Measuring device for contactless current measurement, and method for calibrating said device

Abstract

The invention relates to a measuring device (1, 1') for contactless measurement of the amperages of a direct or alternating current, comprising: at least one first housing part (10, 10'), the construction of which defines a measurement region located outside the first housing part (10, 10'); and a plurality of magnetic-field sensors (101-108, 101'-108') which are arranged in fixed positions and in fixed orientations; and a memory device in which the parameters of the magnetic-field sensors (101-108, 101'-108') are stored. The measuring device (1, 1') is designed to determine, depending on the measured values of the magnetic-field sensors (101-108, 101'-108') and depending on the stored parameters, a value for the amperage of an electric current flowing through at least one conductor (200, 200') when the at least one conductor (200, 200') extends through the defined measurement region in any position and orientation. The invention also relates to a measuring system, and to a method for calibrating the measuring device.

Description

[0001] Measuring device for contactless current measurement and method for its calibration

[0002] Description

[0003] The invention relates generally to a contactless measurement of the current intensity of an electric current flowing in a conductor, and more particularly to a measuring device designed for this purpose and to a method for calibrating such a measuring device.

[0004] Various measuring methods are known for determining the current flowing in a conductor. For example, the voltage drop across a resistor such as a shunt resistor can be determined, and with the known resistance value, the flowing current can be determined according to Ohm's law. In addition, current measuring arrangements with a ferromagnetic core are known which operate according to the transformer principle. In this case, the conductor with the current to be measured is passed through a core. The conductor with the current to be measured forms the primary conductor of a transformer. Via a secondary winding wound on the core, the primary current can be determined from the current flowing through a resistor connected to the secondary winding, known as a burden. The secondary current is proportional to the primary current and is determined by the turns ratio between the secondary winding and the primary winding.However, the transformer principle is limited in its application to measuring alternating currents.

[0005] Furthermore, it is possible, for example, to measure the magnetic field caused by a current using Hall sensors and use this to infer the current causing it. In this way, currents, including direct currents, can be measured contactlessly. In particular, methods are known that do not require a ferromagnetic core to focus the magnetic field. In particular, the magnetic field strength can be evaluated according to Ampere's law, according to which the measured current is based on the solution of a path integral of the magnetic field. For this purpose, the formula I m = s Hds are used, where I mdenotes the electric current to be measured, S describes a closed path in space that encloses the current, and where H denotes the vectorial magnetic field strength and ds the differential of the integration path. If the magnetic flux density is measured pointwise in one spatial direction using sensors, the approximation is given by formula I ma ~ where Ima denotes the approximate current to be measured and po the permeability of the vacuum and i is a counting index that runs from 1 to N, where N is the number of magnetic field sensors and Bi is the magnetic flux density detected by the i-th sensor in the direction of the path element with the length s;. The path elements s; must be arranged in such a way that they form a closed path in space that encloses the conductor to be measured. The approximation of the current is exact when the number of magnetic field sensors tends to infinity. If the number of sensors is finite, an exact solution can also be obtained if, for example, the magnetic field sensors are arranged equidistantly on a circular path and aligned tangentially to it and the current to be measured passes exactly perpendicularly through the area in which the circular path is located and through which the current passes exactly through the center of the circular path.However, the conditions for an exact solution are usually not met in practice.

[0006] Measuring arrangements which use the measuring principle described above based on Ampere's law are described, for example, in EP 3 589 961 Bl, US 11,150,272 B2, EP 3 958 003 A1 and EP3259603B1.

[0007] Mechanisms for compensating for interfering magnetic fields are described, for example, in US 11029342 B2 and US 2021 / 0231709 A1. EP 3948310 A1 further describes a measuring arrangement which, for this purpose, comprises a filter unit for homogenizing external magnetic fields, i.e., magnetic fields that are not caused by the electric current to be measured. In order to determine the current intensity of the electric current flowing through a conductor based on a magnetic field generated by a current-carrying conductor by measuring the magnetic field using magnetic field sensors, without using the measuring principle based on Ampere's law described above, the position of the current-carrying conductor relative to the magnetic field sensors must be known.

[0008] For this purpose, the measuring arrangements described, for example, in WO 2022030287 A1, EP 2821798 B1, EP 2921864 B1, and EP 3106884 B1 each provide for fixing the electrical conductor to be measured in a predetermined position. WO 2010 / 096344 A1 describes a current measuring device for measuring an alternating current in a conductor, which includes a plurality of measuring coils by means of which the position of the conductor is determined.

[0009] EP 3761044 A1 further discloses a current measuring device with two magnetic field sensors, wherein the conductor position and orientation and the current to be measured are deduced from the measured values ​​of the magnetic field sensors, wherein complex triaxial magnetic field sensors are used for this purpose, i.e. magnetic field sensors that measure the magnetic field in all three spatial axes. A measurement error in the method described in EP 3761044 A1 arises from the fact that the calculation assumes that the components of the magnetic field detected by the respective triaxial sensor in the three spatial directions refer to an identical spatial point, wherein this is only approximately the case due to the design, since a triaxial sensor is constructed from separate, spatially adjacent sensors for the respective spatial direction.

[0010] The invention is based on the object of showing a way in which the current intensity of an electric current flowing through a conductor can be determined in a simplified and / or improved manner, wherein in particular a contactless measurement of both direct and alternating currents is to be made possible, and wherein in particular a corresponding measuring device is to be proposed which is suitable for retrofitting, ie for a retrofit, on existing lines for different line cross-sections, and which dispenses with the use of a ferromagnetic core.

[0011] This object is achieved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, wherein the stated features and advantages can essentially apply to all independent claims.

[0012] According to a first aspect of the invention, a measuring device is provided for contactless measurement of the current intensity of an electrical direct or alternating current flowing through at least one conductor, wherein the measuring device comprises at least a first housing part, which by its design defines a measuring area arranged outside the first housing part, and a measuring arrangement with a plurality of magnetic field sensors which are arranged at fixed positions and in fixed orientations relative to the defined measuring area.

[0013] Furthermore, the measuring device comprises a memory device in which parameters of the magnetic field sensors are stored, wherein the parameters comprise information on the positions, the orientations and the metrological properties of the magnetic field sensors, as well as a processing unit connected to the magnetic field sensors and the memory device, which is designed to determine a value for the current intensity of the electrical current flowing through the at least one conductor as a function of the measured values ​​of the magnetic field sensors and as a function of the parameters stored in the memory device when the at least one conductor extends through the defined measuring range in any position and orientation.

[0014] In order to ensure that a conductor to be measured remains within the defined measuring range during a current measurement, the measuring device comprises a retaining device which is designed to form, together with the first housing part, an openable and closable conductor feedthrough, wherein the retaining device is designed such that a conductor introduced into the conductor feedthrough extends through the defined measuring range.

[0015] In order to output values ​​determined by the processing unit, the measuring device has at least one output interface for outputting the determined value for the current intensity and / or a value derived from the determined value of the current intensity.

[0016] According to a second aspect of the invention, a measuring system is provided which comprises at least two measuring devices described above, which are communicatively connected to one another for the exchange of measurement data.

