle parameters and the measured values in the form (m ₁ - m ₀ ) = T{x}, where T{• } denotes a nonlinear transformation. The latter can be specified, for example, in the form of a non-linear algebraic equation (m ₁ -m ₀ )=F ₀ x +x ^T _F1 x + higher-order terms, with the Jacobi matrix F ₀ and the Hessian matrix F ₁ . By using an iterative solution method, eg a Newton-Raphson solver, the inverse problem x = T ^-1 {m ₁ - m ₀ } can be solved approximately. In many cases it is sufficiently accurate to solve the linearized problem (m ₁ - m ₀ ) ≈ F ₀ x by applying the least squares method according to $x\approx {\left(f_0^T{f}_0\right)}^{-1}{f}_0^T\left({\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="DE102020131604A1\_0002.png"\; state="\{\{state\}\}">m</figure-callout>}}_1-m_0\right)$

to solve approximately. The position and shape parameters, for example, can be determined directly from the particle value vector x determined in this way using the corresponding particle parameters. Particle velocities can be determined by determining the center of gravity coordinates available for several consecutive measurements or measurement cycles and forming their derivation over time. If there are several particles within the measurement volume at the same time, inaccuracies can occur in the approximate solution of the inverse problem. Therefore, in the case of high particle densities, the method can be expanded to include complete electrical tomography. A complete electrical tomography can also be provided in other cases, for example when the internal structure of the fluid to be characterized is unknown and, for example, it is not known at all whether there are particles in the fluid.

In the case of complete electrical tomography, in contrast to the method explained above, no particle value vector is used, but rather the spatial distribution of the electrical property to be determined (eg the conductivity α(r) or the permittivity ε(r)) is discretized. The property values of disjoint volume elements (voxels) within the measurement volume are combined in an object value vector s. A relation (m ₁ - m ₀ ) = T{s} can also be formally set up for this and s can be determined analogously to the procedure above. In this case, one obtains with s an image of the spatial distribution of the electrical property (eg the conductivity distribution or the permittivity distribution) in the measurement volume, which can be evaluated with further analysis methods, for example digital image processing methods.

According to a further aspect of the invention, a fluidic arrangement with a measuring device according to one of the embodiments explained above is provided. The fluidic arrangement has a pipeline for conducting a fluid and a measuring device according to one of the embodiments explained above for characterizing the fluid, with at least the probe rods of the measuring probe of the measuring device being arranged within the pipeline. For example, it can be provided that the entire measuring probe of the measuring device is arranged inside the pipeline. The pipeline has a tube axis, which can be given in particular by the longitudinal axis of the tube. In particular, it can be provided that all probe rods are arranged with probe rod longitudinal axes running parallel to one another, and that the probe rods or the measuring probe are arranged in the pipeline in such a way that the probe rod longitudinal axes are aligned parallel to the pipe axis. As an alternative to this, provision can be made, for example, for the probe rods or the measuring probe to be arranged in the pipeline in such a way that the longitudinal axes of the probe rod are aligned perpendicularly to the pipe axis. When arranging the probe rods or the measuring probe in the pipeline, the distance between the measuring electrodes can be kept smaller than when the measuring electrodes are positioned on the pipe wall, which, for example, allows the resulting electric field to be limited to a smaller spatial area. In addition, the measuring electrodes are in direct contact with the fluid and not in contact with the pipe wall, so that the influence of the wall on the electric field can be reduced or prevented.

• 1 eine Messvorrichtung gemäß einer Ausführungsform,
• 2 eine Draufsicht auf die Messsonde der Messvorrichtung gemäß 1,
• 3 eine Schnittdarstellung eines Sondenstabes gemäß einer Ausführungsform,
• 4 eine Schnittdarstellung eines Sondenstabes gemäß einer anderen Ausführungsform,
• 5 eine strömungstechnische Anordnung mit einer Messvorrichtung gemäß einer Ausführungsform, und
• 6 eine weitere strömungstechnische Anordnung mit einer Messvorrichtung gemäß einer Ausführungsform.

The invention is explained below on the basis of exemplary embodiments with reference to the accompanying figures, in which identical or similar features are provided with the same reference symbols, in which case they show schematically:

• 1 a measuring device according to an embodiment,
• 2 a plan view of the measuring probe of the measuring device according to FIG 1 ,
• 3 a sectional view of a probe rod according to an embodiment,
• 4 a sectional view of a probe rod according to another embodiment,
• 5 a fluidic arrangement with a measuring device according to an embodiment, and
• 6 a further fluidic arrangement with a measuring device according to an embodiment.

