METHOD FOR MONITORING A LINE, AND MEASURING ARRANGEMENT CONTAINING LINE

Abstract

A method for monitoring a line is done in a simple manner by feeding test pulses and determining any interference on the test pulses by reflected portions of the same test pulses. In a normal state of the line, the measuring pulses have a transit time which is known in advance due to the predetermined length of the line, and the respective reflected portions of the measuring pulses are generated which propagate in an opposite direction to the measuring pulses. A deviation of the transit time from a previously known transit time, and a deviation from the normal state are recognized in dependence on the overlay.

Claims

1. A method for monitoring a line having a predetermined length and a measuring conductor, which comprises the steps of: feeding a plurality of measuring pulses into the measuring conductor, and in a normal state of the line, the measuring pulses have a transit time which is known in advance due to the predetermined length of the line, and respective reflected portions of the measuring pulses are generated which propagate in an opposite direction to the measuring pulses; monitoring the line and a determination is made as to whether an overlay of the measuring pulses with the respective reflected portions is present at a predetermined measuring point; and recognizing, in dependence on the overlay, a deviation of the transit time from a previously known transit time, and a deviation from the normal state.

2. The method according to claim 1, wherein the measuring pulses and the respective reflected portions are overlaid at the measuring point in the normal state of the line.

3. The method according to claim 1, which further comprises measuring the overlay by checking whether an overvoltage with respect to a transmitted voltage of the measuring pulses is present at the predetermined measuring point.

4. The method according to claim 1, wherein the measuring pulses are composed of a digital measuring signal.

5. The method according to claim 1, which further comprises repeatedly generating the measuring pulses with a settable clock rate which is adjusted until the measuring pulses and the respective reflected portions are overlaid at an adjusted clock rate.

6. The method according to claim 1, which further comprises determining an operating parameter of the line on a basis of the adjusted clock rate.

7. The method according to claim 6, which further comprises disposing a material along the measuring conductor and having a dielectric coefficient that depends on the operating parameter of the line.

8. The method according to claim 1, wherein the measuring conductor is connected to a measuring terminal of a measuring unit, by means of which the measuring pulses are generated and by means of which the overlay is measured.

9. The method according to claim 6, wherein the operating parameter of the line is temperature.

10. A measuring configuration, comprising: a line having a predetermined length and a measuring conductor; a measuring unit configured for monitoring said line, said measuring unit configured to: feed a plurality of measuring pulses into said measuring conductor, in a normal state of said line, the measuring pulses have a transit time which is known in advance due to the predetermined length of said line, and respective reflected portions of the measuring pulses are generated which propagate in an opposite direction to the measuring pulses; and monitor said line and a determination is made as to whether an overlay of the measuring pulses with the respective reflected portions is present at a predetermined measuring point, and depending on the overlay, a deviation of the transit time from a previously known transit time, and a deviation from the normal state, are recognized.

11. The measuring configuration according to claim 10, wherein said measuring unit is configured such that the measuring pulses are generated with a clock rate, and the clock rate is set depending on the previously known transit time in the normal state and depending on the predetermined length of said line.

12. The measuring configuration according to claim 10, wherein said line has at least one core as well as a neutral fiber, which does not undergo a change in length in a presence of bending stress, and with respect to which said measuring conductor is disposed further outward in a radial direction than the core.

13. A measuring method, which comprises the steps of: providing a line having a measuring conductor and a measuring unit in an on-board network, said measuring unit programmed to: feed a plurality of measuring pulses into the measuring conductor, and in a normal state of the line, the measuring pulses have a transit time which is known in advance due to the predetermined length of the line, and respective reflected portions of the measuring pulses are generated which propagate in an opposite direction to the measuring pulses; monitor the line and a determination is made as to whether an overlay of the measuring pulses with the respective reflected portions is present at a predetermined measuring point; and recognize, in dependence on the overlay, a deviation of the transit time from a previously known transit time, and a deviation from the normal state.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0033] FIG. 1 is a diagrammatic, sectional view of a measuring arrangement according to the invention;

[0034] FIG. 2 is an illustration showing a measuring signal;

[0035] FIG. 3 is an illustration showing a measuring pulse and a reflected portion of the same; and

[0036] FIG. 4 is an illustration showing an overlay of the measuring pulse and the reflected portion.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a measuring arrangement 2. This contains a line 4 which in turn contains a measuring conductor 6, which extends in a longitudinal direction along the line 4. In the exemplary embodiment illustrated, the line 4 is a simple, single-core line 4, i.e. one core 8 with a central conductor 10 that is surrounded by insulation 12. The measuring conductor 6 is embedded in this insulation 12. In a variant, not illustrated, the line 4 contains a plurality of cores 8, which may differ from one another under some circumstances, and/or other line or functional elements.

[0038] The measuring conductor 6 is connected to a measuring unit 14, so that the line 4 can be monitored in respect of a deviation from a normal state. Examples for such a deviation include an excessive heating of the line 4 above a predetermined operating temperature, and a fracture as a result of an excessive bending of the line 4. The monitoring of the line 4 is explained in more detail below with respect to FIGS. 2 to 4.

