Apparatus, and measurement and analysis system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HYDAC ACCESSOIRES GMBH
- Filing Date
- 2026-01-14
- Publication Date
- 2026-07-23
Smart Images
Figure EP2026050799_23072026_PF_FP_ABST
Abstract
Description
[0001] HYDAC ACCESSORIES GMBH
[0002] Hirschbachstraße 2, 66280 Sulzbach / Saar, Germany
[0003] Device as well as measuring and evaluation system
[0004] The invention relates to a device for detecting at least one fluid level, comprising a receiving device extending to a predefinable height for receiving the fluid, the upper surface of which forms the respective fluid level, a measuring object whose position correlates with the respective fluid level, and an evaluation device for detecting the respective position of the measuring object. The invention further relates to a measuring and evaluation system based on such a device.
[0005] Devices of this type are known and are also referred to in technical terms as liquid level controls (LLCs). They serve to indicate the level of a liquid within a container, such as a tank, with the device itself being mounted outside the container but connected to it via at least one fluid connection in the manner of communicating vessels. With such a device, the current fill level can be displayed optically, for example, by visually observing the position of a float serving as the measuring object. Alternatively, an electrical switching signal can be generated at a predefined fill level value, which corresponds, for example, to a maximum or minimum value. This signal is generated by the triggering element, usually in the form of a permanent magnet on the float, acting on the detector element of the switching device at a predefined position within its range of motion.When the signal occurs, the necessary actions can be carried out manually or automatically once the relevant fill level is reached.
[0006] DE 102019001 310 A1 discloses a device for indicating a fluid level, comprising a device housing with a viewing window that provides a view of a transparent indicator body, which can be at least partially filled with the fluid via at least one connecting piece, the cavity of which is penetrated by a fixing element that has a fluid guide and serves to fix the device housing to a third component, such as a fluid storage tank, wherein the connecting piece has a support structure, at least consisting of individual ribs that connect plate-shaped wall parts of the connecting piece to each other and wherein the support structure encompasses the cavity.
[0007] Because the connector is not a solid body but a structure formed from individual ribs, costs are reduced by using less material, and the rib structure avoids the large differences in wall thickness found in a solid body. This means that, thanks to uniform wall thicknesses, potential distortion caused by temperature variations during operation is minimized, ensuring that the intended geometry for the sealing areas of the device is not unduly altered and thus guaranteeing long-term operational reliability.
[0008] DE 102009023 343 A1 discloses a device for displaying and / or controlling fluids, comprising at least one fluid connection opening into a riser pipe in which a float is guided to move within a display path depending on the fluid level, on which a triggering element is arranged which, by acting on at least one detector element located at a position on the device corresponding to a predetermined fluid level, triggers a switching operation of an electrical switching device, wherein an adjustment device is provided by means of which the at least one detector element can be adjusted to selectable positions corresponding to different fluid levels.
[0009] In this way, the known device can be easily adapted to the requirements of the respective application with regard to display and / or control functions. By adjusting the position of the respective detector element along the display path, individual switching points for the electrical switching device can be defined, signaling predetermined maxima or minima of the fill level in the form of step values. A reed switch is used as the detector element, and a permanent magnet arranged in a float serves as the triggering element and measuring object. Instead of reed switches as detectors and magnets as triggering elements, other sensor devices can also be used for position detection, for example, photoelectric sensors.For the visual display of the current fill level or fluid level, the riser tube can be designed as a (Plexiglas) tube, so that the position of the float can be directly observed by a viewer if necessary.
[0010] Based on this prior art, the invention aims to further improve known devices, in particular to enable stepless displacement measurement of the object being measured, preferably using digital technology. A device with the features of claim 1 in its entirety, as well as a measuring and evaluation system with the features of claim 9, achieves this objective.
[0011] By having, according to the characterizing part of claim 1, the evaluation device comprise a plurality of individual sensors which, in a stationary arrangement, extend in succession along a predefinable path along which the object being measured is guided and which detect the respective position of the object being measured, a continuously operating, preferably digital, path measurement for the object being measured is achieved.Due to the stationary arrangement of the individual sensors, which is provided from the outset and is free from any on-site position adjustment, they can be positioned with utmost precision along a predefined path or measuring section within a narrowly defined framework, thus eliminating measurement errors and ensuring high measurement accuracy. This contrasts with prior art systems, where detectors or sensors guided on a carriage must first be precisely positioned before determining switching points by means of tracking or adjustment, which regularly leads to measurement inaccuracies and thus makes precise position determination of the object being measured, usually in the form of a float with a permanent magnet, unattainable.
