TDR MEASURING APPARATUS FOR DETERMINING THE DIELECTRIC CONSTANT

Abstract

Disclosed is a TDR measuring apparatus for determining the dielectric constant and material properties derived therefrom of a medium flowing through a pipeline. The apparatus includes signal generation electronics which generate TDR measurement signals, transmitting and receiving electronics, a coupling-in/coupling-out apparatus which couples the TDR measurement signals into and out of an electrically conductive measuring probe of a predefined length, and control/evaluation electronics which use the propagation time of the TDR measurement signals to determine the dielectric constant. The measuring probe is arranged in an electrically insulated manner outside of the pipeline. Alternately, the measuring probe is placed in the pipeline such that the outer surface of the measuring probe facing the medium terminates flush with the inner surface of the pipeline and is configured such that the propagation time and the amplitude of the measurement signals on the measuring probe are dependent on the dielectric constant of the medium.

Claims

1-13. (canceled)

14. A Time Domain Reflectometry (TDR) measuring device for the determination of at least the dielectric constant of a medium flowing through a pipeline, comprising: signal generation electronics configured to generate TDR measurement signals; transmission and reception electronics configured to transmit and to receive the TDR measurement signals; a coupling/decoupling device embodied to couple the TDR measurement signals to an electrically conductive measurement probe having a predetermined length and to decouple the TDR measurement signals from the measuring probe; and a control/evaluation electronics configured to determine the dielectric constant and material properties derived therefrom, including a moisture content and a conductivity of the medium, on the basis of a propagation time and a damping of the TDR measuring signals on the measuring probe, wherein the measuring probe is arranged outside the interior of the pipeline, through which the medium flows the measuring probe is placed in the pipeline such that an outer surface of the measuring probe facing the medium is flush with an inner surface of the pipeline facing the medium, and wherein the measuring probe is configured such that the propagation time of the measuring signals on the measuring probe is dependent on the dielectric constant of the medium flowing through the pipeline.

15. The TDR measuring device according to claim 14, wherein the measuring probe includes two electrodes, wherein a first electrode of the two electrodes carries the TDR measuring signals, and wherein a second electrode of the two electrodes is configured as a guard or ground electrode.

16. The TDR measuring device according to claim 15, wherein the first electrode and the guard or ground electrode are arranged on or in mutually opposite surface regions of the pipeline.

17. The TDR measuring device according to claim 15, wherein the measuring probe includes a third electrodes, wherein the first electrode carries the TDR measuring signals and is arranged centrally with respect to the second and third electrodes designed as guard electrodes or ground electrodes.

18. The TDR measuring device according to claim 15, wherein the electrodes are arranged on the wall of the pipeline or in the pipe wall of the pipeline.

19. The TDR measuring device according to claim 17, wherein the electrodes are arranged parallel to one another and spirally with respect to the pipeline.

20. The TDR measuring device according to claim 17, wherein the electrodes are arranged parallel to one another in the form of partial circles perpendicular to the direction of flow of the flowing medium through the pipeline.

21. The TDR measuring device according to claim 17, wherein the electrodes have a same length, but differ in width.

22. The TDR measuring device according to claim 15, wherein at least two measuring probes are arranged offset to each other in the flow direction of the medium, wherein one measuring probe is designed such that it determines the dielectric constant of the medium and wherein the second measuring probe is designed such that it detects a change of state of the wall of the pipeline, which is caused by abrasion of the wall of the pipeline or deposits on the inside of the wall of the pipeline facing the medium.

23. The TDR measuring device according to claim 15, wherein the signal generation electronics, the transmitting and/or receiving electronics, the coupling/decoupling device, and the measuring probe are arranged on a multilayer circuit board.

24. The TDR measuring device according to claim 23, wherein a bore is provided in the circuit board, which is dimensioned such that the pipeline can be arranged approximately flush in the bore.

25. The TDR measuring device according to claim 24, wherein the electrodes are arranged in the layer structure of the circuit board and relative to the bore in the circuit board such that the measurement signals guided in the first electrode interact with the medium flowing in the pipeline and/or are influenced by a change of state occurring in the pipeline.

26. The TDR measuring device according to claim 24, wherein the pipeline is a hose or a measuring capillary which, at least in the region of the passage through the bore, is embodied of a non-conductive material.

Description

[0034] The invention is explained in more detail with reference to the following figures. These show:

[0035] FIG. 1: a schematic illustration of a first embodiment of the TDR measuring device according to the invention,

[0036] FIG. 2: a first embodiment of the TDR measuring probe,

[0037] FIG. 3: a second embodiment of the TDR measuring probe,

[0038] FIG. 4: a third embodiment of the TDR measuring probe and

[0039] FIG. 5: a schematic representation of a second embodiment of the TDR measuring device according to the invention,

[0040] FIG. 1 shows a schematic representation of a first embodiment of the TDR measuring device according to the invention for the contactless or non-invasive determination of at least the dielectric constants and optionally derived properties of the medium of a medium 2 passing through a pipeline 1 and/or for detecting a change in state of the pipeline 1 through which the medium 2 flows. 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 are spaced apart from one another and connected to one another by the measuring line 14. The measuring line 14 is preferably a coaxial cable.

