Force-measuring bolt, and method for manufacturing a force-measuring bolt

Abstract

The invention relates to a force-measuring bolt (1) for measuring forces and / or torques in components to which forces and / or torques are applied, said force-measuring bolt comprising a force-measuring surface (2) to which a strain-based sensor (3) is applied, wherein the sensor (3) comprises a sensor layer system (4) which has a layer thickness of less than 200 µm, wherein the sensor layer system (4) has an electrically insulating insulation layer (5) which lies directly on the force-measuring surface (2), and a deformation-sensitive measuring layer (6) which is applied to the insulation layer (5).

Description

[0001] Force measuring bolt and method for manufacturing a force measuring bolt

[0002] The present invention relates to a force-measuring bolt for measuring forces and / or moments in components subjected to forces and / or moments, comprising a force-measuring surface on which a strain-based sensor is applied. The invention further relates to a method for manufacturing a force-measuring bolt.

[0003] Several solutions already exist for load-sensing pins, aimed at enabling the measurement of strains within and on components subjected to load. Of particular interest are so-called load-sense pins, which are specifically designed for strain measurement. These load-sensing pins are used to precisely detect mechanical loads and convert them into electrical signals.

[0004] A significant disadvantage of existing technologies known from the prior art lies in the high process temperatures required to deposit the strain sensors. Temperatures of 400°C and above are common, especially for thick-film sensors. These high temperatures considerably limit the choice of materials for the force-measuring bolt, as many potentially suitable materials, such as heat-treated steels, cannot withstand these temperatures without compromising their mechanical properties.

[0005] These high process temperatures severely limit the use of certain materials such as unhardened or hardened steel or aluminum, which offer better mechanical properties and higher load-bearing capacity at lower temperatures. This restricts the applicability of force-measuring bolts in various industrial and technical applications.

[0006] In this context, there is also a continuing need to save installation space and weight. This is particularly important in applications where space and weight are critical factors, such as in aerospace, the automotive industry, or portable devices. Current technology often fails to provide satisfactory solutions here, as the sensors and their associated components are too large or too heavy.

[0007] In summary, while the state of the art in force-measuring bolts has made some progress, it still exhibits significant problems and disadvantages. In particular, the size of the sensor, the required process temperatures and the associated material limitations, as well as the challenges in reducing installation space and weight, present considerable obstacles.

[0008] The present invention aims to overcome these disadvantages and to provide an improved solution for strain measurement in components subjected to force and moment.

[0009] This problem is solved by a force measuring bolt for measuring forces and / or moments in components subjected to forces and / or moments, comprising a force measuring surface on which a strain-based sensor is applied, wherein the sensor has a sensor layer system having a layer thickness of less than 200 pm, wherein the thin-film system has an electrically insulating insulating layer that is directly adjacent to the force measuring surface, and a deformation-sensitive measuring layer which is applied on the insulating layer.

[0010] This offers the advantage that, by using a sensor layer system with a layer thickness of less than 200 pm, the sensor can be designed to be particularly compact and lightweight. The electrically insulating layer, which is in direct contact with the force-measuring surface, ensures excellent electrical insulation and protects the underlying substrate from electrical interference. The deformation-sensitive measuring layer on the insulating layer enables precise and reliable measurement of forces and moments, as it reacts directly to mechanical deformations. This design contributes to miniaturization while simultaneously increasing the measurement accuracy and reliability of the force-measuring bolt. For the purposes of this patent application, a force-measuring bolt is a special bolt designed to measure forces and / or moments in components that are subjected to these forces and / or moments.The force measuring bolt is integrated into the components and detects the mechanical loads acting on it using suitable sensors.

[0011] The force-measuring bolt comprises a force-measuring surface onto which a strain-based sensor is applied. The sensor is designed to detect the strains and deformations of the force-measuring surface. This enables the determination of the forces and moments acting on the bolt. The sensor comprises a sensor layer system with a layer thickness of less than 200 pm.

[0012] The sensor layer system features an electrically insulating layer that is in direct contact with the force-measuring surface. This insulating layer ensures optimal electrical isolation and protects the underlying substrate from electrical interference. On top of the insulating layer is a deformation-sensitive measuring layer that converts mechanical deformations into electrical signals based on changes in electrical properties. These signals are used to evaluate the mechanical loads.

[0013] Preferably, the sensor layer system is protected by a cover and / or protective layer and / or plastic compound that covers the insulating layer and measuring layer at least partially, preferably completely. This cover and / or protective layer and / or plastic compound provides additional protection against mechanical and chemical influences, which increases the durability and reliability of the force-measuring bolt.

