EP3791171A1

EP3791171A1 - Tdr measuring apparatus for determining the dielectric constant

Info

Publication number: EP3791171A1
Application number: EP19719246.1A
Authority: EP
Inventors: Timo CAMEK; Gerd GRITSCH; Stefan Rolf
Original assignee: IMKO Micromodultechnik GmbH
Current assignee: IMKO Micromodultechnik GmbH
Priority date: 2018-05-09
Filing date: 2019-04-18
Publication date: 2021-03-17
Also published as: DE102019110256A1; CN112236672A; US20210270761A1; US11656194B2; WO2019214924A1

Abstract

The invention relates to a TDR measuring apparatus for determining at least the dielectric constant and material properties possibly derived therefrom, in particular the moisture and/or the conductivity, of a medium (2) flowing through a pipeline (1), having signal generation electronics (3) which generate TDR measurement signals, transmitting and/or receiving electronics (4) which emit and/or receive the TDR measurement signals, a coupling-in/coupling-out apparatus (5) which couples the TDR measurement signals into an electrical conductive measuring probe (6) of a predefined length (L) and couples said signals out of the measuring probe (6), and control/evaluation electronics (7) which use the propagation time of the TDR measurement signals on the measuring probe (6) to determine at least the dielectric constant and material properties possibly derived therefrom, in particular the moisture and/or the conductivity, wherein the measuring probe(6) is arranged in an electrically insulated manner outside the interior (8) of the pipeline (1) through which the medium (2) flows, or wherein the measuring probe (6) is placed in the pipeline (1) in such a manner that the outer surface of the measuring probe (6) facing the medium (2) terminates in a manner flush with the inner surface of the pipeline (1) facing the medium (2), and is configured such that the propagation time and/or the amplitude of the measurement signals on the measuring probe (6) is/are dependent on the dielectric constant of the medium (2) flowing through the pipeline (1).

Description

TDR measuring device for determining the dielectric constant

The invention relates to a TDR measuring device for determining the

Dielectric constant and / or derived material properties, in particular the humidity and / or the conductivity of a medium flowing through a pipe medium. It goes without saying that the pipeline can be any conduit capable of carrying a medium. It may therefore be a closed line or even a channel-shaped line.

The dielectric TDR measurement principle for determining the moisture content of a medium is used in many industrial applications. Here, the dielectric constant (DK) of a material is measured by a high-frequency electromagnetic field, wherein the electromagnetic high-frequency field penetrates the material to be measured. The dielectric constant of water has a value of 80 at 20 ° C and thus differs greatly from the dielectric constant of solids, which have DK values of 3 to 30, depending on the material. With this strong dielectric contrast, the dielectric constant can thus be used as a measure of the water content or the moisture content of the material.

The TDR (Time Domain Reflectometry, also known as cable radar) measuring principle used for DK measurements has become increasingly popular over the last 20 years as a precise measurement method for demanding applications in industry. For corresponding TDR measurements, two- or three-wire parallel waveguides are usually used. The waveguide arrangement corresponds to the actual sensor or the measuring probe. This is in the form of rods or plates in the too

introduced medium.

For DK measurement, a voltage jump or a signal edge is preferably generated, which propagates along a coaxial cable which is connected to the waveguides. If the voltage jump on the waveguide, it comes to a

Partial reflection. The propagating portion of the measuring signal is completely reflected at the end of the probe. The step response of a waveguide can be over the

Measuring time range, wherein the reflection time is the measure of the water content or the complete dielectric properties.

The basis for the application of the TDR technology for moisture measurement is the following physical relationship:

Accordingly, the propagation velocity c of an electromagnetic wave in vacuum is equal to the speed of light c ₀ . Outside the vacuum is the

Propagation speed c depends only on the dielectric constant and the magnetic permeability pr of the material in which the wave propagates. The latter can be set equal to 1 in non-magnetic materials, so that the propagation speed depends only on the dielectric constant (DK).