[0017] According to a third aspect of the invention, a method for calibrating a measuring device described above is provided, wherein the calibration method provides for at least one calibration conductor, through which a current of predeterminable current intensity flows, to be introduced successively in different arrangements into the defined measuring range, and for each arrangement the following steps are carried out:

[0018] A) Measuring by each of the magnetic field sensors of the measuring arrangement, a value for the magnetic flux density along at least one spatial direction at the location of the respective magnetic field sensor,

[0019] B) Setting the values ​​for a plurality of sensor variables and calibration conductor variables to respective starting values, wherein the sensor variables represent parameters of the plurality of magnetic field sensors, including in particular the position, orientation and / or metrological properties of the respective magnetic field sensor, and wherein the calibration conductor variables comprise variables that represent the position and orientation of the at least one calibration conductor relative to the measuring arrangement,

[0020] C) Calculating expected values ​​for the values ​​measured by the magnetic field sensors depending on the values ​​of the majority of sensor variables and calibration ladder variables,

[0021] D) Determining a value of a predeterminable second quality function depending on the values ​​calculated in step C) and the values ​​measured in step A), E) as long as a predeterminable second termination criterion is not yet met, varying the values ​​of the calibration ladder variables depending on a predeterminable second optimization algorithm and repeating steps C) and D),

[0022] F) if the second termination criterion is met, saving the values ​​of the calibration ladder variables,

[0023] G) Calculating expected values ​​for the values ​​measured by the magnetic field sensors depending on the values ​​of the sensor variables and the stored calibration ladder variables,

[0024] H) Determining a value of a predeterminable third quality function depending on the values ​​calculated in step G) and the values ​​measured in step A),

[0025] I) as long as a predefined third termination criterion is not yet met, varying the values ​​of the sensor variables depending on a predefined third optimization algorithm and repeating steps G) and H),

[0026] J) if the third termination criterion is met, saving the values ​​of the sensor variables,

[0027] K) as long as a predefined fourth termination criterion is not yet met, repeat steps C) to J) with the stored values ​​of the sensor variables and calibration ladder variables as starting values,

[0028] L) if the fourth termination criterion is met, storing the stored values ​​of the sensor variables as parameters of the magnetic field sensors in the memory device of the measuring device.

[0029] Using the described calibration method, the parameters of the magnetic field sensors can be determined with very high accuracy and stored in the memory device of the measuring device, advantageously enabling the processing unit to determine a value for the current intensity of the electrical current flowing through the at least one conductor with high accuracy. This determination is carried out as a function of the measured values ​​of the magnetic field sensors and as a function of the parameters stored in the memory device. Since the at least one conductor can extend through the defined measuring range in any position and orientation during the measurement, the measuring device can advantageously be used for conductors with different cross-sections.

[0030] The device advantageously enables contactless measurement of AC and DC currents using magnetic field sensors without the use of a ferromagnetic core. Its design also advantageously allows it to be retrofitted around existing power lines without the need to secure the line in the measuring opening. By additionally measuring the voltage between the conductor and a reference potential, a power measurement can also be performed, with multiphase measurement also being possible by connecting multiple devices.

[0031] The invention is explained in more detail below using exemplary embodiments in conjunction with the drawings. They show:

[0032] Figure 1 is a schematic representation of a first preferred embodiment of a measuring device according to the invention in a perspective view,

[0033] Figure 2 is a schematic side view of the measuring device shown in Fig. 1, Figure 3 is a schematic front view of the measuring device shown in Fig. 1,

[0034] Figure 4 is a schematic front view of the measuring device shown in Fig. 1, with the housing partially opened to show a measuring arrangement arranged in the housing,

[0035] Figure 5 is a schematic representation of a second preferred embodiment of a measuring device according to the invention in a perspective view,

[0036] Figure 6 is a schematic representation of another exemplary embodiment of a measuring arrangement in perspective view,

[0037] Figure 7 is a schematic block diagram of a preferred embodiment of a measuring chain of the measuring device shown in Figure 1, Figure 8 is an exemplary schematic flow diagram of steps for determining the current intensity of an electrical current flowing through at least one conductor by the measuring device,

[0038] Figure 9 is an exemplary schematic flow diagram of steps of a preferred embodiment of a calibration method for determining parameters relating to magnetic field sensors arranged in the measuring device,

[0039] Figure 10 schematically shows an exemplary calibration arrangement for carrying out the calibration method shown in Figure 9 in plan view, and

[0040] Figure 11 schematically shows an exemplary circuit arrangement for the selective selection of current-carrying calibration conductors of the calibration arrangement shown in Figure 10.

[0041] Fig. 1 shows a schematic representation of a first preferred embodiment of a measuring device 1 according to the invention in a perspective view. The measuring device 1 is designed for contactless measurement of the current intensity of an electrical direct or alternating current flowing through at least one conductor 200 and comprises at least a first housing part, which, due to its design, defines a measuring area arranged outside the first housing part. In the illustrated embodiment, the first housing part is formed by the housing part 10.

[0042] The U-shape of the housing part 10 defines the measuring range, with the conductor 200 in Fig. 1 being positioned within this measuring range.

[0043] The measuring device 1 further comprises a measuring arrangement with a plurality of magnetic field sensors arranged at fixed positions and in fixed orientations relative to the defined measuring range. This measuring arrangement is advantageously arranged within the housing part 10 to protect the components and is therefore not shown in Fig. 1. However, the measuring arrangement is shown, for example, in Fig. 4.

[0044] In order to ensure that a conductor 200 to be measured remains within the defined measuring range during a current measurement, the measuring device 1 comprises a retaining device which is designed to form, together with the first housing part 10, an openable and closable conductor feedthrough, wherein the retaining device is designed such that a conductor introduced into the conductor feedthrough remains within the defined measuring range when the conductor feedthrough is closed.

[0045] In the embodiment shown in Fig. 1, the retaining device is designed as a retaining bracket 20 movably attached to the first housing part 10, which is rotatable by means of a pivot joint 22. Various other designs of a retaining bracket and various other types of movable fastening are conceivable. For example, a sliding retaining device could also be provided. The retaining device can also advantageously be formed by a cable tie, a rubber band, or a tab with attached locking hooks, each of which is designed and / or arranged to close the opening formed by the U-shape of the first housing part 10.

[0046] It is important to note that the retaining device is not designed to mechanically fix the conductor to be measured.

[0047] The measuring device 1 further comprises at least one output interface for outputting the determined current value and / or a value derived from the determined current value. The measuring device 1 shown in Fig. 1 comprises, for example, a user interface 50 and a communication interface 30 for outputting values. Furthermore, the measuring device 1 is advantageously designed for measuring an electrical voltage, wherein the measuring device 1 has, in particular, input terminals 40 for voltage measurement for this purpose.

[0048] The communication interface 30 can in particular serve for communication with at least one further, in particular similar, measuring device, wherein the measuring device 1 is in particular designed to exchange measurement data with the at least one further measuring device, wherein the measurement data, in particular for measured values ​​contained in the measurement data, each comprise an associated time stamp which indicates at which time the measured values ​​were determined.

[0049] In the embodiment shown in Fig. 1, the measuring device 1 is also preferably designed to be supplied with an operating voltage via the communication interface 30.

[0050] In the embodiment shown in Fig. 1, the measuring device 1 is also designed for mounting on a support rail 90, which is designed, for example, as a top-hat rail, wherein appropriately adapted top-hat rail supports 91 can advantageously be provided for this purpose.

[0051] Advantageously, the measuring device can be designed as a measuring transducer, wherein in this case the measuring device is preferably designed to determine a value for an electrical power and / or a value for an electrical energy as a function of at least one determined value for the current intensity of the electrical current flowing through the at least one conductor and / or as a function of at least one value of a measured electrical voltage and / or as a function of measurement data received via the at least one communication interface.

