LU503820B1 - Measuring device for contactless current measurement and method for its calibration - Google Patents

Abstract

The invention provides a measuring device (l, l') for contactless measurement of the current intensity of a direct or alternating current, comprising at least a first housing part (10, 10'), which by its construction defines a measuring area arranged outside the first housing part (10, 10'), as well as a plurality of magnetic field sensors (101-108, 10T-108'), which are arranged at fixed positions and in fixed orientations, and a storage device in which parameters of the magnetic field sensors (101-108, 101'-108') are stored. The measuring device (l, l') is designed to determine a value for the current intensity of an electric current flowing through at least one conductor (200, 200') depending on the measured values of the magnetic field sensors (101-108, 101'-108') and depending on the stored parameters when the at least one conductor (200, 200') extends through the defined measuring range in any position and orientation. The invention also provides a measuring system and a method for calibrating the measuring device.

Description

Measuring device for contactless current measurement and method for its calibration

Description

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

To determine the current flowing in a conductor, various

Measurement methods are known. For example, the voltage drop across a

Resistance such as a shunt resistor can be determined and the flowing current can be determined using the known resistance value according to Ohm’s law. In addition, current measuring arrangements with a ferromagnetic core are known that work according to the transformer principle. The conductor with the current to be measured is passed through a core. The

The conductor with the current to be measured forms the primary conductor of a transformer.

The primary current can be determined via a secondary winding wound on the core by 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.

It is also possible, for example, to use Hall sensors to measure the magnetic field caused by a current and use this to determine the current causing it. In this way, currents, including direct currents, can be measured without contact. In particular, methods are known that do not require a ferromagnetic

core to focus the magnetic field.

In particular, an evaluation of the magnetic field strength according to the

Ampère’s law, according to which the measured current is based on the solution of a

The formula [,,, = $, Hds can be used for this, where Im is the electric current to be measured, S describes a closed path in space that encloses the current, and where H is the vectorial magnetic field strength and ds is the differential of the integration path. If the magnetic flux density is measured using sensors at specific points in a

spatial direction, the approximation is the formula Ia = XE B;s;, where Ima is the approximate current to be measured and po is the permeability of the

vacuum and i is a counting index running from 1 to N, where N is the number of magnetic field sensors and B: the magnetic field detected by the i-th sensor.

Flux density in the direction of the path element with the length si. The path elements sı 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 towards infinity. If the number of

Finally, an exact solution can also be obtained if, for example, the magnetic field sensors are arranged equidistantly on a circular path and are 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.

Measuring arrangements that use the measuring principle described above based on Ampère’s

Act are described, for example, in EP 3 589 961 B1, US 11,150,272 B2,

EP 3 958 003 A1 and EP3259603B1.

Mechanisms for compensating for disturbing magnetic fields are described, for example, in US 11029342 B2 and US 2021/0231709 A1. EP 3948310 A1 also describes a measuring arrangement which, for this purpose, includes a filter unit for

Homogenization of external magnetic fields, i.e. magnetic fields that are not caused by the electrical 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 Ampère's law described above, the position of the current-carrying conductor relative to the magnetic field sensors must be known.

For example, in WO 2022030287 A1, EP 2821798 B1, EP 2921864 B1 and

In the measuring arrangements described in EP 3106884 B1, the electrical conductor to be measured is fixed in a predetermined position. In WO 2010/096344 A1, a current measuring device for measuring a

alternating current in a conductor, in which a plurality of measuring coils are provided, by means of which the position of the conductor is determined.

From EP 3761044 A1 a current measuring device with two magnetic field sensors is also known, whereby the measured values of the magnetic field sensors are used to

Conductor position and orientation and the current to be measured can be determined using complex triaxial magnetic field sensors, 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 results from the fact that the calculation assumes that the components of the

magnetic field to an identical point in space, although 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.

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, whereby in particular a contactless measurement of both direct and alternating currents is to be made possible, and whereby in particular a corresponding measuring device is to be proposed which is suitable for a

Retrofitting, i.e. for a retrofit, of existing lines for different

cable cross-sections and does not require the use of a ferromagnetic core.

This problem is solved by the features of the independent claims.

Advantageous embodiments are the subject of the dependent claims, wherein the specified features and advantages can essentially apply to all independent claims.

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 due to its design has a

Housing part arranged measuring range defined, as well as 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 range.

Furthermore, the measuring device comprises a storage device in which parameters of the

Magnetic field sensors are stored, whereby the parameters provide information about the

Positions, orientations and metrological properties of the

Magnetic field sensors, as well as a connection to the magnetic field sensors and the

Processing unit connected to the storage device, which is designed to

Dependence of the measured values of the magnetic field sensors and in dependence of the

to determine a value for the current intensity of the electric current flowing through the at least one conductor when the at least one conductor moves in any position and orientation through the defined

extends through the measuring range.

To ensure that a conductor to be measured remains within the defined measuring range during a current measurement, the measuring device includes a

Retaining device which is designed to form an openable and closable conductor feedthrough together with the first housing part, wherein the

The retaining device is designed such that a conductor inserted into the conductor feedthrough extends through the defined measuring area.

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.