The challenge with the TDR measurement lies in the very short duration of the electromagnetic wave on the probe. Therefore short-term and steep-edged pulses (rise time <300 picoseconds) must be used for the measurement.

A method as well as a device for determining the humidity of a

Products / media via a TDR method have become known from EP 0 478 815 A1. In the known method, a rectangular signal is applied to a measuring line by means of a measuring signal generator. The pulse duration of the signal here is twice as long as the running time of the signal on the test lead. The signal is reflected on the test lead or at the end of the test lead. Therefore, at the input of the measuring line or at the output of the measuring signal transmitter, the superimposition of the amplitudes of the signal fed to the measuring line forms

Measuring signal and reflected at or at the end of the measuring line measuring signal the sum signal. The measuring line is in this case preferably designed as a probe.

In the TDR method, it must be ensured that an electrical pulse can propagate along the measuring line / probe and is reflected at the end of the measuring line / probe. Over the duration of the pulse, the moisture of the medium is determined. In the known solution, the pulse, triggered by the signal processing electronics via a cable to the first measuring line, from the end of the first measuring line to the beginning of the second measuring line, is reflected at the end of the second measuring line and runs back to the signal processing electronics. The duration of the pulse is calculated as a humidity value and over standard analog signals, e.g. based on the 0-20mA or the 4-20mA standard. In parallel, however, the moisture can also be transmitted via a digital interface, such as a RS 485, are issued.

The applicant develops and distributes various measuring devices based on the TDR measuring principle. In particular, measuring devices are offered under the names Sono-Vario, Sono-Silo, Trime-Pico. The measuring devices each consist of the sensor or the measuring probe and a TDR measuring electronics, each on a circuit board housed in the probe housing or outside the probe housing. The TDR measuring electronics are always on (internally in the probe housing, or externally) via

High frequency cable / coaxial cable connected to the sensor or the probe.

The different probe designs are optimally designed for different industrial applications. In particular, sensors are offered which vary in length, in particular between 0.05 m and 0.5 m. The known solutions are mainly realized via rod arrangements or via planar sensors; these are either coated or uncoated.

The object of the invention is to propose a TDR measuring device which non-invasively measures parameters of the medium flowing through a pipeline and / or recognizes a change in state of the pipeline. The term 'non-invasive' is understood in the context of the invention that the flow of the medium through the measuring device is not hindered or disturbed.

The invention is achieved by a TDR measuring device for determining the

Dielectric constant and derived material properties, in particular the humidity and / or the conductivity of a medium flowing through a pipe medium. According to one embodiment of the invention, the solution according to the invention is also suitable for detecting a change in state of the pipeline through which the medium flows or for detecting the condition of a medium flowing through the pipeline.

The TDR measuring device comprises signal generation electronics which generate TDR measurement signals, preferably jump signals as described in EP 0 478 815 A1, a transmitting and / or receiving electronics unit which transmits and / or receives the TDR measurement signals Input / output device, which couples the TDR measuring signals to an electrically conductive measuring probe of a predetermined length or decoupled from the measuring probe, and control / evaluation electronics which, based on the transit time of the TDR measuring signals, the dielectric constant and derived therefrom

Material properties, in particular the humidity and / or the conductivity of the

Medium. The connection of the electronics to the sensor is preferably via an RF cable. The electronics are either located at the sensor, or they are spatially separated from the sensor, the distance is usually between 1-2m.

The measuring probe is preferably outside of the medium through which the medium flows

Interior of the pipeline arranged electrically isolated and designed such that the duration of the measurement signals on the probe depends on the

Dielectric constant of the flowing medium through the pipe. Alternatively, the probe is arranged to be flush with the flowable medium closes facing inner surface of the pipeline. It goes without saying that in this case at least two electrodes carrying the measuring signals must be provided, which are electrically insulated from one another. This alternative positioning of the measuring probe is particularly suitable when measuring the concentration of flowable media with very high dielectric constants, eg sugar solutions for soft drinks. In these applications, an isolation of the probe to the flowable medium would lead to a significantly reduced accuracy of measurement. The dielectric constants of corresponding media are above 50, often between 60-80. If the conductivity of the medium is greater than 25mS / cm, the measurement signal is so strongly attenuated by electrical short circuit that, depending on the probe geometry, it may no longer be possible to receive it. Incidentally, the frequency used for the measurement signals is preferably in the range of 500 MHz - 2 GHz.

