MONITORING SYSTEM AND CABLE

Abstract

A monitoring system includes an evaluation unit and a cable which has a cable core around which a multilayer sheath is disposed. The multilayer sheath has an inner and an outer electrode of a capacitor. A hygroscopic intermediate layer is disposed between the two electrodes. The evaluation unit is configured to monitor the cable for moisture based on the capacitance of the capacitor. A cable is also provided.

Claims

1. A monitoring system, comprising: a cable including a cable core, a multilayer sheath disposed around said cable core, said multilayer sheath including an inner electrode and an outer electrode of a capacitor, and a hygroscopic intermediate layer disposed between said electrodes; and an evaluation unit configured to monitor said cable for moisture based on a capacitance of said capacitor.

2. The monitoring system according to claim 1, wherein said intermediate layer has a swellable material for absorbing moisture and leading to a change in a distance between said electrodes.

3. The monitoring system according to claim 1, wherein said intermediate layer has a superabsorber.

4. The monitoring system according to claim 1, wherein said intermediate layer has a thickness of less than 0.1 mm in a dry initial state.

5. The monitoring system according to claim 4, wherein said thickness increases by at least a factor of 10 or 20 until a moist final state of said intermediate layer is reached.

6. The monitoring system according to claim 1, wherein at least one of said electrodes is a screen layer.

7. The monitoring system according to claim 1, wherein at least one of said electrodes is permeable to moisture.

8. The monitoring system according to claim 7, wherein said at least one electrode is formed as a braid or a helix.

9. The monitoring system according to claim 1, wherein said inner electrode is permeable to moisture.

10. The monitoring system according to claim 9, wherein said inner electrode is formed as a braid or a helix.

11. The monitoring system according to claim 1, wherein said intermediate layer is extruded onto said inner electrode.

12. The monitoring system according to claim 1, wherein said sheath has an outer sheath layer of an elastic material.

13. The monitoring system according to claim 1, wherein said capacitor is not wired to an inductance present within said cable.

14. The monitoring system according to claim 1, wherein said evaluation unit: is configured to measure the capacitance directly, has an external inductance being wired to said capacitor of said cable to form a tuned circuit and is configured to measure a resonant frequency, and is configured to output a measuring signal and evaluate a propagation time of the measuring signal.

15. A cable, comprising: a cable core; and a multilayer sheath disposed around said cable core, said multilayer sheath including an inner electrode and an outer electrode of a capacitor and a hygroscopic intermediate layer of a swellable material disposed between said electrodes.

16. The cable according to claim 15, which further comprises an integrated evaluation unit connected to said capacitor and configured to determine a capacitance of said capacitor.

17. The cable according to claim 16, which further comprises a connector, and a cable end fastened to said connector, said evaluation unit being disposed in said connector.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0030] FIG. 1 is a diagrammatic, exemplary cross-sectional view of a cable;

[0031] FIG. 2 is a highly-simplified, longitudinal-sectional view of a measurement structure; and

[0032] FIG. 3 is a highly-simplified, side-elevational view of a cable with a connector having an integrated evaluation unit fastened to the end.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring now in detail to the figures of the drawings, in which parts acting in the same way are provided with the same designations, and first, particularly, to FIG. 1 thereof, there is seen a cable 2 that has an inner central cable core 4, which is surrounded by a multilayer sheath 6. A first layer of this multilayer sheath 6 is an inner electrode 8, which is surrounded concentrically by an intermediate layer 10, which is in turn surrounded concentrically by an outer electrode 12. The two electrodes 8, 12 form a capacitor 13 with the intermediate layer 10. Finally, the cable 2 also has an outer sheath 14 on the outside.

[0034] The cable core 4 can in principle have an extremely wide range of configurations. In the exemplary embodiment of FIG. 1, the cable core 4 is formed as a wire having a conductor 18 which is surrounded by an insulation 16 and which, in the exemplary embodiment, is formed as a stranded wire. Alternatively, the cable core is, for example, a data transmission core having multiple data transmission lines which, for example, are twisted in pairs or untwisted and are formed with or without a pair screen. In principle, the specific configuration of the cable core does not matter in the present case. In general, electrical and/or optical transmission elements or else media conduits (hoses) are disposed within the cable core 4.

[0035] The two electrodes 8, 12 are each formed as screen layers disposed concentrically with respect to each other. In particular, the inner electrode 8 is moisture-permeable and specifically formed as a braided screen or helical screen. The outer electrode 12 is, for example, likewise formed as a braided screen or helical screen. Alternatively, it is formed as a screen foil or has a screen foil, so that a certain amount of sealing is achieved, in order for example to avoid the penetration of moisture into the inner cable structure.

[0036] The intermediate layer has a thickness D. This thickness D preferably lies in the range <0.1 mm and in particular in the range from about 20 m to 70 m and, for example, around 50 m. The thickness D simultaneously corresponds to a spacing of the two electrodes 8, 12 relative to each other.

[0037] The intermediate layer 10 has a swellable material or is formed by such a swellable material. Specifically, the intermediate layer 10 has a superabsorber as a swellable material. Such superabsorbers are known in principle.

[0038] The aforementioned thickness D in the range <0.1 mm relates to the thickness D in a dry initial state of the intermediate layer 10. In the event of the penetration of moisture, the intermediate layer 10 swells, so that the thickness D and therefore the distance between the two electrodes 8, 12 increases considerably. The distance increases by a factor of 10 to 20 from the dry initial state up to a moist final state of the intermediate layer. In a moist final state, the swellable material has absorbed the maximum amount of moisture.

[0039] As a result of this pronounced distance change, the capacitance of the capacitor 13 formed by the two electrodes 8, 12 decreases considerably. This capacitance change is measured and evaluated.

[0040] A measuring configuration, which is illustrated in a highly simplified manner, is shown in FIG. 2. In FIG. 2, it is possible to see firstly the two electrodes 8, 12 and an evaluation unit 20 which is connected to the two electrodes 8, 12. The capacitance of the capacitor 13 is determined by the evaluation unit 20 as previously described. In the left-hand half of FIG. 2, only the capacitor formed by the two electrodes 8, 12 with the intermediate layer 10 of the swellable material is illustrated. A dashed line indicates the position of the outer electrode 12 in the initial state, and a continuous line indicates the position of the outer electrode 12 in a moist final state. The original distance between the two electrodes 8, 12 increases considerably by a distance change .

[0041] FIG. 3, finally, shows by way of example a side illustration of a cable 2 with a connector 22, in which the evaluation unit 20 is integrated and fastened to a cable end at one end. The cable 2 is used generally in a conventional way as a data cable or else a supply cable. Monitoring of the cable 2 for the penetration of moisture is made possible through the use of the integrated capacitor 13 with the intermediate layer 10. Specifically in the integrated configuration according to FIG. 3, a pre-configured cable 2 is provided with integrated moisture monitoring.