Magnetic detection system for detecting the movement of a movable object

Abstract

The invention is a magnetic detection system (10; 10') for detecting the movement of a movable object (12; 12'), comprising an excitation unit (16; 16') having at least one excitation magnet (24; 24') for generating an excitation magnetic field, and a sensor unit (18; 18') having a power Wiegand module (30; 30') configured to generate a power output signal when excited by the excitation magnetic field and a sensor Wiegand module (28; 28') configured to generate a sensor output signal when excited by the excitation magnetic field. Here, the sensor Wiegand wire assembly (34; 34') of the sensor Wiegand module (28; 28') is different from the power Wiegand wire assembly (40; 40') of the power Wiegand module (30; 30') and / or the sensor Wiegand wire coil (32; 32') of the sensor Wiegand module (28; 28') is different from the power Wiegand coil (38; 38') of the power Wiegand module (30; 30'). The sensor unit also comprises an energy storage device (44; 44') configured to store electrical energy provided by a power output signal of the power Wiegand module (30; 30') and an evaluation unit (50; 50') configured to evaluate the sensor output signal of the sensor Wiegand module (28; 28') to determine at least one movement parameter. Either the excitation unit (16; 16') or the sensor unit (18; 18') is configured to be attached to the movable object (12; 12') so as to move in conjunction with the movable object (12; 12'), and the other is configured to be arranged stationary.

Description

[Technical Field]

[0001] The present invention relates to a magnetic detection system for detecting movement of a movable object, the detection system comprising: an excitation unit having at least one excitation magnet generating an excitation magnetic field; and a sensor unit having a sensor Wiegand module including a sensor Wiegand coil and a sensor Wiegand wire assembly at least a portion of which is arranged within the sensor Wiegand coil, the sensor Wiegand wire assembly being configured to generate an output signal in the sensor Wiegand coil when excited by the excitation magnetic field; an evaluation unit being configured to evaluate the output signal of the sensor Wiegand module to determine at least one movement parameter, wherein either the excitation unit or the sensor unit is attached to the movable object so as to move relative to the movable object, and the other is configured to be stationary so that the excitation magnetic field generated at the location of the sensor Wiegand module changes in response to movement of the movable object. [Background technology]

[0002] Such sensing systems may also be referred to as linear encoders, displacement encoders, displacement measurement / detection systems, rotary encoders, rotational angle measurement / detection systems, or rotational angle sensors. The movement of the object being sensed can generally be any type of movement, but is typically linear or rotational.

[0003] Wiegand modules having a Wiegand coil and a Wiegand wire assembly at least partially disposed within the Wiegand coil are well known in the art. The Wiegand wire assembly includes at least one Wiegand wire, which is generally a magnetically bistable wire having a hard magnetic shell and a soft magnetic core, or vice versa. Within the meaning of the present invention, Wiegand wires or Wiegand modules may also be referred to as pulse wires or pulse wire modules, respectively. Under the influence of an external magnetic field, such as an excitation magnetic field generated by an excitation unit, the magnetization direction of at least one Wiegand wire, i.e., the magnetization direction of the entire Wiegand wire assembly, changes relatively rapidly, generating a relatively short voltage pulse in the Wiegand coil radially surrounding the Wiegand wire assembly. This effect is referred to as the Wiegand effect and is well known to those skilled in the art. The voltage pulse generated in the Wiegand coil is hereinafter referred to as the output signal of the Wiegand module.

[0004] Those skilled in the art will know that the number / frequency of the voltage pulses of the output signal can be used to determine the distance and / or speed of movement of the movable object, and that the detection system can operate completely energy self-sufficiently, since the electrical energy of the voltage pulses of the output signal can be stored in an energy storage device and used to power the evaluation unit.

[0005] However, the relatively low electrical energy provided by the output signal of a typical Wiegand module having a single Wiegand wire severely limits the number and complexity of components that can be powered by the electrical energy provided by the output signal of the Wiegand module, which in turn limits the range of applications of such detection systems.

