Method and equipment for testing the dielectric strength of the insulation of an electrical cable set

Abstract

Method for checking the dielectric strength of the insulation of an electrical cable set (2) which has at least one conductor (4) with a conductor (6) surrounded by an insulating sheath (11), wherein a test probe (24) is provided and a test voltage (V) is applied between the test probe (24) and the conductor (6), characterized in that the test probe (24) is attached to an adjustment device (20) and, within the scope of a measurement cycle, the adjustment device (20) moves the test probe (24) to at least several measuring points on the cable set (2) and the dielectric strength of the insulation is checked at least at the several measuring points.

Description

[0001] The invention relates to a method and a system for testing the dielectric strength of an insulation of an electrical cable set, which has at least one line with a conductor surrounded by an insulating sheath, wherein a test probe is provided and a test voltage is applied between the test probe and the conductor in order to test the dielectric strength of the insulation.

[0002] For cable harnesses, especially high-voltage cable harnesses and especially for cable harnesses in the automotive sector, a safety and quality inspection is regularly required at the end of the cable harness production process (so-called "end-of-line" inspection). This inspection checks the integrity of the insulation. This check determines whether the insulation of the cable harness has a specified insulation resistance and thus the required dielectric strength. Typically, the cable harness is tested on a test bench in its final installation position in the vehicle.

[0003] The cable sets are usually pre-assembled, often branched cable sets, in which additional electrical components, such as a plug, a control box or a fuse box, are already connected to at least one cable.

[0004] Whenever reference is made here to a high-voltage cable harness or high-voltage cable, this means that the cable harness is designed for an operating voltage of more than 30V for AC voltage and more than 60V for DC voltage, and that such voltages are present during operation. Furthermore, the cable harness is also specifically designed for voltages of several hundred V, for example, from more than 200V up to 1000 V. Such high-voltage cable harnesses are used specifically in electric motor-driven vehicles to connect components of the electric drive, such as the high-voltage battery, electric traction motor, and possibly inverter, etc.

[0005] For shielded cables, the dielectric strength is tested, for example, by applying a test voltage between the shield and the inner conductor. Testing a shielded cable is described, for example, in DE 10 2017 005 306 A1. However, such a test is not possible for unshielded cables.

[0006] DE 10 2019 210 866 A1 describes a test pocket into which the cable harness to be tested is inserted and which has an electrically conductive sheath. A test voltage is applied between the sheath and at least one conductor of the cable harness. To ensure the sheath fits as tightly as possible to the cable harness, the air can be extracted from the test pocket.

[0007] DE 10 2020 101 432 A1 describes a method for testing the dielectric strength of a high-voltage cable harness, in which a two-part housing with flexible contact networks is provided, whereby the cable harness is inserted between the two housing halves.

[0008] Furthermore, continuous testing of endless cables is also known. For example, GB 848 180 A provides a system in which a cable is unwound from a supply reel, passed through a testing device, and then rewound. The testing device consists of a tube filled with a test gas into which a test electrode is immersed, to which a test voltage is applied. If insulation is damaged, ionization occurs, which is also indicated acoustically in this system. A comparable system can be found in GB 991 686 A.

[0009] Compressed air tests are also possible, in which compressed air is introduced between the insulation sheath and the conductor to detect insulation damage by measuring pressure loss. However, microcracks and superficial damage cannot be detected in this way.

[0010] Another option is to inspect the cable harness in a chamber filled with conductive gas. However, this is very costly for large cable harnesses, and the applied voltages would have to be very high to even detect damage. Finally, there is also the option of immersing the cable harness in a saltwater bath, but this would result in saltwater residue and potentially damage to the cable harness.

[0011] DE 975 957 B describes a method for testing the dielectric strength of a cable insulation, in which the cable to be tested is pulled through an electrode consisting of metal wire brushes.

[0012] JP S55 - 113 967 A describes a method in which a brush is moved along the cable to be tested and water is sprayed onto the cable to be tested.

[0013] Based on this, the object of the invention is to provide a method and a system for testing the dielectric strength of a cable harness, in particular a high-voltage cable harness for a motor vehicle, which are suitable for series testing in a cost-effective manner and with little effort.

[0014] The object is achieved according to the invention by a method and a system for checking the dielectric strength of the insulation of an electrical cable harness, in particular a high-voltage cable harness, and especially such a cable harness for a motor vehicle.