[0052] In an advantageous embodiment of the measuring device 1, the latter is designed to determine the current intensity of an electric current flowing through at least one conductor 200 by determining the position and orientation of the conductor as a function of the measured values ​​of the magnetic field sensors, wherein the position and orientation of the conductor are determined, for example, by the displacements x shown in Fig. 1 s and y sin the x- or y-direction relative to the center of the measuring range and the angles 201 and 202 can be defined. In the example shown, the angle 201 indicates the directional angle of the conductor 200 in the xz-plane and the angle 202 indicates the directional angle of the conductor 200 in the yz-plane. In the side view shown in Fig. 2, the angle 202 is shown again. Alternatively, other angles could also be used, such as the directional angle 203 in the xy-plane, which is shown as an example in Fig. 3. Fig. 4 shows a schematic front view of the measuring device 1 shown in Fig. 1, with the housing partially opened to show a measuring arrangement arranged in the housing. In the exemplary embodiment shown, the measuring device 1 comprises a measuring arrangement with a plurality of magnetic field sensors 101'-108', which are arranged at fixed positions and in fixed orientations relative to the defined measuring range.Preferably, the plurality of magnetic field sensors 101'-108' are arranged at fixed positions and in fixed orientations on a rigid support 110' arranged within the first housing part 10, which support is advantageously designed as a printed circuit board. The printed circuit board preferably has a U-shape due to a recess provided in the printed circuit board. The recess forms two printed circuit board arms, between which the measuring range defined by the design of the housing part 10 lies, and at least one of the plurality of magnetic field sensors 101'-108' is arranged on each of the two printed circuit board arms.

[0053] Parameters of the magnetic field sensors 101'-108' are stored in a memory device of the measuring device, wherein the parameters include information on the positions, orientations and metrological properties of the magnetic field sensors 10L-108'.

[0054] Furthermore, the measuring device 1 comprises a processing unit connected to the magnetic field sensors 101'-108' and the memory device, which is designed to determine a value for the current intensity of the electrical current flowing through the at least one conductor 200 as a function of the measured values ​​of the magnetic field sensors and as a function of the parameters stored in the memory device when the at least one conductor 200 extends through the defined measuring range in any position and orientation. A microcontroller 130 is preferably provided as the processing unit, which may include the memory device. Alternatively, a separate memory device (not shown in Fig. 4) may also be provided. Fig.4 further shows a voltage measurement input 150, which is connected to the terminals 40 for voltage measurement, as well as an analog-to-digital converter 120 and an output unit 140, which can be connected in particular to an output interface.

[0055] Figure 5 shows a schematic representation of an alternative embodiment of a measuring device 1' in perspective view. In this embodiment, the retaining device is designed as a second housing part 20' that can be releasably connected to a first housing part 10', wherein, in particular, the first and second housing parts 10' and 20' each have locking elements 11' and 21' that are complementary to one another. Alternatively, another suitable type of releasable connection could also be provided, such as a screw connection in which the first and second housing parts 10' and 20' can be connected by means of a screw connection.

[0056] Similar to the measuring device 1 described above, the measuring device 1' shown in Fig. 5 has a communication interface 30', input terminals 40 for voltage measurement, and a user interface 50. Furthermore, the measuring device 1' is provided with a terminal 70 for connecting a voltage supply, as well as display and / or control elements 60.

[0057] In the embodiment shown in Fig. 5, the first and second housing parts 10' and 20' are designed to form an openable and closable conductor feedthrough.

[0058] Analogous to the measuring device 1 described above, the measuring device 1' also comprises a processing unit connected to magnetic field sensors and a memory device, which is designed to determine a value for the current intensity of the electrical current flowing through at least one conductor 200' depending on the measured values ​​of the magnetic field sensors and the parameters stored in the memory device when the at least one conductor 200' extends through the defined measuring range in any position and orientation, wherein a microcontroller 130 can again preferably be provided as the processing unit. Accordingly, in the measuring device 1' shown in Fig. 5, the conductor to be measured can in principle be positioned in any position and orientation in the measuring range and can have different conductor cross-sections up to a maximum conductor cross-section predetermined by the design of the measuring device. In Fig.5 shows an example of a conductor 200' with such a maximum conductor cross-section.

[0059] For mounting on a mounting rail 90, appropriately adapted top-hat rail supports 91 can be provided. It should be noted that, depending on the design, the first housing part 10 or the retaining device can be designed for mounting on a mounting rail 90.

[0060] It should also be noted that preferably all electrical and electronic components of the measuring device 1 or 1' are arranged exclusively in the first housing part 10 or 10' and accordingly the respective retaining device 20 or 20' does not comprise any electrical or electronic components.

[0061] Fig. 6 schematically shows a perspective view of an alternative embodiment of a measuring arrangement 100 that can be used in a measuring device according to the invention for measuring the current intensity of an electric current flowing through a conductor 200. The measuring arrangement 100 comprises a processing unit 130 and a plurality of magnetic field sensors 101-108 connected to the processing unit. In the embodiment shown in Fig. 6, the processing unit comprises a microcontroller 130, which is advantageously designed to execute instructions stored in a memory. Instead of a microcontroller, the processing unit can alternatively comprise a microprocessor or a CPU (Central Processing Unit).

[0062] Any magnetically sensitive sensor can serve as the magnetic field sensor, in particular a Hall sensor, a fluxgate sensor, a magnetoresistive sensor, or a magneto-optical sensor. The magnetic field sensors 101-108 are designed to detect the magnetic flux density in a spatial direction, each indicated by arrows. The circuit board 110 has a U-shaped contour, which allows a conductor 200, which carries a current to be measured, to be inserted into the area between the sensors 101-108.

[0063] The current-carrying conductor 200 does not pass through the exact center of the area, but the point of passage has a displacement x s in a first spatial direction, shown in Fig. 6 as x-axis, and a displacement y sin a second spatial direction, shown in Fig. 6 as the y-axis. In the illustrated embodiment, the magnetic field sensors are arranged in a plane, wherein the conductor 200 does not pass perpendicularly through the plane in which the sensors are located, but has a directional angle α and a tilt angle β relative to the plane, wherein in the illustrated embodiment, both angles are not equal to 90°. It should be noted that the directional angle α represents the direction of the projection of the conductor 200 into the xy plane, and the tilt angle β denotes the intersection angle between the conductor 200 and the xy plane.

[0064] The exemplary embodiments described above show variants of the measuring device's design, each of which preferably includes a current measurement input, a voltage measurement input, a power supply connection, and an interface for data output and communication. The measuring device can advantageously be divided into two components by splitting or folding them open, which can be connected to each other, for example, by a hinge or by snap-in hooks or tabs.

[0065] The current measurement input is realized, for example, by the 8 magnetic field sensors described above on a circuit board.

[0066] The elements for measuring value recording shown in Fig. 6, for example, consisting of an analog-to-digital converter (ADC) 120 and a downstream microcontroller unit (MCU) 130, use an algorithm to determine the current flowing in conductor 200. The existing voltage input can be used to measure a voltage present on the line 200 or 200' to be measured, for example by tapping a voltage at terminal points. Based on the values ​​determined for current and voltage from the two measuring inputs, power and energy can be calculated in the measuring device designed as a measuring transducer. These values ​​can be stored in the measuring device using logging and, depending on the device variant, output via an analog output or digital interfaces, such as Modbus RTU (interface via RS485), Modbus TCP (RJ45 socket), USB (USB-C interface).