[0006] In this context, German Patent Application No. 19925884 and International Publication No. 2020 / 160766 disclose a Wiegand module including a Wiegand wire assembly having multiple Wiegand wires. Due to the large number of Wiegand wires, the output signal of the disclosed Wiegand module provides more electrical energy than the typical output signal of a Wiegand module including a single Wiegand wire. However, the magnetization directions of the multiple Wiegand wires generally do not change simultaneously, but rather change one after the other with a slight delay. This results in a voltage pulse generated in the Wiegand coil being relatively wide or split into multiple voltage pulses, making it very difficult or even impossible to reliably determine the movement parameters based on the output signal. Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a reliable and versatile magnetic detection system for detecting the movement of a movable object. [Means for solving the problem]

[0008] This object is achieved by a magnetic detection system having the features of claim 1.

[0009] The magnetic detection system of the present invention comprises an excitation unit including at least one excitation magnet for generating an excitation magnetic field, and a separate sensor unit for detecting the excitation magnetic field. Either the excitation unit or the sensor unit is mounted to move in conjunction with a movable object to be detected, while the other is configured to be stationary. As a result, the excitation magnetic field generated by the excitation unit at a defined position of the sensor unit changes in response to the movement of the movable object, thereby enabling the sensor unit to determine at least one movement parameter based on the detected excitation magnetic field. The excitation unit and the sensor unit are particularly designed such that an alternating excitation magnetic field is generated at a defined position of the sensor unit when the movable object moves.

[0010] The sensor unit of the present invention includes two separate Wiegand modules: a power Wiegand module and a sensor Wiegand module. The power Wiegand module includes a power Wiegand wire assembly having a power Wiegand coil and at least one power Wiegand wire, with at least a portion of the power Wiegand wire assembly disposed within the power Wiegand coil. The power Wiegand wire assembly is configured to generate a power output signal in the power Wiegand coil when excited by an excitation magnetic field. The sensor Wiegand module includes a sensor Wiegand coil and at least one sensor Wiegand wire, with at least a portion of the sensor Wiegand wire assembly disposed within the sensor Wiegand coil, with the sensor Wiegand wire assembly being configured to generate a sensor output signal in the sensor Wiegand wire coil when excited by an excitation magnetic field.

[0011] The magnetic detection system of the present invention also includes an evaluation unit for determining at least one movement parameter, wherein the evaluation unit is supplied with electrical energy provided by the power output signal of the power Wiegand module and is configured to evaluate the sensor output signal of the sensor Wiegand module to determine the at least one movement parameter.

[0012] The magnetic detection system of the present invention also includes an energy storage device configured to store the electrical energy provided by the power output signal of the power Wiegand module. The energy storage device has at least one energy reservoir, which may be a simple capacitor or any other device capable of storing electrical energy. The electrical energy stored in the energy storage device is used to power the evaluation unit and / or other components of the sensor unit.

[0013] In the present invention, the sensor Wiegand module, whose output signal is evaluated by an evaluation unit, and the power Wiegand module, whose output signal's electrical energy is stored in an energy storage device for powering the evaluation unit and / or other components of the sensor unit, are designed differently. In particular, the sensor Wiegand wire assembly is different from the power Wiegand wire assembly, and / or the sensor Wiegand coil is different from the power Wiegand coil. The sensor Wiegand wire assembly and the power Wiegand wire assembly can be configured with, for example, different numbers of Wiegand wires or Wiegand wire diameters. The sensor Wiegand coil and the power Wiegand coil can be configured with, for example, different numbers of turns or different coil diameters.

[0014] The use of two separate Wiegand modules, one for providing electrical energy and the other for providing a sensor output signal for determining the movement parameter, allows for individual optimization of each Wiegand module for each application. In particular, the power Wiegand module of the present invention can be optimized to generate a power output signal that provides a particularly high electrical energy, and the sensor Wiegand module of the present invention can be optimized to generate a sensor output signal that allows for a reliable and accurate determination of the movement parameter. The high electrical energy provided by the power Wiegand module allows, for example, the operation of a relatively complex evaluation unit, additional sensor components, and / or a wireless data interface.

[0015] Therefore, the sensor unit with two different Wiegand modules of the present invention allows for the realization of a reliable and versatile magnetic detection system for detecting the movement of a movable object.