1 1 shows a measuring device 1 according to an embodiment when characterizing a fluid 3. The fluid 3 is, for example, a multiphase fluid 3 with a continuous first phase as a carrier medium and particles 5 of a second phase present therein. The measuring device 1 has a measuring probe 7 with a probe body 9 and several rod-shaped probe elements 11 . Such a rod-shaped probe element 11 is also referred to as a probe rod 11 . The measuring probe 7 has at least three probe rods 11 ; in the present example, the measuring probe 7 has four probe rods 11 .

The probe body 9 is designed as an example in the form of a right circular cylinder with two flat circular surfaces as bases, the two bases forming outer surfaces of the probe body 9 and parallel to the xy plane of the in 1 shown Cartesian xyz coordinate system. All probe rods 11 are fastened to the probe body 9 in such a way that they protrude from one of the base surfaces of the probe body 9, this base surface also being referred to as the front surface 13 of the probe body. Each probe rod 11 is attached to the probe body 9 at one of its two longitudinal ends, this longitudinal end also being referred to as the first longitudinal end. The other longitudinal end of each probe rod 11 is a free longitudinal end, this longitudinal end also being referred to as the second longitudinal end. Each probe rod 11 is attached to the probe body 11 in such a way that its longitudinal axis 12 is perpendicular to the end face 13 of the probe body 11 . All probe rods 11 are thus arranged parallel to one another, with the longitudinal axes 12 of the probe rods 11 being parallel to the z-axis of the in 1 shown xyz coordinate system.

The positions at which the probe rods 11 adjoin the end face 13 of the probe body 11 or protrude from the end face 13 are also referred to as the probe rod base positions 15 . Each probe rod base position 15 corresponds to the position of the first longitudinal end of one of the probe rods 11. All probe rods 11 are arranged on the end face 13 of the probe body 11 in such a way that the first longitudinal end or the probe rod base position 15 of each probe rod 11 is at a respective position along the Edge or the boundary line 17 of a convex flat surface is arranged, the convex surface being a circle as an example. The boundary line 17 is in 2 illustrated by the dashed line 17. Accordingly, the area or polygon formed by the straight lines connecting each probe rod base position 15 to the two nearest adjacent probe rod base positions 15 is a convex polygon, here by way of example a regular polygon in the shape of a square.

All probe rods 11 are of identical design and protrude from the probe body 9 with the same length. Each probe rod 11 has one or more electrodes functioning as measuring electrodes. In the present example, each probe rod 11 has two measuring electrodes 19, namely a first measuring electrode 19.1 and a second measuring electrode 19.2. In addition, each probe rod 11 has one or more electrodes functioning as shielding electrodes. In the present example, each probe rod 11 has two shielding electrodes 21, namely a first shielding electrode 21.1 and a second shielding electrode 21.2. The measuring electrodes 19 and shielding electrodes 21 are designed and arranged in such a way that each of these electrodes has an uncovered outer surface that is exposed to the outside, which is also referred to as the contact surface of the respective electrode. The outer surfaces of the measuring electrodes 19 that are exposed to the outside form measuring electrode contact surfaces 20 for contacting the fluid 3.

The outwardly exposed outer surfaces of the shielding electrodes 21 form shielding electrode contact surfaces 22 for contacting the fluid 3. In particular, the outwardly exposed outer surface 20.1 of the first measuring electrode 19.1 forms a first measuring electrode contact surface 20.1, and the outwardly exposed outer surface 20.2 of the second measuring electrode 19.2 a second measuring electrode contact surface 20.2, the exposed outer surface 22.1 of the first shielding electrode 21.1 a first shielding electrode contact surface 22.1, and the exposed outer surface 22.2 of the second shielding electrode 21.2 a second shielding electrode contact surface 22.2.

The measuring device 1 has a control and evaluation device 23 which is connected to the measuring probe 7 and is designed to control and read out the measuring electrodes 19 and the shielding electrodes 21 of all probe rods 11 . The measuring device 1 has a number of electrical lines 25 for electrically connecting the measuring electrodes 19 and the shielding electrodes 21 to the control and evaluation device 23 . Each measuring electrode 19 and each shielding electrode 21 is electrically contacted by means of an electrical line 25 and connected to the control and evaluation device 23, the lines 25 according to FIG 1 are shown summarized in connection 25. Each measuring electrode 19 is electrically contacted by means of a separate electrical line and connected to the control and evaluation device 23 . In addition, it can be provided that each shielding electrode 21 is contacted by means of a separate electrical line and is connected to the control and evaluation device 23 . However, it can also be provided that the electrical lines for contacting the shielding electrodes of a probe rod 11 or all probe rods 11 are brought together to form a common electrical bus line and this bus line is connected to the control and evaluation device 23 .

the 3 and 4 show different possible configurations of the probe rods 11.

