Devices for capacitive measurement of the filling level of powders and rotary presses

Abstract

The invention relates to a device for capacitively measuring the powder filling level in a filling device for filling a die cavity of a die plate of a rotary press with powder material to be compressed in the rotary press, the device comprising a filling tube of the filling device, characterised in that a first measuring electrode is arranged on the filling tube, the first measuring electrode forming a first capacitor with a reference electrode so that an electric field can be formed between the first measuring electrode and the reference electrode, and the first measuring electrode is covered on its side facing away from the filling tube by an electrically conductive protective shield, wherein the protective shield is at ground potential. The invention further relates to a rotary press.

Description

Technical Field

[0001] The invention relates to a device for capacitively measuring the powder filling level in a filling device for filling a die cavity of a die plate of a rotary press with powder material to be compacted in the rotary press, comprising a filling tube of the filling device.

[0002] In addition, the present invention relates to a rotary press, comprising a rotor that can be rotated by means of a rotary drive, wherein the rotor has an upper punch guide for an upper punch of the rotary press and a lower punch guide for a lower punch of the rotary press, and a die plate arranged between the punch guides, wherein the punch cooperates with the die cavity of the die plate, and the rotary press comprises a filling device, through which the powder material to be compacted is filled into the die cavity of the die plate, the filling device comprises a filling tube, the rotary press further comprises at least one upper pressing device and at least one lower pressing device, the at least one upper pressing device and at least one lower pressing device cooperate with the upper punch and the lower punch during operation to compact the powder material in the die cavity of the die plate, and the rotary press further comprises a discharge device, in which the pressed product produced in the die cavity is discharged. Background Art

[0003] In a rotary press, the powder material filled in the die cavity is squeezed into a pressed product, especially a tablet, by means of an upper punch and a lower punch. The powder material is filled into the die cavity by means of a filling device of the rotary press. Such a filling device usually comprises a filling tube, through which the powder material usually falls into the filling cavity due to gravity, and the filling material usually reaches the die cavity from the filling cavity by means of gravity. It is desirable to monitor the filling level in the filling device, especially in the filling tube, so as to ensure sufficient powder availability at any time. It has been proposed that a sensor is arranged inside the filling tube for this purpose. However, arranging a sensor in the powder material flow may lead to an obstruction to the powder material flow, for example, the formation of a bridge. This may damage the powder availability in an undesirable manner.

[0004] In a rotary press, the powder material filled in the die cavity is squeezed into a pressed product, especially a tablet, by means of an upper punch and a lower punch. The powder material is filled into the die cavity by means of a filling device of the rotary press. Such a filling device usually comprises a filling tube, through which the powder material usually falls into the filling cavity due to gravity, and the filling material usually reaches the die cavity from the filling cavity by means of gravity. It is desirable to monitor the filling level in the filling device, especially in the filling tube, so as to ensure sufficient powder availability at any time. It has been proposed that a sensor is arranged inside the filling tube for this purpose. However, arranging a sensor in the powder material flow may lead to an obstruction to the powder material flow, for example, the formation of a bridge. This may damage the powder availability in an undesirable manner.

[0005] EP2400275A1 describes a device for non-invasive, non-contact capacitive measurement of the filling level of bulk material in a container, for example. The filling level sensor is not in contact with the filling medium, the filling height of which is to be determined. Instead, electrodes are provided, which are arranged like an open plate capacitor and between which a high-frequency alternating electric field is generated, which passes through the material to be measured without loss. The capacitance of the capacitor formed depends on the dielectric constant of the filling material. In this case, the filling material to be measured has a different dielectric constant than air. In this way, covering the sensor surface with the material to be measured at different heights results in different capacitances of the capacitor. From this, the filling height of the material in the container can be inferred.

[0006] External influences, such as external electromagnetic fields or external objects, such as the operator's hand near the measuring electrode, can pose a problem. In order to reduce the possibility of being susceptible to external influences, it is proposed in EP2400275A1 that multiple measuring electrodes are arranged on different horizontal planes, which define a measuring surface with a vertical extension dimension, and at least one reference electrode is arranged, which defines a reference surface with a vertical extension dimension. Each of these multiple measuring electrodes, together with the reference electrode, constitutes a capacitor. At least two capacitors are measured and the measured values ​​are related to each other. External influences as interference sources should be calculated and eliminated by credibility checks. However, known devices require very large structural and evaluation technology costs. And credibility analysis does not always provide reliable results.

