Current measuring arrangement, adjustment system, adjustment method and manufacturing method for a current measuring arrangement

Abstract

The invention relates to a current measuring arrangement (1) comprising a current measuring resistor (2) with two connection parts (4, 5) made of a conductor material and an intermediate resistance element (8) made of a resistance material, as well as a printed circuit board (3) which is electrically and mechanically connected to the current measuring resistor (2) and has two voltage taps (12, 13) for measuring the voltage drop across the current measuring resistor (2). The invention provides that one of the two voltage taps (12, 13) on the printed circuit board (3) has a plurality of separate conductor tracks (15) made of a conductor material, which branch off from the second contact surface (13) and are brought together at a junction point (16), such that the conductor tracks (15) form a parallel circuit. The invention further comprises a balancing system, a balancing method, and a manufacturing method for such a current measuring arrangement.

Description

Technical Field of the InventionThe invention relates first to a current measuring arrangement for measuring an electric current by means of a low-resistance current measuring resistor ("shunt"). The invention further relates to a balancing system for balancing the temperature coefficient (TK) of the resistance value of such a current measuring resistor. In addition, the invention also comprises a corresponding matching method. Finally, the invention also relates to a production method for a current measurement arrangement according to the invention having a low-resistance current measurement resistor.BACKGROUND OF THE INVENTIONIt is known from the prior art (e.g. EP 0 605 800 A1) to measure an electrical current by means of a low-resistance current measuring resistor according to the four-conductor technique. In this case, the electrical current to be measured is conducted through the low-impedance current measuring resistor, wherein the voltage drop across the low-impedance current measuring resistor is measured and, according to Ohmic Law, is a measure of the electrical current.It is also known from the prior art (e.g. DE 10 2009 031 408 A1) to arrange a printed circuit board on such a low-ohmic current measuring resistor, wherein the printed circuit board is electrically and mechanically connected to the low-ohmic current measuring resistor. In this case, measurement electronics (e.g. ASIC-Application-specific integrated circuit) are arranged on the printed circuit board in order to measure the voltage drop across the low-impedance current measurement resistor. For this purpose, the printed circuit board has two voltage taps which act on the two connection parts of the low-impedance current measuring resistor in order to measure the voltage drop across the resistance element of the low-impedance current measuring resistor.The problem with the above-described current measurement according to the four-conductor technique using a low-resistance current measuring resistor is the fact that the temperature coefficient (TK) of the resistance value of the low-resistance current measuring resistor is subject to component scattering, which leads to corresponding measurement errors.US 2007 / 0 177 318 A1 discloses a corresponding current measuring arrangement having a current measuring resistor and a printed circuit board, wherein the printed circuit board measures the voltage across the resistor element of the current measuring resistor via a plurality of spatially separated pairs of voltage taps and the individual voltage taps each start from a separate contact surface on the printed circuit board. Here, the measurement geometry is at most adapted by adjusting the evaluation of the various voltage measurement values.For the general technical background of the invention, reference is also made to DE 10 2016 010 012 B4.DESCRIPTION OF THE INVENTIONThe invention is therefore based on the object of solving the problem of component scattering of the temperature coefficient of the resistance value of the low-resistance current measuring resistor during the current measurement according to the four-conductor technique.This object is achieved by a current measuring arrangement according to the invention, a corresponding balancing system, a balancing method or a production method according to the independent claims.The current measuring arrangement according to the invention first has a low-resistance current measuring resistor ("shunt") in accordance with the known current measuring arrangement described at the beginning. The low-resistance current measuring resistor has two connection parts made of a conductor material (e.g. copper) for introducing the current to be measured into the current measuring resistor or for discharging the electrical current to be measured from the current measuring resistor. In addition, the current measuring resistor according to the invention has a resistor element made of a resistor material (e.g. Manganin®), wherein the resistor element is arranged between the two connection parts in the current flow direction, such that the electrical current to be measured flows through the resistor element during operation. Such a low-resistance current measuring resistor is known, for example, from EP 0 605 800 A1 and therefore does not need to be described in more detail.In addition, the current measuring arrangement according to the invention in accordance with the prior art described at the beginning (e.g. DE 10 2009 031 408 A1) also comprises a printed circuit board which is electrically and mechanically connected to the current measuring resistor and can carry, for example, measuring electronics in order to measure the voltage drop across the low-impedance current measuring resistor. For this purpose, the printed circuit board has two voltage taps each having a contact surface made of a conductor material (e.g. copper), in order to contact the two connection parts of the low-resistance current measuring resistor. The two contact surfaces for contacting the low-impedance current measuring resistor are preferably arranged on the underside of the printed circuit board facing the current measuring resistor and are connected to the upper side of the printed circuit board via vias.The current measuring arrangement according to the invention is now distinguished from the prior art in that at least one of the two voltage taps on the printed circuit board has a plurality of separate conductor tracks made of a conductor material, which branch off from the respective contact surface and are joined together at a joining point, so that the conductor tracks form a parallel circuit. The individual conductor tracks of these parallel circuits can each be