According to a second aspect of the invention, a measuring system is provided which comprises at least two measuring devices as described above, which are used for exchanging

Measurement data are communicatively linked.

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 into the defined measuring range in different arrangements one after the other, and for each arrangement the following steps are carried out:

A) Measuring by each of the magnetic field sensors of the measuring arrangement, one

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 number of sensor variables and calibration

Ladder variables to respective starting values, whereby the sensor variables are parameters of the

A 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 representing the position and orientation of the at least one calibration conductor relative to the measuring arrangement,

C) Calculating expected values for the magnetic field measured by the

Values depending on the values of the majority of sensor variables and

calibration ladder 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 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),

F) if the second termination criterion is met, saving the values of the calibration

ladder variables,

G) Calculating expected values for the magnetic field measured by the

Values 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, saving the stored values of the

Sensor variables as parameters of the magnetic field sensors in the storage device of the

measuring device.

Using the described calibration procedure, the parameters of the

Magnetic field sensors with a very high accuracy and in the

The data can be stored in the measuring device’s memory, so that the

Determining a value for the current intensity of the electrical current flowing through the at least one conductor by the processing unit, which

Dependence of the measured values of the magnetic field sensors and in dependence of the

The parameters stored in the memory device can be read with a high degree of accuracy.

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 be advantageously used for conductors with different cross-sections.

The device advantageously enables contactless measurement of AC and DC currents using magnetic field sensors without using a ferromagnetic core and, due to its design, is also advantageously able to be mounted around existing power lines in the sense of a retrofit without the line having to be

By additionally measuring the voltage between the conductor and a reference potential, it is also possible to

Performance measurement can be carried out, whereby by connecting several devices a

Multiphase measurement is possible.

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

Figure 1 is a schematic representation of a first preferred

Embodiment of a measuring device according to the invention in perspective view,

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,

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,

Figure 5 is a schematic representation of a second preferred

Embodiment of a measuring device according to the invention in perspective view,

Figure 6 is a schematic representation of another exemplary

Embodiment of a measuring arrangement in perspective view,

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

Determination of the current intensity of an electric current flowing through at least one conductor by the measuring device,

Figure 9 is an exemplary schematic flow diagram of steps of a preferred embodiment of a calibration method for

Determination of parameters relating to the measuring device

magnetic field sensors,

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

Figure 11 schematically shows an exemplary circuit arrangement for selective

Selection of current-carrying calibration conductors of the type shown in Figure 10

calibration arrangement.

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 has a

The measuring range is defined by the housing part, whereby in the illustrated

embodiment, the first housing part is formed by the housing part 10.

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.

The measuring device 1 further comprises a measuring arrangement with a plurality

Magnetic field sensors which are arranged at fixed positions and in fixed orientations relative to the defined measuring range, whereby this measuring arrangement is

Protection of the components is advantageously arranged within the housing part 10 and is therefore not shown in Fig. 1. The measuring arrangement is shown, for example, in Fig. 4.

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 an openable and closable conductor feedthrough together with the first housing part 10, wherein the

Retaining device is designed in such a way that a conductor inserted into the conductor bushing remains within the defined measuring range when the

conductor feedthrough is closed.

In the embodiment shown in Fig. 1, the retaining device is designed as a retaining bracket 20 which is movably attached to the first housing part 10 and which can be rotated by means of a swivel joint 22. Various other

Designs of a restraint bar and various other types of movable fastening are conceivable. For example, a sliding

The restraint device can also be advantageously provided by a cable tie, a rubber band or a strap with applied

Latching hooks may be formed, each of which is designed and/or arranged to close the opening formed by the U-shape of the first housing part 10.

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

The measuring device 1 further comprises 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

The measuring device shown in Fig. 1 | comprises

Outputting values, for example, a user interface 50 and a

Communication interface 30. Furthermore, the measuring device 1 is advantageously designed to measure an electrical voltage, wherein the measuring device 1 has, for this purpose, in particular input connections 40 for voltage measurement.

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 particularly designed to be connected to the at least one further

Measuring device to exchange measurement data, whereby the measurement data in particular to

The measured values contained in the measurement data each include an associated timestamp that indicates the point in time at which the measured values were determined.

In the embodiment shown in Fig. 1, the measuring device 1 is also preferably designed to communicate via the communication interface 30 with a

to be supplied with operating voltage.

In the embodiment shown in Fig. 1, the measuring device 1 is also designed to

Mounting on a mounting rail 90, for example designed as a top hat rail, whereby for this purpose appropriately adapted

DIN rail carrier 91 can be provided.

Advantageously, the measuring device can be designed as a measuring transducer, whereby the

Measuring device in this case preferably for determining 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.

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

To determine the measured values of the magnetic field sensors, whereby the position and orientation of the

Conductor can be defined, for example, by the displacements xs and ys shown in Fig. 1 in the x- and y-direction relative to the center of the measuring range and the angles 201 and 202. In the example shown, the angle 201 indicates the direction angle of the conductor 200 in the x-z plane and the angle 202 indicates the direction angle of the conductor 200 in the y-z plane. In the side view shown in Fig. 2, the

Angle 202 is shown. Alternatively, other angles could be used, such as the direction angle 203 in the x-y plane, which is shown as an example in

Fig. 3 is shown.