[0012] In addition to the known step-by-step measurement acquisition using the respective reed switch, which inherently makes continuous monitoring of the object being measured impossible, the stepless displacement measurement according to the invention enables continuous, preferably digital, monitoring of the object being measured across its entire range of motion or travel. This significantly improves the accuracy of the position measurements and makes processes in which the device is integrated more reliable. This has no equivalent in the prior art. A measurement and evaluation system based on such a device and equipped with corresponding evaluation electronics, in conjunction with a customer-specific evaluation unit, allows for a multitude of customer interfaces to be implemented, such as...
[0013] - 4 to 20 mA
[0014] - 0 to 10 V
[0015] - CAN
[0016] Profi net
[0017] - HSI
[0018] - further interface designs.
[0019] Accordingly, any customer or user who has a need for level monitoring of liquid media can make use of the device according to the invention and create special measuring and evaluation systems for fluid process monitoring based on it, which creates a high degree of flexibility.
[0020] In a preferred embodiment of the device according to the invention, the receiving device is formed by a riser pipe which has a fluid connection at each of its free, opposite ends. This connection, passing through a container wall, establishes a fluid-carrying link between the interior of a container, such as a storage tank, and the interior of the riser pipe. In this way, a lower fluid connection can supply fluid from the container into the riser pipe, and the other, opposite upper fluid connection serves to remove air from the riser pipe to prevent obstructions during measurement. In this respect, the two fluid connections function like communicating vessels between the riser pipe and the interior of the container.
[0021] In a further preferred embodiment of the device according to the invention, the object being measured is a float guided in the riser tube, which has a magnetic field-generating device, preferably in the form of a permanent magnet. Preferably, the evaluation unit is also arranged parallel to the orientation of the riser tube and outside of it. The individual sensors of this evaluation unit, maintaining a predefinable distance from one another, follow this orientation and, depending on the respective fluid level, detect the position of the object being measured within the riser tube in real time. In this way, continuous measurement is enabled, which is wear-free through the use of so-called solid-state components.Only semiconductor components developed using solid-state physics are used for the evaluation of the respective level measurements, and these preferably do not include electromechanical components such as reed switches or electron tubes, which increases the reliability within the signal processing.
[0022] In another preferred embodiment of the device according to the invention, the respective sensor operates according to the Hall effect, and preferably all Hall sensors used are of the same design. Unipolar, digital Hall effect sensors, which are therefore polarity-independent, are particularly preferred. In this way, a Hall effect sensor located in a magnetic field detects changes in the Hall voltage in order to determine the position of ferromagnetic objects. The use of such unipolar Hall sensors increases the measurement accuracy, and the range of variation in any tolerances that may still occur during the measurement is also extremely small. Bipolar sensors can also be used, however.
[0023] In a further particularly preferred embodiment of the device according to the invention, all Hall sensors used are connected to at least one analog-to-digital converter, which converts the detected analog measurement signals into digital evaluation signals. Preferably, the respective Hall sensor and the respective analog-to-digital converter are mounted on a circuit board and terminate via conductive traces at an interface that ensures data transmission to evaluation electronics, such as a microcontroller. This results in a reliable output of measured values for further processing by a microcontroller, which, being composed of semiconductor chips, can contain a processor and peripheral functions. Modern microcontrollers often also incorporate complex peripheral functions, such as CAN (Controller Area Network) interfaces, etc.
[0024] In a further preferred embodiment of the device according to the invention, the circuit board is chambered within a receiving housing, which is arranged on the inside of one leg of a U-shaped device housing that at least partially encompasses the riser tube, and the interface, designed in the form of a connector, extends through this leg with a predefinable projection. In this way, both the Hall sensors and the analog-to-digital converter are arranged on a single circuit board in a space-saving manner, which helps to avoid errors in data transmission and leads to the desired miniaturization in the design of the measurement electronics.
[0025] The circuit board is integrated into a housing and thus protected from damaging environmental influences. The circuit board and the housing form a standardized unit that can be easily adapted to a variety of liquid level indicators in different lengths, thus reducing manufacturing costs in a modular fashion. Since the circuit board is already protected by the housing, the housing is further protected by the U-shaped device housing, which overlaps the housing on at least one side. The connector of the housing is preferably standardized and can be reliably coupled with corresponding standardized connectors for data transmission.