3 shows a central longitudinal section through a probe rod 11 according to an embodiment. According to the design 3 Each probe rod 11 has a rod-shaped inner element 27 made of electrically insulating material, with the two measuring electrodes 19.1 and 19.2 and the two shielding electrodes 21.1 and 21.2 made of electrically conductive material being applied to the lateral surface of the inner element 27, and the outer surfaces of the electrodes 19.1, 19.2 , 21.1 and 21.2 form contact surfaces 20.1, 20.2, 22.1 and 22.2 for contacting the fluid 3. The measuring electrodes 19.1, 19.2 and the shielding electrodes 21.1, 21.2 are arranged at a distance from one another in different longitudinal sections of the inner element 27 or the probe rod 11, so that in particular all measuring electrodes 19.1, 19.2 and all shielding electrodes 21.1, 21.2 are electrically insulated from one another. According to this configuration, each probe rod 11 is formed (by means of a corresponding configuration of the inner element 27) with a cavity 29 which is open on one side at the first longitudinal end of the probe rod 11 (on the probe body side). For each probe rod 11, there is a first electrical line 25.1 for electrically contacting the first measuring electrode 19.1, a second electrical line 25.2 for electrically contacting the second measuring electrode 19.2, and a third electrical line 25.3 for electrically contacting the two shielding electrodes 21.1 and 21.2 . The first electrical line 25.1 contacts the first measuring electrode 19.1 at one end, is routed through the inner element 23 into the cavity 29 of the respective probe rod 11, runs in the cavity 29 to the open first longitudinal end of the respective probe rod 11 and from here through the probe body 9 and to the control and evaluation device 23, to which it is connected at its other end. The second electrical line 25.2 contacts the second measuring electrode 19.2 at one end, is routed through the inner element 23 into the cavity 29 of the respective probe rod 11, runs in the cavity 29 to the open first longitudinal end of the respective probe rod 11 and from here through the probe body 9 and to the control and evaluation device 23, to which it is connected at its other end. The third electrical line 25.3 has at one end within the cavity 29 a branch with two branch ends, the first branch end contacting the first shielding electrode 21.1, the second branching end contacting the second shielding electrode 21.2, the two branching ends through the inner element 23 into the Cavity 29 run and are brought together here to form a common line 25.3, which runs in the cavity 29 to the open first longitudinal end of the respective probe rod 11 and from here through the probe body 9 and to the control and evaluation device 23, on which it connected to its other end. The inner element 27 of each probe rod 11 is - apart from the passages of the lines 25.1, 25.2 and 25.3 - rotationally symmetrical with respect to its longitudinal axis 12, which coincides with the longitudinal axis 12 of the respective probe rod 11. Accordingly, each probe rod 11 - apart from the passages of the lines 25.1, 25.2 and 25.3 through the inner element 23 - is rotationally symmetrical with respect to its longitudinal axis 12.

4 shows a central longitudinal section through a probe rod 11 according to another embodiment. According to the design 4 each probe rod 11 has a coaxial arrangement, which alternately consists of electrically conductive elements 19, 21 and electrically insulating elements 31, which are arranged coaxially with respect to the longitudinal axis 12 of the respective probe rod 11 and are also referred to as coaxial elements. In the present example, the probe rod 11 has a rod-shaped central element 19.2, which is successively surrounded by a plurality of hollow-cylindrical elements 31.3, 21.2, 31.2, 19.1, 31.1 and 21.1. The coaxial elements 19.1, 19.2, 21.1 and 21.2 are made of electrically conductive material, such as metal. The coaxial elements 19.1 and 19.2 form the first and second measuring electrodes of the probe rod 11 according to FIG 4 . The coaxial elements 21.1 and 21.2 form the first and second shielding electrodes of the probe rod 11 according to FIG 4 . The coaxial elements 31.1, 31.2 and 31.3 consist of electrically insulating material (e.g. an electrically insulating ceramic), so that by means of these electrically insulating coaxial elements 31.1, 31.2, 31.3 in particular all measuring electrodes 19.1, 19.2 and all shielding electrodes 21.1, 21.2 are electrically insulated from one another. The length of the coaxial elements 19.2, 31.3, 21.2, 31.2, 19.1, 31.1, 21.1 outside the probe body decreases in this order, so that each of these coaxial elements mente is exposed or uncovered to the outside at its longitudinal end facing away from the probe body 9 and thus has or forms a contact surface for contacting the fluid 3 here. In particular, the outer surfaces of the outwardly exposed end sections of the first measuring electrode 19.1 and the second measuring electrode 19.2 form a first measuring electrode contact area 20.1 and a second measuring electrode contact area 20.2. In addition, the outer surfaces of the outwardly exposed end sections of the first shielding electrode 21.1 and the second shielding electrode 21.2 form a first shielding electrode contact surface 22.1 and a second shielding electrode contact surface 22.2. The coaxial elements (ie the central element 19.2 and the hollow cylinder elements 31.3, 21.2, 31.2, 19.1, 31.1 and 21.1) of the probe rod 11 according to FIG 4 are rotationally symmetrical with respect to the probe rod longitudinal axis 12, thus the probe rod 11 according to 4 rotationally symmetrical with respect to its longitudinal axis 12. Analogous to the embodiment 3 can according to the design 4 for each probe rod 11, a first electrical line 25.1 used to electrically contact the first measuring electrode 19.1, a second electrical line 25.2 used to electrically contact the second measuring electrode 19.2, and a third electrical line 25.3 used to electrically contact the two shielding electrodes 21.1 and 21.2 (in 4 not shown), each of these lines contacting the respective electrode at one end, passing through the probe body 9 and to the control and evaluation device and being connected to the same at the other end.