The flowable media can be liquid or viscous. However, the medium may also be a bulk material or a powdery substance.

The TDR measuring device according to the invention enables non-invasive inline measurement of various physical properties of liquid / viscous media or bulk materials as they flow through a pipeline. Since the measuring probe is arranged outside the flow path of the medium, the medium can flow undisturbed and uninfluenced by the measuring probe through the pipeline. The TDR measuring device also makes it possible to detect changes in the wall of the pipeline through which the medium flows. This information can subsequently be used for compensation purposes or for error status detection. A change of state in the area of the pipeline can e.g. be triggered by fouling.

The TDR meter is used for the non-invasive determination of the dielectric constant, permittivity and / or conductivity of the medium flowing through the pipeline. In particular, the TDR measuring device according to the invention allows improved accuracy in the determination of moisture or conductivity.

According to an advantageous embodiment of the TDR measuring device according to the invention, the measuring probe consists of at least two preferably designed as interconnects electrodes, wherein a first electrode performs the TDR measurement signals and wherein the at least one further electrode is configured as a shield or ground electrode.

Preferably, sensors for acquiring measured values via the TDR technology each consist of one or two electrically conductive electrodes at ground potential and an electrically conductive electrode into which the high-frequency measurement signal is coupled. The electrodes are guided in parallel and each electrically contacted at one end. At the "open", not electrically contacted end of the

High frequency signal reflected. The probe is connected to a TDR via a coaxial cable. Measuring electronics (which is usually arranged on a circuit board) connected. The TDR measuring electronics generates the high-frequency signal, measures the running time of the am

Probe end reflected signal, evaluates the measured data and provides the measurement result. Depending on the application, the board can be integrated directly into a sensor housing. It depends, however, on the particular one

Application possible to arrange the board remote from the sensor housing.

It is to be regarded as essential in the invention that the dimensioning and / or the design of the measuring probe are configured such that the electromagnetic field generated by the measuring signals at least approximately completely penetrates the interior of the pipeline. The arrangement and configuration of the at least one grounded electrode, the field geometry can be selectively influenced. Thus, a first advantageous embodiment of the measuring probe provides that the first electrode and the shield or ground electrode are arranged substantially on or in opposite surface areas of the pipeline.

Incidentally, the measuring probe preferably consists of three electrodes designed as conductor tracks, one of the electrodes carrying the TDR measuring signals and being arranged substantially centrally with respect to the two electrodes designed as shielding or grounding electrodes.

One embodiment provides - as already described - that there is no direct contact between the electrodes and the medium. Here, the electrodes are arranged either on the outer wall of the pipeline or in the pipe wall of the pipeline. It goes without saying that the pipe itself is made of an electrically non-conductive material at least in the area in which the measuring probe is located. It is also possible to design the corresponding pipe section with the electrodes as a separate unit, wherein the separate unit in the

Pipe is used. Here, the pipe and the separate unit preferably have the same inner pipe diameter. In a further embodiment already mentioned above, the electrodes are placed with respect to the inner surface of the pipeline such that their outer surface facing the medium terminates flush with the inner surface of the pipeline facing the medium.

According to a development of the measuring probe, the electrodes are arranged substantially parallel to one another and spirally with respect to the pipeline. An alternative embodiment provides that the electrodes are arranged parallel to each other in the form of partial circles (see Fig. 4) substantially perpendicular to the flow direction of the flowing medium through the pipe. In the chosen designs, it must be ensured that the interior of the pipeline in the area of the measuring probe is complete or at least largely interspersed by the electromagnetic field of the measuring signals running along the measuring probe. In the first two embodiments, the degrees of freedom with respect to the length of the electrodes are greater than in the last-mentioned arrangement of the electrodes.