separated individually, whereby the measurement geometry and the electrical resistance value of the parallel circuit change. In the current measuring arrangement according to the invention, the individual conductor tracks of the parallel circuit between the respective contact surface and the combining point can thus be separated individually in each case in order to enable adaptation. This adaptation can serve various purposes, which will be briefly described below.In one variant of the invention, the separation of the individual conductor tracks of the parallel circuit serves to set or balance the temperature coefficient of the resistance value of the current measuring resistor and thereby solve the problem of disturbing component scattering of the temperature coefficient of the resistance value of the current measuring resistor. For this purpose, as many conductor tracks of the parallel circuit can then be separated as is necessary in order to balance the temperature coefficient of the resistance value of the current measuring resistor to the desired value. By separating the individual conductor tracks of the parallel circuit, the measurement geometry and the resistance value of the parallel circuit change at the respective contact surface.In another variant of the invention, the separation of the individual conductor tracks serves, on the other hand, to adapt the circuit board provided for different types of current measuring resistors and designed as a universal circuit board to the respective type of current measuring resistor. Here too, use is made of the fact that the measurement geometry and also the resistance value of the parallel circuit at the respective contact surface change as a result of the separating of the conductor tracks of the parallel circuit, which enables adaptation to the respective type of current measurement resistor.In a preferred exemplary embodiment of the invention, the parallel conductor tracks run directly on the printed circuit board, namely preferably substantially parallel to the main current flow direction in the current measuring resistor and preferably also parallel to the longitudinal side edge of the current measuring resistor.Moreover, it has already been mentioned above that the contact surfaces for contacting the two connection parts of the current measuring resistor are preferably located on the underside of the printed circuit board facing the current measuring resistor, whereas the parallel and individually separable conductor tracks of the aforementioned parallel circuit are preferably located on the upper side of the printed circuit board facing away from the current measuring resistor. This is advantageous because the parallel conductor tracks are thus freely accessible on the upper side of the printed circuit board and can therefore be easily separated. The electrical connection between the respective contact surface on the underside of the printed circuit board and the parallel conductor tracks on the upper side of the printed circuit board can be effected by a through-connection in the printed circuit board, wherein such through-connections are known per se from the prior art and therefore do not need to be described in more detail.Furthermore, in the preferred exemplary embodiment of the invention, cuts ("current shadows") are preferably located in the two connection parts in order to influence the current density in the current measuring resistor. Incisions of this type are also referred to in the usual technical terminology as current shadows and are known, for example, from DE 10 2021 103 241 A1.The aforementioned notches ("current shadows") preferably start here from a longitudinal side edge of the current measuring resistor, namely preferably from the same longitudinal side edge of the current measuring resistor. It should also be mentioned here that the two incisions transverse to the longitudinal side edge can optionally have the same depth or a different depth.In a further development of the invention, the printed circuit board has not only two voltage taps in order to contact the two connection parts of the low-impedance current measuring resistor. Rather, the printed circuit board can have a total of four voltage taps in order to contact the connection parts of the current measuring resistor at four measurement points, which enables an optimization of the voltage measurement at the low-impedance current measuring resistor. Thus, the four voltage taps can be arranged in each case in two pairs on the two connection parts of the low-resistance current measuring resistor, with the result that the two voltage taps of a pair are in each case located next to one another with respect to the main current flow direction.In these further voltage taps, too, there is the possibility that in each case a plurality of separate conductor tracks are present, which form a parallel circuit and can in each case be individually separated in order to enable adaptation, as has already been described above.It should generally be mentioned that the conductor material of the connection parts of the low-resistance current measuring resistor or of the contact surfaces of the printed circuit board preferably has a smaller specific electrical resistance than the resistor material of the resistor element.For example, the conductor material can be copper, a copper alloy, aluminum or an aluminum alloy.It should also be mentioned in general that the connection parts and the resistance element, as well as the complete current measuring resistor, are preferably plate-shaped, as is also known from the prior art.The current measuring resistor is preferably low-ohmic and preferably has a very small resistance value, which is preferably less than 1 Ω, 500 m Ω, 250 m Ω, 100 m Ω, 50 m Ω, 20 m Ω, 10 m Ω, 5 m Ω, 2 mQ, 1 m Ω, 500 μ Ω, 250 μ Ω, 100 μ Ω or 50 μ Ω.Moreover, it is generally mentioned that the conductor material has a specific electrical resistance which is preferably less than 10 -6 Ω·m or 10 -7 Ω·m.In contrast, the resistance material of the resistance element preferably has an electrical resistivity that is less than 10 -4 Ω·m, 10 -5 Ω·m, or 10 -6 Ω·m.It has already been mentioned above that a resistor alloy can be used as the resistor material for the resistor element of the low-resistance current measuring resistor. For example, this can be a copper-manganese-nickel alloy, in particular CuMn12Ni or CuMnNi 25-10. Alternatively, there is the possibility of using a copper-nickel alloy, in particular CuNi44. In addition, there is alternatively also the possibility of using a nickel-chromium alloy, in particular NiCRbOAlSi, NiCr3020. However, the above examples of resistor alloys are merely exemplary and do not limit the scope of protection.It should also be mentioned that the resistance element can be connected to