[0016] The sensor unit is provided with multiple power Wiegand modules, each having a power Wiegand coil and a power Wiegand wire assembly at least partially disposed within the power Wiegand coil. The power Wiegand wire assembly is preferably configured to generate a power output signal in the power Wiegand coil when excited by an excitation magnetic field. Each power Wiegand module is designed differently from the sensor Wiegand module. In particular, the power Wiegand wire assembly of each power Wiegand module is different from the sensor Wiegand wire assembly and / or the power Wiegand coil is different from the sensor Wiegand coil. Different designs are typically possible for all power Wiegand modules. Preferably, all power Wiegand modules are substantially identical, which allows for more efficient production of the power Wiegand sensor. The energy storage device is configured to store electrical energy provided by the power output signals of all power Wiegand modules, allowing the total energy of the power output signals of all power Wiegand modules to be used to power the evaluation unit and / or other components of the sensor unit. The use of multiple power Wiegand modules allows a significant increase in the amount of electrical energy generated by the sensor unit, enabling it to power more or more complex components, making it possible to realize a particularly reliable and versatile magnetic sensing system for detecting the movement of movable objects.

[0017] The power Wiegand modules are preferably arranged displaced relative to one another in the direction of movement of the movable object, for example displaced circumferentially for a rotatable object or displaced linearly for a linearly movable object. The power Wiegand modules are preferably distributed equidistantly along the distance of movement of the movable object, for example displaced equidistantly along the circumference for a rotatable object or displaced equidistantly along the linear distance of movement for a linearly movable object. This allows for a relatively efficient and relatively continuous supply of electrical energy by the power Wiegand modules during movement of the movable object.

[0018] The total power Wiegand wire volume of the power Wiegand wire assembly, which is the total volume of all power Wiegand wires in each power Wiegand wire assembly of each power Wiegand module, is preferably larger than the total sensor Wiegand wire volume of the sensor Wiegand wire assembly of the sensor Wiegand module, which is the total volume of all sensor Wiegand wires in the sensor Wiegand wire assembly. For example, the power Wiegand wire assembly may have a larger number of power Wiegand wires compared to the number of sensor Wiegand wires in the sensor Wiegand wire assembly and / or may have power Wiegand wires with larger diameters compared to the diameters of the sensor Wiegand wires. Because the total power Wiegand wire volume of the power Wiegand wire assembly is relatively large, the power Wiegand wire module can generate more electrical energy compared to the sensor Wiegand wire module. On the other hand, because the total sensor Wiegand wire volume of the sensor Wiegand wire assembly is relatively small, the sensor Wiegand wire module can provide a sensor output signal with a relatively sharp voltage pulse that can be reliably evaluated by the evaluation unit. This allows for a reliable and versatile magnet-based detection system for detecting the movement of a movable object.

[0019] The power Wiegand coil inductance of the power Wiegand coil of each power Wiegand module is preferably higher than the sensor Wiegand coil inductance of the sensor Wiegand coil of the sensor Wiegand module. For example, the power Wiegand coil may have a larger number of turns or a larger coil diameter compared to the number of turns of the sensor Wiegand coil. Because the power Wiegand coil has a relatively high power Wiegand coil inductance, the power Wiegand wire module may generate more electrical energy compared to the sensor Wiegand wire module. On the other hand, because the sensor Wiegand coil has a relatively low Wiegand coil inductance, the sensor Wiegand wire module may provide a sensor output signal that can be reliably evaluated by an evaluation unit. This allows for the realization of a particularly reliable and versatile magnetic detection system for detecting the movement of a movable object.

[0020] The evaluation unit is preferably electrically connected to the energy storage device so that it receives electrical energy stored in the energy storage device. This allows the relatively complex evaluation unit to be powered without the need for an external energy source. This allows for a particularly reliable and versatile magnetic detection system for detecting the movement of a movable object.

[0021] The sensor unit preferably has a wireless data interface for wireless data transmission, which is electrically connected to the energy storage device so that the energy storage device is supplied with stored electrical energy. The wireless data interface allows data, such as movement parameters and / or configuration data, to be transmitted to and from the sensor unit completely wirelessly. Because the wireless data interface is supplied with electrical energy stored in the energy storage device via the power output signal of at least one power Wiegand module, no external energy supply is required to operate the wireless data interface. Therefore, the sensor unit can be installed without requiring a wired connection. This allows for the realization of a particularly versatile magnetic detection system for detecting the movement of a movable object.