Furthermore, it is provided that the electrodes preferably have the same length, but differ in width. With the aforementioned different

Embodiments of the electrodes, the probe can be optimally adapted to the respective application within wide limits. If the electrodes face each other, the penetration of the interior space with the electromagnetic field of the measuring signals running along the measuring probe over the cross section of the pipeline is guaranteed.

Furthermore, it is proposed to design the TDR measuring device in such a way that, in addition to determining the dielectric constant of the medium flowing through the pipeline, it also provides information about a change in state of the wall of the pipeline. While the first measuring probe is designed such that the electromagnetic field generated by the measuring signals, that is to say the measuring field, at least approximately completely penetrates the interior of the pipeline, the second is

Measuring probe designed so that the generated by the measuring signals

electromagnetic field only a portion of the interior of the pipeline interspersed in the vicinity of the pipe wall. Whereas in the case of the first measuring probe the propagation time and / or the attenuation of the measuring signals running along the measuring probe provide information about the dielectric constant of the medium, the propagation time and / or the attenuation of the measuring signals in the second measuring probe provide information about one

Change of state of the pipeline. This makes it possible to detect any abrasion occurring on the inner wall of the pipeline as well as deposits / buildup of the medium on the inner wall of the pipeline. Preferably, both probes are arranged axially offset from one another on the pipeline. The two measurements can be performed alternately by means of a switch or in parallel.

An embodiment of the TDR measuring device according to the invention provides a

Multisensor arrangement of, for example, three preferably axially offset and differently designed probes before. While a first measuring probe is designed such that the electromagnetic field generated by the measuring signals at least approximately completely passes through the interior of the pipeline, a second measuring probe and a third measuring probe are designed such that the electromagnetic fields generated by the measuring signals in the interior of the pipeline annular areas of different thickness in the region of the wall of the pipeline push through. Such a configuration of the TDR measuring device makes it possible, for example, to detect whether the medium flows through the pipeline in a laminar manner. In addition, it can also be detected with such a TDR measuring device, whether at a

Multi-component medium flowing through the pipeline, a homogeneous

Mixing or whether the medium flowing through the pipeline has its different components, e.g. Oil and water, has split.

Furthermore, it is considered advantageous in connection with the invention if the measuring probe is arranged in a housing acting as a Faraday cage.

A very interesting embodiment of the TDR measuring device according to the invention suggests that the signal generation electronics, the transmission and / or

Receiving electronics, the input / output device and the probe are arranged on a multi-layer, preferably a three-layer printed circuit board. In particular, a bore is provided in this embodiment in the circuit board, the so

is dimensioned that the pipe is approximately flush in the hole can be arranged. In this embodiment of the measuring probe is further suggested that the electrodes are arranged in the layer structure of the printed circuit board and relative to the bore in the circuit board, that the guided in the first electrode measuring signals interact with the medium flowing in the pipe medium.

Furthermore, it is provided that the pipeline is a flexible or rigid hose or a measuring capillary which, at least in the region of

Passage through the hole consists of a non-conductive material.

The solution according to the invention in the different embodiments is characterized by the following advantages:

The measuring probes according to the invention can be equipped with suitable

Miniaturize manufacturing process. As a result, the probes or sensors for integration into other components, in e.g. Plugs / couplings or housing, ideally suited. The probes according to the invention can also be integrated into a printed circuit board.

The measuring probe according to the invention operates without contact - in this case the electrodes therefore have no direct contact with the medium. Thus, the

Electrodes protected against environmental influences and against the medium. Abrasion does not occur. Both in the non-contact and in the non-invasive embodiment of the solution according to the invention, the electrodes can be in the wall of the probe - or in an alternative embodiment - in the Integrate board yourself. For example, the IMKS process (integrated metal / plastic injection molding) is used here.

The measuring probe can surround the pipeline in which the medium flows.