the connection parts in each case by a welded connection, in particular by an electron beam welding.Moreover, it should be noted that the printed circuit board may have an interface for outputting the measured voltage drop across the resistance element.Regarding the aforementioned parallel connection of separable conductive lines, it should be noted that the number of the parallel-connected and individually separable conductive lines may be larger than two, three, four, five, seven or ten to enable accurate adjustment of the temperature coefficient (TK).Furthermore, the printed circuit board can carry a measurement circuit which is connected to the voltage taps on the connection parts of the current measurement resistor in order to measure the voltage dropped across the current measurement resistor.It has already been mentioned above that the separation of the individual conductor tracks of the parallel circuit enables the temperature coefficient of the resistance value of the low-resistance current measuring resistor to be adjusted. For this purpose, preferably so many of the parallel-connected conductor tracks are separated that the temperature coefficient (TK) of the resistance value of the current measuring resistor is less than ±500 ppm / K, 250 ppm / K, ±100 ppm / K, ±50 ppm / K, ±25 ppm / K, ±10% / K or ±5 ppm / K.It should also be mentioned that the parallel-connected conductor tracks preferably all branch off from the second contact surface in the direction of the first contact surface, while the parallel-connected conductor tracks, starting from the second contact surface, preferably all run substantially parallel to that of the longitudinal side edge of the current measuring resistor.It has already been mentioned above that the separation of the individual conductor tracks of the parallel circuit enables the adjustment of the current measurement resistor. For this purpose, the individual conductor tracks are preferably separated from the outside to the inside, so that in practice usually only external conductor tracks are separated from the parallel-connected conductor tracks.Furthermore, within the scope of the invention, there is the possibility that a trimming cut is introduced into the resistor element of the current measuring resistor in order to set the resistance value of the current measuring resistor.In addition, a continuous bore can be arranged in the first connection part and / or in the second connection part for electrical and mechanical contacting, as is also known, for example, from EP 0 605 800.It is also to be mentioned in general that the conductor material in one of the two connection parts can be copper or a copper alloy, while the conductor material in the other connection part is aluminum or an aluminum alloy. The connection parts of the current measuring resistor can therefore consist of different conductor materials.The current measuring arrangement according to the invention has been described above. However, the invention also comprises a calibration system for calibrating the temperature coefficient of the resistance value of the current measuring resistor in such a current measuring arrangement. For this purpose, the balancing system according to the invention has a current source in order to supply the current measuring resistor with an electric current. In addition, the balancing system according to the invention has a temperature control device in order to be able to control the temperature of the current measuring resistor to a predefined temperature in each case. In addition, the balancing system according to the invention also has a voltage measuring device in order to measure the voltage drop across the resistance element of the current measuring resistor. Furthermore, the balancing system according to the invention has a separating device in order to be able to separate the parallel conductor tracks of the parallel circuit individually, which enables a balancing of the temperature coefficient. In addition, the balancing system according to the invention also comprises an evaluation device for determining the number of elevator-separating conductor tracks for balancing the temperature coefficient of the resistance value of the current measuring resistor as a function of the measured voltage drops at different temperatures. The balancing system according to the invention thus sets different temperatures of the current measuring resistor and measures the respective voltage drops, which then enables a calculation of the temperature coefficient. In each case, so many of the parallel conductor tracks are then separated that the temperature coefficient is matched.In addition, the invention also comprises a calibration method for calibrating the temperature coefficient of the resistance value of the current measuring resistor of the current measuring arrangement according to the invention. The calibration method according to the invention comprises the following steps:• Temperature-controlling the current-sensing resistor to a specific temperature,• supplying the current measuring resistor with an electric current,• measuring the voltage drop across the resistance element of the current sense resistor, and• separating at least one of the conductor tracks of the second voltage tap as a function of the electric current, the measured voltage drop and the temperature.In the preferred exemplary embodiment of the inventive balancing method, the following steps are provided:• Temperature control of the current measuring resistor to a predetermined first temperature, in particular to room temperature,• supplying the current measuring resistor with an electric current at the first temperature,• measuring a first voltage drop across the resistor element at the first temperature of the current sense resistor,• optionally calculating a first resistance value from the measured first voltage drop,• tempering the current measuring resistor to a predetermined second temperature,• supplying the current measuring resistor with an electric current at the second temperature,• measuring a second voltage drop across the resistor element at the second temperature of the current sense resistor,• optionally calculating a second resistance value from the measured second voltage drop.Furthermore, within the scope of the inventive matching method, there are two alternatives of refinements which are briefly described below.Thus, an alternative additionally provides the following steps:• calculating a number of conductor tracks of the second voltage tap to be separated for adjusting the temperature coefficient (TK) of the resistance value of the current measuring resistor as a function of the two temperatures and the measured voltage drops and the current, in particular such that the temperature coefficient (TK) of the resistance value