Current measuring device and related operating method

Abstract

The invention relates to a current measuring device for measuring a current (I), comprising a current measuring resistor (2), the current (I) to be measured flowing through the current measuring resistor (2), and the current measuring resistor (2) exhibiting an aging-dependent drift in its resistance value (R), the aging-dependent drift depends on a temperature-time curve (TP) of the current measuring resistor (2) during the operating time (t). The current measuring device further comprises a voltage measuring device (3), wherein the voltage measuring device (3) is used for measuring the voltage (U) dropped at the two ends of the current measuring resistor (2); and an evaluation unit (6) which is connected on the input side to the voltage measuring device (3) and which calculates the current (I) flowing through the current measuring resistor (2) according to the Ohm's law as a function of the measured voltage (U) and a resistance value (R) of the current measuring resistor (2). The invention is characterized in that the evaluation unit (6) at least partially compensates for an aging-dependent drift of the resistance value (R) of the current measuring resistor (2) during the calculation of the current (I) according to the Ohm's law. The invention also comprises a corresponding operating method for such a current measuring device.

Description

Technical Field

[0001] This invention relates to a current measuring device for measuring current using a four-wire technique. Furthermore, this invention relates to a method of operating such a current measuring device. Background Technology

[0002] For measuring current, it is known from existing technology (e.g., EP 0605800 A1) to use a low-resistance current-measuring resistor, thereby performing current measurement using a four-wire technique. The current to be measured is conducted through the low-resistance current-measuring resistor, thereby measuring the voltage across the current-measuring resistor. Then, based on Ohm's law, the current flowing through the current-measuring resistor can be calculated using the voltage drop across the current-measuring resistor and the known resistance value of the current-measuring resistor.

[0003] The problem with this well-known type of current measurement is that measurement errors can occur during long-term operation of the current measuring resistor.

[0004] For the general technical background of the present invention, reference is also made to US 2011 / 0298473 A1 and KR 1020190075812A. Summary of the Invention

[0005] Therefore, the present invention is based on the task of creating an improved current measuring device that does not exhibit such measurement errors even during long operating periods.

[0006] This task is accomplished by the current measuring device according to the invention or by the associated operating method according to the independent claim.

[0007] This invention is based on the concept that inaccurate current measurements occurring over long operating periods are due to the aging-related drift in the resistance value of the current-measuring resistor. This means that the resistance value of the current-measuring resistor is not constant over time, but rather changes gradually with operating time. Ignoring this aging-related gradual change in the resistance value of the current-measuring resistor leads to measurement errors when calculating the current based on the voltage drop across the resistor and its resistance value.

[0008] Therefore, the present invention is configured to at least partially compensate for aging-related drift in the resistance value of the current measuring resistor in order to avoid aging-related measurement errors.

[0009] The current measuring device according to the invention initially has a low-resistance current measuring resistor according to the known current measuring device described at the beginning, wherein the current to be measured is conducted through the current measuring resistor, which is also the case for conventional current measurement according to the four-wire technique.

[0010] Additionally, the current measuring device according to the invention further includes a voltage measuring device according to a known current measuring device described at the beginning, which is used to measure the voltage drop across the current measuring resistor.

[0011] Furthermore, according to the known current measuring device described at the beginning, the current measuring device according to the invention also has an evaluation unit connected to the voltage measuring device on the input side, which calculates the current flowing through the current measuring resistor based on Ohm's law, according to the measured voltage and the specified resistance value of the current measuring resistor.

[0012] The present invention is further provided that, when the evaluation unit calculates the current according to Ohm's law, it at least partially compensates for the aging-related drift of the resistance value of the current measuring resistor.