[0015] The cable harness has at least one (high-voltage) cable with a conductor surrounded by an insulating sheath. A test probe is provided, wherein a test voltage is applied between the test probe and the conductor. The test probe is attached to an adjustment device and, as part of a measuring cycle for checking the dielectric strength, the adjustment device, together with the test probe, moves to at least several measuring points on the cable harness, and the dielectric strength of the insulation is checked at the at least several measuring points. For moving the test probe, the system has a control unit which is configured to move the adjustment device and thus the test probe to the at least several measuring points on the cable harness.

[0016] The actual test is performed in the usual way by applying the test voltage between the conductor and the test probe, thus creating a voltage difference across the insulation. The system features, among other things, a connection terminal to which the conductor is electrically connected.

[0017] The system also features a test unit designed to generate and apply the test voltage between the connection terminal and the test probe. This test voltage is checked for voltage dips using a suitable evaluation device. This evaluation device is a component of the test unit and preferably forms a single unit with it. Therefore, the evaluation device is generally used to measure and check / monitor the test voltage applied between the test probe and the conductor. In the event of defective insulation, a discharge or arc occurs between the two test electrodes, which are formed by the conductor on the one hand and the test probe on the other. Such an arc, and thus a voltage dip, is detected by the evaluation unit. The evaluation device is therefore designed to check the dielectric strength.If a lack of dielectric strength is detected, it emits a warning signal. The applied test voltage is preferably greater than 1 kV, for example, in the range between 1 kV and 5 kV.

[0018] The cable harness to be tested is, in particular, a high-voltage cable harness for a motor vehicle, which is therefore installed in a motor vehicle during operation. The cable harness is specifically used to connect components of the motor vehicle's electric drive system.

[0019] The at least one cable is, in particular, a single-core sheathed cable, which therefore has only a central conductor (cable core) surrounded by a core sheath, which at least in sections forms the insulating sheath. At least in these sections, the cable consists exclusively of the conductor and the insulating sheath. In some variants, the core sheath is also partially surrounded by a tubular protective sheath, which then forms part of the insulating sheath. Preferably, the cable harness has, in particular, two such cables, which are used during operation as the positive line and the negative line (ground line) of a DC cable harness.

[0020] In general, the cable is preferably an unshielded cable.

[0021] By arranging the test probe on the adjustment device, it is easy to move the test probe along the cable harness. The adjustment device therefore moves the test probe in space and relative to the cable harness. The cable harness is positioned in a fixed position. This allows even complex cable harness geometries to be precisely traversed, allowing reliable testing of the cable harness with minimal effort. Using the adjustment device, the test probe is moved against the insulation at the multiple measuring points and, in particular, pressed against it. The cable harness to be tested is clamped in a suitable device, for example, or rests on a solid base.

[0022] This method does not require any additional measures such as test pockets, test tubes, or other test enclosures or test chambers. It also does not use test gases. The cable harness is also not immersed in a bath.

[0023] The test probe acts as a type of test or measuring electrode. One advantage is that the voltage difference is only present and measured locally at the location of the test probe.

[0024] This method also enables and performs a spatially resolved test in a simple manner. This specifically means that the location information of the test probe is recorded and stored during the test. If a damaged area in the insulation is identified, the location of the damaged area is also immediately determined and identified.

[0025] Preferably, the test probe is moved along at least one test section of the cable harness. The dielectric strength is continuously checked over the length of the test section. The test probe is moved towards the insulation and pressed against it. As it slides along the insulation, the test voltage is continuously applied and evaluated. The length of the test section is in particular in the range of several centimeters, more preferably in the range of more than 10 cm. In particular, the test section extends over at least a large part of the length of the cable, for example over at least 50% or at least 75% of the cable. In an expedient embodiment, the test probe is moved continuously along the entire length of the cable and more preferably also over the entire length of the cable harness.This allows a particularly complete inspection of the cable's insulation sheath and, in particular, the insulation of the entire cable set.

[0026] In a preferred embodiment, the test probe is pressed against the insulation of the cable harness, and in particular against the insulating sheath of the cable, with a defined, predetermined contact force. This ensures defined test conditions and, in particular, ensures that the test probe is reliably in contact with the insulation. The distance between the test probe and the conductor is minimized, with the distance being determined in particular by the sheath thickness of the insulating sheath.

