Measuring device for carrying out an electrical measurement on an electric vehicle

Abstract

In order to be able to carry out electrical measurements on electric vehicles (20), in particular in the surroundings of a workshop, in a simplified and process-reliable manner using a measuring device (1), according to the invention the measuring device (1) comprises a portable measuring probe (3) with a measuring tip (5) and a measuring cable (4) that connects the measuring plug (2) and the measuring probe (3), the measuring plug (2) comprising charging plug contacts (6), and the charging plug contacts (6) and the measuring tip (5) being connected to a measuring unit (7) in the measuring device (1), and the measuring unit (7) being configured to carry out an electrical measurement on the electric vehicle (20).

Description

[0001] Measuring device for performing an electrical measurement on an electric vehicle

[0002] The present invention relates to a measuring device for performing an electrical measurement on an electric vehicle, wherein the measuring device comprises a measuring plug for connecting to a charging socket of the electric vehicle. The invention also relates to a method for performing an electrical measurement with the measuring device.

[0003] For the purposes of this application, electric vehicles are defined as vehicles that operate with alternating currents (AC) above 30 V up to 1 kV or with direct currents (DC) above 60 V up to 1.5 kV. This includes vehicles with electric drive such as electric cars, hybrid vehicles, vehicles with fuel cells or batteries.

[0004] Due to the high voltages (typically 400V or 800V DC), electric vehicles present an additional challenge, particularly the risk of electric shock. To minimize this risk, electric vehicles are equipped with appropriate safety mechanisms. These include, for example, the insulation monitor and the equipotential bonding system, which connects all high-voltage components with low electrical resistance. In new vehicles, these safety mechanisms are generally assumed to be fully functional. However, all vehicles are subject to environmental influences, wear and tear, or damage over their lifespan. These factors usually have a negative impact on the safety mechanisms.

[0005] Therefore, as part of regular vehicle inspections in workshops, a number of electrical measurements on the electrical system of the electric vehicle are useful for electric vehicles, for example a measurement of the insulation resistance or potential equalization.

[0006] To protect people from the risk of electric shock, the electrical measurement of easily accessible components of the high-voltage system is particularly important. This includes, in particular, the vehicle's AC and / or DC charging socket, the housings of accessible high-voltage (HV) components, and / or the charging cable. To perform measurements on an electric vehicle's charging socket or cable, adapters are used that are plugged into the socket or cable and then allow the necessary measurements via touch-safe test points, such as standardized laboratory sockets. However, these measurements require a separate electrical measuring device, which must be connected to the test points using probes. This necessitates two separate devices for the measurement and increases the effort required due to the need to connect the probes.Furthermore, this arrangement presents an increased potential for error, as incorrectly connecting the test probes of the electrical measuring device to the adapter's test ports can lead to inaccurate measurements. Especially in workshop settings, however, an easy-to-use and reliable measuring device is crucial.

[0007] This creates a need for a measuring device that simplifies and reliably performs electrical measurements on electric vehicles, especially in the vicinity of a workshop.

[0008] This task is solved by a measuring device comprising a portable probe with a measuring tip and a measuring cable connecting the probe and the measuring plug. The measuring plug includes charging plug contacts, and these contacts and the probe are connected to a measuring unit within the device. This measuring unit is configured to perform electrical measurements and record electrical quantities on the electric vehicle. This enables a measurement to be performed by simply plugging the measuring plug into the charging socket of an electric vehicle.

[0009] According to the invention, the measuring connector and all measuring technology, including the measuring probe, are integrated into a single measuring device. This eliminates the need for a separate measuring device and the need to connect a separate measuring device to measuring contacts. Measurements on electric vehicles, particularly in a workshop environment, can thus be simplified and performed reliably.

[0010] Advantageously, the measuring unit is designed to perform electrical measurements either by connecting the measuring probe to one of the charging plug contacts or by connecting two charging plug contacts together. Furthermore, the measuring unit is configured to record the result of the electrical measurement obtained from the connection of the measuring probe to the connected charging plug contact or the connection between the two connected charging plug contacts. By inserting the measuring plug into a charging socket of an electric vehicle, the charging plug contacts are connected to the charging socket contacts, thus enabling a simple electrical measurement to be performed with the measuring device, for which the measuring probe can also be used if necessary.Advantageously, the measuring unit detects an electrical quantity, such as an electric current or voltage, between the measuring tip and the connected charging plug contact, or between the two connected charging plug contacts. Particularly advantageously, the measuring unit determines an electrical resistance between the measuring tip and the connected charging plug contact, or between the two connected charging plug contacts. This enables, in particular, important insulation resistance or equipotential bonding measurements.