[0007] In order to protect against external interference sources during capacitive fill level measurement, so-called active shielding is also known in practice, in which an electrode used as a shield is controlled to the same potential as the measuring electrode during the measurement. Although the influence of external interference sources can be reduced by active shielding, there is still a demand for further improved protection against external interference during capacitive fill level measurement. Summary of the invention

[0008] Starting from this prior art, the object of the present invention is to provide a device and a rotary press of the type mentioned at the outset, with which the filling level in a filling device of a rotary press can be measured without obstructing the powder flow and with minimal external interference influences.

[0009] The present invention achieves the above object by means of an improved subject matter. Advantageous designs are described in the description and the drawings.

[0010] The invention achieves the object in a device of the type mentioned at the outset by providing a first measuring electrode on the filling tube, which forms a first capacitor with a reference electrode so that an electric field can be formed between the first measuring electrode and the reference electrode, and by covering the first measuring electrode on its side facing away from the filling tube by a conductive protective shield, wherein the protective shield is at ground potential.

[0011] The invention achieves this object in a rotary press of the type mentioned at the outset in that the rotary press comprises a device according to the invention for capacitively measuring the filling level of a powder in a filling device.

[0012] The rotary press can be a rotary tablet press in particular. In the rotary press, the powder material to be processed is conveyed to the die plate via a filling tube. The powder material can be conveyed by gravity through the filling device and the filling tube. The filling tube can therefore constitute a drop tube. The filling tube can be arranged to be suitable for this. For example, the longitudinal axis of the filling tube can be fully inclined relative to the horizontal, in particular, it can extend vertically, for example. The filling device can also have at least one filling cavity, from which the powder material reaches the filling tube. The powder material is conveyed from the filling cavity to the die cavity of the die plate, in particular again by gravity, where the powder material is pressed into a pressed product, in particular a tablet, by an upper punch and a lower punch in a known manner. The die cavity can be formed directly by a hole in the die plate. However, a releasably fixed die sleeve can also be arranged in the die plate, and the die cavity is formed in the die sleeve.

[0013] In order to capacitively measure the powder filling level in the filling tube, a first measuring electrode is provided in the filling tube. The first measuring electrode cooperates with the reference electrode of the device. The electrodes together form a capacitor, similar to a plate capacitor. The first measuring electrode extends along the axial direction of the filling tube over a certain measuring area. The reference electrode can also extend over this area. An electric field is formed between the first measuring electrode and the reference electrode during operation, so that the interior of the filling tube and the powder material to be measured are passed through without loss. The capacitance of the capacitor depends on the dielectric constant of the medium passed by the electric field, as explained. Therefore, air has a dielectric constant different from the powder material to be processed in the rotary press. From this, the degree to which the electrode is covered by the powder material can be derived from the capacitance of the measuring capacitor. From this, the filling level of the powder material in the filling tube can be derived. Of course, multiple first measuring electrodes can also be provided. The reference electrode can also include multiple (sub) reference electrodes or be formed by multiple (sub) reference electrodes.

[0014] According to the invention, the first measuring electrode is covered, in particular completely covered, by a conductive and grounded protective shield on its side facing away from the filling tube. The filling tube can be made of metal, such as high-quality steel, for example. The protective shield can also be made of metal, such as aluminum or high-quality steel. According to the invention, it is recognized that the active shielding proposed in the prior art for measuring the filling level of powder material in the filling device of the rotary press is not sufficient to achieve reliable measurement results in the application according to the invention despite the presence of possible external interference sources. In the prior art, active shielding is provided for closed tanks and for measuring liquids. However, the inventors of the present invention have recognized that it is precisely the conveying of powder material through the filling device, in particular the filling tube, that causes other problems compared to measuring the filling level of liquid in a closed tank. That is, according to the inventors' recognition, the conveying of powder material through the filling device leads to static electricity of the powder material on the one hand, which may affect the measurement result. In addition, the powder material to be processed in the rotary press has a smaller dielectric constant than the liquid to be measured in the tank in the prior art. Such a difference in use requires higher measurement accuracy in the application according to the invention. This in turn has the consequence that external influences, for example those caused by external electromagnetic fields or persons in the vicinity of the measuring device, must be excluded even more reliably.

[0015] This is achieved by a protective shield according to the invention which is electrically conductive and at ground potential. The protective shield reliably shields the first measuring electrode from external electromagnetic interference sources. Therefore, according to the invention, the filling level of the powder material to be processed in the filling tube can be reliably determined in a rotary press. At the same time, a costly arrangement with multiple measuring electrodes and a complex and unreliable credibility analysis is avoided. The internal geometry of the filling tube remains unobstructed and the powder flow is not disturbed or influenced by the measuring sensor. External interferences, such as electrical equipment in the rotary press or external interferences caused by the operator's touch, are not calculated and eliminated from the measurement result as in the prior art, but are effectively suppressed from the beginning.