Non-contact or non-invasive probes also have the advantage that they do not affect the flow path of the medium. Pressure losses in the pipeline or turbulence of the medium thus do not occur. Also, the particular installation position in the pipeline does not have to be special

Pay attention. Distance requirements with regard to inlet or outlet sections are eliminated. Likewise, the measuring probes according to the invention can be installed in pipe bends. In addition, the probe can

have different geometries or cross sections. For example, the cross section may be round, angular or oval.

The invention will be explained in more detail with reference to the following figures. It shows:

1 shows a schematic representation of a first embodiment of the TDR measuring device according to the invention,

2 shows a first embodiment of the TDR measuring probe,

3 shows a second embodiment of the TDR measuring probe,

4 shows a third embodiment of the TDR measuring probe and

5 shows a schematic representation of a second embodiment of the

TDR measuring device according to the invention,

Fig. 1 shows a schematic representation of a first embodiment of

TDR measuring device according to the invention for non-contact or non-invasive determination of at least the dielectric constant and possibly derived therefrom properties of the medium flowing through a pipe 1 medium 2 and / or to detect a change in state of the pipe 1, which is traversed by the medium 2. The TDR measuring device consists of a sensor or a measuring probe 6 and a measuring electronics 16. In the case shown, the two

Components 6, 16 spaced apart and interconnected by the measuring line 14. The measuring line 14 is preferably a coaxial cable.

On the printed circuit board 12, the electronic components of the measuring electronics 16 are arranged: the signal generating electronics 3, the transmitting and / or receiving electronics 4, the input / Decoupling device 5 and the control / evaluation 7. The

Signal generating electronics 3 generates the TDR measurement signals, the transmitting and / or receiving electronics 4 transmits the TDR measurement signals and / or receives the reflected on the probe TDR measurement signals. The coupling and decoupling of the TDR measurement signals on the measuring line 14 and the measuring probe 6 via the input / output device 5. From here, the measurement signals via a high-frequency connector 18 to which a high-frequency cable 14 is connected to the

Probe 6 headed. Based on the duration of the TDR measurement signals on the measuring probe 6, the control / evaluation electronics determines at least the dielectric constant and / or the permittivity and, if appropriate, derived properties or parameters of the medium. These medium properties are, in particular, the moisture and / or the conductivity. Furthermore, the TDR measuring device according to the invention is suitable for alternatively or additionally detecting a change in state of the pipeline 1. The state change is caused, for example, by deposits on the inner wall of the pipeline 1. The measurement data or the data on a change in state of the pipeline 1 via the interface 15 to a

Parent control / display device forwarded. The forwarding can be wired or wireless.

Preferred embodiments of the sensor or of the measuring probe 6 are described in greater detail in FIGS. 2 to 5.

The sensors or measuring probes 6 according to the invention differ from the previously known sensors in that they are connected to the pipeline 1, in which the

examining medium, are connected in such a way that they are isolated from the medium. The measuring probes 6 can be mounted on the outer wall of the pipeline 6, but can also be integrated into the wall of the pipeline 1. Furthermore, the measuring probes 6 can be placed so that the surface of the electrodes 9, 10, 11 which faces into the interior of the pipeline 6 terminates flush with the inner surface of the pipeline 6. Advantageously, a pipeline section and the electrodes 9, 10,

1 1 preferably in one process step with the IMKS method (Integrated

Metal / plastic injection molding). The corresponding component can then be subsequently introduced via a suitable attachment in the pipeline. Alternatively, the electrodes 9, 10, 1 1 can also be applied to the outer surface of an existing pipeline 1.

Fig. 2 shows a first embodiment of the TDR measuring probe 6. In the shown

Embodiment, the sensor has two electrodes 9, 10, which are arranged in the direction of the longitudinal axis 19 of the pipe 1 on or in the pipeline 1. The pipe 1 - in the context of the invention also commonly referred to as a measuring body - has a be electrical insulator (eg plastic / ceramic ...), otherwise the measuring field can not propagate in the pipe 1 and therefore can not be influenced by the medium 2. The electrodes 9, 10 advantageously have the same length L, but different widths B. By varying the width B and / or the length L of the electrodes 9, 10, the measuring field can be optimally adapted to the respective measuring task.