[0011] The measuring device also enables the testing of an electric vehicle's immobilizer by connecting two charging plug contacts via a defined resistance for a predetermined time, and displaying the resistance as a result of the measurement on the display unit.

[0012] The present invention is explained in more detail below with reference to Figures 1 to 3, which show exemplary, schematic, and non-limiting advantageous embodiments of the invention.

[0013] Fig. 1 shows an embodiment of a measuring device according to the invention, Fig. 2 shows a block diagram of a measuring device according to the invention, and Fig. 3 shows the use of the measuring device according to the invention for checking a charging cable.

[0014] Fig. 1 shows a measuring device 1 according to the invention for carrying out an electrical measurement on an electric vehicle 20 (only indicated because it is well known). The measuring device 1 comprises a measuring plug 2, which can be inserted into a charging socket 21 of the electric vehicle 20 to carry out the electrical measurement. The measuring device 1 further comprises a portable measuring probe 3 with a measuring tip 5. The measuring probe 3 is particularly easy to carry by hand for a person carrying out the electrical measurement. The measuring plug 2 and the measuring probe 3 are connected to each other via a measuring cable 4. The measuring cable 4 contains all the necessary electrical conductors (which depend on the implementation of the measuring device 1) between the measuring plug 2 and the measuring probe 3. The measuring tip 5 enables the electrical contact of a component for carrying out an electrical measurement and is therefore electrically conductive, at least in the area of ​​the free end of the measuring tip 5.

[0015] There are a number of different charging ports on electric vehicles. Common in Europe are, for example, the Type 2 charging port according to IEC 62196 for charging with AC voltage, or the Combined Charging System (CCS) charging port according to IEC 62196 for charging with AC voltage (with a Type 2 port) or DC voltage. There are also Type 1 charging ports for charging with single-phase AC voltage according to IEC 62196, which are widespread in Asia. The CHAdeMO charging port according to IEC 62196 is also known. Furthermore, proprietary charging ports are also used, such as the Tesla Supercharger charging port.

[0016] A charging socket 21 comprises a plurality of charging socket contacts 22, depending on the design of the charging socket 21. For example, a Type 2 charging socket for charging with an AC voltage comprises, in a known and standardized manner, three AC charging voltage contacts L1, L2, L3, a neutral conductor contact N, an earth contact PE, and two control contacts PP, CP. For charging with a DC voltage, a Type 2 charging socket is, for example, equipped with two DC charging voltage contacts DC+, DC-, an earth contact PE, and two control contacts PP, CP.

[0017] The measuring plug 2 can be configured for any charging socket 21 and accordingly has corresponding charging plug contacts 6 that are complementary to the charging socket contacts 22. By inserting the measuring plug 2 into the charging socket 21, one charging plug contact 6 and one charging socket contact 22 are electrically connected.

[0018] The measuring plug 2 can be of any type, for example, a Type 2 charging plug. To enable the use of the measuring plug 2 with other charging sockets 21, corresponding measuring plug adapters 15 (indicated in Fig. 2) can be used, which convert the charging plug type of the measuring plug 2 to another charging plug type, for example, from a Type 2 charging plug to a Type 1 charging plug. The measuring plug adapter 15 is thus positioned between the charging socket 21 and the measuring plug 2.

[0019] The charging plug contacts 6 of the measuring plug 2 are connected to a measuring unit 7 provided in the measuring device 1. For this purpose, corresponding connecting leads 8 are provided in the measuring plug 2, with each connecting lead 8 connecting one of the charging plug contacts 6 to the measuring unit 7. Likewise, the measuring tip 5 of the measuring probe 3 is connected to the measuring unit 7, preferably via at least one connecting lead 8. A connecting lead 8 can also be routed within the measuring cable 4 if required. The measuring unit 7 is configured to perform an electrical measurement on the electric vehicle 20. The measurement is carried out via the charging plug contacts 6 and / or via the measuring tip 5. For measurement via the charging plug contacts 6, these are connected to the charging socket contacts 22 of the electric vehicle 20 by inserting the measuring plug 2 into the charging socket 21.For measurement via the measuring tip 5, the measuring tip 5 is held against an electrically conductive component of the electric vehicle 20, so that the measuring tip 5 makes electrical contact with the electrically conductive component of the electric vehicle 20.