[0027] In a preferred embodiment, the applied contact force is recorded and, in particular, measured directly using a suitable measuring device. The measuring device is, for example, integrated into the test probe or part of the adjustment device. It is specifically designed as a force sensor. When integrated into the test probe, it is therefore designed like a tactile measuring tip, which performs a dual function: applying the test voltage and measuring the contact force.

[0028] Preferably, the contact force is controlled and adjusted depending on the determined contact force. The contact force is therefore continuously monitored, and if the current actual value deviates from a target value, the contact force is adjusted accordingly. This is achieved, in particular, by appropriately controlling the adjustment device through which the contact force is typically exerted. Controlling and, in particular, regulating the contact force ensures gentle, defined pressing of the test probe without damaging the cable harness.

[0029] In a preferred development, the value of at least one test parameter selected from test voltage and contact force is varied during the measuring cycle. By varying the test conditions, the test conditions are therefore varied within the scope of a measuring cycle, in particular depending on the properties of the cable harness or depending on the position of the test probe. This is based on the consideration that different sections exist along the length of the cable harness, which differ either in terms of their structure and / or in terms of a risk potential for damage to the insulation, for example as a result of assembly processes. Preferably, defined, particularly critical sections are identified, in which the test voltage and / or the contact force are changed and, in particular, increased compared to other sections.In critical insulation areas, the test conditions are preferably tightened so that, for example, even microcracks in the insulation can be identified.

[0030] In a preferred embodiment, the values ​​of the test parameters are generally varied depending on the location along the cable set.

[0031] In a useful further development, a recognition unit is provided with the aid of which different sections of the cable harness are identified, wherein the value of the at least one test parameter is controlled depending on the information determined by the recognition unit. During the execution of the measuring cycle, the position of the test probe in relation to the cable harness is therefore continuously determined and / or the shape, structure or other properties of the cable harness are identified with the aid of the recognition unit. The recognition unit is in particular a camera, preferably with associated image analysis. Alternatively, the recognition unit can also be an analysis unit which identifies the different sections of the cable harness based on current position data of the test probe and by comparing it with stored data on the structure of the cable harness.

[0032] Based on the information determined by the detection unit, the test parameters are automatically set differently for different sections in preferred training.

[0033] In a preferred embodiment, the cable has a protective section in which the cable has an additional protective sheath in addition to the core sheath. This, together with the core sheath, forms the insulating sheath. The contact pressure is preferably increased in the area of ​​the protective section compared to (normal) sections without a protective sheath. Preferably, the test voltage is also increased in this section.

[0034] Such protective sheaths, for example, are a protective tube that is attached in sections. An air gap may exist between the protective sheath and the wire sheath of the cable. The increased contact force ensures that the protective sheath is pressed against the wire sheath and thus rests directly against it, which is advantageous for reliable testing.

[0035] In a preferred development, the test voltage is increased in a connection section in which the cable is connected to another component, especially compared to a normal section away from the component and without a protective sheath. Such a connection section is a critical section because special loads occur in this section during assembly of the cable harness. These are caused, for example, by necessary measures for stripping insulation and / or connecting contact elements, so that the risk of damage is increased in this area. By increasing the test voltage in this specific section, the test requirements are deliberately increased in order to be able to reliably rule out damage in this critical area.

[0036] In general, when the special sections are reached, e.g. the protection section or the connection section, the value of the respective test parameter is set to a section-specific setpoint, which is different and in particular higher than a setpoint for other (normal) sections.

[0037] The cable harness is, in particular, a prefabricated cable harness in which another component is connected to at least one cable. This additional component is, in particular, a connector. Alternatively or additionally, a control box or fuse box is connected directly to the cable as an additional component, in which additional (electronic) components, such as control elements, fuse elements, or other electrical circuit components, are integrated.

[0038] In a preferred embodiment, the cable harness has two lines, and preferably exactly two lines, which form a forward and return line of a direct current line. These two lines are connected to the electrical component at their ends, and preferably at both ends, in particular together. In one embodiment, the cable harness is therefore formed by exactly two lines with at least one electrical component connected to them. Alternatively, an additional branch line is provided, which branches off from these two aforementioned lines, which form a main line. In general, in a configuration with a main line and at least one branch line branching off from it, the cable harness has a branched structure.

[0039] The additional component connected to the at least one cable typically has a housing. Preferably, the test probe is also moved to the housing, and the insulation strength of the housing is tested. This measure therefore particularly checks the entire cable set.