[0026] An associated measurement and evaluation system consists at least of a device as described above and of evaluation electronics, typically in the form of a microcontroller, which can be releasably connected to the connector of the evaluation unit via a corresponding plug. This creates an interface that allows the device according to the invention to be connected to a variety of different evaluation electronics for measurement processes. Preferably, it is further provided that the evaluation electronics, particularly in the form of the microcontroller, can be connected to a customer-specific evaluation unit, such as a computing unit or computer, via a preferably standardized connection.
[0027] The invention further relates to a method for determining the position of a permanent magnet using several Hall sensors, preferably four Hall sensors, in particular provided for a device as described above and using an associated measuring and evaluation system as set out, which comprises at least the following steps:
[0028] - Reading out characteristic curves in the form of displacement-voltage profiles for the individual Hall sensors,
[0029] - Recording average sensor voltages for defined positions of the permanent magnet and creating corresponding measurement series,
[0030] - Calculating characteristic values with regard to absolute deviations of the individual sensors from the respective mean value based on the measurement series, - Forming at least one specific signature from the combination of mean values and deviation values for each position of the permanent magnet, and
[0031] - Storing the respective signature as a retrievable data record in a memory.
[0032] The associated software implements a method for determining the position of a permanent magnet using Hall sensors, preferably four Hall sensors. This solves the central technical problem of being able to unambiguously determine a magnet's position even when it is unknown whether the north or south pole is moving towards the Hall sensors. In practical applications, a polarity reversal often leads to mirror-image changes in the sensor signals, which can make conventional methods prone to errors or ambiguous. During operation, the current sensor voltages of the Hall sensors are continuously measured. For each stored reference data set, the software calculates an error measure, which is the difference between the expected deviations from the data set and the actually observed deviations of the current measured values.
[0033] Since the method does not use the absolute direction of the magnetic flux, but rather the deviation pattern of the sensors relative to each other, it remains stable even with reversed magnetic polarity. The reference data set with the smallest error is identified as the one that best corresponds to the actual magnetic position. A continuous position value is then derived from the index of this data set and subsequently output via a digital-to-analog converter.
[0034] The technical core of the method thus lies in the use of a feature space consisting of mean values and absolute deviations, which remains sufficiently asymmetrical despite any polarity reversal to allow for unambiguous assignment. This results in a particularly resource-efficient method that does not require complex magnetic field models and operates reliably in resource-constrained microcontroller systems. This has no equivalent in the prior art.
[0035] The device according to the invention, together with an associated measuring and evaluation system, will be explained in more detail below with reference to the drawing. The drawing shows, in a general and not to scale, the
[0036] Figure 1, in the form of an exploded view, shows the essential components of the device along with connectable evaluation electronics;
[0037] Figure 2, also in the form of an exploded view, shows a populated circuit board intended for chambered mounting in a mounting housing;
[0038] Figure 3 shows a perspective top view of the assembled device according to the respective representations in Figures 1 and 2;
[0039] Figure 4 shows the device according to Figure 3 in conjunction with a customer-specific evaluation unit, in particular in the form of a conventional computer, and Figure 5 shows in tabular form the signal processing of four Hall effect sensors as used for the device according to Figures 1 to 4.
[0040] The embodiment shown in the respective figure comprises a device housing 10 which has a rectangular cutout along its front face 11 facing the viewer. This cutout forms a viewing window 12, providing a view of a type of indicator element in the form of a hollow cylindrical riser tube 14 made of a transparent glass or plastic material. This allows for the direct visual observation of a liquid level or fluid level of a fluid located in the riser tube 14. The device housing 10 consists of a one-piece profile section, preferably made of aluminum, which has a U-shaped cross-section with lateral profile legs 16, 18. These legs connect laterally to a profile web 20 forming the front face 11 with the viewing window 12 and laterally surround the riser tube 14, leaving the rear area of the device housing 10 open.In the profile web 20, a bore 22 is formed centrally near the upper end of the profile and the lower end of the profile, which is provided for the passage of a hollow screw 24.