Fig. 3 shows a second embodiment of the TDR measuring probe 6, which is referred to as a spiral sensor or axial spiral. In the embodiment shown, three electrodes 9, 10,

1 1 along the longitudinal axis 19 of the pipe 1 and the measuring body attached. The measuring body 1 must again be made of an electrically insulating material (eg plastic / ceramic ...), at least in the area of the measuring probe, since otherwise the measuring field does not propagate in the inner space 8 of the pipeline 1 or of the measuring body and interacts with the latter can occur to be measured medium 2. The length L of the electrodes 9, 10, 1 1 is determined significantly the sensitivity of the sensor 6, since the duration of the measuring signals at longer electrodes 9, 10, 1 1 extended to the end of the electrode and back. In the spiral sensor shown, there are many options with regard to the length L but also the width B.

In the spiral sensor, the electrodes 9, 10, 1 1 are parallel in spiral form around the

Spiral pipe 1 or the measuring body wound. The electrodes 9, 10, 1 1 are advantageously the same length, but can also be of different width in this design. With the width and length of the electrodes 10, 1 1, 12 and with the slope of the spiral, the measuring field can be advantageously adapted to the respective measurement task.

A third embodiment of the TDR measuring probe 6 can be seen in FIG. 4. In this sensor 6, which is referred to as a concentric sensor 6 or a partial circuit conductor, three electrodes 9, 10, 11 are arranged concentrically to the longitudinal axis 19 on or in the pipeline 1, but the circles are not closed. Again, the pipe needs

I or the pipe section with the measuring probe 6 again be an electrical insulator (for example plastic / ceramic ...), since otherwise the measuring field can not propagate into the interior 8 of the measuring body 1 and can interact with the medium to be measured. The electrodes 9, 10, 1 1 are advantageously the same length, the width may be the same or different. About the variation of the width and / or length of the electrodes 9, 10,

I I can advantageously dimension the measuring field for the respective measuring task.

Fig. 5 shows a schematic representation of a second embodiment of

TDR measuring device 17 according to the invention, which can be referred to as PCB on-board solution. On a description of the individual electronic components 3, 4, 5, 7 of Measuring electronics 16 are dispensed with because they are identical to the components shown in FIG. 1, with one exception.

The measuring probe 6 or the sensor preferably corresponds to that shown in FIG. 4

Pitch ladder. However, in this embodiment, the measuring circuit 6 consisting of partial circuits is not arranged concentrically on or in the pipeline 1, in which the medium 2 to be measured is guided, but concentrically in a bore 13, which is provided in the printed circuit board 12. Through this hole 13, the pipe 1 is guided. Preferably, the bore 13 is located in the vicinity of the high-frequency connection or the input / output electronics. The preferably three concentric around the bore 13 arranged part-circular electrodes 9, 10, 1 1 are arranged in three layers of the printed circuit board 12. The high-frequency connector 18 and the coaxial cable 14 shown in FIG. 1 are dispensed with in the embodiment of the TDR measuring device 17 according to the invention shown in FIG. 5. In the middle region of the part-circular track sensors 9, 10,

1 1 there is the bore 13 through which, for example, a measuring capillary 1 or a hose is guided, in which / flows the liquid medium to be measured 2. The measuring body 1 is made at least in the region of the passage through the bore 13 of the printed circuit board 12 made of an electrically non-conductive material.

LIST OF REFERENCE NUMBERS

1 pipeline

2 medium

3 signal generation electronics

4 transmitting / receiving electronics

5 input / output device

6 probe or sensor

7 control / evaluation electronics

8 Interior of the pipeline

9 electrode or thermistor

10 ground or shield electrode

1 1 ground or shield electrode

12 circuit board

13 hole

14 test lead / coax cable

15 interface

16 measuring electronics

17 TDR measuring device

18 high frequency connector

19 longitudinal axis

Claims

claims

1.TDR measuring device for determining at least the dielectric constant and optionally derived therefrom material properties, in particular the humidity and / or conductivity of a flowing through a pipe (1) medium (2) with a