[0040] The adjustment device is, in particular, a robot to which the test probe is attached and whose movement path is programmable. The robot is, for example, a so-called multi-axis industrial robot, as is commonly used in industrial production. The robot typically has several mutually adjustable robot arms. The test probe is attached to a so-called robot hand. This can be moved freely in space by appropriate movement of the various robot arms. Programming the robot's movement path enables easy adaptation to different cable sets. Different cable set designs are stored in the robot's control program, so that when changing cable sets, only a different control program needs to be selected.

[0041] An exemplary embodiment of the invention is explained in more detail below with reference to the single figure. This figure shows a simplified, schematic representation of a DC cable harness, a robot with an attached test probe, and an exemplary curve of an applied test voltage and an applied contact force along the length of the cable harness.

[0042] A cable harness 2 shown in the figure is designed as a direct current cable harness 2, which in the exemplary embodiment has exactly two (high-voltage) cables 4, which form a positive line and a negative line during operation and when connected. Each cable 4 is designed as a single-core cable and has a central conductor 6 surrounded by a wire sheath 7.

[0043] In the exemplary embodiment, each cable 4 has a protective tube in a protective section 8, which forms a protective sheath 10. This, together with the wire sheath, forms an insulating sheath 11 of the cable 6 surrounding the conductor 6.

[0044] At one end, a (high-voltage) connector is connected to the two lines 4 as an electrical component 12. This connector generally has a housing 14 into which a respective line 4 is inserted, in particular sealed against the ingress of dust and moisture. The respective conductor 6 is suitably contacted inside the component 12. In the exemplary embodiment, contact elements 16 of the connector are also schematically shown, with which the connector is connected to another electrical component via a plug connection.

[0045] Additionally, the figure also shows a system 18 designed to test the dielectric strength of the insulation of the cable harness 2 shown. The insulation is formed in particular by the insulating sheath 11 and preferably also by the housing 14 of the electrical component 12.

[0046] The system 18 comprises a robot 20 as an adjustment device, which is designed as a multi-axis industrial robot. This robot has several robot arms, each of which can be adjusted around several axes in a known manner. At a front end, the robot 20 has a robot hand to which a test probe 24 is attached. This probe can be moved in space along a programmable path of motion with the aid of the robot 20.

[0047] The system 18 further comprises a control unit 26, via which the system 18 and in particular the robot 20 are controlled. The system 18 further comprises a test unit 28 and connection terminals 30, to each of which the respective conductor 6 is connected to perform the test. The connection terminals 30 are, for example, screw terminals or clamp terminals. The test unit 28 is designed to generate a test voltage V and to apply it to the connection terminals 30 on the one hand and to the test probe 24 on the other hand, so that a voltage difference exists between the test probe 24 and the respective conductor 4. The test probe 24 is a type of measuring tip or electrode that is at a predetermined voltage potential (test voltage V) with respect to the connection terminals 30. For this purpose, the test unit 28 is suitably connected to the test probe 24 via an electrical line.

[0048] Finally, the system further comprises a detection unit 32, which in the exemplary embodiment is designed as an optical camera. This is connected in particular to the control unit 26.

[0049] Furthermore, the system 18 is designed to detect a contact force F with which the test probe 24 is pressed against the insulation, and specifically against the insulating jacket 11, during the test. For this purpose, a force sensor 34 is arranged, for example, on the robot hand between the hand and the test probe 24 or integrated into the test probe 24.

[0050] When checking the dielectric strength of the insulation of cable set 2, proceed as follows: With the help of the control unit 26, the robot 20 is controlled such that the test probe 24 is pressed against the insulation, specifically against the insulating sheath 11, of one of the cables 4. The test probe 24 is pressed against the insulation by the robot 20 with a defined contact force F. This contact force F is specifically measured using the force sensor 34. The contact force F is automatically regulated to a particularly variable setpoint using the control unit 26.

[0051] During the test, a predetermined test voltage V is applied between the test probe 24 and the respective conductor 6.

[0052] The test probe 24 is then moved along the insulating sheath 11 while maintaining the contact force F over at least a predetermined length of a test section 36. In the exemplary embodiment, the test section 36 is formed by the entire length of the cable 4 and, if necessary, also by the entire length of the complete cable harness 2, i.e., including the connected component 12. The test probe 24 moves continuously along the test section 36; specifically, the test probe 24 moves at least along the entire length of the respective cable 4.