of the current measuring resistor is less than ±500 ppm / K, ±250 ppm / K, ±100 ppm / K, ±50 ppm / K, ±25 ppm / K, ±10% ppm / K or 5 ppm / K, and• Separating the calculated number of conductor tracks of the second voltage tap.Another alternative of the calibration method according to the invention, however, provides in a development the following additional steps:• calculating the temperature coefficient of the resistance value as a function of the two temperatures, the voltage drops measured and the current,• checking whether the calculated temperature coefficient of the resistance value is within a predetermined acceptable range, and• separating at least one of the conductive paths if the calculated temperature coefficient is not within the predetermined acceptable range, and repeating the above steps until the calculated temperature coefficient is within the predetermined acceptable range.Furthermore, it should be mentioned in general that the separation of the parallel-connected conductor tracks in the current measuring arrangement according to the invention can be effected, for example, by milling, scribing, drilling, reading or lithography, to name just a few examples.Finally, the invention also claims protection for a novel manufacturing method for a current sensing arrangement using a universal printed circuit board suitable for many different types of current sensing resistors. The separation of the individual conductor tracks of the parallel circuit enables here an adaptation of the universal printed circuit board to the respective type of current measuring resistor. The production process according to the invention preferably comprises the following steps:• Provision of a current sensing resistor, wherein the current sensing resistor belongs to one of several different types of current sensing resistors,• Determination of the type of current measuring resistor,• Provision of a printed circuit board having a first voltage tap with a first contact surface made of a conductor material for voltage measurement at the current measurement resistor, in particular at the first connection part of the current measurement resistor, and a second voltage tap with a second contact surface made of a conductor material for voltage measurement at the current measurement resistor, in particular at the second connection part of the current measurement resistor, wherein the second voltage tap on the printed circuit board has a plurality of separate conductor tracks made of a conductor material, which branch off from the second contact surface and are joined together at a joining point, such that the conductor tracks form a parallel circuit, wherein the printed circuit board is a universal printed circuit board which is suitable for the different types of the current measurement resistors,• Determination of the number of parallel-connected conductor tracks of the printed circuit board to be separated in order to adapt the printed circuit board to the type of the current measuring resistor, in particular by reading out the number of parallel-connected conductor tracks to be separated from a database as a function of the type of the current measuring resistor, and• separating the determined number of parallel-connected conductor tracks of the printed circuit board in order to adapt the printed circuit board to the type of current measuring resistor.The number of parallel conductor tracks to be separated can be read out from a database, for example, depending on the type of current measuring resistor, wherein the number of conductor tracks to be separated is stored in the database for the different types of current measuring resistor.Other advantageous developments of the invention are characterized in the dependent claims or are explained in more detail below together with the description of the preferred exemplary embodiments of the invention on the basis of the figures.Brief Description of the DrawingsFIG. 1A shows a schematic plan view of a current measurement arrangement according to the invention with a low-resistance current measurement resistor and a printed circuit board. FIG. 1B shows a detailed view from FIG. 1A. FIG. 1C shows the detailed view from FIG. 1B, wherein some conductor tracks of the parallel circuit are separated in order to balance the temperature coefficient. FIG. 2 shows a diagram for illustrating the temperature coefficient as a function of the number of separated conductor tracks of the parallel circuit at the measurement point. FIG. 3 shows a modification of the first exemplary embodiment according to FIGS. 1A-1C with four contact areas for voltage measurement at the low-impedance current measuring resistor. FIG. 4 shows a flow chart for illustrating the inventive matching method. FIG. 5 shows a greatly simplified schematic illustration of a calibration system according to the invention. FIG. 6 is a flow chart illustrating the matching of a general purpose circuit board to a particular type of current sensing resistor. FIG. 7 shows a modification of the flow chart of FIG. 4. FIG. 8A is a perspective view of a modified current sensing arrangement. FIG. 8B shows a sectional view through the current measurement arrangement according to FIG. 8A. FIG. 9 shows a modification of FIG. 8B. FIG. 10 shows a further modification of the sectional view according to FIG. 8B.Detailed Description of the DrawingsIn the following, the exemplary embodiment of a current measurement arrangement 1 according to the invention shown in FIGS. 1A-1C will first be described.Thus, this exemplary embodiment initially comprises a low-resistance current measuring resistor 2 ("shunt") and a printed circuit board 3, wherein the printed circuit board 3 is electrically and mechanically connected to the current measuring resistor 2, as will be described in detail below.The current measuring resistor 2 itself is largely of conventional design and essentially comprises two plate-shaped connection parts 4, 5 made of a conductor material (e.g. copper) for introducing an electric current I to be measured into the current measuring resistor 2 or for discharging the electric current I to be measured from the current measuring resistor 2.The two connection parts 4, 5 are provided with bores 6, 7 for electrically contacting the two connection parts 4, 5, as is known per se from the prior art.In addition, the current measuring resistor 2 has a resistor element 8 which is arranged between the two connection parts 4, 5 and through which the electrical current I to be measured flows during a measurement. The resistance element 8 is electrically and mechanically connected to the two adjacent connection parts 4, 5 via two welded seams 9, 10.It should be mentioned here that the resistor element 8 consists of a low-resistance resistor alloy (e.g. Manganin®), which, however, has a