[0014] The cover and / or protective layer can be, for example, a lacquer, a coating, a film, a plastic compound, and / or a foam adhesive. A printed circuit board (PCB) can also be used as a cover. In this case, it is particularly advantageous that the PCB is bonded to the measuring layer, at least partially, and preferably completely, via a potting compound. Furthermore, it is preferred that the sensor layer system has an insulating layer of stoichiometric Al₂O₃ or non-stoichiometric aluminum oxide. It is also preferred that the measuring layer be made of NiCr.

[0015] For the purposes of this patent application, a force-measuring surface is a specified area of ​​the force-measuring bolt designed to absorb the mechanical strains caused by the forces and moments acting on the force-measuring bolt and to transmit these strains to an applied sensor. The force-measuring surface ensures that the strains can be measured precisely and reliably. The force-measuring surface consists of a material that can efficiently transmit the mechanical strains to the layers applied to it. Preferred materials are aluminum, composite materials, or unhardened or hardened steel. It is particularly preferred that the force-measuring surface is formed integrally, and especially monolithically, with the force-measuring bolt.The function of the force-measuring surface is therefore essentially to transmit the mechanical deformations caused by the acting forces and moments to the sensor, i.e., the sensor layer system, without damping or distorting them. This is ensured by the specific arrangement and structure of the various layers of the sensor layer system. The deformation-sensitive measuring layer converts the mechanical strains into electrical signals, which can then be evaluated by the connected electronics.

[0016] For the purposes of this patent application, an active surface is the area of ​​a force-measuring bolt on which the strain-based sensor, in particular the sensor layer system, is applied and which is directly involved in the measurement of forces and moments. The active surface is responsible for detecting the mechanical deformations and converting them precisely and reliably into electrical signals. The active surface comprises the force-measuring surface of the force-measuring bolt onto which the sensor layer system is applied. For the purposes of this patent application, a sensor is a component that detects mechanical deformations, forces, or moments and converts them into electrical signals. The sensor is applied to the force-measuring surface of a force-measuring bolt and comprises a sensor layer system that enables precise and reliable measurement.The sensor's function is essentially to detect mechanical deformations caused by forces and moments acting on the force-measuring bolt and to convert these into electrical signals. The deformation-sensitive measuring layer reacts to the strains by, for example, changing its electrical resistance. These changes in resistance are measured by the evaluation electronics and converted into proportional electrical signals that can be further processed and analyzed.

[0017] For the purposes of this patent application, a sensor layer system is a multilayer coating applied to a force-measuring surface to measure mechanical deformations caused by forces and moments. The sensor layer system preferably consists of a combination of layers providing electrical insulation, deformation sensitivity, and protection. The function of the sensor layer system is to convert mechanical strains caused by forces and moments acting on the force-measuring bolt into electrical signals. The insulation layer ensures that the measuring layer remains electrically isolated while the measuring layer responds to mechanical deformations by changing its electrical resistance. These resistance changes are detected by the evaluation electronics and converted into proportional electrical signals, which are used for analysis and further processing.

[0018] For the purposes of this patent application, an insulating layer is an electrically insulating layer applied to a force-measuring surface of a force-measuring bolt to provide electrical isolation between the force-measuring surface and the overlying deformation-sensitive measuring layer. The insulating layer adheres directly to the force-measuring surface and forms a preferably smooth and uniform surface for the subsequent measuring layer. Sufficient adhesion and mechanical integrity are crucial to ensure that the layer does not delaminate or become damaged during operation. The main function of the insulating layer is to provide electrical isolation between the force-measuring surface and the deformation-sensitive measuring layer. This prevents electrical short circuits and interference that could impair measurement accuracy.

[0019] For the purposes of this patent application, a measuring layer is a deformation-sensitive layer applied to an electrically insulating layer of a force-measuring bolt, which converts mechanical deformations into electrical signals. The main function of the measuring layer is to convert mechanical deformations caused by forces and moments acting on the force-measuring bolt into electrical signals. For example, under mechanical strain, the electrical resistance of the measuring layer can change, which can be used as a measurement signal.

[0020] According to an advantageous embodiment of the invention, the sensor layer system may include a protective layer that covers the insulating layer at least partially, preferably completely. This protective layer provides additional mechanical protection against environmental influences such as moisture, dust, and chemical substances. This extends the service life of the force-measuring bolt and improves its reliability under adverse conditions.