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. In the illustrated embodiment, the measuring device 1 comprises a

Measuring arrangement with a plurality of magnetic field sensors 101°-108°, which are mounted on 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 within the first

Housing part 10 arranged rigid support 110°, which advantageously serves as

The printed circuit board preferably has a

The recess provided in the circuit board has a U-shape, whereby the recess forms two circuit board arms, between which the

Housing part 10 defined measuring range, and wherein on each of the two

Circuit board arms of at least one of the plurality of magnetic field sensors are arranged 101°-108°.

Parameters of the magnetic field sensors 101°-108° are stored in a memory device of the measuring device, whereby the parameters contain information on the positions, the

Orientations and metrological properties of the magnetic field sensors 101‘- 108‘.

Furthermore, the measuring device 1 comprises a magnetic field sensor 101‘-108° and the

Processing unit connected to the storage device, which is designed to

Dependence of the measured values of the magnetic field sensors and in dependence of the

The method is used to determine a value for the current intensity of the electric current flowing through the at least one conductor 200 from 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, and this can include the memory device. Alternatively, a separate

storage device must be provided.

Fig. 4 also 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.

Figure 5 shows a schematic representation of an alternative embodiment of a

Measuring device 1' is shown in perspective view. In this embodiment, the

Retaining device is designed as a second housing part 20° which can be detachably connected to a first housing part 10', wherein in particular the first and second

Housing part 10° and 20° each have complementary locking elements 11° and 21° respectively. Alternatively, another suitable type of detachable

A connection may be provided, such as a screw connection, in which the first and second housing parts can be connected at 10° and 20° by means of a screw connection.

Similar to the measuring device 1 described above, the one shown in Fig. 5

Measuring device 1° a communication interface 30‘, input connections 40 for

Voltage measurement and a user interface 50. Furthermore, the

Measuring device 1° a connection 70 for connecting a power supply, as well as

Display and/or control elements 60 are provided.

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.

Analogous to the measuring device 1 described above, the measuring device 1° also includes a

A processing unit connected to magnetic field sensors and a storage device, which is designed to calculate 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 depending on the parameters stored in the storage device.

current when at least one conductor is 200° in any position and

Orientation extends through the defined measuring range, whereby

Processing unit can preferably be provided with a microcontroller 130.

Accordingly, in the measuring device 1" shown in Fig. 5, the

In principle, conductors can 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 specified by the design of the measuring device. Fig. 5 shows an example of a 200' conductor with such a maximum conductor cross-section.

For mounting on a 90 mm mounting rail, appropriately adapted

DIN rail support 91. It should be noted that, depending on the design, the first housing part 10 or the retaining device for mounting on a

Support rail 90 can be designed.

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.

Fig. 6 shows schematically a perspective view of an alternative

Embodiment of a measuring arrangement 100 which in an inventive

Measuring device 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 processing units connected to the processing unit

Magnetic field sensors 101-108. In the embodiment shown in Fig. 6, the processing unit comprises a microcontroller 130, which is advantageously designed to execute commands stored in a memory. Instead of a

Microcontroller, the processing unit can alternatively also have a

microprocessor or a CPU (central processing unit).

Any magnetically sensitive sensor can serve as a magnetic field sensor, in particular a Hall sensor, a fluxgate sensor, a magneto-resistive sensor or a magneto-optical sensor. The magnetic field sensors 101-108 are designed to detect the magnetic flux density in a spatial direction indicated by arrows. The circuit board 110 has a U-shaped contour, which makes it possible to

Conductor 200, which carries a current to be measured, is introduced into the area between sensors 101-108.

The current-carrying conductor 200 does not pass through the exact center of the area, but the point of passage has a displacement xs in a first spatial direction, in

Fig. 6 as the x-axis, and a displacement ys in 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 direction angle a and a tilt angle B relative to the plane, wherein in the illustrated

In the example, both angles are not equal to 90°. It should be noted that the

Direction angle a represents the direction of projection of conductor 200 into the x-y plane and tilt angle ß represents the angle of intersection between conductor 200 and x-y plane.

The above-described embodiments show variants of the device structure of the

Measuring device, wherein preferably a current measuring input, a

Voltage measurement input, a supply connection and an interface to

Data output and communication are provided. The measuring device can be divided into 2 components by separating or folding them open, which can be connected to each other, for example, by a hinge or by snap hooks or tabs.

The current measurement input is, for example, controlled by the 8

Magnetic field sensors realized on a circuit board.

The elements shown in Fig.6 for example for the measurement data acquisition consisting of analog-digital converter (ADC) 120 and a downstream

Microcontroller unit (MCU) 130 uses an algorithm to determine the current flowing in conductor 200.

The existing voltage input allows a voltage applied to the line 200 or 200° to be measured, for example, to be measured by a

Voltage taps at terminal points can be measured. Based on the determined values for

Current and voltage from the two measuring inputs can be displayed in the

Power and energy can be calculated using a measuring device designed as a measuring transducer, which can be stored in the measuring device by 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).

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 101-10n and the

Voltage input 150 is connected to an analog to digital converter 120 and converted into a digital data stream. The electrical

Measuring input 150 can be connected to the ADC 120 via a safe separation 155. The digital data stream is passed to a microcontroller 130.