[0041] The viewing window 12, formed by an elongated cutout in the front face 11, terminates at equal intervals relative to the upper and lower bores 22. The two hollow screws 24 have a hexagonal head 26 at one end of their shank and an external thread 28 at the other end, as well as a coaxial internal bore extending from this end to a shank section 30 with a reduced outer diameter, which is located axially at a distance from both the head 26 and the external thread 28. Individual transverse bores 32 are provided in this shank section 30, forming the fluid connection to the internal bore of the hollow screw 24.
[0042] The fluid connection to a third component, such as a tank (not shown), is established via a connecting piece 34, which has an internal cavity in the form of a cylindrical through-section 36. To form a fluid connection from the through-section 36 to the riser pipe 14 forming the indicator body, a supply section 38 opens transversely into the connecting piece 34 and into the through-section 36. The actual fluid connection between the through-section 36 and the third component (tank) is established via the respective hollow screw 24, which, in the assembled state, passes through the through-section 36 and, with its end-end external thread 28, forms a screw connection (not shown) by which the device housing 10, together with the connecting piece 34 and riser pipe 14, is fixed to the third component or tank.In this assembly state, the reduced-diameter shaft part 30 of the hollow screw 24 is located in the area of the junction of the supply section 38 with the through-pass section 36, so that the fluid path to the supply section 38 is formed via the inner axial bore of the hollow screw 24 and its transverse bores 32.
[0043] To secure the device with its housing 10 to a wall of a container, such as a tank (not shown), two locking nuts 40 are located at the rear of the housing 10. These nuts, with their respective internal threads, can be screwed onto the corresponding external thread 28 of the hollow screw 24. The hollow screw 24 then passes through the container wall via corresponding bores, forming communicating vessels. This allows the locking nuts 40 to engage on the side facing away from the housing 10. When tightened, the locking nuts pull the housing 10 against the container wall from the outside until the device is securely fixed to the container wall. Each locking nut 40 has a central opening with an internal thread through which fluid from the container, into which the hollow screw 24 engages with its external angle 28, flows into the interior of the riser pipe 14.It is understood that with suitable sealing sets, in particular sealing rings 42, a fluid-tight seal of the device against the environment is achieved.
[0044] The device shown in Figure 1 serves to detect a fluid level that can change during operation. It includes a receiving device 44 extending to a predetermined height, which is formed here by the transparent riser tube 14. This receiving device receives the fluid, the upper surface of which defines the respective fluid level. Furthermore, a measuring object 46 is provided, the position of which correlates with the respective fluid level. In particular, the measuring object 46 is a cuboid float 48, which is designed as a permanent magnet or carries one. The float 48, which has a square cross-section, is longitudinally movable within the hollow cylindrical riser tube 14 and its rounded quadrilateral sections are in partial contact with the inner contour of the circular riser tube 16.Furthermore, an evaluation unit designated 50 is provided as a whole, which forms a type of measuring device for recording the respective position of the object 46. The evaluation unit 50 has a plurality of individual sensors 52 which, in a stationary arrangement, extend in succession along a predefinable path, along which the object 46 is guided vertically and which synchronously detect the respective position of the object 46 as a function of the prevailing fluid level.
[0045] As can be further seen from Figure 1, the evaluation unit 50 is arranged parallel to and outside the vertical orientation of the riser pipe 14. Its individual sensors 52, spaced at a predetermined discrete distance of equal length from one another, follow this vertical orientation and, depending on the respective fluid level, detect the position of the object 46 or the float 48 within the riser pipe 14 in real time. In this way, continuous, stepless monitoring of the position of the float 48 within the riser pipe 14 is achieved, thus ensuring continuous measurement data acquisition. Each sensor 52 operates according to the Hall effect, and all Hall sensors 52 are of the same design. These are all connected to an analog-to-digital converter 54, which converts the analog measurement signals received by the Hall sensors 52 into digital evaluation signals.The respective Hall sensor 52 and the respective analog-to-digital converter 54 are mounted on a circuit board 56 and interconnected by conductive traces (not shown). Such interconnection via conductive traces is common, so it will not be discussed in detail here; in particular, the conductive traces are not shown individually in the figures. In any case, these conductive traces terminate at an interface 58, which ensures data transmission to evaluation electronics 60, such as a microcontroller.