[0016] According to a practical design, the first measuring electrode is arranged in a non-conductive holding section, which is arranged on the filling tube. In this way, a further improved shielding is achieved. For example, a non-conductive plastic such as polyoxymethylene (POM) can be used. The holding section can be covered as a whole to the outside by the protective shield according to the invention. A housing recess for the first measuring electrode and, if necessary, further measuring electrodes can be provided in the holding section.

[0017] According to another embodiment, the holding section can be arranged in a recess of the filling tube. The filling tube then has a cutout in which the holding section is arranged together with the first measuring electrode. In this way, particularly good measurement accessibility for the powder material in the filling tube and thus particularly precise measurements can be achieved without the risk of obstructing the powder flow.

[0018] According to another design, the conductive filling tube section of the filling device upstream and / or downstream of the filling tube provided with the first measuring electrode is also at ground potential. As explained, the inventor recognizes that during the transportation by the filling device, especially the filling tube, static electricity of the powder material can be generated. According to the inventor's understanding, this is caused by the friction between the powder material and the filling device, especially the components of the guiding powder material of the filling tube. By grounding the conductive filling tube section upstream of the filling tube provided with the first measuring electrode, the static electricity is eliminated before the capacitive measurement filling level, so that the static electricity will not affect the subsequent measurement. After measuring the filling level, during the further transportation of the powder material, the undesirable static electricity of the powder material can occur again. This may adversely affect the processing result in the rotary press. In order to prevent this, the grounding of the conductive filling tube section downstream of the filling tube provided with the first measuring electrode can also be meaningful. This filling tube section can also be made of metal, such as high-quality steel, for example.

[0019] The reference electrode and / or the filling tube provided with the first measuring electrode can also be at ground potential. In this way, in addition to particularly reliable measurement and additional electromagnetic shielding, static electricity of the powder material in the filling tube provided with the first measuring electrode can also be prevented or eliminated.

[0020] According to another design, the reference electrode can also be arranged on the filling tube provided with the first measuring electrode. The reference electrode can also be covered, in particular completely covered, by a conductive protective shield on its side facing away from the filling tube. The reference electrode can also be arranged on a non-conductive holding section.

[0021] According to another embodiment, the reference electrode can be formed by a filling tube provided with a first measuring electrode. In this way, the first measuring electrode directly forms a capacitor with the filling tube as a reference electrode. Thus, compared to the arrangement of the reference electrode on the filling tube, a larger reference electrode is used as the basis for the capacitance measurement. This allows particularly precise and reliable capacitance measurements, in particular when the filling tube and, if applicable, the protective shield are also at ground potential.

[0022] According to another embodiment, it can be provided that a second measuring electrode is also provided on the filling tube, wherein the second measuring electrode and the reference electrode form a second capacitor, so that an electric field can be formed between the second measuring electrode and the reference electrode, and wherein the measuring area of ​​the second measuring electrode is selected so that the measuring area is completely covered by the powder material in the filling tube at any time during the operation of the rotary press. The extension of the second measuring electrode in the longitudinal direction of the filling tube and therefore the measuring area of ​​the second measuring electrode are smaller than the extension of the first measuring electrode in the longitudinal direction of the filling tube and therefore its measuring area. For example, the extension of the second measuring electrode can be no more than 15%, preferably no more than 10% of the extension of the first measuring electrode. The second measuring electrode can be in particular parallel to the first measuring electrode and be substantially flush with its lower end or extend beyond the lower end of the first measuring electrode. By providing such a second measuring electrode that is completely covered by the powder material in the filling tube during the operation of the rotary press, it is possible to measure the filling level even in the case of different powder materials or when the composition of the powder material changes. Therefore, when the second measuring electrode is completely covered by the powder material, it can be assumed that the electric field formed between the second measuring electrode and the reference electrode is completely formed inside the powder material. If the extension of the second measuring electrode in the axial direction of the filling tube is known, the filling level of the powder material can be derived computationally from the capacitance measured for the first measuring electrode, even in the case of different powder materials and without complicated additional calibration measures. This makes it possible to achieve a measurement that is independent of the powder material or possible changes in the composition of the powder material. It has been shown that the accuracy of the measurement can be further improved in this way.