[0013] When compensating for aging-related drift in the resistance value of a current-measuring resistor, it can be assumed that this drift is significantly affected by the temperature-time profile of the current-measuring resistor during its operating life. For example, if the current-measuring device according to the invention is not used for a long period of time, the temperature-time profile during this period will not show any temperature peaks, resulting in only a slight aging-related drift in the resistance value of the current-measuring resistor. On the other hand, if the current-measuring device is continuously used to measure high currents, the temperature-time profile of the current-measuring resistor will show strong temperature peaks, resulting in a correspondingly strong aging-related drift in the resistance value of the current-measuring resistor. Therefore, the current-measuring device according to the invention preferably includes a timer for measuring the used operating time of the current-measuring resistor, since the used operating time of the current-measuring resistor is an important factor affecting the aging-related drift in the resistance value.

[0014] In a variation of the invention, the temperature-time profile of the current-measuring resistor is specified as an estimate without actual measurement. When estimating the temperature-time profile, the manufacturer may, for example, consider the corresponding application profile of the current-measuring device. For instance, using the current-measuring device according to the invention for current measurement in an in-vehicle network of a motor vehicle typically results in a specific temperature-time profile over a period of operation, wherein there is acceptable fluctuation between the estimated temperature-time profile and the actual temperature-time profile. An evaluation unit is then connected to a timer, and the evaluation unit compensates for aging-related drift in the resistance value of the current-measuring resistor based on the estimated temperature-time profile over the used operating time and previous operating times, without measuring the actual temperature-time profile of the current-measuring resistor over the operating time. For this purpose, the evaluation unit receives the resistance value of the current-measuring resistor as a default value, for example, at room temperature and immediately after delivery, i.e., without any aging-related resistance value drift. Then, the evaluation unit can calculate the aging-related change in the resistance value of the current measuring resistor based on the initial resistance value and the used running time, taking into account the estimated temperature-time curve, and use the corrected resistance value as the basis for calculating the current flowing through the current measuring resistor according to Ohm's law.

[0015] In another variation of the invention, the actual temperature of the current measuring resistor is measured using a temperature measuring device.

[0016] Here, the current measuring device preferably also includes a timer for measuring the used operating time of the current measuring resistor, because, in addition to the temperature-time profile, the used operating time of the current measuring resistor is also an important factor affecting the aging-related drift of the resistance value of the current measuring resistor. In this variant of the invention, the evaluation unit is connected to both the temperature measuring device and the timer, and then continuously determines the actual temperature-time profile of the current measuring resistor during its operating time. Therefore, the temperature-time profile of the current measuring resistor is not a simple estimate, but an actual measurement, which allows for more accurate compensation for the aging-related drift of the resistance value. The evaluation unit can then compensate for the aging-related drift of the resistance value of the current measuring resistor based on the measured temperature-time profile and the used operating time. To this end, the evaluation unit calculates a correction resistance value based on the measured temperature-time profile and the used operating time, which also takes into account the aging-related drift of the resistance value of the current measuring resistor. This correction of the resistance value can be based on an aging model determined by the manufacturer based on actual measurements. For example, an aging test can be performed on the current-measuring resistor at the manufacturer's location, in which the current-measuring resistor is exposed to a specific temperature-time profile, thereby measuring the aging-related drift of the current-measuring resistor's resistance value in each case. In this way, an aging model can be stored in the evaluation unit, which can take into account the resistive material, the connection to the resistive material, the location of the current-measuring resistor, and its respective temperature-time profile.

[0017] The aging drift of the current-measuring resistor in a current-measuring device over its operating life can be determined by performing environmental simulation tests on the current-measuring resistor. Environmental simulation tests (such as high-temperature aging or temperature cycling tests) are based on accelerated temperature and / or load profiles, which are calculated using the Arrhenius model or the Coffin-Manson model. The determined aging drift / operating life profile is stored in the current-measuring device for correcting the aging drift of the current-measuring resistor and for use in correction calculations.