Both in the embodiment after 3 as well as in the embodiment according to 4 the measuring electrodes 19.1 and 19.2 and the shielding electrodes 21.1 and 21.2 of each probe rod 11 are rotationally symmetrical with respect to the longitudinal axis 12 of this probe rod 11, so that in particular the contact surfaces 20.1, 20.2, 22.1 and 22.2 are also rotationally symmetrical with the longitudinal axis 12. Each probe rod 11 is thus designed in such a way that the outer surface of the probe rod 11 lying outside the probe body 9 is rotationally symmetrical with respect to the longitudinal axis 12 of the probe rod.

In the embodiments according to 3 and 4 In addition, all measuring electrodes 19.1 and 19.2 are designed and arranged in such a way that their measuring electrode contact surfaces 20.1 and 20.2 are arranged at a distance from the probe body 9 and do not reach as far as the probe body 9. In addition, the measuring electrodes 19.1 and 19.2 are each designed in such a way that the extent of the first measuring electrode contact surface 20.1 and the second measuring electrode contact surface 20.2 along the longitudinal direction (running parallel to the z-direction) of the probe rod 11 is at least five times and a maximum of ten times as large is as large as the maximum cross-sectional dimension of the probe rod 11. Furthermore, the measuring electrodes 19.1 and 19.2 are designed and arranged in such a way that between the first measuring electrode contact surface 20.1 and the second measuring electrode contact surface 20.2 along the (parallel to the z-direction) longitudinal direction of the probe rod 11 there is a distance which is greater than the maximum cross-sectional dimension of the probe rod 11. Since the probe rods 11 according to the 3 and 4 are formed with a rotationally symmetrical outer surface and their cross section thus has a circular contour at each longitudinal position, in the present case the cross-sectional dimension of the probe rod 11 is given by the diameter of the circular cross-sectional contour. The first shielding electrode 21.1 is designed and arranged in such a way that the distance along the longitudinal direction of the probe rod 11 between the first shielding electrode contact surface 22.1 and the first measuring electrode contact surface 20.1 is smaller than the maximum cross-sectional dimension of the probe rod 11. In addition, the second shielding electrode 21.2 designed and arranged in such a way that the distance along the longitudinal direction of the probe rod 11 between the second shield electrode contact surface 22.2 and the first measuring electrode contact surface 20.1 is smaller than the maximum cross-sectional dimension of the probe rod 11, and that the distance along the longitudinal direction of the probe rod 11 between the second shielding electrode contact area 22.2 and the second measuring electrode contact area 20.2 is smaller than the maximum cross-sectional dimension of the probe rod 11.

The contact surface 20.1 of the first measuring electrode 19.1 of a respective probe rod 11 is also referred to as the first measuring electrode contact surface 20.1 of this probe rod 11, the contact surface 20.2 of the second measuring electrode 19.2 of a respective probe rod 11 is also referred to as the second measuring electrode contact surface 20.2 of this probe rod 11. All probe rods 11 are of identical design and protrude from the probe body 9 with the same length, so that the first measuring electrode contact surfaces 20.1 of all probe rods 11 are arranged in a common first plane and the second measuring electrode contact surfaces 20.2 of all probe rods 11 are arranged in a common second plane are. The first and the second plane are also referred to as the first or second measurement plane, these two measurement planes being perpendicular to the longitudinal axes 12 of the probe rods 11 or parallel to the xy plane of the in 1 shown xyz coordinate system.