The processor of the microcontroller 130 calculates from the digital data stream a

Value for the current intensity of the electric current flowing in the conductor 200, wherein the calculation preferably uses an optimization algorithm, which is described in more detail below. From the calculated value for the

A signal is generated 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 intensity (e.g. 0V=0A, 10V=1000A),

Voltage (e.g. OV=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, Profinet etc., or for example via a device-internal web-based management, i.e. on a website accessible via the user interface.

The output unit 140 can also evaluate the calculated value of the

current, voltage or power and, for example, when a certain

threshold value a warning signal at a digital output or by setting a

It is also possible that an analogue to digital converter and a magnetic field sensor are integrated in one component, for example in the form of an IC (Integrated Circuit). In this case, each magnetic field sensor with an integrated analogue to digital converter sends a digital data stream to the

processor, for example using PC.

If several measuring transducers, i.e. several of the measuring devices described above, are connected via a digital interface, such as Modbus RTU, in a

Communication bus connected to each other, thus multi-conductor DC

Networks or e.g. 3-phase AC networks can be measured. For this purpose, the communication interfaces 30 or 30° described above can be used. 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 calculates the temporal progression of current and voltage, as well as the resulting values for power and (taking into account the

times). This data can be output or displayed via the user interface 50, an analog output, a digital interface or via an internal web page.

In addition, data generated during the current determination, such as 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, are exchanged between the measuring instruments in order to reduce the influence of the measuring instruments by the adjacent current-carrying conductors. The combined

Data from multiple transmitters can also provide information about 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

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, which measure the magnetic flux density in one, two or three

Capture spatial directions.

The magnetic field caused by the current to be measured is measured using several

Sensors are measured at different positions and spatial directions. The sensors are fixed in a fixed arrangement, in the illustrated embodiment on a

Printed circuit board 110. The assembly has an opening that allows current conductors to be inserted into the

measuring range without breaking the circuit. It is not necessary to hold the conductor in a certain position or at a certain

Orientation, but it is sufficient if the conductor is at any

Position in any orientation within a defined measuring range.

The defined measuring range is determined in particular by the design of the first

Housing part 10 or 10° or by the design of the adapted measuring

Arrangement 100 is specified, although the design may vary depending on the intended use.

In the embodiment shown in Fig. 6, the measuring arrangement 100 comprises a

Printed circuit board 110 on which the processing unit and the majority of

Magnetic field sensors 101-108 are arranged, wherein the circuit board 110 has a U-shape due to a recess provided in the circuit board, wherein the

Two circuit board arms are formed in the recess, between which the specified

Measuring range of the measuring arrangement, and on each of the two circuit board

Arms of at least one of the plurality of magnetic field sensors 101-108.

In the illustrated embodiment, four of the magnetic field sensors are arranged on each of the two circuit board arms in a row along the extension direction of the respective circuit board arm.

The sensor signals are converted into a digital signal using analog-to-digital conversion.

Data stream is converted into a data stream, which is processed by a processor of the microcontroller or

CPU can be processed to finally output the current to be measured.

The invention preferably provides for the use of an optimization algorithm for the measurement data evaluation. The algorithm has the task of

combination of values for ladder variables that satisfy the existing

Measured values of the magnetic field sensors are “explained” as best as possible, 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.

Optimization algorithms require a cost or quality function that determines the quality of a

Express the estimate in a number. The estimate is then varied to find the value that achieves the highest quality or the lowest cost.

The optimization algorithm can be terminated after a given number of

optimization runs or when the quality criterion falls below a predefined limit.

In the optimization algorithm preferably used here, the

Estimated value from the combination of the values of the ladder variables and thus represents a

N-dimensional vector, where N is defined by the number of conductor variables. Other influencing factors may be the cross-sectional shape of the conductor and

Position, orientation and current strength of any adjacent

Current conductors are taken into account. The position and orientation of the conductor are basically only auxiliary values that arise as a by-product of the optimization algorithm in order to increase the accuracy of the current to be measured. An output of these values is typically not provided.

To determine the current intensity of an electrical signal flowing through at least one conductor 200

current which is in a given measuring range of a measuring

Arrangement 100 with a plurality of magnetic field sensors 101-108 is positioned, 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 which 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 as a function of the

Step c) calculated values and the values measured in step a), e) as long as a predefined first termination criterion is not yet met, varying the

Values of the majority of ladder variables depending on a predeterminable first

Optimization algorithm and repeating steps c) and d), f) if the first termination criterion is met, determining a value for the current intensity of the current flowing through the at least one conductor depending on the values of the

ladder variables.

It should be noted that the at least one conductor advantageously comprises exactly one conductor. The at least one conductor can also comprise several conductors, which are each positioned independently of one another in any position and orientation in 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 also comprise several conductors, the position and

Orientation and, if applicable, current intensity can be represented by conductor variables that satisfy known boundary conditions, for example, in a

Cables with multiple conductors are known to have the same orientation and a fixed distance from each other and, if necessary, the same

These known boundary conditions can be advantageous in the

execution of the optimization algorithm. Furthermore, the at least one conductor can also comprise several conductors, which are however treated as a single conductor, for example in the case of a

bundle conductor. For the sake of clarity and better comprehensibility, only one conductor 200 is shown in Fig. 6.