[0018] The above only concerns measurement errors caused by aging-related drift in the resistance value of the current-measuring resistor. However, the resistance value of the current-measuring resistor also exhibits a temperature-dependent drift corresponding to the actual temperature of the current-measuring resistor. When selecting the resistive material of the current-measuring resistor, care should be taken to ensure that the resistance value exhibits the smallest possible temperature dependence. However, this undesirable temperature dependence cannot be completely avoided. Therefore, in a preferred embodiment of the invention, when calculating the current according to Ohm's law, the evaluation unit also compensates for the temperature-dependent drift of the resistance value of the current-measuring resistor corresponding to the currently measured temperature. The evaluation unit is able to do this because it measures the actual temperature of the current-measuring resistor using a temperature measuring device and knows the temperature coefficient of the resistance value of the current-measuring resistor, or in general, the temperature dependence of the resistance value of the current-measuring resistor.

[0019] Regarding the aging-related drift of the resistance value of a current-measuring resistor, it was mentioned above that an estimate of the temperature-time curve can be specified, and then the aging-related drift of the resistance value of the current-measuring resistor can be compensated based on this estimate. However, within the scope of this invention, another possibility exists: specifying a current load curve that reflects the time progression of the current flowing through the current-measuring resistor during a previous operating period. Depending on the application, specifying such a current load curve is easier than specifying a temperature-time curve. Nevertheless, specifying a current load curve is also suitable for determining and compensating for the aging-related drift of the resistance value of the current-measuring resistor, since the temperature of the current-measuring resistor depends significantly on the current flowing through it. The evaluation unit can then compensate for the aging-related drift of the resistance value based on the operating time and the specified current load curve. The current load curve can again be used as an estimate or specified as an actual measured value.

[0020] Generally, it should be noted that the current measuring resistor is preferably low in resistance, in particular having a resistance value not exceeding 100 mΩ, 25 mΩ, 10 mΩ, 5 mΩ, 2 mΩ, 1 mΩ, 500 µΩ or 250 µΩ.

[0021] In a preferred embodiment of the invention, the current measuring resistor is connected to two connectors made of a conductive material, wherein the connectors and the current measuring resistor are preferably plate-shaped, as is known according to the prior art cited at the beginning (see EP0605800A1).

[0022] The connector of the current measuring resistor is preferably made of a conductive material, such as copper, copper alloy, aluminum, or aluminum alloy.

[0023] On the other hand, the current measuring resistor is preferably made of a resistive material having a specific electrical conductivity lower than that of the conductor material of the connector.

[0024] For example, the resistive material of a current measuring resistor can be one of the following alloys: The copper alloy, particularly, is a copper-manganese-tin alloy, a copper-manganese-nickel alloy, or a copper-chromium alloy; particularly, the copper-manganese-tin alloy is CuMn12Ni2 or CuMn7Sn2.3; particularly, the copper-manganese-nickel alloy is Cu84Ni4Mn12 or Cu65Mn25Ni10. Nickel alloy, specifically, the nickel alloy is NiCr or CuNi.

[0025] Furthermore, it should be generally mentioned that the current measuring resistor is preferably connected to the two connectors in an electrical and mechanical manner, and in particular, the current measuring resistor is connected to the two connectors by means of welding (e.g., electron beam welding).

[0026] Regarding conductivity, it should be noted that the resistive material of the current measuring resistor preferably has a specific electrical resistance (resistivity) of less than 2.10. -4 Ω·m, 2·10 -5 Ω·m or 2·10 -6 Ω·m, and / or greater than 2.10 -6 Ω·m, 2·10 -7 Ω·m, while the conductor material of the connector has a resistivity of less than 10 Ω·m. -6 Ω·m or 10 -7 Ω·m.

[0027] The current measuring device according to the invention described above is independent of the corresponding application. However, the invention also claims protection for a system (e.g., the electrical system of a motor vehicle) having such a current measuring device and an electrical network (e.g., the electrical system of a motor vehicle), wherein the current measured by the current measuring device flows in the network. However, the invention is not limited to current measurement in vehicle electrical systems in terms of its application field, but can also be used in stationary systems.