When operating the measuring device, the probe rods 11 are introduced into the fluid 3 to be characterized, so that all measuring electrodes 19 (i.e. the first measuring electrode 19.1 and the second measuring electrode 19.2 of each probe rod 11) via their measuring electrode contact surfaces 20 and all shielding electrodes 21 (i.e. the first shielding electrode 21.1 and the second shielding electrode 21.2 of each probe rod 11) are in contact with the fluid 3 via their shielding electrode contact surfaces 22. The control and evaluation device 23 is designed to control and read out the measuring electrodes 19 and shielding electrodes 21 of all probe rods 11 in such a way that a measuring cycle with a plurality of consecutive measuring sequences is run through. The control and evaluation device 23 is designed in such a way that it applies a predetermined electric potential that is constant over time to all the shielding electrodes 21 during the entire measurement cycle, this potential also being referred to as the shielding potential. Thus, all shielding electrodes 21 are kept at the shielding potential during all measurement sequences of the measurement cycle. In the present example, the shielding potential is given by the ground potential.

The control and evaluation device 23 is also designed in such a way that it applies an electrical excitation signal to a different one of the measuring electrodes 19 of all probe rods 11 in each measuring sequence, or that it applies a different pair of measuring electrodes 19 of all probe rods 11 to a different pair of measuring electrodes 19 of all probe rods 11 in each measuring sequence electrical excitation signal is applied. The excitation signal is in the form of an electrical voltage signal or an electrical current signal. The measuring electrode to which the excitation signal is applied or the pair of measuring electrodes to which the excitation signal is applied is also referred to as the excitation electrode or excitation electrode pair. The excitation signal creates an electrical field in the fluid 3 that depends on the spatial distribution of the electrical properties within the fluid 3 and causes corresponding electrical response signals at the remaining measuring electrodes 19 that are not exposed to the excitation signal. The control and evaluation device 23 is designed in such a way that it detects such a response signal in each measurement sequence at one or more of the measuring electrodes 19 to which the excitation signal is not applied in the respective measurement sequence. Provision can be made, for example, for a response signal to be detected in each measurement sequence at all of the measurement electrodes 19 in which the excitation signal was not applied in the respective measurement sequence. The measuring electrodes, at which a response signal is recorded in each case, are also referred to as receiver electrodes. The electrical currents or voltages resulting at the receiver electrodes are recorded as response signals.

At least one excitation electrode and at least one receiver electrode of different probe rods 11 are involved in each measurement sequence. Accordingly, the measuring electrodes 19 are controlled or read out by the control and evaluation device 23 in such a way that in each measuring sequence (at least) one measuring electrode 19 of a probe rod 11 acts as an excitation electrode and (at least) one measuring electrode 19 of another probe rod 11 acts as a receiver electrode. Provision can also be made, for example, for at least one measuring electrode 19 of each probe rod 11 to be involved in each measurement sequence, so that in each measurement sequence at least one measuring electrode 19 of each probe rod acts as an excitation electrode or as a receiver electrode.

The measuring device 1 is designed by means of the control and evaluation device 23 based on the excitation signals and response signals of a measuring cycle to characterize the spatial distribution of an electrical property within the probed measuring volume during the measuring cycle, with the measuring volume between the probe rods 11 or between the measuring electrodes 19 of all probe rods 11 arranged spatial volume includes. When operating the measuring device 1, the measuring volume is filled with the fluid 3, so that the measuring device 1 based on the excitation signals and response signals of all measuring sequences of a measuring cycle to characterize the during the measuring cycle within the (located in the measuring volume) fluid 3 present spatial distribution of an electrical property is formed. The measuring device 1 can thus be designed, for example, to determine the spatial distribution of an electrical property within the measuring volume or fluid 3 during the measuring cycle. The electrical property can be, for example, electrical conductivity, electrical permittivity or electrical impedance.