In Fig. 8 the current determination algorithm is shown in the form of a schematic

First, in step 300, the measured values of the

Magnetic field sensors 101-108 are recorded at a first time step. Then, in step 310, parameters of a current conductor for which the current intensity is to be determined are initially specified, i.e. values are determined for a plurality of corresponding conductors.

Variables are set to respective starting values. The conductor variables include variables which represent the position and orientation of the at least one current-carrying conductor 200 relative to the measuring arrangement 100. In the example shown in Fig. 6

The example shown here is a ladder variable which determines the position and orientation of the

conductor, the passage position in x-direction, i.e. xs, the

Passage position in y-direction, i.e. ys, as well as the direction angle o and the

Tilt angle ß is provided. Optionally, the

Current intensity can be considered as another conductor variable. For example, the starting values can be the passage position xs=0, ys=0, the current intensity I=100A, the

Direction angle a=0° and a tilt angle relative to the plane ß=90° are initially specified.

Subsequently, in step 320, the values of the conductors

Variables expected sensor values of the magnetic field sensors are calculated, whereby for these

The Biot-Savart law is advantageously applied for the calculation. The Biot-Savart law can be simplified for an infinitely long straight line

Conductor can be applied. This is in cylindrical coordinates: > I,

B(f) = np Eq

The calculation is also carried out depending on information or parameters of the magnetic field sensors, whereby the parameters in particular include the position, the

Orientation and/or metrological properties of the respective magnetic field sensor. For example, for each magnetic field sensor, information is provided regarding the respective position, the orientation, e.g. as a value of a tilt angle, the gain, i.e. the proportionality between the existing magnetic flux density and

sensor output value and the offset, i.e. a zero point deviation, are taken into account.

These parameters can be advantageously adjusted by a

Calibration procedures are determined in advance and stored in a memory of the measuring arrangement 100, for example a memory of the microcontroller 130.

Advantageously, the parameters taken into account in the calculation of the

Magnetic field sensors can be adapted to the ambient conditions by adjusting the respective parameter values, for example to

To achieve temperature compensation and/or compensation of supply voltage fluctuations. In this case, the measuring arrangement advantageously has 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.

Subsequently, in step 340, a value of a predeterminable first quality or

Cost function is determined depending on 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.

Various cost functions are conceivable. A preferred option is to calculate which magnetic field will be generated if the estimated conductor

Variables at the positions of the individual magnetic field sensors, in particular by applying the Biot-Savart law, in which case the

Costs from the differences between the calculated and the actually measured

Field strengths can be calculated, whereby, for example, a standard deviation or a difference between minimum and maximum can be calculated. In this variant, the current to be measured is taken into account as one of the conductor variables. In the flow chart shown as an example in Fig. 8, such a cost function is used and accordingly the current to be measured is taken into account as one of the conductor variables.

Another possibility for determining the current intensity is to determine an amplification factor from the estimated geometric arrangement of the at least one conductor 200, i.e. from the current estimated values of the conductor variables for each of the magnetic field sensors 101-108, with the aid of which an estimated current intensity is calculated from the actually measured field intensity. If the estimated arrangement of the at least one conductor 200 corresponds to reality, the same current intensity results from each measured value. Accordingly, the deviations of the estimated values for the current intensity can be considered as

The respective amplification factor is again advantageously calculated using the Biot-Savart law, whereby the

The amplification factors are calculated on the basis of standardized magnetic field measurements, whereby 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 strength and only information about the position and

Orientation of the conductor, so that the current to be measured does not have to be considered as one of the conductor variables in this case.

Then, in step 350, it is analyzed whether a termination criterion has been reached.

The termination criterion can be used to analyze the amount of costs calculated by the cost function, with the termination criterion being, for example, the excess or

A threshold value can be provided for. Another

The termination criterion can be the number of previous optimization runs.

If a limit is reached, the determination process is aborted and the determined value of the current to be measured is stored in step 370.

If the termination criterion is not met, the current conductor parameters, i.e. the

Ladder variables, in step 360 using a predefined first optimization

Algorithm optimized, i.e. the values of the majority of ladder variables are

Dependence on the predefinable first optimization algorithm varies, whereby in particular the value of at least one of the ladder variables is changed. For the

Optimization can be carried out using various optimization methods known from the literature.

Algorithms, for example the simplex method according to Nelder and Mead, the particle

Swarm optimization, the trust region method, the Powell method, and many more can be used.

In the example described above, a total of 5 ladder variables are used, which

Current strength, passage position x, passage position y, direction angle a and

tilt angle B, a minimum of 5 magnetic flux density measurements are required for optimization. For example,

Magnetic field sensors are provided, each of which only detects one component of the magnetic

flux density, it is therefore advantageous to have at least 5

Magnetic field sensors are provided. Preferably, a number of magnetic field sensors is provided that is greater than or equal to the number of magnetic field sensors considered in the optimization.

conductor variables. Increasing the number of magnetic field sensors leads to a

Improvement of accuracy, since the determination procedure is then overdetermined and interference such as sensor noise, interference fields from neighboring

Conductors and similar have a lesser influence on the accuracy of the determined

current strength.