[0022] The sensor unit preferably includes an additional sensor element for sensing a physical property, which is electrically connected to the energy storage device so that the additional sensor element is supplied with electrical energy stored in the energy storage device. This additional sensor element may be, for example, a temperature sensor or a pressure sensor. The additional sensor element enables detection of an additional physical property of the movable object or the movable object's surrounding environment. For example, the detected additional physical property may be used to enable the evaluation unit to more accurately determine at least one movement parameter. Because the additional sensor element is supplied with electrical energy stored in the energy storage device, provided by the power output signal of the at least one power Wiegand module, no external energy supply is required to operate the additional sensor element. This enables a particularly reliable magnetic detection system for detecting the movement of a movable object.

[0023] Two embodiments of the present invention will now be described with reference to the accompanying drawings, which are shown below. [Brief explanation of the drawings]

[0024] [Figure 1]FIG. 1 is a schematic diagram of a first embodiment of a magnetic detection system for detecting the movement of a movable object according to the present invention. [Figure 2] FIG. 2 is a schematic diagram of a sensor unit of the magnetic detection system of FIG. [Figure 3] FIG. 3 is a schematic diagram of an excitation unit of the magnetic detection system of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of the power Wiegand module and the sensor Wiegand module of the sensor unit of FIG. [Figure 5] FIG. 5 is a schematic diagram of a second embodiment of a magnetic detection system for detecting the movement of a movable object according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] 1 shows a magnetic detection system 10 configured to detect movement of a movable object 12 along a direction of movement D, where the movable object 12 is a rotatable shaft of an electric motor 14, and the direction of movement D is circumferential to the shaft.

[0026] The magnetic detection system 10 comprises an excitation unit 16 attached to the movable object 12 for movement therewith, and a sensor unit 18 attached to a stationary housing part 20 of the electric motor 14 .

[0027] The excitation unit 16 has a disk-shaped support part 22 attached to the movable object 12 and surrounding the movable object 12 in the radial direction. The excitation unit 16 has four permanent excitation magnets 24 arranged on the surface of the support part 22 facing the sensor unit 18. The four excitation magnets 24 are arranged equidistantly around the circumference of the support part 22 so as to be displaced equidistantly from one another in the direction of movement D of the movable object 12. The four excitation magnets 24 are configured so that the radially inner and outer sides of adjacent excitation magnets 24 have roughly opposite magnetization directions, i.e., have different magnetic poles (N:N pole, S:S pole) on the radially inner and radially outer sides. Thus, the excitation magnets 24 generate an excitation magnetic field at a defined position of the sensor unit 18 that changes with the movement of the movable object 12 in the direction of movement D.

[0028] The sensor unit 18 has a disk-shaped circuit board 26 attached to the housing part 20 and radially surrounding the movable object 12. The sensor unit 18 has one sensor Wiegand module 28 and three power Wiegand modules 30, which are arranged on the surface of the circuit board 26 facing the excitation unit 16. The four Wiegand modules 28, 30 are arranged to be distributed at equal distances on the circumference of the circuit board 26 so as to be displaced at equal intervals from each other in the direction of movement D of the movable object 12.

[0029] The sensor Wiegand module 28 includes a sensor Wiegand coil 32 and a sensor Wiegand wire assembly 34 having one single sensor Wiegand wire 36. The sensor Wiegand wire assembly 34 is partially disposed within the sensor Wiegand coil 32 such that the sensor Wiegand coil 32 radially surrounds the axially central portion of the sensor Wiegand wire 36. The sensor Wiegand wire assembly 34 is thus configured to generate a sensor output signal at the sensor Wiegand coil 32 in response to excitation by the excitation magnetic field generated by the excitation magnet 24.

[0030] Each of the three power Wiegand modules 30 includes a power Wiegand coil 38 and a power Wiegand wire assembly 40 having four power Wiegand wires 42. The power Wiegand wire assembly 40 is partially disposed within the power Wiegand coil 38 such that the power Wiegand coil 38 radially surrounds the axial center of each of the four power Wiegand wires 42. The power Wiegand wire assembly 40 is therefore configured to generate a power output signal within the power Wiegand coil 38 in response to excitation by the excitation magnetic field generated by the excitation magnet 24.