Signal generation electronics (3) which generates TDR measurement signals, a transmitting and / or receiving electronics (4), which emits and / or receives the TDR measurement signals, a coupling / decoupling device (5), the TDR measurement signals to an electrical conductive measuring probe (6) of a predetermined length (L) coupled in or coupled out by the measuring probe (6), and control / evaluation electronics (7) based on the transit time and / or the attenuation of the TDR measuring signals on the measuring probe ( 6) at least the

Dielectric constant and possibly derived therefrom material properties, in particular the humidity and / or conductivity, determined wherein the measuring probe (6) outside of the medium (2) through which the interior space (8) of the pipe (1) is arranged or wherein the measuring probe (6 ) is placed in the pipe (1), that the medium (2) facing outer surface of the measuring probe (6) flush with the medium (2) facing the inner surface of the pipe (1) and is designed such that the duration of the Measuring signals on the probe (6) depends on the

Dielectric constant of the flowing through the pipe (1) medium (2.

2. TDR measuring device according to claim 1,

wherein the measuring probe (6) consists of at least two electrodes (9, 10, 11) preferably designed as conductor tracks, a first electrode (9) carrying the TDR measuring signals and wherein the at least one further electrode (10; Shield or ground electrode is configured.

3. TDR measuring device according to claim 2,

wherein the first electrode (9) and the shield or ground electrode (10, 1 1) in

Are essentially arranged on or in opposite surface areas of the pipe (1).

4. TDR measuring device according to claim 1 or 2,

wherein the measuring probe (6) consists of three electrodes (9, 10, 11) preferably designed as conductor tracks, one of the electrodes (9) carrying the TDR measuring signals and being substantially centered with respect to the two as shielding or grounding electrodes

configured electrodes (10, 1 1) is arranged.

5. TDR measuring device according to one or more of claims 1-4,

wherein the electrodes on the outer wall of the pipeline (1) or in the

Pipe wall of the pipe (1) are arranged.

6. TDR measuring device according to claim 1, 4 or 5,

wherein the electrodes (9, 10, 11) are arranged substantially parallel to one another and spirally with respect to the pipeline (1).

7. TDR measuring device according to claim 1, 4 or 5,

wherein the electrodes (9, 10, 1 1) parallel to each other in the form of pitch circles in

Are arranged substantially perpendicular to the flow direction of the flowing medium (2) through the pipe (1).

8. TDR measuring device according to at least one or the preceding claims, wherein the electrodes (9, 10, 1 1) preferably have the same length (L), but differ in width (B).

9. TDR measuring device according to at least one or the preceding claims, wherein at least two measuring probes are arranged offset in the direction of flow of the medium to each other, wherein a measuring probe is designed so that they

Dielectric constant of the medium determines and wherein the second measuring probe is designed so that it detects a change in state of the wall of the pipe, which is caused by abrasion of the wall of the pipe or deposits on the medium facing the inside of the wall of the pipe

10. TDR measuring device according to at least one or the preceding claims, wherein the signal generating electronics (3), the transmitting and / or receiving electronics (4), the input / output device (5) and the measuring probe (6) on a multilayer, preferably one three-layer printed circuit board (12) are arranged.

1 1. TDR measuring device according to one or more of the preceding claims, wherein in the circuit board (12) has a bore (13) is provided, which is dimensioned so that the pipe (1) is approximately flush in the bore (13) can be arranged ,

12. TDR measuring device according to claim 1 1,

wherein the electrodes (9, 10, 11) are arranged in the layer structure of the printed circuit board (12) and relative to the bore (13) in the printed circuit board (12) such that the measuring signals carried in the first electrode (9) interact with the medium (2) flowing in the pipeline (1) and / or being influenced by a state change occurring on the pipeline (1).

13. TDR measuring device according to claim 9 or 10, wherein the pipeline (1) is a hose or a measuring capillary, which consists at least in the region of the passage through the bore (13) made of a non-conductive material.