[0028] It should also be mentioned that the current measuring device preferably has a control unit that can selectively set the active mode of the current measuring device or the passive mode (standby mode) of the system.

[0029] In the system's active mode, the electrical network is activated, and the current-measuring resistor measures the current flowing during operation, thereby also allowing for the measurement of the temperature-time curve of the current-measuring resistor.

[0030] However, in passive mode, the electrical network is shut off, resulting in no current supply to the current-measuring resistor. In passive mode, it is preferable that the current-measuring device periodically "wakes up" and then performs temperature measurements, allowing the temperature-time profile of the current-measuring resistor to be determined even in passive mode. In passive mode, temperature and / or voltage measurements are preferably performed at much longer intervals than in active mode; that is, the frequency of voltage and / or temperature measurements is much lower in passive mode than in active mode. The evaluation unit can then determine the temperature-time profile of the current-measuring resistor based on the temperature values ​​measured in active and / or passive modes, in order to determine the aging-related drift of the resistance value of the current-measuring resistor based on the thus determined temperature-time profile.

[0031] In addition to the current measuring device according to the present invention and the system having such a current measuring device according to the present invention, the present invention also claims a corresponding operating method, wherein the various steps of the operating method according to the present invention have become apparent from the above description, and therefore there is no need to describe the method steps separately.

[0032] Other advantageous improvements of the invention are pointed out in the dependent claims, or described in more detail below with reference to the accompanying drawings. Attached Figure Description

[0033] Figure 1 A schematic diagram of a current measuring device according to the present invention is shown, which compensates for the aging and temperature-related drift of the resistance value of the current measuring resistor.

[0034] Figure 2 A flowchart illustrating the operation method according to the present invention is shown.

[0035] Figure 3 It shows the Figure 2 The modifications.

[0036] Figure 4 A flowchart illustrating the operation of the current measuring device according to the present invention in active and passive modes is shown. Detailed Implementation

[0037] Figure 1A schematic diagram of a current measuring device according to the present invention for measuring current I using a well-known four-wire technique is shown. Here, the current I to be measured is conducted through a low-resistance current measuring resistor 2 via a current line 1, thereby measuring the voltage U across the current measuring resistor 2 via a voltage measuring device 3 through two voltage taps 4 and 5 on the current measuring resistor 2.

[0038] Furthermore, the current measuring device according to the present invention, in accordance with the prior art, also includes an evaluation unit 6, which calculates the current I flowing through the current measuring resistor 2 based on Ohm's law, the voltage U across the current measuring resistor 2, and the known resistance value R of the current measuring resistor 2. For this current calculation, the evaluation unit 6 has a module 7.

[0039] As explained above, the resistance value R of the current measuring resistor 2 is not constant over time during operation, but exhibits an aging-related drift. This drift depends on the used operating time t and the previous temperature-time curve TP experienced by the current measuring resistor 2 during the used operating time t. To compensate for this aging-related drift of the resistance value R of the current measuring resistor 2, the current measuring device according to the invention therefore firstly includes a timer 8, which is used to measure the operating time t of the current measuring resistor 2.

[0040] In addition, the current measuring device according to the present invention has a temperature measuring device 9, which measures the actual temperature T of the current measuring resistor 2 by means of a temperature sensor 10.

[0041] Evaluation unit 6 now has an additional module 11 connected on the input side to timer 8 and temperature measuring device 9, and the additional module 11 continuously determines the temperature-time curve TP experienced by current measuring resistor 2 during the operating time t, which has a significant impact on the aging-related drift of the resistance value R of current measuring resistor 2.

[0042] To compensate for this aging-related drift, the evaluation unit 6 has an additional module 12 that receives the measured temperature-time curve TP from module 11 on the input side, and also receives a specified resistance value R0 that reflects the resistance value of the current measuring resistor 2 without compensating for aging and temperature-related drift, such as the resistance value at room temperature at the time of delivery.