[0067] Fig. 7 shows a schematic block diagram of a measuring arrangement such as the measuring arrangement 100 shown in Fig. 6. The analog output signals of a plurality of magnetic field sensors 101-1On and the voltage input 150 are connected to an analog-to-digital converter 120 and converted there into a digital data stream. The electrical measuring input 150 can be connected to the ADC 120 via a safe isolation 155. The digital data stream is passed to a microcontroller 130. The processor of the microcontroller 130 calculates a value for the current intensity of the electrical current flowing in the conductor 200 from the digital data stream, wherein an optimization algorithm is preferably used in the calculation, which is described in more detail below. A signal is generated from the calculated value for the current intensity, which is output by means of an output unit 140. The output unit 140 outputs, for example,an analog voltage in the range of 0-10V according to the NAMUR standard, whereby the output voltage value is proportional to the determined value of the current (e.g. 0V=0A, 10V=1000A), voltage (e.g. 0V=V, 10V=1000V) or, depending on the configuration, power (e.g. 0V=0W, 10V=100kW). However, it is also possible to output a current proportional to the current in the conductor, e.g. in the range from 0 to 20mA. The output unit 140 can also output the determined current in digital form, for example via a fieldbus such as Modbus, Profmet, etc., or can be displayed, for example, via device-internal web-based management, i.e. on a website accessible via the user interface. The output unit 140 can also perform an evaluation of the calculated value of the current, voltage or power and, for example, when a threshold value is reached, output a warning signal at a digital output or by setting a register value.It is also possible for an analog-to-digital converter and a magnetic field sensor to be integrated into a single component, for example, in the form of an IC (integrated circuit). In this case, each magnetic field sensor with an integrated analog-to-digital converter sends a digital data stream to the processor, for example, using FC.

[0068] If several measuring transducers, i.e. several of the measuring devices described above, are connected to one another in a communication bus via a digital interface, such as Modbus RTU, then multi-conductor DC networks or, for example, 3-phase AC networks can also be measured. For this purpose, the communication interfaces 30 or 30' described above can be used in particular. For this purpose, one of the devices is preferably configured as the master, with the other devices connected to the bus acting as clients. The master receives the measurement data from the clients and, based on the incoming measurement data provided with a time stamp, calculates the temporal profiles of current and voltage, as well as the resulting values ​​for power and (taking the times into account) the energy. This data can be output or displayed via the user interface 50, an analog output, a digital interface or via an internal website.

[0069] In addition, data generated when determining the current, such as in particular the current intensity of the conductor current, as well as information on the position and orientation of the conductor, e.g. information on position, tilt and inclination direction, can be exchanged between the measuring devices in order to reduce the influence of the measuring devices on the neighboring current-carrying conductors. The combined data from several measuring transducers can also provide information on the symmetry of the load distribution between the individual lines and unintentional earth faults (sum of the phase currents not equal to 0). The embodiment shown in Fig. 6 comprises 8 sensors, each of which detects the magnetic field in one spatial direction. However, other designs are also conceivable in which a different number of sensors are positioned in a different arrangement, detecting the magnetic flux density in one, two or three spatial directions.

[0070] The magnetic field caused by the current to be measured is measured using several sensors at different positions and spatial directions. The sensors are fixed in a rigid arrangement, in the illustrated embodiment on a circuit board 110. The arrangement has an opening that allows current conductors to be brought into the measuring range without breaking the circuit. It is not necessary to fix the current conductor in a specific position or a specific orientation; it is sufficient if the conductor is located at any position in any orientation within a defined measuring range. The defined measuring range is predetermined in particular by the design of the first housing part 10 or 10' or by the design of the measuring arrangement 100 adapted thereto, whereby the design can vary depending on the intended use.

[0071] In the embodiment shown in Fig. 6, the measuring arrangement 100 comprises a circuit board 110 on which the processing unit and the plurality of magnetic field sensors 101-108 are arranged. The circuit board 110 has a U-shape due to a recess provided in the circuit board. The recess forms two circuit board arms, between which the predetermined measuring range of the measuring arrangement lies, and at least one of the plurality of magnetic field sensors 101-108 is arranged on each of the two circuit board arms. In the illustrated embodiment, four of the magnetic field sensors are arranged in a row along the extension direction of the respective circuit board arm on each of the two circuit board arms. The sensor signals are converted into a digital data stream by means of analog-to-digital conversion, which data stream is processed by a processor of the microcontroller orthe CPU can process to finally output the current to be measured.

[0072] The invention preferably provides for the use of an optimization algorithm for the measurement data evaluation. The algorithm's task is to find the combination of values ​​for conductor variables that best "explains" the available measured values ​​of the magnetic field sensors, whereby the conductor variables include, in particular, the position and orientation of the conductor in the measuring range and, optionally, the current to be measured.

[0073] Optimization algorithms require a cost or quality function that expresses the quality of an estimate in a number. The estimate is then varied to find the value that achieves the highest quality or lowest cost. The optimization algorithm can be terminated after a specified number of optimization iterations or when the quality criterion falls below a predefined threshold.

[0074] In the optimization algorithm preferably used here, the estimated value consists of the combination of the values ​​of the conductor variables and thus represents an N-dimensional vector, where N is defined by the number of conductor variables. Further influencing factors that can be considered include the cross-sectional shape of the conductor as well as the position, orientation, and current strength of any adjacent current conductors. The position and orientation of the conductor are essentially only auxiliary variables that arise as a by-product of the optimization algorithm to increase the accuracy of the current to be measured. Output of these values ​​is typically not provided.

[0075] In order to determine the current intensity of an electric current flowing through at least one conductor 200, which is positioned in a predetermined measuring range of a measuring arrangement 100 with a plurality of magnetic field sensors 101-108, the following steps are advantageously provided: a) Measuring, at a first time, by each of the magnetic field sensors 101-108, a value for the magnetic flux density along at least one spatial direction at the location of the respective magnetic field sensor 101-108, b) Setting the values ​​for a plurality of conductor variables to respective starting values, wherein the conductor variables comprise variables that represent the position and orientation of the at least one current-carrying conductor 200 relative to the measuring arrangement, c) Calculating expected values ​​with respect to the values ​​measured by the magnetic field sensors 101-108 as a function of the values ​​of the plurality of conductor variables,d) determining a value of a predeterminable first quality function depending on the values ​​calculated in step c) and the values ​​measured in step a), e) as long as a predeterminable first termination criterion is not yet met, varying the values ​​of the plurality of conductor variables depending on a predeterminable first optimization algorithm and repeating steps c) and d), f) upon fulfillment of the first termination criterion, determining a value for the current intensity of the current flowing through the at least one conductor depending on the values ​​of the conductor variables.

[0076] It should be noted that the at least one conductor advantageously comprises exactly one conductor. However, the at least one conductor can also comprise a plurality of conductors, each of which is positioned independently of one another in any position and orientation within the predetermined measuring range of the measuring arrangement 100. In this case, the number of conductor variables to be optimized increases accordingly, and thus possibly also the number of required magnetic field sensors. The at least one conductor can furthermore also comprise a plurality of conductors, the position and orientation and, if applicable, current intensity can be represented by conductor variables that satisfy known boundary conditions, for example if, in a cable with several conductors, it is known that the conductors have the same orientation and a fixed distance from one another and, if applicable, also have the same current intensity.These known boundary conditions can advantageously be taken into account when executing the optimization algorithm. Furthermore, the at least one conductor can also comprise multiple conductors, which are, however, treated as a single conductor, for example, in the case of a bundled conductor comprising a plurality of individual conductors. For the sake of clarity and better comprehensibility, only one conductor 200 is shown in Fig. 6.