greater specific electrical resistance than the conductor material (e.g. copper) of the connection parts 4, 5.It should also be mentioned that a trimming cut 11 is introduced laterally in the resistor element 8 in order to set the resistance value of the current measuring resistor 2, as is known per se from the prior art.The printed circuit board 3 has on its underside facing the current measuring resistor 2 two contact surfaces 12, 13 made of a conductor material (e.g. copper), wherein the contact surface 12 serves for voltage measurement on the connection part 4, while the other contact surface 13 serves for voltage measurement on the connection part 5. The two contact surfaces 12, 13 are connected by conductor tracks and vias to an interface 14 attached to the upper side of the printed circuit board 3.In this respect, the current measuring arrangement 1 according to the invention also corresponds to known current arrangements, as are known per se from the prior art (e.g. DE 10 2009 031 408 A1). However, the invention is characterized in that the contact surface 13 is connected via a plurality of parallel conductor tracks 15 to a merging point 16, which is then connected to the interface 14 in a conventional manner. The parallel conductor tracks 15 form a parallel circuit in this case and can each be individually separated in order to be able to balance the temperature coefficient (TK) of the resistance value of the current measuring resistor 2. Thus, FIG. 1B shows an initial state in which the conductor tracks 15 are all intact. FIG. 1C, on the other hand, shows a balanced state in which the outer conductor tracks 15 are separated, as a result of which the measurement geometry and the resistance value of the parallel circuit at the contact surface 13 change, which is an influence on the temperature coefficient TK, as can be seen from FIG. 2. During the calibration of the current measuring arrangement 1, as many of the conductor tracks 15 as is required are then separated in order to bring the temperature coefficient TK of the resistance value of the current measuring resistor 2 into an acceptable range. FIG. 2 thus shows the profile of the temperature coefficient TK as a function of the number of separated conductor tracks 15.Furthermore, the drawings also show two so-called current shadows 17, 18 in the connection parts 4, 5.FIG. 3 shows a modification of the exemplary embodiment according to FIGS. 1A-1C, so that reference is made to the above description to avoid repetitions, the same reference numerals being used for corresponding details.A special feature here consists in the fact that two additional contact surfaces 19, 20 are provided in addition to the contact surfaces 12, 13, so that a total of four voltages U 1 a, U 1 b, U 2 a, U 2 bcan be measured at the connection parts 4, 5. The parallel connection of a plurality of parallel conductor tracks described above is provided on all of these four contact surfaces 12, 13, 19, 20, which enables a compensation of the temperature coefficient.A further special feature of this exemplary embodiment is that not only the two current shadows 17, 18 are provided, but also two additional current shadows 21, 22 on the opposite side.The flow chart according to FIG. 4 is now described below, which serves to clarify the inventive matching method.In a first step S 1, the current measuring resistor is first temperature-controlled to a temperature T A=+20 ° C.In the next step S 2, the current measuring resistor is then energized with a measurement current I=I MESS.In the next step S 3, provision is then made for the voltage drop U A across the current measuring resistor to be measured, i.e. at the temperature T A=+20 ° C.In the next step S 4, it is then provided that the resistance value R A= U A / I MESS is calculated.Steps S 1-S 4 are then repeated in the following steps S 5-S 8, but B >+20° C. for a different temperature T.In the next step S 9, the number n of conductor tracks to be separated, which is required to balance the temperature coefficient of the resistance value of the current measuring resistor, is then calculated.In the next step S 10, the previously calculated number n of conductor tracks is then separated.FIG. 5 shows a greatly simplified schematic illustration of a balancing system according to the invention with the current measurement arrangement 1 described above. In addition, the balancing system has a current source 23 in order to be able to supply current to the current measurement resistor 2 during a balancing process.In addition, the balancing system has a temperature control device 24 in order to temperature control the current measuring resistor 2 during the balancing process, as has been described above.Furthermore, the balancing system according to the invention has a voltage measuring device 25 in order to be able to measure the voltage across the current measuring resistor 2.Furthermore, the balancing system according to the invention has an evaluation unit 26 which calculates the number of parallel conductor tracks to be separated which is required to balance the temperature coefficient of the resistance value of the current measuring resistor 2.A trimming device 27 then separates the required number of parallel conductor tracks on the upper side of the printed circuit board 3.FIG. 6 is a flow chart illustrating the matching of a general purpose circuit board to a particular type of current sensing resistor.In this case, in a first step S 1, a universal printed circuit board is provided which is basically suitable for different types of current measuring resistors.In the next step S 2, a current measuring resistor of a specific type is then provided.The next step S 3 then provides that the universal printed circuit board is connected to the current measuring resistor mechanically and electrically.A step S 4 then provides that the type of current measuring resistor is ascertained.In the next step S 5, the number of conductor tracks to be separated is then determined, which is required to adapt the universal printed circuit board to the respective type of current measuring resistor. For example, the number of parallel conductor tracks to be separated can be read out from a database depending on the type of current measuring resistor.In the next step S 6, the previously determined number of parallel conductor tracks on the upper side of the universal printed circuit board is then separated in order to adapt the universal printed circuit board to the respective type of current measuring resistor.FIG. 7 shows a modification of the flow chart according to FIG. 4, so that reference is made to the above description again to avoid repetitions.A particular feature of this exemplary embodiment is that the method is repeated iteratively until the temperature coefficient is within an