[0043] Then, module 12 calculates the aging-compensated resistance value R (TP) based on the stored aging model, which takes into account the aging-related drift of the resistance value R.

[0044] Furthermore, the current measuring device according to the present invention can also achieve temperature compensation for the resistance value R of the current measuring resistor 2. For this purpose, the current measuring device has an additional module 13 that receives the compensated aging resistance value R (TP) from module 12, additionally performs temperature compensation, and outputs the resistance value R (T, TP) to module 7 on the output side. This compensates for the aging-related drift and temperature-related drift of the resistance value R of the current measuring resistor 2, thereby minimizing measurement error.

[0045] The following description Figure 2 The flowchart shown, Figure 2 Explanation Figure 1 The operating mode of the current measuring device is shown.

[0046] In the first step S1, the resistance value R0 of the current measuring resistor 2 is first specified without considering aging effects and at a defined ambient temperature (e.g., room temperature).

[0047] In the next step S2, during the operation of the current measuring resistor 2, the operating time t of the current measuring resistor 2 is continuously measured using the timer 8.

[0048] In the next step S3, the temperature-time curve TP of the current measuring resistor 2 is then continuously measured during the operating time t.

[0049] In the subsequent step S4, the resistance value R(TP) that has changed due to aging is then calculated based on the actual measured temperature-time curve TP.

[0050] In the next step S5, the resistance value R(T,TP) is then compensated for to be temperature dependent based on the current measurement temperature T of the current measuring resistor 2.

[0051] In the next step S6, the voltage across the current measuring resistor 2 is measured, as is known in the prior art.

[0052] In the final step S7, the current I is calculated based on Ohm's law, taking into account the measured voltage U and the resistance value R(T, TP) after aging and temperature adjustment.

[0053] Figure 3 It shows the basis Figure 2 The flowchart has been modified, so please refer to the above description to avoid repetition.

[0054] A key feature of this implementation is that the temperature-time curve is not measured as a factor influencing the aging-related drift of the resistance value of the current-measuring resistor 2. Instead, an estimated current load curve SLP is specified for the lifespan of the current-measuring resistor 2, which is determined according to the application. The current load curve SLP then indirectly affects the aging-related drift of the resistance value R of the current-measuring resistor 2, since the current flowing through the current-measuring resistor 2 has a significant impact on its temperature T.

[0055] The following section describes Figure 4 The schematic flowchart shown is as follows. Figure 4 The active and passive modes of the current measuring device are explained.

[0056] In the first step S1, we first check whether there is normal operation, and then if necessary, we execute step S2.

[0057] In step S2, it is then checked whether the system (e.g., the on-board power supply system of a motor vehicle) is operating and therefore in active mode.

[0058] In active mode, according to step S3, the voltage across the current measuring resistor 2 and the temperature T of the current measuring resistor 2 are measured periodically. This measurement is performed at regular intervals t1.

[0059] In the next step S4, the temperature-time curve TP is then measured during the operating period.

[0060] In the next step S5, the current I is calculated taking into account the measured temperature-time curve TP, with aging and temperature compensations applied.

[0061] In the subsequent step S6, the compensated current I is then output.

[0062] On the other hand, if step S2 determines that the system (e.g., the electrical system of a motor vehicle) is shut down, then according to step S7, the current measuring device operates in passive mode (standby mode). In this standby mode, the current measuring resistor 2 is not actually supplied with current, and therefore no temperature T and / or voltage U is measured. However, in this sleep mode, the current measuring device periodically "wakes up" to measure the voltage U and temperature T at the current measuring resistor 2. This measurement is also performed at a timed interval t2, which is significantly longer than the time interval t1 for measurements performed in active mode. Therefore, in passive mode (sleep mode), the frequency of measurements is much lower than in active mode.