[0077] In Fig. 8, the current determination algorithm is shown in the form of a schematic flow diagram. First, in step 300, the measured values ​​of the magnetic field sensors 101-108 are recorded at a first time step. Subsequently, in step 310, parameters of a current conductor for which the current intensity is to be determined are initially specified, i.e., values ​​for a plurality of corresponding conductor variables are set to respective starting values. The conductor variables include variables that represent the position and orientation of the at least one current-carrying conductor 200 relative to the measuring arrangement 100. In the embodiment shown in Fig. 6, the conductor variables that represent the position and orientation of the conductor are the passage position in the x-direction, i.e., x s , the passage position in the y-direction, ie y s, as well as the direction angle α and the tilt angle β. Optionally, the current to be determined can also be advantageously considered as an additional conductor variable. For example, the initial values ​​can be the passage position xs=0, ys=0, the current I=100A, the direction angle α=0°, and a tilt angle relative to the plane β=90°.

[0078] Subsequently, in step 320, the expected sensor values ​​of the magnetic field sensors are calculated using the specified values ​​of the conductor variables. The Biot-Savart law is advantageously applied for this calculation. For simplicity, the Biot-Savart law can be applied for an infinitely long straight conductor. In cylindrical coordinates, this is:

[0079] The calculation is also performed depending on information or parameters of the magnetic field sensors, wherein the parameters represent, in particular, the position, orientation, and / or metrological properties of the respective magnetic field sensor. For example, for each magnetic field sensor, information regarding the respective position, the orientation, e.g., as the value of a tilt angle, the gain (i.e., the proportionality between the existing magnetic flux density and the sensor output value), and the offset (i.e., a zero-point deviation) are taken into account. These parameters can advantageously be determined in advance by a calibration method described in more detail below and stored in a memory of the measuring arrangement 100, for example, a memory of the microcontroller 130.Advantageously, the parameters of the magnetic field sensors considered in the calculation can be adapted to the ambient conditions by adjusting the respective parameter values, for example, to achieve temperature compensation and / or compensation for supply voltage fluctuations. In this case, the measuring arrangement advantageously comprises corresponding sensors for temperature measurement and / or voltage measurement. The provision of the parameters of the magnetic field sensors is shown in Fig. 8 as step 330.

[0080] Subsequently, in step 340, a value of a predeterminable first quality or cost function is determined as a function of the values ​​calculated in step 320 and the values ​​measured in step 300, wherein in particular the recorded sensor values ​​are compared with the calculated values ​​in order to determine the value of the quality or cost function.

[0081] Various cost functions are conceivable. A preferred option is to calculate which magnetic field would be established at the positions of the individual magnetic field sensors if the estimated conductor variables were present, in particular by applying the Biot-Savart law, whereby in this case the costs result from the differences between the calculated and the actually measured field strengths. For example, a standard deviation or a difference between minimum and maximum can be calculated. In this variant, the current to be measured is considered as one of the conductor variables. In the flow diagram shown as an example in Fig. 8, such a cost function is used and accordingly the current to be measured is considered as one of the conductor variables.

[0082] Another possibility for determining the current strength is to determine an amplification factor from the estimated geometric arrangement of the at least one conductor 200, i.e., from the respective current estimated values ​​of the conductor variables for each of the magnetic field sensors 101-108. This amplification factor is used to calculate an estimated current strength from the actually measured field strength. If the estimated arrangement of the at least one conductor 200 corresponds to reality, the same current strength results from each measured value. Accordingly, the deviations in the estimated values ​​for the current strength can be used as a cost function.The respective amplification factor is again advantageously calculated using the Biot-Savart law, whereby the calculation of the amplification factors is carried out on the basis of standardized magnetic field measured values. The standardization can, for example, provide for dividing the measured values ​​by the largest of the measured values, whereby the standardized values ​​are then independent of the current intensity and only contain information about the position and orientation of the conductor, so that the current intensity to be measured does not have to be taken into account as one of the conductor variables in this case.

[0083] Subsequently, in step 350, it is analyzed whether a termination criterion has been met. The termination criterion can be the amount of the costs calculated by the cost function; for example, exceeding or falling below a threshold can be provided as the termination criterion. Another termination criterion can be the number of previous optimization runs. If a limit is reached, the determination process is terminated, and the determined value of the current to be measured is saved in step 370.

[0084] If the termination criterion is not met, the current conductor parameters, i.e., the conductor variables, are optimized in step 360 using a predeterminable first optimization algorithm. This means that the values ​​of the majority of conductor variables are varied depending on the predeterminable first optimization algorithm, with the value of at least one of the conductor variables being changed in particular. Various optimization algorithms known from the literature can be used for the optimization, for example, the simplex method according to Nelder and Mead, particle swarm optimization, the trust region method, the Powell method, and many more.

[0085] When using a total of 5 conductor variables as described in the example, which represent current strength, passage position x, passage position y, direction angle α and tilt angle β, a minimum of 5 measured values ​​of the magnetic flux density are required for optimization. If, for example, magnetic field sensors are provided that each detect only one component of the magnetic flux density, it is advantageous to provide at least 5 magnetic field sensors. Preferably, the number of magnetic field sensors provided is greater than or equal to the number of conductor variables considered in the optimization. Increasing the number of magnetic field sensors leads to an improvement in accuracy, since the determination method is then overdetermined and interference such as sensor noise, interference fields from neighboring conductors and the like have a lesser influence on the accuracy of the current strength to be determined.

[0086] The arrangement of the magnetic field sensors is advantageously chosen so that the current determination algorithm, i.e. in particular the optimization algorithm, converges well and quickly. The arrangement of magnetic field sensors shown in Fig. 6 and a large number of other arrangements of magnetic field sensors investigated by the inventors result in convex optimization problems that can be solved with most optimization algorithms, with the use of the Powell method for optimization proving particularly advantageous in this regard. The Powell method is described, for example, in "An efficient method for finding the minimum of a function of several variables without calculating derivatives.", MJD Powell, Computer Journal, 7: 155 - 162, 1964. Other influencing factors can advantageously be estimated as conductor variables, such as the position, orientation and current strength of an adjacent current-carrying conductor.Accordingly, the method can advantageously provide that the plurality of conductor variables comprises, for example, variables which represent the current intensity and / or the position and orientation of at least one conductor arranged outside the predetermined measuring range.

[0087] This increases the number of conductor variables to be optimized. Depending on the specific geometric arrangement of the magnetic field sensors, a non-convex optimization problem may arise, characterized by a cost function with multiple local minima. There is a risk that an optimization method will strive for a local optimum while missing the global optimum, resulting in an error in the current to be determined. This can be advantageously avoided by using more complex optimization algorithms that are robust to non-convex cost functions, for example, by using genetic algorithms or stochastic methods.However, since such a problem is already apparent during the development of a model variant of a measuring device when selecting the concrete measuring device structure, the number and arrangement of the magnetic field sensors, the conductor variables to be considered and the optimization algorithm to be used can each be advantageously selected in such a way that a convex optimization problem results.