[0031] Because the number of power Wiegand wires 42 is greater than the number of sensor Wiegand wires 36, the total power Wiegand wire volume of power Wiegand wire assembly 40 is greater than the total sensor Wiegand wire volume of sensor Wiegand wire assembly 34. Also, because the coil diameter of power Wiegand coil 38 is greater than the coil diameter of sensor Wiegand coil 32, the power Wiegand coil inductance of power Wiegand coil 38 is greater than the sensor Wiegand coil inductance of sensor Wiegand coil 32.

[0032] The sensor unit 18 includes an energy storage device 44 electrically connected to each of the three power Wiegand modules 30 and configured to store electrical energy supplied by the power output signals of the three power Wiegand modules 30.

[0033] The sensor unit 18 has a wireless data interface 46 electrically connected to the energy storage device 44 such that it is supplied by the power output signals of the three power Wiegand modules 30 and the electrical energy stored in the energy storage device 44. The wireless data interface 46 is configured to allow wireless transmission, preferably transmission and reception, of data.

[0034] The sensor unit 18 includes an additional sensor element 48 electrically connected to the energy storage device 44 such that the additional sensor element 48 is supplied with electrical energy stored in the energy storage device 44 by the power output signals of the three power Wiegand modules 30. The additional sensor element 48 is configured to sense a physical property and provide a respective sensor element output signal. The additional sensor element 48 may be, for example, a temperature sensor configured to sense temperature and provide a respective temperature signal.

[0035] The sensor unit 18 includes an evaluation unit 50 electrically connected to the energy storage device 44 so as to be supplied with electrical energy stored in the energy storage device 44 by the power output signals of the three power Wiegand modules 30. The evaluation unit 50 is electrically connected to the sensor Wiegand module 28 so as to receive the sensor output signals generated in the sensor Wiegand coil 32 by the sensor Wiegand wire assembly 34. The evaluation unit 50 is electrically connected to the additional sensor element 48 so as to receive the sensor element output signals provided by the additional sensor element 48. The evaluation unit 50 is electrically connected to the wireless data interface 46 so as to enable transmission of data to and from the evaluation unit 50. The evaluation unit 50 includes a data storage device 52.

[0036] The evaluation unit 50 is configured to evaluate the sensor output signals of the sensor Wiegand module 28 and the sensor element output signals of the additional sensor elements 48 to determine a physical property parameter, such as a current temperature, and at least one movement parameter, such as a rotation count value representing a current rotation angle of the movable object 12 and / or a total number of rotations of the movable object 12. The evaluation unit 50 is configured to store the determined physical property parameter and the determined at least one movement parameter in the data storage device 52 and to be able to transmit the determined physical property parameter and the determined at least one movement parameter via the wireless data interface 46. The evaluation unit 50 can be configured to store a history / progression of the physical property parameters.

[0037] Figure 5 shows an alternative magnetic detection system 10' of the present invention. Features of the magnetic detection system 10' that are known from the magnetic detection system 10 are referred to by their respective reference numerals in Figures 1 to 4, but with the addition of an apostrophe character.

[0038] The magnetic detection system 10' is configured to detect the movement of a movable object 12 that is linearly movable along a direction of movement D', where the sensor unit 18' is mounted to move in conjunction with the movable object 12' and the excitation unit 16' is arranged stationary.

[0039] The excitation unit 16' includes an elongated excitation magnet 24' having alternating magnetic north poles N and south poles S in the direction of movement D'. The excitation magnet 24' may be a single permanently magnetized body or may include multiple permanent magnets arranged side by side. The excitation magnet 24' generates an excitation magnetic field at a defined position of the sensor unit 18' that varies with movement of the movable object 12' in the direction of movement D'.

[0040] The structure and function of the sensor unit 18' are substantially identical to those of the sensor unit 18 of the magnetic detection system 10. The main difference is that the sensor unit 18' has only one power Wiegand module 30' arranged adjacent to the sensor Wiegand module 28' in the direction of movement D'. The sensor Wiegand module 28' and the power Wiegand module 30' themselves are also designed substantially identically to the sensor Wiegand module 28 and the power Wiegand module 30 of the sensor unit 18 of the magnetic detection system 10. [Explanation of symbols]