[0063] Optionally, step S8 can be performed from step S1, in which voltage U and current T are measured periodically.

[0064] In step S9, an inspection is then performed to determine whether lifetime dependence needs to be corrected.

[0065] If this is the case, then in step D10, external calibration parameters for the lifetime dependence of the current sensor can be received. For example, the aging model stored in the evaluation unit can be updated.

[0066] This invention is not limited to the preferred embodiments described above. Instead, it encompasses various variations and modifications that also utilize the inventive concept and are therefore within its scope of protection. In particular, this invention also claims protection independently of the claims cited in each case, and especially where the dependent claims lack the features of the principal or independent claims, the subject matter and features of the dependent claims.

[0067] Advantages of the present invention This invention can compensate for aging-related drift in the resistance value of a current measuring resistor, thereby minimizing measurement error.

[0068] In addition, the present invention can also compensate for the temperature-dependent drift of the resistance value of the current measuring resistor, which also minimizes measurement error.

[0069] Compensation for aging-related drift can be performed based on an aging model that has been empirically determined and can be stored in the evaluation unit.

[0070] In a preferred embodiment of the invention, both aging-related and temperature-related drift of the resistance value of the current measuring resistor are compensated for, thereby minimizing measurement error.

[0071] List of reference numerals 1. Current line through the current measuring resistor 2 Current measuring resistor 3. Voltage measuring device for measuring the voltage across a current measuring resistor. 4. Voltage taps on current measuring resistors 5 and 4 6 assessment units The evaluation unit includes a module for calculating current based on Ohm's law. 8. A timer used to measure the running time of a current-measuring resistor. 9. Temperature measuring device for measuring the temperature of a current-measuring resistor. 10 Temperature Sensors Module 11 of the evaluation unit is used to calculate the temperature-time curve of the current-measuring resistor during operation. 12-unit Module for Aging Compensation Module for temperature compensation in the 13 evaluation units Temperature sensor on current measuring resistor I current R0 is the resistance value of the current-measuring resistor that is not compensated for aging and temperature-related drift. R(TP) compensates for the resistance value of the current-measuring resistor after aging-related drift. R(T,TP) is the resistance value of the current-measuring resistor compensated for aging and temperature changes. t Current measuring resistor's operating life T current measures the temperature of the resistor. Temperature-time curve of TP current measuring resistor during operation U is the voltage across a resistor.

Claims

1. A current measuring device for measuring current (I), the current measuring device comprising: a) Current measuring resistor (2), wherein, a1) The current to be measured (I) flows through the current measuring resistor (2), and a2) The current measuring resistor (2) exhibits an aging-related drift in its resistance value (R), which depends on the temperature-time curve (TP) of the current measuring resistor (2) during the operating time (t). b) A voltage measuring device (3), which is used to measure the voltage (U) that drops across the current measuring resistor (2), and c) Evaluation unit (6), which is connected to the voltage measuring device (3) on the input side, and which calculates the current (I) flowing through the current measuring resistor (2) according to Ohm's law, based on the measured voltage (U) and the resistance value (R) of the current measuring resistor (2). Its features are, d) When the evaluation unit (6) calculates the current (I) according to Ohm's law, it at least partially compensates for the aging-related drift of the resistance value (R) of the current measuring resistor (2).

2. The current measuring device according to claim 1, characterized in that, a) The current measuring device includes a timer (8) for measuring the elapsed running time (t) of the current measuring resistor (2). b) The temperature-time curve (TP) of the current-measuring resistor (2) can be used as an estimate without measurement, and c) The evaluation unit (6) is connected to the timer (8), and the evaluation unit (6) compensates for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the estimated temperature-time curve (TP) during the used running time (t) and the previous running time, without measuring the actual temperature-time curve (TP) of the current measuring resistor (2) during the running time (t).

3. The current measuring device according to claim 1, characterized in that, The current measuring device includes a temperature measuring device (9), which is used to measure the actual temperature (T) of the current measuring resistor (2).