[0046] The circuit board 56, which is designed as a flat strip, has four sensors 52 on each side facing away from the viewing window 12, and the analog-to-digital converter (ADC) 54 located below them on the vertical axis. The interface 58, with its socket-like connection points 62, runs approximately in the middle of the strip. The respective conductor track terminates in these connection points, and when the evaluation unit 50 is plugged in, it engages with individual connector pins 64, which are designed in the manner of a connector 66 and are part of the interface 58.
[0047] The strip-shaped circuit board 56 is chambered in a receiving housing 68, which consists of two housing shells 70, 71 that can be connected to each other by means of a snap-fit or clip connection 74. The circuit board 56 is held between them and engages with the socket-like connection points 62 with the corresponding plug pins 64 of the connector 66, which projects with a definable axial overhang beyond a side wall of the first housing shell 70. As shown particularly in Figure 2, a housing shell 72 can also be designed as a flat cover part. In its installed state, the assembled receiving housing 68 then extends along one leg of the U-shaped device housing 10 in the form of the first profile leg 16, specifically on its inner side, which faces the riser tube 14.In this respect, the corresponding profile leg 16 has a U-shaped recess 76 in its central area, which serves to allow the passage of the connector 66, whose connector pins 64 penetrate the wall of the housing shell 70. It is understood that in modified embodiments, particularly in longer liquid level indicators, the circuit board 56 is also correspondingly longer and that, under certain circumstances, more than four Hall sensors 52 may be used, the number of sensors 52 ultimately depending on the measuring range to be covered, which results from the maximum possible travel of the object being measured 46 depending on the respective fill level within the riser pipe 14.
[0048] Figure 5 provides a more detailed understanding of the signal processing to be carried out. The voltage signals of the four Hall-effect sensors 52 are recorded; in particular, the voltage value is recorded for each millimeter of distance and plotted according to the characteristic curve shown in Figure 5. The bold, jagged characteristic curve shown in Figure 5 then represents the curve to be evaluated by the microcontroller or the evaluation electronics 60 in order to determine the respective distance traveled by the measured object 46 inside the liquid level indicator, which is calculated using a third-degree polynomial.
[0049] The evaluation electronics 60 then transmit the first voltage rise after detection by the first Hall effect sensor 52; subsequently, the other Hall sensors 52 are evaluated. The values of the other sensors 52 are determined using a software-defined offset value. This allows for very precise continuous measurement, which has no equivalent in the prior art. The curve of the sensor 52 located at the bottom in the direction of view of Figures 1 and 2 is shown in Figure 5 as Sensor 1 with a solid thin line. The sensor 52 above it is labeled Sensor 2, and its curve is shown with a dashed line. The sensor 52 located above it in Figure 1, labeled Sensor 3, produces a curve with a dashed dotted line. The uppermost sensor 4 is shown with its curve represented by a dotted line.The sum of all characteristic curves results in the jagged curve line, which is represented by a thick line. The preferably five-pin connector 66 has a standard thread, for example M12 x 1, on its free side. This standard thread 78 can be coupled to a corresponding standard thread 80 of a connector part 81 on the evaluation electronics 60, whereby the measurement data are transmitted from the evaluation unit 50 to the evaluation electronics 60 via the corresponding socket-like connection 82.
[0050] The corresponding connection position is shown in more detail in Figures 3 and 4. Figure 4 further illustrates the embodiment of the measuring and evaluation system, in which the evaluation electronics 60 are connected to a customer-specific evaluation unit 86, such as a computer, via a preferably standardized connection 84. Such a customer-specific interface can be one with a current transmission of 4 to 20 mA. Another interface configuration is possible using Bluetooth. Accordingly, the respective measurement of a tank fill level can be transmitted to a control center, which can combine the measurement data acquisition with the control of a complete hydraulic system, in which a tank for receiving the fluid is an essential component. Therefore, employees no longer need to be sent out to check the tank level.In the present solution, an optical inspection with regard to the transparent riser tube 14, which is partially freed by the housing 10, is possible, but in principle such an optical inspection can also be omitted, so that the riser tube 14 does not necessarily have to be transparent.
[0051] The solution according to the invention also modifies and improves the associated state of the art in the software. Previously, the position of the permanent magnet, whether in the form of the object being measured or as part thereof, was determined as follows: Using several circuit boards, the measured values of the Hall sensor voltages were recorded. For specific ranges of these measured values, a function was created using a calculation program, which determined these measurement points as a function of the displacement. The microcontroller now receives these actual values from the circuit board and then decides which sensor provides the most meaningful information about the position of the permanent magnet. It then evaluates the displacement based on the function of only this one sensor.