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. In the arrangement of the

Magnetic field sensors and a variety of other materials investigated by the inventors

Arrangements of magnetic field sensors result in convex optimization problems that can be solved with most optimization algorithms, whereby the

The use of the Powell method for optimization has proven to be 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.”, M. J. D. Powell, Computer Journal, 7:155 - 162, 1964.

As conductor variables, other influencing factors can advantageously be estimated, such as the position, orientation and current strength of a neighboring current-carrying conductor. Accordingly, the method can advantageously provide that the plurality of conductor variables includes, for example, variables which

current intensity and/or the position and orientation of at least one conductor arranged outside the specified measuring range.

This increases the number of conductor variables to be optimized. Depending on the respective geometric arrangement of the magnetic field sensors, a non-convex optimization problem may arise, which is characterized by a cost function with several local minima, where there is a risk that a

Optimization method aims at a local optimum and misses the global optimum, so that an error remains in the current to be determined. This can be advantageously avoided by using more complex optimization algorithms that are robust against non-convex cost functions, for example by using genetic algorithms or stochastic methods. However, since such a problem can already be identified during the development of a model variant of a

Measuring device when selecting the specific measuring device design, it is also advantageous to consider the number and arrangement of the magnetic field sensors, the conductor variables to be considered and the optimization

Algorithms must be chosen in such a way that a convex optimization problem results.

It is also conceivable to estimate the ladder variables, i.e. for example the

Current strength of the electric current flowing through at least one conductor, as well as the conductor position and orientation, with the help of artificial intelligence using neural networks. A neural network can be trained for this purpose, for example, with the help of synthetically generated, i.e. simulated, or real measurement data. As

The evaluation criterion can be a current impressed in the simulation or measurement as

label can be used.

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 carry out the subsequent steps described above. After the termination criterion has been reached and the estimated current strength has been stored, a wait step 380 is carried out in which the estimation algorithm remains until sensor values of the next

If the current is not part of the conductor variable, the current is first calculated by “denormalization” before being saved, whereby this is done by multiplying the sensor values by the reciprocal of the

After the magnetic field sensor values recorded in step 390 for the next time step are available, a value of the predeterminable first quality or cost function is determined in step 340 depending on the sensor values measured in step 390 and the values last calculated in step 320, whereby again 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 stored. This is especially the case when the real conductor parameters, which are determined by the

Ladder variables have not changed or have only changed slightly compared to the previous time step. If the termination criterion is not met, the optimization of the ladder variables is continued as described above.

The optimization, and thus the estimation of the ladder variables, is therefore carried out in the current

Measurement operation is carried out continuously. The last optimization result from the previous time step can be used as the starting value. For this reason, no high convergence speeds are necessary and usually a few iteration steps per time step are sufficient.

As already described above, the current determination algorithm described in Fig. 8 requires information on the magnetic field sensors, which in particular includes position, orientation, offset and gain of the respective magnetic field sensor. This information can be obtained, for example, from design data of the

PCB and sensors and from the technical data sheets of the sensors. Alternatively, these parameters can be determined by measuring existing hardware, for example during a series adjustment in a 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 as a Hall plate within a sensor module housing can vary from specimen to specimen, so that a clear determination of the position and orientation of the

Sensors non-destructive testing methods such as X-ray analysis with high spatial resolution would have to be carried out.

Alternatively, the invention provides a method for calibrating a measuring device described above, by means of which parameters of the plurality of

Magnetic field sensors are used to determine the parameters, in particular the position, orientation and/or metrological properties of the respective

magnetic field sensor, and the determined parameters of the

Magnetic field sensors are stored in the memory device of the measuring device.

In the current determination algorithm described above, the calculation of expected values with respect to the values measured by the magnetic field sensors is preferably carried out depending on the values for the majority of magnetic field sensors with

The parameters of the majority of

magnetic field sensors.

The calibration procedure provides for at least one calibration conductor, through which a current of a predeterminable current intensity flows, to be successively tested in different

arrangements in the specified measuring range and carry out the following steps for each arrangement:

A) Measuring by each of the magnetic field sensors of the measuring arrangement, one

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 number of sensor variables and calibration

Ladder variables to respective starting values, whereby the sensor variables are parameters of the

A 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 representing the position and orientation of the at least one calibration conductor relative to the measuring arrangement,

C) Calculating expected values for the magnetic field measured by the

Values depending on the values of the majority of sensor variables and

calibration ladder 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 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),

F) if the second termination criterion is met, save the values of the calibration

ladder variables,

G) Calculating expected values for the magnetic field sensors measured

Values 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, saving the stored values of the

Sensor variables as parameters of the magnetic field sensors in the storage device of the

measuring device.

Uppercase letters are used for the steps of the calibration procedure to distinguish them from the lowercase steps above.

Advantageously, the calibration conductor variables can comprise at least one variable which represents the current intensity of the current flowing through the at least one calibration conductor, wherein in particular the starting value for the

current strength corresponds to the specified current strength.