[0023] According to another embodiment, it can be provided that a third measuring electrode is also arranged on the filling tube, wherein the third measuring electrode and the reference electrode form a third capacitor, so that an electric field can be formed between the third measuring electrode and the reference electrode, and wherein the measuring area of ​​the third measuring electrode is selected so that the measuring area is always above the filling level of the powder material in the filling tube during the operation of the rotary press. The extension of the third measuring electrode in the longitudinal direction of the filling tube and therefore its measuring area is here again smaller than the extension of the first measuring electrode in the longitudinal direction of the filling tube and therefore its measuring area. For example, the extension of the third measuring electrode can again be no more than 15%, preferably no more than 10%, of the extension of the first measuring electrode. The third measuring electrode can in particular be parallel to the first measuring electrode and be substantially flush with its upper end or extend beyond the upper end of the first measuring electrode. With such a third measuring electrode, which is not covered, or even partially covered, by the powder material conveyed by the filling tube during the operation of the rotary press, it is possible to carry out a measurement taking into account possible properties of the filling device, in particular the filling tube, when the extension of the third measuring electrode in the axial direction of the filling tube is known. In particular, changes in the measuring environment which occur during operation can be detected without influencing the powder material and can be taken into account in the fill level measurement by means of the first measuring electrode.

[0024] As already explained, the reference electrode can include a plurality of (sub-)reference electrodes. However, the reference electrode can also include only one reference electrode. Some or all of the measuring electrodes can form a capacitor with the reference electrode in the described manner. In particular, when the reference electrode includes a plurality of (sub-)reference electrodes, some or all of the measuring electrodes can also form capacitors with different (sub-)reference electrodes in the described manner.

[0025] According to another embodiment, the second and / or third measuring electrode can also be covered, in particular completely covered, by the conductive protective shield on its side facing away from the filling tube. In addition, the second and / or third measuring electrode can also be arranged in the non-conductive holding section. As already explained, a further improvement of the measuring results can be achieved in this way.

[0026] According to another embodiment, the protective shield can form an active protective shield, which is controlled to the same potential as the first measuring electrode and / or the second measuring electrode and / or the third measuring electrode when measuring the fill level. Thus, so-called active shielding can be achieved in order to further improve the shielding against external interference sources and thus further improve the measurement result.

[0027] According to another embodiment, a control and evaluation device can be provided, which controls the measuring electrode and the reference electrode during operation of the rotary press and determines the filling level of the powder material in the filling tube based on the measurement data of the measuring electrode and the reference electrode. The control and evaluation device can be part of the control and evaluation device of the rotary press or be designed separately therefrom.

[0028] According to another design, the measuring and / or reference electrodes can be arranged on a substantially inflexible PCB circuit board. Conventional PCB circuit boards thus have a thickness of generally greater than 1 mm. This results in additional insulation, through which external interference influences can be further minimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Next, an embodiment of the present invention will be explained in detail according to the accompanying drawings. The figure schematically shows:

[0030] Figure 1 The rotary press according to the invention is shown in the illustration with the rotor flattened.

[0031] Figure 2 The device according to the invention for capacitively measuring the filling level of powder in a filling device of a rotary press is shown in a side view,

[0032] Figure 3 Shown along Figure 2 The cross-sectional view of line AA in

[0033] Figure 4 Shown along Figure 3 A cross-sectional view of line BB in FIG. 1 , and

[0034] Figure 5 Shown with protective shield removed Figure 2 . DETAILED DESCRIPTION

[0035] Unless otherwise indicated, the same reference numerals in the figures denote the same objects.

[0036] Figure 1The rotary tablet press shown comprises a rotor driven in rotation by a rotary drive not shown in detail, which has a die plate 10 with a plurality of die cavities 12. The die cavities 12 can be formed, for example, by holes in the die plate 10. In addition, the rotor comprises a plurality of upper punches 14 guided in an upper punch guide 13 and a plurality of lower punches 16 guided in a lower punch guide 15, which rotate synchronously with the die plate 10. A pair consisting of an upper punch 14 and a lower punch 16 is assigned to the die cavity 12. The axial movement of the upper punch 14 and the lower punch 16 in the rotor rotating device is controlled by an upper control curve element 18 and a lower control curve element 20. The rotary tablet press further comprises a filling device 22, which has a filling cavity 24. The filling device 22 further comprises a funnel-shaped filling material storage 26, which is connected to the filling cavity 24 via a filling pipe 28. In this way, in the present example, the powdered filling material passes by gravity via the filling tube 28 into the filling chamber 24 and from there by gravity via the filling opening provided on the underside of the filling chamber 24 into the mold cavity 12 of the die plate 10 .