[0088] It is also conceivable to estimate the conductor variables, i.e., for example, the current strength of the electric current flowing through the at least one conductor, as well as the conductor position and orientation, with the aid of artificial intelligence using neural networks. A neural network can be trained for this purpose, for example, using synthetically generated, i.e., simulated, or real measurement data. A current impressed in the simulation or measurement can be used as a label as an evaluation criterion. Referring again to Fig. 8, the conductor variables adjusted using the optimization method are then used in step 320 to calculate the newly resulting magnetic field sensor values ​​and to execute the subsequent steps already described.After the termination criterion has been reached and the estimated current has been saved, a wait step 380 is executed in which the estimation algorithm pauses until sensor values ​​for the next time step are available. If the current is not part of the conductor variables, the current is first calculated by "denormalization" before saving, whereby this is done by multiplying the sensor values ​​by the inverse of the normalization value. After the magnetic field sensor values ​​recorded for the next time step in step 390 are available, a value of the predeterminable first quality or cost function is again determined in step 340 as a function of the sensor values ​​measured in step 390 and the values ​​last calculated in step 320, whereby again in particular the recorded sensor values ​​are compared with the calculated values ​​in order to determine the value of the quality or cost function.If the measured and calculated sensor values ​​are in good agreement, the termination criterion is met and the estimated current is saved. This is especially the case if the real conductor parameters, which are represented by the conductor variables, have not changed or have changed only slightly compared to the previous time step. If the termination criterion is not met, the optimization of the conductor variables continues as described above.

[0089] The optimization, and thus the estimation of the ladder variables, is therefore performed continuously during ongoing measurement operations. The last optimization result from the previous time step can advantageously be used as the starting value. For this reason, high convergence rates are not necessary, and a few iteration steps per time step are usually sufficient.

[0090] As already described above, the current determination algorithm described in Fig. 8 requires information on the magnetic field sensors, including in particular the position, alignment, offset, and gain of the respective magnetic field sensor. This information can be obtained, for example, from design data for the circuit board and sensors and from the technical data sheets of the sensors. Alternatively, these parameters can be determined by measurement on existing hardware, for example, during a series calibration in final production inspection. Measuring the sensor properties can be complex, and some sensor properties are difficult or even impossible to measure. For example, the position of a magnetic field-sensitive element, such asa Hall plate within a sensor module housing can exhibit specimen scatter, so that non-destructive testing methods such as X-ray analysis with high spatial resolution would have to be carried out to clearly determine the position and orientation of the sensor.

[0091] Alternatively, the invention provides a method for calibrating a measuring device described above, with the aid of which parameters of the plurality of magnetic field sensors are determined, wherein the parameters represent in particular the position, the orientation and / or metrological properties of the respective magnetic field sensor, and wherein the determined parameters of the magnetic field sensors are stored in the memory device of the measuring device.

[0092] In the current determination algorithm described above, the calculation of expected values ​​with respect to the values ​​measured by the magnetic field sensors is then preferably carried out as a function of the parameters of the plurality of magnetic field sensors determined for the plurality of magnetic field sensors with the aid of the calibration method.

[0093] The calibration procedure involves introducing at least one calibration conductor, through which a current of a predefined intensity flows, into the specified measuring range in different arrangements one after the other, and carrying out the following steps for each arrangement:

[0094] A) Measuring, by each of the magnetic field sensors of the measuring arrangement, a value for the magnetic flux density along at least one spatial direction at the location of the respective magnetic field sensor, B) Setting the values ​​for a plurality of sensor variables and calibration conductor variables to respective starting values, wherein the sensor variables represent parameters of the plurality of magnetic field sensors, including in particular the position, orientation and / or metrological properties of the respective magnetic field sensor, and wherein the calibration conductor variables comprise variables that represent the position and orientation of the at least one calibration conductor relative to the measuring arrangement,

[0095] C) Calculating expected values ​​for the values ​​measured by the magnetic field sensors depending on the values ​​of the majority of sensor variables and calibration ladder variables,

[0096] D) Determining a value of a predeterminable second quality function depending on the values ​​calculated in step C) and the values ​​measured in step A),

[0097] E) as long as a predefined second termination criterion is not yet met, varying the values ​​of the calibration ladder variables depending on a predefined second optimization algorithm and repeating steps C) and D),

[0098] F) if the second termination criterion is met, saving the values ​​of the calibration ladder variables,

[0099] G) Calculating expected values ​​for the values ​​measured by the magnetic field sensors depending on the values ​​of the sensor variables and the stored calibration ladder variables,

[0100] H) Determining a value of a predeterminable third quality function depending on the values ​​calculated in step G) and the values ​​measured in step A),

[0101] I) as long as a predefined third termination criterion is not yet met, varying the values ​​of the sensor variables depending on a predefined third optimization algorithm and repeating steps G) and H),

[0102] J) if the third termination criterion is met, saving the values ​​of the sensor variables,

[0103] K) as long as a predefined fourth termination criterion is not yet met, repeating steps C) to J) with the stored values ​​of the sensor variables and calibration ladder variables as starting values, L) when the fourth termination criterion is met, storing the stored values ​​of the sensor variables as parameters of the magnetic field sensors in the memory device of the measuring device.

[0104] Capital letters are used for the steps of the calibration procedure to distinguish them from the lowercase steps above.

[0105] Advantageously, the calibration conductor variables may comprise at least one variable representing the current intensity of the current flowing through the at least one calibration conductor, wherein in particular the starting value for the current intensity corresponds to the predeterminable current intensity.

[0106] An exemplary calibration procedure or calibration measurement procedure is shown as a schematic flow diagram in Fig. 9.

[0107] The calibration measurement method illustrated by way of example can be divided into three sections. In a first section 510, the calibration is initialized. In a second section 520, the parameters of the magnetic field sensors, i.e., values ​​for the plurality of sensor variables, are determined. In a third section 530, the position and orientation of the at least one calibration conductor relative to the measurement arrangement, i.e., values ​​for the plurality of calibration conductor variables, are determined.

[0108] In the first section, a counter m is first set to 1 in step 511, which indicates which calibration measurement is involved. Subsequently, in step 512, the at least one calibration conductor is positioned in the measuring range of the measuring arrangement, and preferably a current intensity of the electrical current flowing through the at least one calibration conductor is specified. As described above, the arrangement of the at least one calibration conductor relative to the measuring arrangement differs for each calibration measurement.

[0109] The current can be supplied, for example, from a current source with a known current intensity, or an unknown current can be supplied, the current intensity of which is determined using a suitable measuring method, for example by means of a shunt measurement, a current transformer, or a Rogowski coil. The position and orientation of the calibration conductor are irrelevant. The point at which the calibration conductor passes through the area defined by the magnetic field sensors, in particular the point at which the calibration conductor passes through a plane in which the magnetic field sensors are arranged, must merely lie within a permitted range located between the magnetic field sensors, in particular within the defined measuring range described above.In the presence of the predetermined current, the sensor signals of the magnetic field sensors are detected in step 513, corresponding to step A) above.

[0110] Subsequently, in step 514, the values ​​for the plurality of sensor variables and the values ​​for the plurality of calibration conductor variables are initially specified, corresponding to step B) above. The sensor positions and orientations can be assumed, for example, from the design data of the circuit board 110, and the gain can be taken from the data sheet. The offset can initially be assumed to be 0.