[0041] The electronic components of the measuring electronics 16 are arranged on the circuit board 12: the signal generation electronics 3, the transmitting and/or receiving electronics 4, the coupling/decoupling device 5, and the control/evaluation electronics 7. The signal generation electronics 3 generate the TDR measuring signals, the transmitting and/or receiving electronics 4 emit the TDR measuring signals and/or receive the TDR measuring signals reflected on the measuring probe. The coupling and decoupling of the TDR measurement signals to the measuring line 14 and the measuring probe 6 takes place via the coupling/decoupling device 5. From here, the measurement signals are transmitted to the measuring probe 6 via a radio frequency plug connector 18, to which a radio frequency cable 14 is connected. Based on the propagation time of the TDR measurement signals on the measuring probe 6, the control/evaluation electronics determine at least the dielectric constant and/or the permittivity and possibly characteristics or parameters of the medium derived therefrom. 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 additively detecting a change in state of the pipeline 1. The change in state is caused, for example, by deposits on the inner wall of the pipeline 1. The measurement data or the data about a change in state of the pipeline 1 are forwarded via the interface 15 to a superordinate control/display device. Forwarding can be wired or wireless.

[0042] Preferred embodiments of the sensor or of the measuring probe 6 are described in more detail in FIGS. 2-5.

[0043] 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 medium to be examined is guided, specifically 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 in such a way that the surface of the electrodes 9, 10, 11 pointing into the interior of the pipeline 6 is flush with the inner surface of the pipeline 6. Advantageously, a pipeline section and the electrodes 9, 10, 11 can preferably be produced in one method step using the IMKS method (integrated metal/plastic injection molding). The corresponding component can then subsequently be introduced into the pipeline via a suitable attachment. Alternatively, the electrodes 9, 10, 11 can also be applied to the outer surface of an existing pipeline 1.

[0044] FIG. 2 shows a first embodiment of the TDR measuring probe 6. In the embodiment shown, the sensor has two electrodes 9, 10, which are arranged on or in the pipeline 1 in the direction of the longitudinal axis 19 of the pipeline 1. The pipeline 1—generally also referred to as a measuring body in connection with the invention—must be an electrical insulator (e.g. plastic/ceramic) since otherwise the measuring field cannot propagate in the pipeline 1 and consequently cannot 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.

[0045] 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, 11 are mounted along the longitudinal axis 19 of the pipeline 1 or of the measuring body. In turn, the measuring body 1 must be made of an electrically insulating material (e.g. plastic/ceramic) at least in the region of the measuring probe, since otherwise the measuring field cannot propagate in the interior 8 of the pipeline 1 or of the measuring body and cannot interact with the medium 2 to be measured. The length L of the electrodes 9, 10, 11 substantially determines the sensitivity of the sensor 6, since the propagation time of the measurement signals to the electrode end and back extends with longer electrodes 9, 10, 11. In the spiral sensor shown, there are many options with regard to the length L, but also the width B.

[0046] In the case of the spiral sensor, the electrodes 9, 10, 11 are wound in parallel in spiral form around the pipeline 1 or the measuring body. The electrodes 9, 10, 11 are advantageously of the same length, but can also be of different widths in this design. With the width and length of the electrodes 10, 11, 12 and with the pitch of the spiral, the measuring field can advantageously be tuned to the respective measuring task.

[0047] A third embodiment of the TDR measuring probe 6 can be seen in FIG. 4. In this sensor 6, referred to as a concentric sensor 6 or as a partial circular 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. Here, too, the pipeline 1 or the pipeline section with the measuring probe 6 must again be an electrical insulator (e.g. plastic/ceramic), since otherwise the measuring field cannot propagate into the interior 8 of the measuring body 1 and cannot interact with the medium to be measured. The electrodes 9, 10, 11 are advantageously of the same length, the width may be the same or different. By varying the width and/or length of the electrodes 9, 10, 11, the measuring field can be advantageously dimensioned for the respective measuring task.

[0048] FIG. 5 shows a schematic representation of a second embodiment of the TDR measuring device 17 according to the invention, which can be referred to as a PCB onboard solution. A description of the individual electronic components 3, 4, 5, 7 of the measuring electronics 16 is dispensed with since, except for one exception, they are identical to the components shown in FIG. 1.

[0049] The measuring probe 6 or the sensor preferably corresponds to the partial circular conductor shown in FIG. 4. In this embodiment, however, the measuring probe 6 consisting of partial circles 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 provided in the circuit board 12. The pipeline 1 is guided through this bore 13.

[0050] The bore 13 is preferably located in the vicinity of the radio frequency connection or the coupling/decoupling electronics. The preferably three partially circular electrodes 9, 10, 11 arranged concentrically around the bore 13 are arranged in three layers of the circuit board 12. The radio frequency plug connector 18 and the coaxial cable 14 shown in FIG. 1 are omitted in the embodiment of the TDR measuring device 17 according to the invention shown in FIG. 5. Located in the central region of the semicircular conductor path sensors 9, 10, 11 is the bore 13, through which, for example, a measuring capillary 1 or a tube is guided, in which the liquid medium 2 to be measured flows. The measuring body 1 is made of an electrically non-conductive material at least in the region of the passage through the bore 13 of the circuit board 12.

LIST OF REFERENCE SIGNS

[0051] 1 Pipeline [0052] 2 Medium [0053] 3 Signal generation electronics [0054] 4 Transmitting/receiving electronics [0055] 5 Coupling/decoupling device [0056] 6 Measuring probe or sensor [0057] 7 Control/evaluation electronics [0058] 8 Interior of the pipeline [0059] 9 Electrode or thermistor [0060] 10 Ground or guard electrode [0061] 11 Ground or guard electrode [0062] 12 Circuit board [0063] 13 Bore [0064] 14 Measuring line/coaxial cable [0065] 15 Interface [0066] 16 Measuring electronics [0067] 17 TDR measuring device [0068] 18 Radio frequency plug connector [0069] 19 Longitudinal axis