acceptable range. If this is not the case, then in a step S 11 the outermost conductor track is respectively separated, which is repeated until the temperature coefficient is in the predefined acceptable range.The modified exemplary embodiment according to FIGS. 8A and 8B will now be described below. This modified exemplary embodiment substantially corresponds to the exemplary embodiments described above, so that, in order to avoid repetitions, reference is made to the above description, the same reference numerals being used for corresponding details.A special feature of this exemplary embodiment is that the printed circuit board 3 has an indentation 28, which runs across the resistance element 8 transversely to the current flow direction. Thereby, the side edges of the circuit board 3 are exposed above the resistance element 8. The two contact surfaces 12, 13 hereby each encompass the side edges of the circuit board 3 in the area of the incision 28 in the form of a cap.It can also be seen from FIG. 8B that the notch 28 of the printed circuit board 3 along the current flow direction has a width which is smaller than the width of the resistance element 8 along the current flow direction.FIG. 9 shows a modification of the sectional view according to FIG. 8B, wherein the width of the notch 28 in the printed circuit board 3 is here substantially equal to the width of the resistance element 8 along the current flow direction.FIG. 10 shows a further modification of the sectional view according to FIG. 8B, wherein the width of the notch 28 in the printed circuit board 3 is greater than the width of the resistance element 8 along the current flow direction.List of reference numbers:1 Current measurement arrangement 2 Current measurement resistor, 3 Printed circuit board 4 Connection part of the current measurement resistor for introducing the current to be measured, 5 Connection part of the current measurement resistor for discharging the current to be measured, 6, 7 Bores in the connection parts for electrical contacting, 8 Resistance element 9, 10 Welded seams 11 Trimming cut in the resistance element 12, 13 Contact surfaces on the underside of the printed circuit board for contacting the connection parts of the current measurement resistor 14 Interface on the printed circuit board 15 Parallel conductor tracks 16 Merging point of the parallel circuit 17, 18 Current shadow in the connection parts of the low-resistance current measurement resistor 19, 20 Contact surfaces on the underside of the printed circuit board for contacting the connection parts of the current measurement resistor 21, 22 current shadow 23 current source for supplying current to the current measuring resistor 24 temperature control device 25 voltage measuring device 26 evaluation unit 27 trimming device 28 cut in the printed circuit board d depth of the current shadows I current through the current measuring resistor U 1 voltage at the connection part for introducing the current into the current measuring resistor U 2 voltage at the connection part for discharging the current from the current measuring resistor U 1 a, U 1 bvoltage at the connection parts for introducing the current into the current measuring resistor U 2 a, U 2 bvoltage at the connection part for discharging the current from the current measuring resistor

Claims

Current measuring arrangement (1) for measuring an electric current (I), having a) a current measuring resistor (2) having a1) a first connection part (4) made of a conductor material, in particular for introducing the current (I) to be measured into the current measuring resistor (2), a2) a second connection part (5) made of a conductor material, in particular for discharging the electric current (I) to be measured from the current measuring resistor (2), and a3) a resistor element (8) made of a resistor material, wherein the resistor element (8) is arranged between the first connection part (4) and the second connection part (5) in the current flow direction, such that the electric current (I) to be measured flows through the resistor element (8) during operation, and b) a printed circuit board (3) which is electrically and mechanically connected to the current measuring resistor (2), with b1) a first voltage tap (12) having a first contact surface (12) made of a conductor material for voltage measurement at the current measuring resistor (2), in particular at the first connection part (4) of the current measuring resistor (2), and b2) a second voltage tap (13) having a second contact surface (13) made of a conductor material for voltage measurement at the current measuring resistor (2), in particular at the second connection part (5) of the current measuring resistor (2), characterized in that c) the second voltage tap (13) on the printed circuit board (3) has a plurality of separate conductor tracks (15) made of a conductor material, which branch off from the second contact surface (13) and are joined together at a joining point (16), such that the conductor tracks (15) form a parallel circuit, and d) the parallel-connected conductor tracks (15) can be individually separated.Current measuring arrangement (1) according to Claim 1, characterized in that a) in that the parallel-connected conductor tracks (15) run directly on the printed circuit board (3), and / or b) in that the parallel-connected conductor tracks (15) run substantially parallel to the main current flow direction in the current measuring resistor (2), and / or c) in that the parallel-connected conductor tracks (15) run substantially parallel to the longitudinal side edge of the current measuring resistor (2), and / or d) in that the second contact surface (13) is arranged on the underside of the printed circuit board (3) facing the current measuring resistor (2), while the parallel-connected conductor tracks (15) are arranged on the upper side of the printed circuit board (3) facing away from the current measuring resistor (2), wherein the second contact surface (13) is connected to the parallel-connected conductor tracks (15) via a plated-through hole in the printed circuit board (3).Current measuring arrangement (1) according to one of the preceding claims, characterized by a) a first notch (17) in the first connection part (4) of the current measuring resistor (2) for influencing the current density in the current measuring resistor (2), and / or b) a second notch (18) in the second connection part (5) of the current measuring resistor (2) for influencing the current density in the current measuring resistor (2).Current measuring arrangement (1) according to claim 3, characterised in that a) the first notch (17) and the second notch (18) start from a longitudinal side edge of the current measuring resistor (2), in particular from the same longitudinal side edge of the current measuring