According to a first embodiment, the measuring device 1 is designed in such a way that in each measuring sequence of the measuring cycle, a different pair of measuring electrodes 19 of all probe rods 11 is supplied with an electrical excitation signal in the form of an electrical current that is constant over time and thus functions as an excitation electrode pair. In this case, the respective excitation electrode pair is preferably supplied with the same current signal in all measurement sequences. According to this embodiment, the measuring device 1 is also designed such that in each measurement sequence at the than Receiver electrodes acting measuring electrodes 19, a response signal is detected in the form of an electrical voltage signal. Provision can be made, for example, to determine the voltage present at a respective receiver electrode in absolute terms relative to ground potential, so that the electrical voltage between the ground potential and the electrical potential of the respective receiver electrode is recorded as a response signal by the measuring device 1 . Alternatively, provision can be made to determine the electrical voltage present between the two receiver electrodes of such a receiver electrode pair for different pairs of receiver electrodes, so that the electrical voltage present between two receiver electrodes is recorded by the measuring device 1 as a response signal. Based on the excitation signals present in the form of the current signals and the response signals present in the form of the voltage signals, the measuring device 1 or its control and evaluation device 23 can be designed to characterize or determine the spatial distribution of the electrical conductivity present in the fluid 3 within the measuring volume , where the electrical property is given by electrical conductivity as an example. The present embodiment is particularly suitable and intended for characterizing electrically conductive fluids. According to this embodiment, it can be provided in particular that the measuring device 1 is designed to characterize the fluid by means of impedance tomography based on the excitation signals present as current signals and the response signals present as voltage signals, wherein, for example, based on the excitation signals present as current signals and the response signals present as voltage signals, the Impedance can be determined between different pairs of measuring electrodes and based on the determined impedances using an image reconstruction algorithm, the material distribution or phase distribution present within the measurement volume can be determined and visualized.

According to a second embodiment, the measuring device 1 is designed in such a way that in each measuring sequence of the measuring cycle, an individual other measuring electrode 19 or another pair of measuring electrodes 19 is subjected to an electrical excitation signal in the form of an electrical voltage signal that varies over time and thus acts as an excitation electrode or excitation electrode pair . Accordingly, a voltage signal that varies over time during the respective measurement sequence acts as an excitation signal, and the voltage signal can preferably be an AC voltage signal. The same voltage signal is preferably applied to the respective excitation electrode or the respective pair of excitation electrodes in all measurement sequences. According to this embodiment, the measuring device 1 is also designed in such a way that in each measuring sequence the measuring electrodes 19 that are not acted upon by the excitation signal in the respective measuring sequence are acted upon by it by means of the control and evaluation device 23 with a predetermined electrical potential that does not change over time, with this potential also referred to as reference potential. Thus, in each measurement sequence, all measurement electrodes 19 that are not acted upon by the excitation signal in the respective measurement sequence are kept at the reference potential. In the present example, the reference potential is given by the ground potential. According to this embodiment, the measuring device 1 is also designed in such a way that in each measuring sequence a response signal in the form of an electrical current signal is detected at the measuring electrodes 19 functioning as receiver electrodes. Based on the excitation signals present in the form of the voltage signals and the response signals present in the form of the current signals, the measuring device 1 or its control and evaluation device 23 can be designed to characterize or determine the spatial distribution of the permittivity present within the measuring volume in the fluid 3. where the electrical property is given by the permittivity as an example. The present embodiment is particularly suitable and intended for characterizing electrically non-conductive fluids. According to this embodiment, it can be provided in particular that the measuring device 1 is designed based on the excitation signals present as voltage signals and the response signals present as current signals for characterizing the fluid by means of capacitance tomography, e.g. based on the excitation signals present as voltage signals and the response signals present as current signals Capacity can be determined between different pairs of measuring electrodes and based on the determined capacities using an image reconstruction algorithm, the material distribution or phase distribution present within the measurement volume can be determined and visualized. However, it can also be provided to determine the impedance between different measuring electrode pairs based on the excitation signals present as voltage signals and the response signals present as current signals and to determine and visualize the material distribution or phase distribution present within the measurement volume based on the determined impedances using an image reconstruction algorithm .

As described above, the measuring device 1 according to the first and second embodiment explained above can be designed in particular for the electrotomographic characterization of the fluid 3 by means of impedance tomography or capacitance tomography. Accordingly, the measuring device 1 can be a tomography device 1 which is designed for the electrotomographic characterization of the fluid 3 based on the excitation signals and the response signals of the measuring cycle. As explained above, the first measuring electrode contact surfaces 20.1 of all probe rods 11 are arranged in a common first measurement plane and the second measuring electrode contact surfaces 20.2 of all probe rods 11 are arranged in a common second measurement plane, with these measurement planes being able to function as tomography planes. The measuring device 1 can be embodied, for example, as a tomography device 1 in such a way that it determines the spatial distribution of the electrical property during the measuring cycle in the first and the second measuring plane based on the excitation signals and response signals of a measuring cycle, wherein according to the aforementioned first embodiment, the electrical property can be, for example, the electrical conductivity, and wherein, according to the aforementioned second embodiment, the electrical property can be, for example, the permittivity. Furthermore, in this case, the measuring device 1 can be designed to generate a two-dimensional tomographic image of the internal structure of the fluid 3 within the first measuring plane based on the spatial distribution of the electrical property determined for the first measuring plane. In addition, the measuring device 1 can be designed to generate a two-dimensional tomographic image of the internal structure of the fluid 3 within the second measuring plane based on the spatial distribution of the electrical property determined for the second measuring plane.