[0020] For measurement purposes, the measuring unit 7 can detect at least one electrical quantity on the electric vehicle 20 via the charging plug contacts 6 and / or via the measuring probe 5, for example, an electrical voltage, an electrical current, or an electrical resistance. The electrical quantity can be the result of the measurement or can be used to determine the result of the measurement.

[0021] The measuring unit 7 can be arranged in the measuring plug 2 or in the measuring probe 3. A distributed arrangement of the measuring unit 7 in both the measuring plug 2 and the measuring probe 3 is also possible. Since the portable measuring probe 3 is preferably designed to be as small as possible because it is carried by one person, the measuring unit 7 is preferably arranged in the measuring plug 2, as shown in Fig. 1.

[0022] Fig. 1 shows a cutaway view of the housing 14 of the measuring connector 2. It can be seen that, in the embodiment of Fig. 1, a circuit board 9 is arranged in the housing 14 of the measuring connector 2, and the measuring unit 7 is arranged on the circuit board 9. However, the circuit board 9 is not a necessary feature of the measuring instrument 1.

[0023] The measuring unit 7 can include electrical circuits for performing the electrical measurement. The measuring instrument 1 can also include a control unit 10 for performing the electrical measurement, as shown in Fig. 2. The control unit 10 can be microprocessor-based hardware, such as a microcontroller or a microcomputer, on which measurement software runs to perform the electrical measurement. The control unit 10 serves, in particular, to control the measuring unit 7 and other components of the measuring instrument 1 for performing the electrical measurement, for example, controlled by the verification software.

[0024] The measuring device 1 can also include a communication module 18, for example a WLAN module, Bluetooth or LAN module, to connect the measuring device 1 to an external device 19 via a communication link, for example to transmit a measurement result to the external device 19 via a wireless or wired communication link. The communication module 18 can be integrated into the measuring connector 2, also into the measuring unit 7 or the control unit 10, or arranged in the measuring probe 3.

[0025] Figure 1 further shows that an electrical energy storage device 16 can be provided in the measuring instrument 1 to supply the measuring unit 7 with electrical energy for performing an electrical measurement. Alternatively, an external energy storage device or an external power supply could be provided, which is connected to the measuring instrument 1. The energy storage device 16 can be housed in the measuring connector 2 (as in the embodiment according to Figure 1) or in the measuring probe 3. Advantageously, electrical supply lines are also provided in the measuring cable 4 to supply the electrical energy to the measuring connector 2 or the measuring probe 3. Naturally, the necessary supply lines for the power supply of the respective electrical components are provided in the measuring connector 2 and in the measuring probe 3, for example on the circuit board 9 (not shown in Figure 1 for the sake of clarity).

[0026] In a preferred embodiment, the measuring probe 3 includes a display unit 11, which shows the result of an electrical measurement. This allows the user of the measuring device 1 to see the measurement result directly. The display unit 11 can also be located on the measuring connector 2, or on both the display unit 11 and the measuring connector 2. The display unit 11 provides any type of optical, acoustic, or haptic feedback to the user regarding the measurement result. For example, the display unit 11 could be a display such as an LCD display, an LED, an acoustic buzzer, or a haptic vibratory motor. This allows the user of the measuring device 1, who is performing the measurement, to see the result quickly and easily. Without the display unit 11, the measurement result can be displayed, for example, on an external device 19.

[0027] An input unit 12, such as buttons, switches, knobs, etc., may also be provided on the measuring probe 3 and / or the measuring connector 2. The input unit 12 can be used to switch the measuring instrument 1 on and off or to select and start a specific measurement.

[0028] Similarly, an output unit 13, for example a signal lamp, can be provided on the measuring probe 3 and / or on the measuring connector 2. An output unit 13 can be used to indicate the status of the measuring instrument 1, for example, whether it is switched on or whether a measurement is currently being performed.

[0029] The input unit 12 and / or the output unit 13 is preferably connected to the control unit 10 (Fig.2).