4. The current measuring device according to claim 3, characterized in that, a) The current measuring device includes a timer (8) for measuring the elapsed running time (t) of the current measuring resistor (2). b) The evaluation unit (6) is connected to the temperature measuring device (9) and the timer (8), and the evaluation unit (6) determines the temperature-time curve (TP) of the current measuring resistor (2) during the running time (t), and c) The evaluation unit (6) compensates for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the temperature-time curve (TP) measured during the previous operating time.

5. The current measuring device according to any one of claims 3 to 4, characterized in that, a) The current measuring resistor (2) exhibits a temperature-dependent drift in its resistance value (R) corresponding to the actual temperature (T) of the current measuring resistor (2). b) When the evaluation unit (6) calculates the current (I) according to Ohm's law, it compensates for the temperature-dependent drift of the resistance value (R) of the current measuring resistor (2) based on the actual measured temperature (T).

6. The current measuring device according to any one of the preceding claims, characterized in that, a) The current measuring device includes a timer (8) for measuring the elapsed running time (t) of the current measuring resistor (2). b) The evaluation unit (6) is connected to the timer (8), and the evaluation unit (6) determines the actual current load curve during operation, wherein the current load curve reflects the time progression of the current (I) flowing through the current measuring resistor (2) during the previous operating time, and c) The evaluation unit (6) compensates for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the used operating time (t) and the measured current load curve (SLP) during the previous operating time of the current measuring resistor (2).

7. The current measuring device according to claim 1, characterized in that, a) The current measuring device includes a timer (8) for measuring the elapsed running time (t) of the current measuring resistor (2). b) The current load curve (SLP) can be used as an estimate without measurement, and c) The evaluation unit (6) is connected to the timer (8), and the evaluation unit (6) compensates for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the estimated current load curve (SLP) during the used running time (t) and the previous running time, without measuring the actual current load curve (SLP).

8. The current measuring device according to any one of the preceding claims, characterized in that, a) The current measuring resistor (2) is low-resistance, and in particular, the current measuring resistor (2) has a resistance value (R) of at most 100 mΩ, 25 mΩ, 10 mΩ, 5 mΩ, 2 mΩ, 1 mΩ, 500 µΩ or 250 µΩ, and / or b) The current-measuring resistor (2) is connected to two connectors made of conductive material, and / or c) The conductor material of the connector is copper, copper alloy, aluminum, or aluminum alloy, and / or d) The current measuring resistor (2) is made of a resistive material having a specific conductivity lower than that of the conductor material of the connector, and / or e) The resistive material of the current measuring resistor (2) is one of the following alloys: e1) Copper alloys, particularly copper-manganese-tin alloys, copper-manganese-nickel alloys, or copper-chromium alloys, particularly copper-manganese-tin alloys such as CuMn12Ni2 or CuMn7Sn2.3, and particularly copper-manganese-nickel alloys such as Cu84Ni4Mn12 or Cu65Mn25Ni10. e2) Nickel alloy, specifically, the nickel alloy is NiCr or CuNi, and / or f) The current measuring resistor (2) is electrically and mechanically connected to the two connectors, specifically, the current measuring resistor (2) is connected to the two connectors by welding, specifically, the current measuring resistor (2) is connected to the two connectors by electron beam welding, and / or g) The current measuring resistor (2) and / or the connector are plate-shaped, and / or h) The resistive material has a resistivity of less than 2.

10. -4 Ω·m, 2·10 -5 Ω·m or 2·10 -6 Ω·m, and / or i) The resistive material has a resistivity greater than 2.

10. -6 Ω·m, 2·10 -7 Ω·m, and / or j) The conductor material of the connector has a resistivity of less than 10. -6 Ω·m or 10 -7 Ω·m.