[0111] Analogous to the optimization algorithm described above in connection with the method for determining the current intensity of an electric current flowing through at least one conductor, the values ​​for the calibration conductor variables can now be determined in step 515, corresponding to steps C), D) and E) above. It should be noted that, accordingly, in step 515, initially only the calibration conductor variables are optimized with constant sensor variables. In step 516, the determined calibration conductor variables are stored, corresponding to step F) above. The described initialization is repeated for all calibration measurements, for which purpose the counter m is incremented in step 517 and in step 518 it is checked whether the counter m has exceeded a maximum value mm®, where the value m max corresponds to the number of calibration measurements. As long as this is not the case, steps 512 to 517 are repeated. Each magnetic field sensor is advantageously characterized by a sensor position x, a sensor position y, a sensor tilt angle, a sensor rotation angle, a sensor offset, and a sensor gain, wherein in this case each magnetic field sensor has 6 degrees of freedom and therefore 6 corresponding sensor variables are provided for each magnetic field sensor. The sensor position x and the sensor position y preferably refer to a defined coordinate system, which is selected, for example, depending on the design of the circuit board 110. The sensor tilt angle and sensor rotation angle preferably indicate the respective angles relative to a plane defined in particular by the circuit board 110.Since, as described below, the sensor variables are determined separately for each magnetic field sensor, this results in a total of 6 degrees of freedom, so that in this case at least m is required to optimize the sensor variables. m ax=6 calibration measurements are required. A larger number of calibration measurements increases robustness against external influences, such as noise. Preferably, the positioning or arrangement of the at least one calibration conductor differs as much as possible in the individual calibration measurements to ensure a convex cost function for sensor parameter optimization. For an accurate determination of the offset, it is advantageous to perform one of the calibration measurements in the absence of an electrical current.

[0112] The phase 520 of determining the sensor parameters following the initialization phase is now carried out successively for each of the n magnetic field sensors, with n=8 for the measuring arrangement 100 shown in Fig. 6. For this purpose, a sensor counting index i is initially set to 1 in step 521.

[0113] Subsequently, in step 522, the sensor variables are adjusted using a suitable optimization method, corresponding to the above steps G), H) and I). For this purpose, the previously determined values ​​of the calibration ladder variables and the recorded magnetic field sensor values ​​for the respective magnetic field sensor i are specified and the corresponding sensor variables assigned to the magnetic field sensor i, for example, position Xi, position yi, rotation angle a £, tilt angle ßi, OFFSETi, and GAINi are adjusted so that the calculated sensor signals are in the best possible agreement with the measured sensor signals for all calibration measurements m performed. The determined sensor parameters are saved in step 523, corresponding to step J) above.

[0114] The described optimization of the sensor variables is performed for all magnetic field sensors. For this purpose, the sensor count index i is incremented in step 524, and a check is performed in step 525 to determine whether the sensor count index i has exceeded the number n of magnetic field sensors. As long as this is not the case, steps 522 to 524 are repeated.

[0115] Subsequently, in step 526, it is checked whether a termination criterion is met, which in particular corresponds to the fourth termination criterion defined in step K) above. The termination criterion can expediently be an exceeding of a predefined number of iterations performed between optimization of the sensor variables and optimization of the calibration ladder variables, or an undershoot of a predefined residual error with respect to the optimized values ​​of the calibration ladder variables and sensor variables. If the termination criterion is met in step 526, the calibration process is terminated in step 527, and the stored sensor variables are stored as parameters of the magnetic field sensors in the memory device of the measuring device.

[0116] If the termination criterion in step 526 is not met, the values ​​of the calibration ladder variables for the individual calibration measurements can be optimized again using the determined sensor variables. In the flow chart shown in Fig. 9, the counter m is first set back to 1 in step 528 and then the stored sensor variables are retrieved in step 531 and used to calculate the expected magnetic field sensor values ​​in step 532. Using the newly determined values ​​of the calibration ladder variables, the sensor variables can then be optimized again, corresponding to step K) above. As shown in Fig. 9, steps 533, 534, 535 and 536 are carried out to redetermine the values ​​of the calibration ladder variables, whereby these correspond to steps 515 to 518. Investigations by the inventors have shown that with suitable placement and orientation of the sensors, for example according to the method shown in Fig.6, with 10 calibration measurements with different arrangements of the at least one calibration conductor, comprising arrangements in which a calibration conductor is positioned in the center of the U-shaped recess of the circuit board 110, and those in which a calibration conductor is arranged at other positions distributed within the recess, and with 4 iterations of optimizations of the sensor variables and the calibration conductor variables, a calibration of the sensor parameters is achieved with sufficient accuracy.

[0117] As described above, the calibration should preferably be set to m max different configurations regarding the arrangement of the at least one calibration conductor are provided. For this purpose, a calibration conductor can be moved in the measuring area manually or automatically, for example, with the aid of mechanical actuators. Alternatively, a calibration arrangement can be provided for calibration, as shown schematically in Fig. 10.

[0118] In the calibration arrangement shown schematically in plan view in Fig. 10, calibration conductors K1 to K9 are shown as the at least one calibration conductor, which are positioned within the measuring range of the measuring arrangement 100 shown in Fig. 6, wherein a return conductor KR is also provided in the calibration arrangement shown. The calibration conductors K1 to K9 are positioned in the area between the magnetic field sensors 101 to 108, the return conductor KR is positioned outside the measuring range and all calibration conductors run perpendicular to the representation plane in the illustrated embodiment. A possible displacement in the x and y directions and a current direction that is not perpendicular to the representation plane, i.e. tilting and / or twisting, of the calibration conductor are possible but are not shown in order to keep the representation clear.The direction of the currents in the calibration conductors K1 and K3 to K9 runs into the display plane, while the current in the calibration conductor K2 flows out of the display plane. Various calibration configurations with different numbers of calibration conductors and current directions other than those shown are conceivable. It is preferably intended that the position, tilt, and rotation of the individual calibration conductors do not change during calibration. For this purpose, mechanical fixation of the calibration conductors can be provided. The individual calibration conductors can be charged with a current I. m be energized.

[0119] An exemplary circuit diagram is shown in Fig. 11. A controllable current source 620 can be configured for the respective calibration configuration m with m E {1, ... , m max ] can be configured via a control input 610 and thus the calibration current I mbe specified. Via a controllable switching matrix 630, the calibration current can be supplied to the calibration conductors Kl to Kn and the calibration return conductor KR, which is located outside the measuring range, via the switches S 1,1 to Sn,l, Sl,2 to Sn,2 and SR. It is possible that no calibration conductor, a calibration conductor and the calibration return conductor, a calibration conductor pair or several calibration conductors and / or the return conductor are connected to the controllable current source. In this way, a large number of calibration configurations can be provided by means of permutations for a small number of calibration conductors. It is also possible for the current in the individual calibration conductor pairs to be equal by connecting the calibration conductor pairs in series. For the sake of simplicity of illustration, only one possible parallel connection is shown in Fig. 11. In order to, as described above, to use the 6 degrees of freedom of the individual magnetic field sensors, i.e.In order to determine sensor parameters or the values ​​of the sensor variables, the calibration configurations shown in the following table can be provided with the help of three calibration conductors Kl, K2, K3, the return conductor KR and the switching matrix. The entry "0" means that no current flows into the relevant calibration conductor, + indicates a positive current, i.e. into the representation plane of Fig. 10, and - a negative current, i.e. out of the representation plane of Fig. 10. The conductor parameters determined in configurations 2, 3 and 4, i.e. the values ​​of the corresponding calibration conductor variables, can advantageously be used in configurations 5 to 10, taking into account the current direction and the current amplitude I. m be reused.