[0030] To perform the electrical measurement, the measuring unit 7, for example controlled by a control unit 10, is preferably configured to selectively connect either the measuring tip 5 to one of the charging plug contacts 6 or to connect two charging plug contacts 6 together. The measuring unit 7 is advantageously further configured to record the result of the electrical measurement resulting from the connection of the measuring tip 5 to the connected charging plug contact 6 or the connection between the two connected charging plug contacts 6. The result of the measurement is, in particular, an electrical quantity, especially an electric current, an electric voltage, or an electric resistance, between the measuring tip 5 and the connected charging plug contact 6 or between the two connected charging plug contacts 6. The result of the measurement is then displayed to the user on the display unit 11 of the measuring probe 3.

[0031] The following describes examples of electrical measurements.

[0032] For a potential equalization measurement, the measuring plug 2 is inserted into the charging socket 21 of the electric vehicle 20. This connects the protective earth conductor PE (PE charging plug contact 6) of the measuring plug 2 to the reference potential of the electric vehicle 20 via the charging socket 21, or via the protective earth conductor of the charging socket 21 (PE charging socket contact 22). The reference potential of the electric vehicle 20 is usually fixed at the vehicle body, and all housings of the high-voltage components of the electric vehicle 20 must be connected to the reference potential with low resistance, as required, for example, in the ECE-R100 standard. The measuring unit 7 then connects the protective earth conductor PE of the measuring plug 2 to the measuring probe 5 and generates a predetermined electrical measuring current, preferably constant, for example, >200 mA.The measuring probe 5 is then held by the person performing the measurement against the housing of a high-voltage (HV) component of the electric vehicle 20, so that the probe 5 makes contact with the housing. The measuring unit 7 conducts the measuring current through the probe 5, allowing the electrical resistance between the probe 5 and the protective earth (PE) conductor of the measuring plug 2 to be determined. For example, the electrical voltage between the probe 5 and the protective earth (PE) conductor of the measuring plug 2 can be measured, and the resistance can be determined from the measuring current and the measured voltage. With correct equipotential bonding, the measured resistance is very small, in particular <0.10 Ω. With insufficient equipotential bonding, i.e., if the resistance between the housing and the protective earth (PE) conductor becomes too large, in particular >0.10 Ω, dangerous potential differences can occur in the electric vehicle.The measured resistance can be displayed as a result of the measurement on the display unit 11 of the measuring probe 3. This check can be repeated successively for each housing of each HV component of the electric vehicle 20 for a complete equipotential bonding test.

[0033] To measure the insulation resistance at the charging socket 21 of the electric vehicle 20, the measuring plug 2 is inserted into the charging socket 21 of the electric vehicle 20. Then, one of the charging plug contacts 6 (not the earth conductor PE) is connected to the earth conductor PE of the measuring plug 2 – thus connecting two charging plug contacts 6 together. The measuring unit 7 then measures the resistance between the charging plug contact 6 and the earth conductor PE of the measuring plug 2. This measures the insulation resistance between the charging plug contact 6 and the earth conductor PE, allowing the insulation resistance of the charging socket 2 to be determined. The insulation resistance should, of course, be very high, for example, in the MQ range.For this purpose, a predetermined electrical voltage, for example 250 VDC, can be applied between the charging plug contact 6 and the connected earth conductor PE of the measuring plug 2, and the electrical current flowing through a measuring resistor connecting the charging plug contact 6 and the earth conductor PE is measured. The resistance can then be determined from the voltage and the measured current. The determined (insulation) resistance can then be displayed as the result of the measurement on the display unit 11 of the measuring probe 3. The insulation resistance can be determined and displayed for a complete insulation resistance measurement between each charging plug contact 6 (other than the earth conductor PE) and the earth conductor PE, for example N -> PE, L1 -> PE, L2 -> PE, L3 -> PE, DC+ -> PE, DC- -> PE. In this way, a resistance between other charging plug contact pairs can of course also be determined as the result of the measurement.

[0034] Electrical resistance can be measured in various ways, including the well-known four-wire measurement. The measuring probe 5 is designed for performing a four-wire measurement.

[0035] A preliminary zero-level measurement can also be performed before carrying out the above measurements. For this purpose, the measuring probe 5 can be connected to the PE charging plug contact 6 of the measuring plug 2, for example by inserting the measuring probe 5 into the corresponding charging plug contact 6. The resistance between the measuring probe 5 and the PE charging plug contact 6 can then be determined (for example, as described above). This internal resistance, caused by the measuring device 1, can then be taken into account when measuring the resistance (insulation or equipotential bonding) to obtain a more accurate measurement result.