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

The calibration measurement procedure shown as an 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

A plurality of sensor variables are determined and in the third section 530 the

Position and orientation of at least one calibration conductor relative to the measuring

arrangement, i.e. values for the majority of calibration ladder variables, are determined.

In the first section, a counter m is first set to 1 in step 511, which indicates which calibration measurement is involved. Then, 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 current flowing through the at least one calibration conductor is measured.

Conductor flowing electrical current is predetermined, wherein, as described above, the arrangement of the at least one calibration conductor relative to the measuring arrangement differs for each calibration measurement.

The current can be specified, for example, from a current source with a known current strength or an unknown current can be specified whose

Current intensity using a suitable measuring method, for example using a shunt

Measurement, a current transformer or a Rogowski coil. It is irrelevant where the at least one calibration conductor is placed and what orientation the calibration conductor has. The point of passage of the at least one calibration conductor through the area defined by the

Magnetic field sensors, in particular the passage point through a

The plane in which the magnetic field sensors are arranged must only lie within a permitted area that is located between the magnetic field sensors, in particular within the defined measuring range described above.

In the presence of the specified current, in step 513 the sensor signals of the

Magnetic field sensors, according to step A) above.

Then, 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 alignments can be assumed, for example, from design data of the circuit board 110 and gain can be taken from the data sheet. The offset can initially be assumed to be 0.

Analogous to the procedure described above in connection with the determination of

The optimization algorithm described for the current intensity of an electric current flowing through at least one conductor can now be used in step 515 to determine the values for the

Calibration ladder variables are determined according to steps C above),

D) and E). It should be noted that accordingly in step 515 only the

Calibration ladder variables can be optimized with constant sensor variables. In

In step 516, the determined calibration ladder variables are stored, corresponding to step F above. The described initialization is repeated for all

Calibration measurements are repeated, for which purpose the counter m is incremented in step 517 and it is checked in step 518 whether the counter m has a maximum value

Mmax, where mmax 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, where 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

Angle relative to a plane defined in particular by the circuit board 110.

Since, as described below, the sensor variables for each

Magnetic field sensor are determined separately, a total of 6 degrees of freedom result, so that in this case at least mmax=6 is required for an optimization of the sensor variables.

Calibration measurements are required. A larger number of calibration measurements increases the robustness against external influences, such as noise. Preferably, the positioning or arrangement of the at least one

Calibration conductors in the individual calibration measurements should be as different as possible in order to ensure a convex cost function of the sensor parameter optimization. For an accurate determination of the offset, it is advantageous to use one of the

To perform calibration measurements in the absence of an electrical current.

The phase 520 following the initialization phase of determining the

Sensor parameters are now carried out for each of the n magnetic field sensors one after the other, whereby n=8 for the measuring arrangement 100 shown in Fig. 6. For this purpose, a sensor count index i is initially set to 1 in step 521.

Subsequently, in step 522, the sensor variables are determined using a suitable

optimization procedure according to steps G), H) and I) above.

For this purpose, the previously determined values of the calibration conductor variables and the recorded magnetic field sensor values are specified for the respective magnetic field sensor i and the corresponding sensor variables assigned to the magnetic field sensor i, for example position x;, position yi, angle of rotation α, tilt angle β;, OFFSET; and GAIN; are adjusted so that the calculated sensor signals correspond to the measured

Sensor signals for all calibration measurements performed m in the best possible

The determined sensor parameters are stored in step 523, corresponding to step J) above.

The described optimization of the sensor variables is carried out for all magnetic field sensors, whereby for this purpose the sensor count index 1 is incremented in step 524 and in step 525 it is checked whether the sensor count index i has exceeded the number n of magnetic field sensors. As long as this is not the case, the

Repeat steps 522 to 524.

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 exceedance of a predetermined number of iterations carried out between optimization of the sensor

Variables and optimization of the calibration ladder variables or a fall below a predefined residual error with regard to the optimized values of the calibration

Conductor variables and sensor variables must be provided. If the termination criterion is in

Step 526 is fulfilled, the calibration procedure is terminated in step 527 and the stored sensor variables are used as parameters of the magnetic field sensors in the

storage device of the measuring device.

If the termination criterion in step 526 is not met, the determined sensor

Variables the values of the calibration ladder variables for the individual

Calibration measurements can be optimized again, whereby in the case shown in Fig. 9

Flowchart first in step 528 the counter m is reset to 1 and then the stored sensor variables are retrieved in step 531 and used for

Calculating 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, according to the above

Step K). As shown in Fig. 9, to recalculate the values of the

Calibration ladder variables, steps 533, 534, 535, and 536 are performed, which correspond to steps 515 to 518.

Investigations by the inventors have shown that with appropriate placement and

Orientation of the sensors, for example according to the arrangement 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 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 ladder variables a calibration of the

sensor parameters are achieved with sufficient accuracy.

As described above, the calibration preferably involves specifying Mmax different configurations with respect to the arrangement of the at least one

Calibration conductor is provided. For this purpose, a calibration conductor can be moved in the measuring area manually or automatically, for example with the help of mechanical actuators. Alternatively, a calibration arrangement can be provided for the calibration, as shown schematically in Fig. 10.