resistor (2), and / or b) the first notch (17) and the second notch (18) have the same depth (d) or a different depth transversely to the longitudinal side edge.Current measuring arrangement (1) according to one of the preceding claims, characterized by a) a third voltage tap (19) on the printed circuit board (3) having a third contact surface (19) made of a conductor material for voltage measurement on the current measuring resistor (2), in particular on the first connection part (4) of the current measuring resistor (2), and b) a fourth voltage tap (20) on the printed circuit board (3) having a fourth contact surface (20) made of a conductor material for voltage measurement on the current measuring resistor (2), in particular on the second connection part (5) of the current measuring resistor (2).Current measurement arrangement (1) according to Claim 5, characterized in that a) the first voltage tap (12) and the third voltage tap on the first connection part (4) are arranged next to one another with respect to the main current flow direction, and / or b) in that the second voltage tap (13) and the fourth voltage tap on the second connection part (5) are arranged next to one another with respect to the main current flow direction.Current measuring arrangement (1) according to Claim 6, characterized in that a plurality or all of the voltage taps (12, 13, 19, 20) each have a plurality of separate conductor tracks (15) made from a conductor material, which branch off from the respective contact surface (12, 13, 19, 20) and are joined together at a joining point (16) in each case, such that the conductor tracks (15) form a parallel circuit.Current measurement arrangement (1) according to one of the preceding claims, characterized in that a) the conductor material has a smaller specific electrical resistance than the resistor material of the resistor element (8), and / or b) the conductor material is copper, a copper alloy, aluminum or an aluminum alloy, and / or c) the first connection part (4) and / or the second connection part (5) and / or the resistor element (8) is plate-shaped, in particular in the form of a planar or curved plate, and / or d) the current measurement resistor (2) has a resistance value which is smaller than 1 Ω, 500 mΩ, 250 mΩ, 100 mΩ, 50 mΩ, 20 mΩ, 10 mΩ, 5 mΩ, 2 mS2, 1 mΩ, 500 μΩ, 250 μΩ, 100 μΩ or 50 μΩ, and / or e) that the conductor material has a specific electrical resistance that is less than 10 -6 Ω·m or 10 -7 Ω·m, and / or f) that the resistance material of the resistance element (8) has a specific electrical resistance that is less than 10 -4 Ω·m, 10 -5 Ω·m or 10 6 Ω·m, and / or g) that the resistance material is a resistance alloy, in particular g1) a copper-manganese-nickel alloy, in particular CuMn12Ni or CuMnNi 25-10, g2) a copper-nickel alloy, in particular CuNi44 or g3) a nickel-chromium alloy, in particular NiCRbOAISi, NiCr3020, and / or h) in that the resistance element (8) is in each case connected to the connection parts (4, 5) by a welded connection, in particular by an electron beam weld, and / or i) in that the printed circuit board (3) has an interface (14) for outputting the measured voltage drop across the resistance element (8), and / or j) in that the number of parallel-connected and individually separable conductor tracks (15) is greater than two, three, four, five, seven or ten in order to enable precise adjustment of the temperature coefficient (TK), and / or k) in that the printed circuit board (3) carries a measurement circuit, which is connected to the first voltage tap (12) and to the merging point (16) of the second voltage tap for measuring the voltage dropped across the current measuring resistor (2), on the one hand, and / or I) so that so many of the parallel-connected conductor tracks (15) are separated that the temperature coefficient (TK) of the resistance value of the current measuring resistor (2) is less than ±500 ppm / K, 250 ppm / K, ±100 ppm / K, ±50 ppm / K, ±25 ppm / K, ±10% ppm / K or ±5 ppm / K, and / or m) that the parallel-connected conductor tracks (15) all branch off from the second contact surface (13) in the direction of the first contact surface (12), and / or n) that the parallel-connected conductor tracks (15), starting from the second contact surface (13), all run substantially parallel to that of the longitudinal side edge of the current measuring resistor (2), and / or o) that only outer conductor tracks (15) are separated from the parallel-connected conductor tracks (15), and / or p) that a trimming cut (11) is introduced into the resistor element (8) of the current measuring resistor (2) in order to set the resistance value of the current measuring resistor (2), and / or q) that a continuous bore (6, 7) is arranged in the first connection part (4) and / or in the second connection part (5) for electrical and mechanical contacting, and / or r) that the conductor material in one of the two connection parts (4, 5) is copper or a copper alloy, while the conductor material in the other connection part (4, 5) is aluminum or an aluminum alloy.Current measuring arrangement (1) according to one of the preceding claims, characterized in that a) the printed circuit board (3) has an incision (28) which runs transversely to the current flow direction, and / or b) the first voltage tap (12) surrounds a side edge of the printed circuit board (3) in a cap-shaped manner with the first contact surface (12), in particular at a side edge to the incision (28), and / or c) the second voltage tap (13) surrounds a side edge of the printed circuit board (3) in a cap-shaped manner with the second contact surface (13), in particular at a side edge to the incision (28), and / or d) the incision (28) has a width in the printed circuit board (3) along the current flow direction which d1) is equal to the width of the resistance element along the current flow direction, d2) is greater than the width of the resistance element along the current flow direction or d3) is less than the width of the resistance element along the current flow direction.Calibration system for calibrating the temperature coefficient (TK) of the resistance value of a current measuring resistor (2), having a) a current measuring arrangement (1) according to one of the preceding claims, b) a current source (23) for energizing the current measuring resistor (2) with an electric current (I MESS), c) of a temperature control device (24) for temperature controlling the current measuring resistor (2) to a predefined temperature (T A, T B), and d) of a voltage measuring device (25) for measuring the voltage drop (U A, U B) across the resistor element (8) of the current measuring resistor (2) during energization by the current source (23) and at the temperature set by the temperature control device (24), e) a separating