[0053] The applied test voltage V and / or the applied contact force F constitute test parameters whose values ​​are automatically varied and adjusted during the measurement cycle, i.e., when testing a respective cable 4 or when checking the cable harness 2. The test voltage V and / or the contact force F are controlled to section-specific, different target values.

[0054] For example, in a preferred embodiment, it is provided that at least the test voltage V and / or the contact force F is increased in the area of ​​the protective section 8 and the protective cover 10 compared to the areas in front without the protective cover 10.

[0055] The section of a respective cable 4 in the area in front of the electrical component 12 forms a connection section 38. In this section, the test voltage V is changed and, in particular, increased compared to normal sections 40 of the cable harness, which are located away from the component 12 and in which no protective sheath 10 is formed.

[0056] A respective normal section 40 is therefore defined by the fact that the core sheath 7 defines the outermost sheath. Furthermore, the normal section 40 is spaced, for example, by at least 5 cm or at least 10 cm from the connected component 12 or another attached element, such as a connection terminal. The connection section has, in particular, a length of at least 5 cm or at least 10 cm and, for example, a maximum of 20 cm.

[0057] With the help of the detection unit 32, the different sections, i.e. the protective section 8, the connecting section 38 and the normal section 40, are automatically identified and the test parameters are set and, in particular, regulated according to stored and different section-specific (target) values.

[0058] The test unit 28, in particular the aforementioned evaluation unit, continuously monitors the applied test voltage V for deviations from the target value. In the case of defective insulation, this is detected, for example, by a voltage drop. The test unit 28 is designed to issue a warning signal in the event of an impermissible deviation. This signal, in particular, includes location information so that the position of the defective insulation can be precisely determined. For this purpose, the test unit 28 receives, for example, position data from the control unit 26.

[0059] A voltage source and preferably also the aforementioned evaluation unit are integrated within the test unit 28, thus being arranged within a common structural unit. In principle, the various required units of the test unit, such as the voltage source and evaluation unit, can also be distributed across different structural units. For example, it is possible for the evaluation unit to be integrated into the control unit 26. The test unit 28 can also be integrated entirely within the control unit 26.

[0060] The test probe 24 is moved either along a straight, linear path along the respective line 4. In a preferred embodiment, the test probe 24 is moved not only in the longitudinal direction of the line 4, but also at least partially in the circumferential direction around the line 4. For this purpose, for example, a test path running spirally around the line 4 or a meandering test path is provided, along which the test probe 24 is moved. In the meandering test path, the test probe 24 is pivoted alternately to the left and to the right during the forward movement.

[0061] Preferably, the test probe is also guided along the housing 14 in the area of ​​the component 12, so that the dielectric strength of the housing 14 is also checked.

[0062] The upper part of the figure shows the curves of the test voltage V and the contact force F over the length of the cable harness 2. Such a curve is set for each cable 4, and a corresponding test is performed. The two cables 4 are therefore tested one after the other using the test probe 24 guided by the robot 20.

[0063] In the exemplary embodiment, the same qualitative curve is provided for the test voltage V and the contact force F. Alternatively, the curves for the test voltage V and the contact force F differ from each other.

[0064] In the printout example, the test is performed from left to right, i.e., the test probe 24 is moved from left to right along the line 4. Initially, the test voltage V and the contact force F are adjusted to a respective first setpoint value, which is valid for the normal section 40. As soon as the detection unit 32 detects that the protective section 8 with the protective sheath 10 has been reached, the test voltage V and / or the contact force F are adjusted to a second setpoint value, which in the exemplary embodiment is higher than the first setpoint value.

[0065] The test sheath 10 is followed by the connection section 38, in which a third setpoint value for the test voltage V and / or for the contact force F is set, which in the exemplary embodiment lies between that for the normal section and that for the protective section 8.

[0066] In the illustrated embodiment, the test voltage V as well as the contact force F are largely reduced in the area of ​​the housing 14. In this case, no test of the insulation of the housing 14 is performed. Alternatively, however, a further setpoint can also be specified in the area of ​​the housing 14, for example, by regulating the test voltage V to a maximum setpoint.

[0067] As an alternative to the previously described test, in which the test probe is continuously moved along the entire length of line 4, an alternative variant provides for the targeted approach and testing of specific, critical sections. In this case, therefore, only individual (longitudinal) sections (test sections 36) of the respective line 4 are tested.