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 area and all calibration conductors run perpendicular to the

A possible shift in the x and y direction and a current direction that is not perpendicular to the plane of representation, i.e. a tilting and/or twisting of the calibration conductor are possible but not shown in order to

The direction of the currents in the calibration conductors K1 and K3 to K9 runs into the representation plane, the current in the calibration conductor K2 flows out of the representation plane. Various calibration configurations with different numbers of calibration conductors and other than those shown are possible.

It is preferably provided that the position, the

Tilting and twisting of the individual calibration conductors does not change during calibration. For this purpose, a mechanical fixation of the calibration conductors can be provided. The individual calibration conductors can be energized with a current Im.

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 € {1, ..., Mmax} via a control input 610 and thus the calibration current Im can be specified. The calibration current can be fed to the calibration conductors K1 to Kn and the calibration return conductor KR, which is outside the measuring range, via the switches S1,1 to Sn,1, S1,2 to Sn,2 and SR via a controllable switching matrix 630. It is possible that no calibration conductor at all, a calibration conductor and the

Calibration return conductor, a calibration conductor pair or several calibration conductors and/or the

Return conductors are connected to the controllable current source. In this way, a large number of calibration configurations can be provided by permutations for a small number of calibration conductors. It is also possible to have the same current in each calibration conductor pair by connecting the calibration conductor pairs in

For the sake of simplicity, only one possible parallel connection is shown in Fig. 11. In order to connect the 6

The degrees of freedom of the individual magnetic field sensors, i.e. sensor parameters or the values of the sensor variables, can be determined using 3 calibration conductors K1, K2,

K3, the return conductor KR and the switching matrix shown in the following table

Calibration configurations are provided. 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 be advantageously used in configurations 5 to 10 under

Taking into account the current direction and the current amplitude Im.

Configuration | Power | Power | Power | Power switch closed

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Cr 1510108

Cs [ee es

Ce fee ems

CE [ss

Ce Le 810 ss

Cr eee sess

Cs eo sess

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With the help of 3 calibration conductors and a return conductor, 10

Calibration measurements can be carried out. For configurations 8-10, the

Current in the individual calibration conductors is measured, since due to unequal

Conductor resistances, contact resistances, etc. may result in a not exactly equal distribution of the parallel flowing currents. In addition to the above-described

Sensor parameters position x, position y, tilt and inclination angle, offset and gain as well as other parameters such as sensor nonlinearity, temperature-dependent

Gain and offset etc. by appropriate adjustment of the optimization procedure and

The calibration parameters can be determined by adding further calibration conditions, such as temperature. It is also possible to assume that sensor parameters that do not exhibit large deviations, such as the sensor orientation, i.e. the angle of rotation, are fixed, which reduces the number of measurements required or

Robustness against noise increased for a given number of measurements.

Claims (12)

patent claims 1. Measuring device (1, 1°) for contactless measurement 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 range 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 device connected to the magnetic field sensors (101-108, 101'-108') and the storage device, which is designed to determine a value for the current intensity of the electrical current flowing through the at least one conductor (200, 200°) depending on the measured values of the magnetic field sensors (101-108, 101°-108°) and depending on the parameters stored in the storage 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 an openable and closable conductor feedthrough together with the first housing part (10, 10°), wherein the retaining device (20, 20°) is designed such that a conductor (200, 200°) introduced into the conductor feedthrough extends through the defined measuring range, and - at least an 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, attached 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 connections (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 in particular designed to exchange measurement data with the at least one further measuring device, wherein the measurement data, in particular for measurement values contained in the measurement data, each comprise an associated time stamp which indicates at which point in time the measurement 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 carrier (110) arranged within the first housing part (10, 10°). 8. Measuring device according to claim 7, wherein the carrier (110) is designed as a circuit board, and wherein the circuit board has a U-shape due to a recess provided in the circuit board, wherein two 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 circuit board arms. 9. Measuring device according to one of the preceding claims, wherein the processing unit (130) is designed to carry out the following steps for determining 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 predefinable first termination criterion is not met: a) varying the values of a plurality of conductor variables as a function of a predefinable first optimization algorithm, wherein the conductor variables comprise variables which represent the position and orientation of the at least one conductor (200, 200°) through which current flows 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 in Dependence of the parameters stored in the storage device, wherein 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. Method for calibrating a measuring device (1, 1°) according to one of claims 1 to 9, wherein the calibration method provides for introducing at least one calibration conductor (K1-K9), through which a current of predeterminable current intensity flows, into the defined measuring range one after the other in different arrangements, and for each arrangement the following steps are carried out: A) measuring by each of the magnetic field sensors (101-108, 101-108') of the measuring arrangement (100), in each case 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°), comprising 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 which represent 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 predeterminable second termination criterion is not yet met, varying the values of the calibration conductor variables depending on a predeterminable second optimization algorithm and repeating steps C) and D), F) when the second termination criterion is met, storing 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 predeterminable third termination criterion is not yet met, varying the values of the sensor variables depending on a predeterminable third optimization algorithm and repeating steps G) and H), J) when the third termination criterion is met, storing the values of the sensor variables, K) as long as a predeterminable 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 start values, L) when 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 which represents 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 predefinable current intensity.