For example, it can be provided that each measurement cycle has two sub-cycles, namely a first and a second sub-cycle. Accordingly, e.g. the first part-cycle can have several measurement sequences such that in each of the measurement sequences of the first part-cycle a different first measuring electrode 19.1 or a different pair of the first measuring electrodes 19.1 of the probe rods 11 is acted upon by the excitation signal and at one or more of the respective remaining ( i.e. a response signal is detected in the respective measurement sequence not with the first measuring electrodes 19.1 to which the excitation signals are applied. In addition, e.g. the second partial cycle can have several measurement sequences such that in each of the measurement sequences of the second partial cycle, a different second measuring electrode 19.2 or a different pair of second measuring electrodes 19.2 of the probe rods 11 is acted upon by the excitation signal and at one or more of the remaining ( i.e. a response signal is detected in the respective measurement sequence not with the second measuring electrodes 19.2 to which the excitation signals are applied. Accordingly, only the first measuring electrodes 19.1 of the probe rods 11 are involved as excitation electrodes and receiver electrodes in the first partial cycle, with the second measuring electrodes 19.2 not being involved in the first partial cycle. In addition, only the second measuring electrodes 19.2 of the probe rods 11 are involved in the second partial cycle, with the first measuring electrodes 19.1 not being involved in the second partial cycle.

the 5 and 6 each show a fluidic arrangement 33 according to one embodiment, the arrangement 33 each having a pipeline 35 for conducting the fluid 3 and a measuring device 1 with a measuring probe 7 and a control and evaluation device 23 according to one of the embodiments explained above. The probe rods 11 are arranged inside the pipeline 35 . In the present case, the entire measuring probe 7 is arranged within the pipeline 35 as an example. The pipeline 33 has a longitudinal axis or pipe axis 37 . In the embodiment according to 5 the measuring probe 7 is arranged in the pipeline 33 in such a way that the longitudinal axes 12 of all probe rods 11 run parallel to the pipe axis 37 (with the probe body 9 being arranged downstream of the probe rods 11). In the embodiment according to 6 the measuring probe 7 is arranged in the pipeline 33 in such a way that the longitudinal axes 12 of all probe rods 11 run perpendicular to the pipe axis 37 .

Reference List

1

Measuring device / tomography device

3

fluid to be characterized

5

Particles of the second phase of the fluid

7

measuring probe

9

probe body

11

rod-shaped probe element / probe rod

13

flat front surface / outer surface of the probe body

15

Probe rod base position

17

Boundary line of a convex surface

19

measuring electrode

19.1

first measuring electrode of a probe rod

19.2

second measuring electrode of a probe rod

20

measuring electrode contact area

20.1

Contact surface of the first measuring electrode of a probe rod

20.2

Contact surface of the second measuring electrode of a probe rod

21

screen electrode

21.1

first shielding electrode of a probe rod

21.2

second shielding electrode of a probe rod

22

shield electrode contact surfaces

22.1

Contact surface of the first shielding electrode of a probe rod

22.2

Contact surface of the second shielding electrode of a probe rod

23

Control and evaluation device

25

electrical line / connection

25.1

electrical line for contacting the first measuring electrode

25.2

electrical line for contacting the second measuring electrode

25.3

electrical line for contacting the shielding electrodes

27

electrically insulating inner element

29

cavity

31

electrically insulating element

33

flow arrangement

35

pipeline

37

Pipe axis / longitudinal axis of the pipeline

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102012102870 B4 [0001]
• DE 102017123032 A1 [0006]
• EP 2910907 A1 [0007]

Claims (15)