[0041] 10;10' Magnetic detection system 12;12' movable object 14 Electric motor 16;16' excitation unit 18;18' sensor unit 20 Housing section 22 Support parts 24 Excitation magnet 26;26' circuit board 28;28' Sensor Wiegand Module 30;30' Power Wiegand Module 32;32' Sensor Wiegand Coil 34;34' Sensor Wiegand Wire Assembly 36;36' Sensor Wiegand Wire 38;38' Power Wiegand Coil 40;40' Power Wiegand Wire Assembly 42;42' Power Wiegand Wire 44;44' Energy storage device 46 Wireless Data Interface 48 additional sensor elements 50;50' evaluation unit 52 Data storage device D;D' Movement direction N magnetic north pole S magnetic south pole

Claims

1. A magnetic detection system (10; 10') for detecting the movement of a movable object (12; 12'), said magnetic detection system (10; 10') comprising: an excitation unit (16; 16') having at least one excitation magnet (24; 24') for generating an excitation magnetic field; a sensor unit (18; 18') having a power Wiegand module (30; 30'), a sensor Wiegand module (28; 28'), an energy storage device (44; 44') and an evaluation unit (50; 50'), The power Wiegand module (30; 30') Power Wiegand coil (38; 38') and a power Wiegand wire assembly (40; 40') at least partially disposed within the power Wiegand coil (38; 38'); the power Wiegand wire assembly (40; 40') is configured to generate a power output signal to the power Wiegand coil (38; 38') when excited by the excitation magnetic field; The sensor Wiegand module (28; 28') Sensor Wiegand coil (32; 32') and a sensor Wiegand wire assembly (34; 34') at least partially disposed within the sensor Wiegand coil (32; 32'); a total power Wiegand wire volume of the power Wiegand wire assembly (40; 40') is greater than a total sensor Wiegand wire volume of the sensor Wiegand wire assembly (34; 34'), and / or a power Wiegand coil inductance of the power Wiegand coil (38; 38') is greater than a sensor Wiegand coil inductance of the sensor Wiegand coil (32; 32'); the sensor Wiegand wire assembly (34; 34') is configured to cause the sensor Wiegand coil (32; 32') to generate a sensor output signal when excited by the excitation magnetic field; the energy storage device (44; 44') is configured to store electrical energy provided by the power output signal of the power Wiegand module (30; 30'); the evaluation unit (50; 50') is configured to evaluate the sensor output signal of the sensor Wiegand module (28; 28') to determine at least one movement parameter, A magnetic detection system (10; 10') in which either the excitation unit (16; 16') or the sensor unit (18; 18') is configured to be attached to the movable object (12; 12') so as to move in conjunction with the movable object (12; 12'), and the other is configured to be stationary.

2. The sensor unit (18) includes a plurality of power Wiegand modules (30), each of which includes a power Wiegand coil (38) and a power Wiegand wire assembly (40) at least a portion of which is disposed within the power Wiegand coil (38), and the total power Wiegand wire volume of the power Wiegand wire assembly (40) of each power Wiegand module (30) is greater than the total sensor Wiegand wire volume of the sensor Wiegand wire assembly (34), and / or 2. The magnetic detection system of claim 1, wherein the power Wiegand coil inductance of the power Wiegand coil is higher than the sensor Wiegand coil inductance of the sensor Wiegand coil, the power Wiegand wire assembly is configured to generate a power output signal to the power Wiegand coil when excited by the excitation magnetic field, and the energy storage device is configured to store electrical energy provided by the power output signals of all the power Wiegand modules.

3. 3. The magnetic sensing system (10) of claim 2, wherein the power Wiegand modules (30) are arranged displaced relative to one another with respect to the direction of movement (D) of the movable object (12).

4. 4. The magnetic detection system (10; 10') according to claim 1, wherein the evaluation unit (50; 50') is electrically connected to the energy storage device (44; 44') so as to be supplied with electrical energy stored in the energy storage device (44; 44').

5. 5. The magnetic detection system (10; 10') according to claim 1, wherein the sensor unit (18; 18') further comprises a wireless data interface (46) for wireless data transmission, the wireless data interface (46) being electrically connected to the energy storage device (44; 44') so as to be supplied with electrical energy stored in the energy storage device (44; 44').

6. 6. The magnetic detection system (10; 10') according to claim 1, wherein the sensor unit (18; 18') further comprises an additional sensor element (48) for sensing a physical property, the additional sensor element (48) being electrically connected to the energy storage device (44; 44') so as to be supplied with electrical energy stored in the energy storage device (44; 44').

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