[0036] In a further measurement, the immobilizer of the electric vehicle 20 can be checked. If a charging plug is inserted into the charging socket 21 of the electric vehicle 20, then an immobilizer must be activated in the electric vehicle 20, which prevents the electric vehicle 20 from being moved as long as the charging plug is inserted. The charging process follows a standardized protocol and stipulates, among other things, that a defined resistor, for example 680 Ω, is connected on the external charger side between a control line PP, CP (usually PP) and the earth conductor PE of the charging plug to signal the presence of a charging cable to the electric vehicle 20. In this measurement, the measuring plug 2 is inserted into the charging socket 21 of the electric vehicle 20. Subsequently, the defined resistor R is switched between the control line PP and the earth conductor PE for a defined time by means of a switch S (Fig.2), whereby one charging plug contact 6 (control line PP) is connected to another charging plug contact 6 (ground conductor PE) (here via the resistor R). During the defined time, the electric vehicle 20 must not be able to move, which can be verified by the user wearing the measuring probe 3 and performing this check. As a result of the check, the applied resistance R and / or the elapsed time (timer) during which the resistance R is applied can be displayed on the display unit 11 of the measuring probe 3. This makes it possible to determine whether the electric vehicle 20 can be moved or not while the resistance R is applied, and possibly also during the elapsed time.

[0037] In addition, other measurements on the electric vehicle 20 are of course possible via the charging socket 21.

[0038] The selection of different measurements is made, for example, via the input units 12 on the measuring probe 3, such as selection buttons. The measurement can also be started via an input unit 13, such as a start button on the measuring probe 3.

[0039] However, the measuring device 1 can not only be used to perform measurements on the electric vehicle 20, but could also be used to check a charging cable 25, as shown in Fig. 3.

[0040] In a charging cable 25 of an electric vehicle 20, a control contact, usually the PP contact, is known to be connected to the PE contact via a defined resistance Rc on both ends of the charging cable 25 (for example, in the plugs of the charging cable 25). The value of the defined resistance determines the permissible current-carrying capacity of the charging cable 25, i.e., how much electrical current may be conducted through the charging cable 25 at most. The permissible current-carrying capacity is also specified for a charging cable 25. It can now be checked whether the specification of the charging cable 25 corresponds to the actual design of the charging cable 25. This can be done as follows.

[0041] The measuring plug 2 is connected to a first plug 27 of the charging cable 25 via a measuring adapter 26. In the measuring adapter 26, all plug contacts, except for the two control contacts PP and CP, are looped through. On the side of the measuring adapter 26 that is connected to the charging cable 25, the two control contacts PP and CP are connected to each other via a bridge, i.e., short-circuited via the bridge. Now, the measuring probe 5 is connected to a first control contact, for example, PP in Fig. 3, for example, by holding it against this contact. This closes a circuit via the defined resistance Rc on the side of the charging cable 25 facing away from the measuring adapter 26 and the PE charging plug contact in the measuring plug 2. In this circuit, the resistance corresponding to the defined resistance Rc can be measured with the measuring unit 7 of the measuring instrument 1. The measuring probe 5 is then connected to the other control contact, for example, CP in Fig.3 connected (indicated by a dashed line), for example, by holding the device against this contact. This closes a circuit via the bridge in the measuring adapter 26 through the defined resistance on the side of the charging cable 25 facing the measuring adapter 26 and the PE charging plug contact in the measuring plug 2. The resistance corresponding to the defined resistance can then be measured again in this circuit using the measuring unit 7 of the measuring device 1. The two control contacts PP, CP on the two sides of the measuring adapter 26 could, of course, also be connected differently to measure the resistance Rc with the measuring device 1. In this way, the defined resistances R. c 25 can be determined on both sides of the charging cable.

[0042] The plug contacts looped through in the measuring adapter 26 allow continuity or insulation tests to be performed on the electrical power contacts of the charging cable. The power contacts are all contacts, e.g., N, PE, L1, L2, L3, except for the control contacts, e.g., PP, CP. For the continuity test, the measuring probe 5 is connected successively to the corresponding contacts of the second plug 28 of the charging cable 25, for example, by holding it against the contacts, and the resistance between the measuring probe 5 and the respective charging plug contact 6 in the measuring plug 2 is measured (e.g., as described above). This allows a broken or damaged wire in the charging cable 25 to be detected. For an insulation test between the power contacts, the measuring unit 7 is used to measure the resistance between one power contact (e.g., L1) and another power contact (e.g., PE) of the measuring plug 2.Since the power contacts are electrically connected to the power contacts of the charging cable 25 via the measuring adapter 26, the insulation resistance of the power contacts can be measured. The insulation resistance can be determined and displayed for a complete insulation resistance measurement between each charging plug contact 6 (other than the earth conductor PE) and the earth conductor PE, for example, N -> PE, L1 -> PE, L2 -> PE, L3 -> PE, DC+ -> PE, DC- -> PE. In this way, a resistance between other charging plug contact pairs can also be determined as a result of the measurement on the charging cable 25.