[0068] The method described here achieves a series-ready (end-of-line) inspection of high-voltage cable harnesses during cable harness production, enabling reliable testing with minimal effort. Using a programmable robot, different cable harness designs can be easily inspected. This requires only an adjustment of the robot's trajectory. List of reference symbols 2 cable sets 4 Line 6 ladders 7 core sheath 8 Protection Section 10 protective cover 11 Insulating jacket 12 electrical components 14 housings 16 Contact element 18 Appendix 20 robots 24 test probe 26 Control unit 28 test unit 30 connection terminal 32 detection unit 34 force sensor 36 test section 38 connecting section 40 normal section V test voltage F contact pressure

Claims

[1] Method for testing the dielectric strength of an insulation of an electrical cable set (2) which has at least one line (4) with a conductor (6) surrounded by an insulating sheath (11), wherein a test probe (24) is provided and a test voltage (V) is applied between the test probe (24) and the conductor (6), characterized by that the test probe (24) is attached to an adjusting device (20) and, within the scope of a measuring cycle, the adjusting device (20) moves to at least several measuring points on the cable set (2) with the test probe (24) and the dielectric strength of the insulation is checked at least at the several measuring points. [2] Method according to the preceding claim, characterized bythat the test probe (24) is moved along at least one test section (36) of the cable set (2) and the dielectric strength is continuously checked over the length of the test section (36), wherein the test section (36) preferably extends over the entire length of the at least one line (4). [3] Method according to one of the preceding claims, characterized by that the test probe (24) is pressed against the insulation with a defined contact force (F) and the contact force (F) is measured and controlled. [4] Method according to one of the preceding claims, characterized by that the value of at least one test parameter selected from test voltage (V) and contact force (F) is varied during the measuring cycle. [5] Method according to the preceding claim, characterized by that the value of at least one test parameter is varied depending on the location. [6] Method according to one of the preceding claims, characterized by that a recognition unit (32) is provided, with the aid of which different sections (8, 38, 40) of the cable harness (2) are identified, wherein the recognition unit (32) is preferably a camera. [7] Method according to the preceding claim and according to one of claims 4 or 5, characterized by that the value of the at least one test parameter is set as a function of the information determined by the recognition unit (32). [8] Method according to one of the preceding claims, characterized by that the line (4) has a protective section (8) in which the line (4) has an additional protective sheath (10), wherein the contact force (F) in the region of the protective section (8) is set to a predetermined section-specific target value and in particular is increased. [9] Method according to one of the preceding claims, characterized bythat in a connection section (38) in which the line (4) is connected to a further component (12), the test voltage (V) is set to a predetermined section-specific target value and in particular increased. [10] Method according to one of the preceding claims, characterized by that the cable set (2) is a prefabricated cable set (2) which has the at least one line (4) and preferably two lines (4), wherein the at least one line (4) is connected to a further component (12), in particular to a plug. [11] Method according to the preceding claim, characterized by that the further component (12) has a housing (14) and the test probe (24) is also moved to the housing (14) and the insulation strength of the housing (14) is checked. [12] Method according to one of the preceding claims, characterized bythat the adjustment device is a robot (20) to which the test probe (24) is attached and whose movement path is programmable. [13] System (18) for testing the dielectric strength of an insulation of an electrical cable set (2) which has at least one line (4) with a conductor (6) surrounded by an insulating sheath (11), the system (18) having - an adjusting device (20), in particular a programmable robot, with a test probe (24) attached thereto, - a connection terminal (30) for electrically contacting the conductor (6), - a test unit (28) designed to apply a test voltage (V) between the connection terminal (30) and the test probe (24), - a control unit (26) which is designed to move the adjusting device (20) with the test probe (24) to at least several measuring points on the cable set (2) during operation. [14] System (18) according to the preceding claim, which is designed to detect a contact force (F) of the test probe (24) and to control this contact force (F). [15] System (18) according to one of the two preceding claims, which has a recognition unit (32), in particular a camera, with the aid of which different sections of the cable harness (2) can be identified, wherein the control unit (26) and / or the testing unit (28) are designed such that the value of at least one test parameter selected from contact force (F) and test voltage (V) is set as a function of the section (8, 38, 40) identified by the recognition unit (32).

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