device (27) for separating at least one of the parallel-connected conductor tracks (15) of the second voltage tap (13), and f) an evaluation device (26) for determining the number of conductor tracks (15) to be separated for adjusting the temperature coefficient (TK) of the resistance value of the current measuring resistor (2) as a function of the measured voltage drops (U A, U B) at different temperatures (T A, T B), in particular such that the temperature coefficient (TK) of the resistance value of the current measuring resistor (2) is less than ±500 ppm / K, ±250 ppm / K, ±100 ppm / K, ±50 ppm / K, ±25 ppm / K, ±10 ppm / K or ±5 ppm / K.Calibration method for calibrating the temperature coefficient (TK) of the resistance value of a current measuring resistor (2) of a current measuring arrangement (1) according to one of Claims 1 to 9, having the following steps: a) tempering the current measuring resistor (2) to a specific temperature (T A, T B), b) energizing the current measuring resistor (2) with an electrical current (I MESS), c) measuring the voltage drop (U A, U B) across the resistor element (8) of the current measuring resistor (2), and d) separating at least one of the conductor tracks (15) of the second voltage tap (13) as a function of d1) the electrical current (I MESS), d2) the measured voltage drop (U A, U B) and d3) of the temperature (T A, T B).The balancing method according to claim 11, characterized bythe following steps: a) tempering the current measuring resistor (2) to a predetermined first temperature (T A), in particular to room temperature, b) energizing the current measuring resistor (2) at the first temperature (T A) with an electric current (I MESS), c) measuring a first voltage drop (U A) across the resistor element (8) at the first temperature (T A) of the current measuring resistor (2), d) optionally calculating a first resistance value (R A) from the measured first voltage drop (U A), e) tempering the current measuring resistor (2) to a predetermined second temperature (T B), f) energizing the current measuring resistor (2) at the second temperature (T B) with an electric current (I MESS), g) measuring a second voltage drop (U B) across the resistor element (8) at the second temperature (T B) of the current measuring resistor (2), h) optionally calculating a second resistance value (R B) from the measured second voltage drop (U B).The balancing method according to claim 12, characterized bythe following steps: a) calculating a number of conductor tracks (15) of the second voltage tap (13) to be separated for balancing the temperature coefficient (TK) of the resistance value of the current measuring resistor (2) as a function of the two temperatures (T A, T B) and the measured voltage drops (U A, U B) and the current (I MESS), in particular such that the temperature coefficient (TK) of the resistance value of the current measuring resistor (2) is less than ±500 ppm / K, ±250 ppm / K, ±100 ppm / K, ±50 ppm / K, ±25 ppm / K, ±10 ppm / K or 5 ppm / K, and b) separating the calculated number of conductor tracks ( 15) of the second voltage tap ( 13).Balancing method according to claim 12, characterised bythe following steps: a) calculating the temperature coefficient (TK) of the resistance value as a function of a1) the two temperatures (T A, T B), a2) the measured voltage drops (U A, U B) and a3) the current (I MESS), b) checking whether the calculated temperature coefficient (TK) of the resistance value lies in a predetermined acceptable range, and c) breaking up at least one of the conductor tracks (15) if the calculated temperature coefficient does not lie in the predetermined acceptable range and repeating the steps of claim 13 and the steps of claim 15, until the calculated temperature coefficient (TK) is within the predetermined acceptable range.The calibration method according to any one of claims 11 to 14, characterized in that the parallel-connected conductor tracks (15) of the second voltage tap (13) at the current measuring resistor (2) are separated by one of the following methods: a) milling, b) scribing, c) drilling, d) lasers, e) lithography.The balancing method according to one of claims 11 to 15, characterized in that the conductor tracks (15) of the second voltage tap (13) on the current measuring resistor (2) are cut apart starting from the outside to the inside during the balancing.Production method for a current measurement arrangement (1) according to one of Claims 1 to 9, having the following steps: a) providing a current measurement resistor (2), wherein the current measurement resistor (2) belongs to one of a plurality of different types of current measurement resistors, b) determining the type of the current measurement resistor (2), c) providing a printed circuit board (3) having c1) a first voltage tap (12) with a first contact surface (12) made of a conductor material for voltage measurement at the current measurement resistor (2), in particular at the first connection part (4) of the current measurement resistor (2), and c2) a second voltage tap with a second contact surface (13) made of a conductor material for voltage measurement at the current measurement resistor (2), in particular at the second connection part (5) of the current measurement resistor (2), c3), wherein the second voltage tap (13) on the printed circuit board (3) has a plurality of separate conductor tracks (15) made of a conductor material, which branch off from the second contact surface (13) and are joined together at a joining point (16), such that the conductor tracks (15) form a parallel circuit, c4) wherein the printed circuit board (3) is a universal printed circuit board (3) which is suitable for the different types of current measuring resistors, d) determining the number of parallel-connected conductor tracks (15) of the printed circuit board (3) to be separated in order to adapt the printed circuit board (3) to the type of current measuring resistor (2), in particular by reading out the number of parallel-connected conductor tracks (15) to be separated from a database as a function of the type of current measuring resistor (2), and e) separating the determined number of parallel-connected conductor tracks ( 15) of the printed circuit board ( 3) in order to adapt the printed circuit board ( 3) to the type of the current measuring resistor ( 2).Production method according to claim 17, characterised in that the number of parallel-connected conductor tracks (15) to be separated is read out from a database depending on the type of current measuring resistor (2), wherein the number of conductor tracks (15) of the universal printed circuit board (3) to be separated is stored in each case in the database for the different types of current measuring resistors.

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