Measuring device (1) for characterizing a fluid (3), having: - a measuring probe (7) with at least three rod-shaped probe elements (11), - wherein each of the rod-shaped probe elements (11) has at least one measuring electrode (19.1, 19.2) with an outwardly exposed contact surface (20.1, 20.2) for contacting the fluid (3), - wherein the measuring device (1) is designed to carry out a measuring cycle with several different measuring sequences in such a way that in each of the different measuring sequences a different measuring electrode (19.1, 19.2) or a different pair of measuring electrodes (19.1, 19.2) of the probe elements (11) an electrical excitation signal is applied and an electrical response signal is detected at at least one of the remaining measuring electrodes (19.1, 19.2). measuring device claim 1 , wherein the measuring device (1) based on the excitation signals and the response signals of a measurement cycle for characterizing the during the measurement cycle within the fluid (3) present spatial distribution of an electrical property is formed. measuring device claim 1 or 2 , wherein the measuring device (1) is designed based on the excitation signals and the response signals of a measuring cycle for characterizing the fluid (3) by means of electrical tomography. Measuring device according to one of Claims 1 until 3 , wherein the measuring probe (7) has a probe body (9) and the rod-shaped probe elements (11) are arranged on the probe body (9), and wherein the measuring electrodes (19.1, 19.2) are designed and arranged in such a way that the contact surface (20.1, 20.2) of each measuring electrode (19.1, 19.2) is arranged at a distance from the probe body. Measuring device according to one of Claims 1 until 4 , wherein all probe elements (11) are formed identical to each other. Measuring device according to one of Claims 1 until 5 , wherein all probe elements (11) are arranged parallel to each other. Measuring device according to one of Claims 1 until 6 , wherein the measuring electrodes (19.1, 19.2) are designed in such a way that the expansion of the contact surface (20.1, 20.2) of each measuring electrode of a probe element (11) along the longitudinal direction (12) of this probe element is at least five times as large and at most ten times as large as the maximum cross-sectional dimension of this probe element. Measuring device according to one of Claims 1 until 7 , wherein each probe element (11) has at least a first measuring electrode (19.1) with a first contact surface (20.1) and a second measuring electrode (19.2) with a second contact surface (20.2), the first contact surface (20.1) being at a distance from the second Contact surface (20.2) is arranged, the distance being at least as large as the maximum cross-sectional dimension of the probe element (11). Measuring device according to one of Claims 1 until 8th , each probe rod (11) having n measuring electrodes (19), each of the measuring electrodes (19) having an outwardly exposed contact surface (20) and the contact surface (20) of the mth measuring electrode (19) of a probe rod (11) is referred to as the mth measuring electrode contact surface of this probe rod, and the probe rods (11) and measuring electrodes (19) are designed and arranged in such a way that the mth measuring electrode contact surfaces (20) of all probe rods (11) are each in a common m-th level, where n is a natural number equal to or greater than two, and m is a natural number smaller than or equal to n. measuring device claim 9 , wherein the measuring device (1) is designed to determine the spatial distribution of the electrical property in each of the n planes based on the excitation signals and response signals of a measuring cycle. Measuring device according to one of Claims 1 until 10 , wherein each of the rod-shaped probe elements (11) has at least one shielding electrode (21.1, 21.2) with a contact surface (22.1, 22.2) exposed to the outside, and wherein the measuring device (1) for applying the shielding electrodes (21.1, 21.2) of the probe rods ( 11) is formed with a predetermined electrical potential that is constant over time across all measurement sequences. Measuring device according to one of Claims 1 until 11 , wherein each measuring electrode (19.1, 19.2) of a respective rod-shaped probe element (11) is designed and arranged such that its contact surface (20.1, 20.2) is rotationally symmetrical with respect to the longitudinal axis (12) of the probe element (11). Measuring device according to one of Claims 1 until 12 , wherein the measuring device (1) for driving the measuring electrodes (19.1, 19.2) for Carrying out a measuring cycle with several different measuring sequences is designed in such a way that in each of the different measuring sequences a different pair of measuring electrodes is supplied with an electrical excitation signal in the form of a temporally constant electric current, and on at least one of the remaining measuring electrodes (19.1, 19.2). electrical response signal is detected in the form of an electrical voltage signal. Measuring device according to one of Claims 1 until 12 , wherein the measuring device (1) for controlling the measuring electrodes (19.1, 19.2) for carrying out a measuring cycle with several different measuring sequences is designed in such a way that in each of the different measuring sequences a different measuring electrode or a different measuring electrode pair with an electrical excitation signal in the form of a time-varying electrical voltage signal is applied, and an electrical response signal in the form of an electrical current signal is detected on at least one of the remaining measuring electrodes (19.1, 19.2). Fluidic arrangement, comprising: - a pipe for conducting a fluid (3), and - A measuring device (1) according to any one of the preceding claims, wherein at least the rod-shaped probe elements (11) of the measuring probe (7) of the measuring device (1) are arranged within the pipeline.

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