9. A system, particularly, an on-board electrical system for a motor vehicle, the system comprising: a) A current measuring device according to any one of the preceding claims, and b) An electrical network, specifically, the electrical network being the vehicle's onboard network, wherein, The current (I) measured by the current measuring device flows in the network.

10. The system according to claim 9, characterized in that, a) The current measuring device includes a control unit, which selectively sets the system to either an active mode or a passive mode. b) In the active mode, the electrical network is turned on and supplies current to the current measuring resistor (2), and c) In the passive mode, the electrical network is turned off and no current is supplied to the current measuring resistor (2).

11. The system according to claim 10, characterized in that, a) In the active mode, the current measuring device periodically measures the following variables at a first time interval: a1) The voltage (U) across the current measuring resistor (2), and / or a2) The temperature (T) of the current measuring resistor (2). b) In the passive mode, the current measuring device periodically measures the following variables at a second time interval: b1) The voltage (U) across the current measuring resistor (2), and / or b2) The temperature (T) of the current measuring resistor (2), and c) Preferably, in the passive mode, a separate voltage source is provided for powering the current measuring device and / or the evaluation unit (6). d) The second time interval is preferably significantly longer than the first time interval; in particular, the second time interval is at least 10 times, 100 times, 1000 times, or 10000 times longer than the first time interval. e) Preferably, the evaluation unit (6) determines the temperature-time curve (TP) of the current measuring resistor (2) based on the temperature (T) value measured in the active mode and / or the passive mode.

12. A method of operating a current measuring device according to any one of claims 1 to 7 or a system according to any one of claims 9 to 11, the method of operating comprising the following steps: a) Pass the current to be measured (I) through the current measuring resistor (2). b) When the current to be measured (I) flows through the current measuring resistor (2), the voltage (U) across the current measuring resistor (2) is measured, and c) Based on Ohm's law, the current (I) flowing through the current measuring resistor (2) is calculated using the voltage (U) across the current measuring resistor (2) and the resistance (R) of the current measuring resistor (2). Its features The following steps: d) When calculating the current (I) flowing through the current measuring resistor (2), the aging-related drift of the resistance value (R) of the current measuring resistor (2) is compensated.

13. The operating method according to claim 12, characterized in that, In order to compensate for the aging-related drift of the resistance value (R) of the current measuring resistor (2) when calculating the current (I) flowing through the current measuring resistor (2), the following steps are performed: a) Specify the estimated temperature-time curve (TP) of the current-measuring resistor (2) over the operating time (t) without temperature measurement. b) The used running time (t) of the current measuring resistor (2) is measured, and c) Compensate for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the used operating time (t) of the current measuring resistor (2) and the estimated temperature-time curve (TP) of the current measuring resistor (2).

14. The operating method according to claim 12, characterized in that, In order to compensate for the aging-related drift of the resistance value (R) of the current measuring resistor (2) when calculating the current (I) flowing through the current measuring resistor (2), the following steps are performed: a) The running time (t) of the current measuring resistor (2) is measured. b) The temperature (T) of the current measuring resistor (2) during the operating time (t) is measured. c) Based on the measured operating time (t) and the measured temperature (T) of the current measuring resistor (2), calculate the actual temperature-time curve (TP) of the current measuring resistor (2) during the operating time (t), and d) Compensate for the aging-related drift of the resistance value (R) of the current measuring resistor (2) based on the used operating time (t) of the current measuring resistor (2) and the temperature-time curve (TP) of the current measuring resistor (2) measured during the used operating time of the current measuring resistor (2).

15. The method of operation according to any one of claims 12 to 14, characterized in that, a) The current measuring resistor (2) exhibits a temperature-dependent drift in its resistance value (R) corresponding to the actual temperature (T) of the current measuring resistor (2). b) Measure the actual temperature (T) of the current measuring resistor (2), and c) Compensate for the temperature-dependent drift of the resistance value (R) of the current measuring resistor (2) based on the currently measured temperature (T).

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