[0039] The measuring unit 14 generates a measuring signal 16 which consists of periodically recurring measuring pulses 18 with pauses 20 inserted between them. A section of such a measuring signal 16 is plotted in FIG. 2 as a voltage U against time t. The measuring signal 16 illustrated is here a digital measuring signal 16, in which the measuring pulses 18 and the pauses 20 are realized as a bit sequence. A respective measuring pulse 18 here corresponds to a single 1-bit, while a pause 20 is composed of a plurality of 0-bits. The individual bits are suggested by vertical dashed lines. The measuring pulses 18 are significantly shorter than the pauses 20, in particular at least an order of magnitude shorter. Altogether a recurring rectangular signal arises.

[0040] A respective measuring pulse 18 contains a pulse time T1 which typically lies in the range between 1 and 10 ns. A respective pause 20 lasts for a pause time T2, which is typically between 0.1 and 100 s. From this, a clock rate, i.e. a repetition rate of the measuring pulses 18, in the range between several tens of kilohertz up to several hundreds of megahertz, or even a few gigahertz, arises. Such a bit sequence can be realized particularly easily by a digital circuit, so that the measuring unit 14, which then contains such a circuit, is particularly simple and compact.

[0041] The measuring pulses 18 are fed into the measuring conductor 6 to monitor the line 4, this being done at a measuring terminal 22 at which the measuring unit 14 is connected to the measuring conductor 6, and which is thus a feed point at the same time. At the measuring terminal 22, a respective measuring pulse 18 has a voltage U, which is referred to as the transmitted voltage U1. The measuring pulse 18 propagates along the measuring conductor 6, and is usually weakened as it does so, i.e. attenuated. A portion of the measuring pulse 18 is reflected as a reflected portion 24 at the end, and propagated in the opposite direction, i.e. back in the direction of the measuring terminal 22. This is illustrated in FIG. 3 which illustrates the line 4 schematically, along with a measuring pulse 18 at the left-hand end, i.e. at the measuring terminal 22, and the reflected portion 24 of the measuring pulse 18 at the right-hand end.

[0042] Since measuring pulses 18 are fed in continuously, the returning, reflected portion 24 necessarily meets another measuring pulse 18 that was fed in later, and is overlaid upon it. This is shown schematically in FIG. 4, which shows a section of the line 4, as well as an overlay of the reflected portion 24 of a first measuring pulse 18 with a second measuring pulse 18, which was fed in at a later time following the first measuring pulse 18. The overlay results in a voltage U which is greater than the original transmitted voltage U1. The difference is precisely a reflected voltage U2, i.e. the voltage of the reflected portion 24. In total, therefore, an overvoltage is present.

[0043] The presence of this overvoltage is now checked, in order to monitor the line 4. The voltage in the measuring conductor 6 is measured at a predetermined, i.e. specified, measuring point 26, for this purpose. As in the exemplary embodiment, the measuring point 26 is preferably the same as the measuring terminal 22. A different position along the measuring conductor 6 is, however, also conceivable. A determination is made at the measuring point 26 as to whether an overlay is present, in that, for example, a check is made for an overvoltage. An elaborate measurement of transit time is omitted.

[0044] The clock rate is set in the present case such that an overlay is present at the measuring point 26 in the normal state. If the environmental conditions are changed, or if the line 4 is damaged, the state of the line 4 thus changes. The line 4 is, for example, heated, and the insulation 10 has a temperature-dependent dielectric coefficient, so that the heating leads to a changed transit time of the measuring pulses 18 in the measuring conductor 6. As a result, however, the previously set overlay is also lost, which means that the initially set synchronization between the measuring pulses 18 fed in and reflected portions 24 at the measuring point 26 becomes lost. An overvoltage is no longer created. This is recognized by the measuring unit 14, from which it is concluded that there is a deviation from the normal state.

[0045] Alternatively or in addition to the heating, a mechanical wear of the line 4 can also be recognized. In the presence of a bending movement the measuring conductor 6 is necessarily also subjected to a correspondingly mechanical stress. A damaged location, or even a fracture location, then arises in the presence of wear to the measuring conductor 6, effectively leading to a shortened measuring conductor 6, so that here again the initial overlay becomes lost, as a result of which the measuring unit 14 recognizes the wear.

[0046] In order to make sure that the measuring conductor 6 fractures before the conductor 10 of the core 8, the measuring conductor 6 is arranged further outward in the radial direction R than the core 8 with respect to a neutral fiber 28 of the line 4. As a result, the measuring conductor 6 is subjected to a heavier mechanical stress, and wears correspondingly faster.

[0047] The determination of whether an overlay is or is not present is in itself sufficient to realize monitoring of the line 4. In one variant, however, a quantitative monitoring is carried out in addition to or instead of such a merely qualitative monitoring, which also permits a determination of an operating parameter, e.g. the temperature of the line 4. For this purpose, the clock rate is adjusted by means of the measuring unit 14, and is changed until an overlay is present. The clock rate is thus modified in the presence of a change to the transit time, in order to establish an overlay again, i.e. the measuring pulses and the reflected portions are synchronized. The modified clock rate is then a measure of the magnitude of the change of the state of the line 4. A quantitative temperature measurement is, for example, realized through regular or continuous adjustment of the clock rate. The clock rate is adjusted, for example, in that the pauses 20 are extended or shortened, i.e. in that 0-bits are added or removed.