[0120] This means that with the help of 3 calibration leads and one return lead, 10 calibration measurements can be carried out. In configurations 8-10, the current in the individual calibration leads is preferably measured, since unequal conductor resistances, contact resistances, etc. can lead to an inexactly equal distribution of the parallel flowing currents. In addition to the sensor parameters described above, position x, position y, tilt and inclination angle, offset and gain, other parameters such as sensor non-linearity, temperature-dependent gain and offset, etc. can be determined by suitable adaptation of the optimization procedure and the inclusion of further calibration conditions such as temperature. It is also possible to assume sensor parameters that do not exhibit large deviations, for example the sensor alignment, i.e. the angle of rotation, as fixed, which reduces the number of required measurements or even eliminates them.increases robustness against noise for a given number of measurements.

Claims

Patent claims 1. Measuring device (1, 1') for contactless measuring of the current intensity of an electrical direct or alternating current flowing through at least one conductor (200, 200'), comprising - at least one first housing part (10, 10'), which by its design defines a measuring area arranged outside the first housing part (10, 10'), - a measuring arrangement (100) with a plurality of magnetic field sensors (101-108, 101 '-108') which are arranged at fixed positions and in fixed orientations relative to the defined measuring range, - a storage device in which parameters of the magnetic field sensors (101-108, 101'-108') are stored, the parameters comprising information on the positions, orientations and metrological properties of the magnetic field sensors (101-108, 101'-108'), - a processing unit (130) connected to the magnetic field sensors (101-108, 101'-108') and the memory device, which processing unit is designed to determine a value for the current intensity of the electric current flowing through the at least one conductor (200, 200') as a function of the measured values of the magnetic field sensors (101-108, 101'-108') and as a function of the parameters stored in the memory device when the at least one conductor (200, 200') extends through the defined measuring range in any position and orientation, - a retaining device (20, 20') which is designed to form, together with the first housing part (10, 10'), an openable and closable conductor feedthrough, wherein the retaining device (20, 20') is designed such that a conductor (200, 200') introduced into the conductor feedthrough extends through the defined measuring area, and - at least one output interface (140, 50, 30, 30') for outputting the determined value for the current intensity and / or a value derived from the determined value of the current intensity.

2. Measuring device according to claim 1, wherein the retaining device is designed as a retaining bracket (20) which is movably, in particular rotatably or slidably, fastened to the first housing part (10) or the retaining device is formed by a cable tie, a rubber band or a tab with applied locking hooks. 3 Measuring device according to claim 1, wherein the retaining device is designed as a second housing part (20') which can be detachably connected to the first housing part (10'), wherein in particular the first and second housing parts each have locking elements (11', 21') which are complementary to one another or the first and second housing parts can be connected by means of a screw connection.

4. Measuring device according to one of the preceding claims, further designed to measure an electrical voltage, wherein the measuring device in particular has input terminals (40) for voltage measurement.

5. Measuring device according to one of the preceding claims, comprising at least one communication interface (30, 30') for communication with at least one further, in particular similar, measuring device, wherein the measuring device is designed in particular to exchange measurement data with the at least one further measuring device, wherein the measurement data, in particular for measured values contained in the measurement data, each comprise an associated time stamp which indicates at which time the measured values were determined.

6. Measuring device according to one of the preceding claims, designed as a measuring transducer, and designed to determine a value for an electrical power and / or a value for an electrical energy as a function of at least one determined value for the current intensity of the electrical current flowing through the at least one conductor (200, 200') and / or as a function of at least one value of a measured electrical voltage and / or as a function of measurement data received via the at least one communication interface (30, 30').

7. Measuring device according to one of the preceding claims, wherein the plurality of magnetic field sensors (101-108, 101'-108') are arranged at fixed positions and in fixed orientations on a rigid support (110) arranged within the first housing part (10, 10').

8. Measuring device according to claim 7, wherein the carrier (110) is designed as a printed circuit board, and wherein the printed circuit board has a U-shape due to a recess provided in the printed circuit board, wherein two printed circuit board arms are formed by the recess, between which the measuring range defined by the design of the housing lies, and wherein at least one of the plurality of magnetic field sensors (101-108, 101'-108') is arranged on each of the two printed circuit board arms.

9. Measuring device according to one of the preceding claims, wherein the processing unit (130) is designed to determine the value for the current intensity of the electric current flowing through the at least one conductor (200, 200') as a function of measured values of the magnetic field sensors (101-108, 101'-108'), as long as a predeterminable first termination criterion is not met, by carrying out the following steps: a) varying the values of a plurality of conductor variables as a function of a predeterminable first optimization algorithm, wherein the conductor variables comprise variables that represent the position and orientation of the at least one current-carrying conductor (200, 200') relative to the measuring arrangement (100), b) calculating expected values with respect to the values measured by the magnetic field sensors (101-108, 101'-108') as a function of the values of the plurality of conductor variables, and depending on the parameters stored in the memory device,where, in particular, the Biot-Savart law for an infinitely long straight conductor is used to calculate the expected values, and c) determining a value of a predeterminable first quality function as a function of, the values calculated in step b) and the measured values of the magnetic field sensors (101-108, 101'-108').

10. Measuring system comprising at least two measuring devices (1, 1') according to one of claims 1 to 9, which are communicatively connected to one another for the exchange of measurement data.

11. A method for calibrating a measuring device (1, 1') according to one of claims 1 to 9, wherein the calibration method provides for at least one calibration conductor (K1-K9), through which a current of predeterminable current intensity flows, to be introduced successively in different arrangements into the defined measuring range, and for each arrangement to carry out the following steps: A) measuring by each of the magnetic field sensors (101-108, 101'-108') of the measuring arrangement (100), a value for the magnetic flux density along at least one spatial direction at the location of the respective magnetic field sensor (101-108, 101'-108'), B) setting the values for a plurality of sensor variables and calibration conductor variables to respective starting values, wherein the sensor variables represent parameters of the plurality of magnetic field sensors (101-108, 101'-108'), including in particular the position, orientation and / or metrological properties of the respective magnetic field sensor (101-108, 101'-108'), and wherein the calibration conductor variables comprise variables representing the position and orientation of the at least one calibration conductor (K1-K9) relative to the measuring arrangement (100), C) Calculating expected values for the values measured by the magnetic field sensors (101-108, 101 '-108') depending on the values of the plurality of sensor variables and calibration conductor variables, D) Determining a value of a predeterminable second quality function depending on the values calculated in step C) and the values measured in step A), E) as long as a predefined second termination criterion is not yet met, varying the values of the calibration ladder variables depending on a predeterminable second optimization algorithm and repeating steps C) and D), F) if the second termination criterion is met, saving the values of the calibration ladder variables, G) Calculating expected values for the values measured by the magnetic field sensors (101-108, 101 '-108') depending on the values of the sensor variables and the stored calibration ladder variables, H) Determining a value of a predeterminable third quality function depending on the values calculated in step G) and the values measured in step A), I) as long as a predefined third termination criterion is not yet met, varying the values of the sensor variables depending on a predefined third optimization algorithm and repeating steps G) and H), J) if the third termination criterion is met, saving the values of the sensor variables, K) as long as a predefined fourth termination criterion is not yet met, repeat steps C) to J) with the stored values of the sensor variables and calibration ladder variables as starting values, L) if the fourth termination criterion is met, storing the stored values of the sensor variables as parameters of the magnetic field sensors (101-108, 101'-108') in the memory device of the measuring device (1, 1').

12. The method according to claim 11, wherein the calibration conductor variables comprise at least one variable representing the current intensity of the current flowing through the at least one calibration conductor (K1-K9), wherein in particular the starting value for the current intensity corresponds to the predeterminable current intensity.

Images