[0037] The rotary tablet press further comprises a pressing device 30. The pressing device 30 comprises a pre-pressing device with an upper pre-pressing roller 32 and a lower pre-pressing roller 34, and a main pressing device with an upper main pressing roller 36 and a lower main pressing roller 38. The rotary tablet press further comprises a discharge device 40, in the present case with an ejector 42, which delivers the tablets 44 produced in the rotary press to a tablet outlet 46.

[0038] The evaluation and control device 48 controls the operation of the rotary press and is also connected to the rotary drive of the rotor via lines (not shown in detail).

[0039] Furthermore, a device 50 for capacitively measuring the powder filling level in the filling tube 28 is arranged on the filling tube 28 . The device 50 is likewise connected to the evaluation and control device 48 .

[0040] exist Figures 2 to 5 In the figure, a device 50 for capacitively measuring the powder filling level is shown in different views. Figure 3 and 4As can be seen in the drawing, the filling tube 28 has a recess 52 in which a holding section 54 made of a non-conductive material, for example a plastic, such as POM, is arranged. The holding section 54 carries a first measuring electrode 56 extending in the axial direction of the filling tube 28 and a second and a third measuring electrode 58, 60 arranged parallel to the first measuring electrode 56, each extending parallel to the first measuring electrode and over approximately 10% of the length of the first measuring electrode 56. The second measuring electrode 58 is arranged in the region of the lower end of the first measuring electrode 56 and the third measuring electrode 60 is arranged in the region of the upper end of the first measuring electrode 56, as in particular Figure 5 The holding section 54 together with the measuring electrodes 56, 58 and 60 is also covered on its side facing away from the filling tube 22 by a non-conductive protective shield 62 which is at ground potential. Figure 5 The protective shield 62 is not shown for reasons of clarity. The filling tube 28 is also at ground potential in the example shown. The filling tube 28 and the protective shield 62 can be made of metal, for example. For example, the filling tube 28 can be made of high-quality steel and the protective shield 62 can be made of aluminum.

[0041] In the embodiment shown in the figure, the filling tube 28 forms a reference electrode for the measuring electrodes 56, 58 and 60. The measuring electrodes 56, 58 and 60 thus form three capacitors with the filling tube 28 as a reference electrode, so that an electric field can be formed between each measuring electrode 56, 58 and 60 and the reference electrode 22. During the operation of the rotary press, the second measuring electrode 58 can be completely covered by the powder material in the filling tube 28 at any time, while the third measuring electrode 60 can be above the filling level of the powder material in the filling tube 28. The first measuring electrode 56 forms a measuring area for measuring the powder filling level in the filling tube 28 with its longitudinal extension. During operation, an electric field is formed between the measuring electrodes 56, 58 and 60 and the filling tube 28 used as a reference electrode, respectively, and the capacitance of the capacitor formed accordingly is measured by the evaluation and control device 48. The evaluation and control device 48 derives the powder filling level in the filling tube 28 from the capacitance measurement. External interference influences can be minimized as much as possible by the protective shield 62 at ground potential. By using the filling tube 22 as a reference electrode, which is also at ground potential, a particularly precise and reliable capacitance measurement can be achieved. Influences on the measurement result caused by changes in the properties of the powder material or the filling tube 22 can be minimized by the second and third measuring electrodes 58, 60.

[0042] List of reference numerals:

[0043] 10 Concave mold plate

[0044] 12 cavities

[0045] 13 Upper punch guide

[0046] 14 Upper punch

[0047] 15 Lower punch guide

[0048] 16 lower punch

[0049] 18 upper control curve element

[0050] 20 control curve elements

[0051] 22 Filling device

[0052] 24 Filling cavity

[0053] 26 Filling material storage

[0054] 28 Filling tube

[0055] 30 Extrusion device

[0056] 32 upper pre-pressing roller

[0057] 34 Lower pre-pressing roller

[0058] 36 Upper main pressure roller

[0059] 38 Lower main pressure roller

[0060] 40 discharge device

[0061] 42 Ejector

[0062] 44 tablets

[0063] 46 Tablets Export

[0064] 48 Evaluation and control devices

[0065] 50 devices

[0066] 52 Notches

[0067] 54 Keep section

[0068] 56 first measuring electrode

[0069] 58 second measuring electrode

[0070] 60 third measuring electrode

[0071] 62 protection shield

Claims

1. A device for capacitively measuring the powder filling level in a filling device (22) for filling a die cavity (12) of a die plate (10) of a rotary press with powder material to be compacted in the rotary press, the device comprising a filling pipe (28) of the filling device (22), characterized in that A first measuring electrode (56) is arranged on a filling tube (28), the first measuring electrode and a reference electrode forming a first capacitor so that an electric field can be formed between the first measuring electrode (56) and the reference electrode, and the first measuring electrode (56) is covered by a conductive protective shield (62) on its side facing away from the filling tube (28), wherein the protective shield (62) is at ground potential, the first measuring electrode (56) is arranged in a non-conductive holding section (54), and the holding section (54) together with the first measuring electrode (56) is arranged in a cutout of the filling tube (28).

2. The device according to claim 1, characterized in that Electrically conductive filling tube sections of the filling device (22) which are located upstream and / or downstream of the filling tube (28) provided with the first measuring electrode (56) are likewise at ground potential.

3. The device according to claim 1, characterized in that The reference electrode is also at ground potential.

4. The device according to any one of claims 1 to 3, characterized in that The filling tube (28) provided with the first measuring electrode (56) is likewise at ground potential.

5. The device according to any one of claims 1 to 3, characterized in that The reference electrode is likewise arranged on the filling tube (28) on which the first measuring electrode (56) is arranged.

6. The device according to any one of claims 1 to 3, characterized in that The reference electrode is formed by a filling tube (28) provided with a first measuring electrode (56).

7. The device according to any one of claims 1 to 3, characterized in that A second measuring electrode (58) is also arranged on the filling tube (28), wherein the second measuring electrode (58) and the reference electrode form a second capacitor so that an electric field can be formed between the second measuring electrode (58) and the reference electrode, and the measuring area of ​​the second measuring electrode (58) is selected so that it is completely covered by powder material in the filling tube (28) during operation of the rotary press.

8. The device according to claim 7, characterized in that A third measuring electrode (60) is also arranged on the filling tube (28), wherein the third measuring electrode (60) and the reference electrode form a third capacitor so that an electric field can be formed between the third measuring electrode (60) and the reference electrode, and the measuring area of ​​the third measuring electrode (60) is selected so that it is above the filling level of the powder material in the filling tube (28) during operation of the rotary press.

9. The device according to claim 8, characterized in that The second measuring electrode (58) and / or the third measuring electrode (60) are also covered on their side facing away from the filling tube by the electrically conductive protective shield (62).

10. The device according to claim 8, characterized in that The second measuring electrode (58) and / or the third measuring electrode (60) are also arranged in the electrically non-conductive holding section (54).

11. The device according to claim 8, characterized in that The protective shield (62) forms an active protective shield which, when measuring a fill level, is controlled to the same potential as the first measuring electrode (56) and / or the second measuring electrode (58) and / or the third measuring electrode (60).

12. The device according to claim 8, characterized in that Furthermore, a control and evaluation device (48) is provided, which controls the first measuring electrode, the second measuring electrode, the third measuring electrode and the reference electrode during operation of the rotary press and determines the filling level of the powder material in the filling tube (28) based on the measurement data of the first measuring electrode, the second measuring electrode, the third measuring electrode and the reference electrode.

13. The device according to claim 8, characterized in that The first measuring electrode and / or the second measuring electrode and / or the third measuring electrode and / or the reference electrode are arranged on a substantially non-flexible PCB circuit board.

14. A rotary press comprising a rotor rotatable by means of a rotary drive, wherein: The rotor comprises an upper punch guide (13) for an upper punch (14) of a rotary press and a lower punch guide (15) for a lower punch (16) of the rotary press, and a die plate (10) arranged between the upper punch guide (13) and the lower punch guide (15), wherein the upper punch (14) and the lower punch (16) cooperate with the die cavity (12) of the die plate (10), and the rotary press further comprises a filling device (22), by which the powder material to be compacted is filled into the die cavity (12) of the die plate (10), wherein the filling device (22) comprises a filling device (22) Tube (28), the rotary press further comprises at least one upper extrusion device and at least one lower extrusion device, which cooperate with the upper punch (14) and the lower punch (16) during operation to compact the powder material in the mold cavity (12) of the die plate (10), the rotary press further comprises a discharge device (40), in which the pressed product produced in the mold cavity (12) is discharged, and is characterized in that a device (50) for capacitively measuring the powder filling level in the filling device (22) is provided according to any one of claims 1 to 13.

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