Claims

Patent claims 1. Measuring device for performing an electrical measurement on an electric vehicle (20) wherein the measuring instrument (1) has a measuring plug (2) for plugging into a charging socket (21) of the electric vehicle (20) comprises, characterized in that the measuring device (1) comprises a portable measuring probe (3) with a measuring tip (5) and a measuring cable (4) which connects the measuring plug (2) and the measuring probe (3), wherein the measuring plug (2) comprises charging plug contacts (6) and the charging plug contacts (6) and the measuring tip (5) are connected to a measuring unit (7) in the measuring device (1), and that the measuring unit (7) is set up to carry out an electrical measurement on the electric vehicle (20).

2. Measuring device according to claim 1, characterized in that the measuring unit (7) is configured to either connect the measuring tip (5) to one of the charging plug contacts (6) or to connect two charging plug contacts (6) together for carrying out the electrical measurement, and that the measuring unit (7) is configured to detect a result of the electrical measurement resulting from the connection of the measuring tip (5) and the connected charging plug contact (6) or the connection between the two connected charging plug contacts (6).

3. Measuring instrument according to claim 1 or 2, characterized in that the measuring probe (3) and / or the measuring plug (2) comprises a display unit (11) and a result of the measurement can be displayed on the display unit (11).

4. Measuring device according to claim 2 or 3, characterized in that the measuring unit (7) is configured to detect an electrical measurement quantity as a result of the measurement between the measuring tip (5) and the connected charging plug contact (6) or between the two connected charging plug contacts (6).

5. Measuring device according to claim 4, characterized in that the measuring unit (7) is configured to determine, as a result of the measurement, an electrical resistance between the measuring tip (5) and the charging plug contact (6) connected thereto or between the two charging plug contacts (6) connected to each other.

6. Measuring device according to claim 2 or 3, characterized in that the measuring unit (7) is configured to connect two charging plug contacts (6) to each other via a defined resistance (R) for a predetermined time and to indicate the presence of the resistance (R) as a result of the measurement.

7. Method for carrying out an electrical measurement on an electric vehicle (20) using a measuring device (1), wherein the measuring device (1) has a measuring plug (2) for plugging in a charging socket (21) of the electric vehicle (20), characterized in that the measuring device (1) comprises a portable measuring probe (3) with a measuring tip (5) and a measuring cable (4) which connects the measuring plug (2) and the measuring probe (3), wherein the measuring plug (2) is inserted into a charging socket (21) of an electric vehicle (20) for carrying out the electrical measurement, and that with the measuring plug (2) inserted, an electrical measurement is carried out on the electric vehicle (20) with a measuring unit (7) of the measuring device (1) which is connected in the measuring device (1) to the charging plug contacts (6) and the measuring tip (5).

8. Method according to claim 7, characterized in that the measuring unit (7) for carrying out the electrical measurement either connects the measuring tip (5) to one of the charging plug contacts (6) or connects two charging plug contacts (6) together, and that the measuring unit (7) detects a result of the electrical measurement resulting from the connection of the measuring tip (5) and the connected charging plug contact (6) or the connection between the two connected charging plug contacts (6).

9. Method according to claim 7 or 8, characterized in that the result of the measurement is displayed on a display unit (11) of the measuring instrument (1).

10. Method according to claim 8 or 9, characterized in that the measuring unit (7) detects an electrical measurement quantity as a result of the measurement between the measuring tip (5) and the connected charging plug contact (6) or between the two connected charging plug contacts (6).

11. Method according to claim 10, characterized in that the measuring unit (7) determines as a result of the measurement an electrical resistance between the measuring tip (5) and the charging plug contact (6) connected thereto or between the two charging plug contacts (6) connected to each other.

12. Method according to claim 8 or 9, characterized in that the measuring unit (7) connects two charging plug contacts (6) via a defined resistance (R) for a predetermined time and the resistance is displayed on the display unit (11) as a result of the measurement.

Images