[0052] Based on this, the software was further developed within the framework of the solution according to the invention as follows:
[0053] The same values were recorded from the different circuit boards (sensors) for Hall sensor voltage measurements as a function of the path, both for the south pole of the permanent magnet and for the north pole.
[0054] From these measurements, a table of mean values for the North and South Poles was created, and from this, a table of the deviations from the mean of both tables was generated. The microcontroller now measures the incoming actual values, again calculates the deviation from the mean of the two tables, and searches for the mean values that have the smallest deviation from the mean of the two tables.
[0055] This has the significant advantage that all sensor voltages are used in parallel to determine the displacement, which greatly increases accuracy. Furthermore, by using the deviation of the mean values from both the north pole and south pole characteristic curves, the polarity of the permanent magnet becomes irrelevant. Consequently, the accuracy of the measuring device could be improved from +5 mm to +1 mm, while requiring less memory for the software, and the polarity of the magnet no longer plays a role, since the mean values of both the north pole and south pole characteristic curves are used for comparison.
Claims
Patent claims 1. Device for detecting at least one fluid level, comprising a receiving device (44) extending up to a predefinable height for receiving the fluid, the upper surface of which forms the respective fluid level, a measuring object (46) whose position correlates with the respective fluid level, and an evaluation device (50) for detecting the respective position of the measuring object (46), characterized in that the evaluation device (50) has a plurality of individual sensors (52) which, in a stationary arrangement, extend in succession along a predefinable path, along which the measuring object (46) is guided to move and which detect the respective position of the measuring object (46).
2. Device according to claim 1, characterized in that the receiving device (44) is formed from a riser pipe (14) which has a fluid connection (24) in the area of its free, opposite ends, which establishes a fluid-carrying connection between the interior of the container and the interior of the riser pipe (14) by passing through a container wall of a container, such as a storage tank.
3. Device according to claim 1 or 2, characterized in that the measuring object (46) is a float body (48) guided in the riser tube (14) which has a magnetic field generating device, preferably in the form of a permanent magnet.
4. Device according to one of the preceding claims, characterized in that the evaluation device (50) is arranged parallel to the orientation of the riser pipe (14) and outside of it, the individual sensors (52) of which follow this orientation having a predefinable distance from each other and which, depending on the respective fluid level, detect the position of the object being measured (46) inside the riser pipe (14) in real time.
5. Device according to one of the preceding claims, characterized in that the respective sensor (52) operates according to the Hall effect and that preferably all Hall sensors (52) used are of the same design.
6. Device according to one of the preceding claims, characterized in that all Hall sensors (52) used are connected to at least one analog-to-digital converter (54), which converts the detected analog measurement signals into digital evaluation signals.
7. Device according to one of the preceding claims, characterized in that the respective Hall sensor (52) and the respective analog-to-digital converter (54) are located on a circuit board (56) and terminate via conductor tracks at an interface (58) which ensures data transmission to an evaluation electronics (60), such as a microcontroller.
8. Device according to one of the preceding claims, characterized in that the circuit board (56) is chambered within a receiving housing (68) which is arranged on the inside of a profile leg (16) of a U-shaped device housing (10) which at least partially encompasses the riser tube (14), and that the interface (58) is designed in the form of a connector (66) and extends through this leg (16) with a definable projection.
9. Measuring and evaluation system comprising at least a device according to one of the preceding claims and an evaluation electronics unit (60) which can be releasably connected to the connector (66) of the evaluation unit (50) by means of a corresponding connector part (81).
10. Measurement and evaluation system according to claim 9, characterized in that the evaluation electronics (60) is connected to a customer-specific evaluation unit (86) via a preferably standardized connection (84).
11. Method for determining the position of a permanent magnet using several Hall sensors, in particular provided for a device according to one of claims 1 to 8 and using a measuring and evaluation system according to claims 9 and 10, comprising the following steps: - Reading out characteristic curves in the form of displacement-voltage profiles for the individual Hall sensors, - Recording average sensor voltages for defined positions of the permanent magnet and creating corresponding measurement series, - Calculating characteristic values with regard to absolute deviations of the individual sensors from the respective mean value based on the measurement series, - Forming at least one specific signature from the combination of mean and deviation values for each position of the permanent magnet, and - Storing the respective signature as a retrievable data record in a memory.