[0021] According to a further preferred embodiment of the invention, the insulating layer may also comprise one or more oxides, in particular oxide layers, and / or oxynitrides and / or polymers. This offers the advantage that the use of oxides, oxynitrides, and / or polymers as materials for the insulating layer ensures a high degree of adaptability to various applications and requirements. Oxides and oxynitrides offer excellent electrical insulation properties as well as high chemical resistance, while polymers allow for additional flexibility and adaptability during manufacturing. Furthermore, according to another advantageous embodiment of the invention, the force-measuring area covered with the sensor layer system may comprise at least 5%, preferably at least 10%, and particularly preferably at least 20% of the active area of ​​the force-measuring bolt.This large covered area allows for a more even distribution of strain measurements, resulting in a more accurate and representative recording of the forces and moments acting on the bolts. This improves the overall accuracy and reliability of the measurement results.

[0022] According to a further particularly preferred embodiment of the invention, the total thickness of the layer sequence applied to the force-measuring surface, comprising the measuring layer and the insulating layer, can be less than 50 pm. This results in minimal influence on the mechanical properties of the force-measuring bolt and enables the integration of the sensor into compact and space-saving designs. The small thickness of the layers also ensures a fast and precise response of the sensor to mechanical loads, which increases the measurement accuracy.

[0023] Furthermore, the invention can also be further developed in that the measuring layer comprises a metallic or metallic-alloyed layer, preferably selected from the group consisting of NiCr, FeNi, FePt, FePd, FeMn, CoMn, FeNiPt, FeNiMn, CoMnFe, CrFe, CrMn, CoCr and / or diamond-like carbon layers. These materials offer excellent mechanical and electrical properties that are crucial for strain measurement. The variety of possible materials makes it possible to optimally adapt the sensors to the specific requirements of the respective application.

[0024] In a further preferred embodiment of the invention, the measuring layer can also be structured such that strain sensors and / or measuring grids, in particular in the form of half- or full-bridges, are formed. These structures enable high precision and sensitivity in the measurement of mechanical deformations. Half- or full-bridge arrangements also offer improved temperature compensation and reduce the effects of temperature changes on the measurement results, leading to higher accuracy and reliability.

[0025] It can also be advantageous to further develop the invention such that the force-measuring bolt is made of aluminum and / or a composite material and / or unhardened or hardened steel. These materials offer high strength and stiffness, which increases the load-bearing capacity and durability of the force-measuring bolt. Aluminum and composite materials also offer low weight, which is particularly advantageous in applications with weight restrictions. Unhardened or hardened steel, on the other hand, offers particularly high wear resistance and resistance to mechanical stress.

[0026] According to a further preferred embodiment of the invention, the force-measuring bolt may comprise at least one additional component selected from the group consisting of measuring amplifiers, temperature sensors, and evaluation electronics. The integration of such components into the force-measuring bolt enables direct signal processing and evaluation on-site, which improves the efficiency and accuracy of the measurements. This leads to a reduction in signal interference and losses and enables more compact and efficient system integration.

[0027] It is also preferred that a metallic adhesion promoter is applied between the insulating layer and the force measuring surface, in particular based on Cr and / or Al and / or Zr.

[0028] The metallic adhesion promoter significantly improves the adhesion of the insulating layer to the force-measuring surface. This is particularly important to ensure the mechanical integrity of the layers and prevent the insulating layer from delaminating or peeling under operating conditions. The adhesion promoter also acts as a buffer between the rigid force-measuring surface and the relatively flexible insulating layer. This reduces mechanical stresses that can arise from differing coefficients of thermal expansion of the materials. By reducing these stresses, the risk of cracking and damage in the sensor layer system is minimized, resulting in a longer service life and improved performance of the force-measuring bolt.Improved adhesion and reduced mechanical stresses also contribute to a more precise transfer of strains and deformations of the force-measuring surface to the insulating layer and the overlying measuring layer. This leads to higher measurement accuracy, as the mechanical deformations can be converted into electrical signals without distortion.

[0029] The force-measuring bolt is preferably cylindrical. This cylindrical shape offers several technical advantages, including a uniform distribution of the forces and moments acting on the bolt, as well as easy integration into existing bores and fastening systems. The cylindrical force-measuring bolt enables precise and reliable measurement of the mechanical loads acting upon it.

[0030] Despite the preferred cylindrical shape, the force-measuring bolt can also exhibit deviations from a perfectly cylindrical form. These deviations can be achieved, for example, by selectively removing material along its axial length. Such modifications can be made, for instance, to adapt to specific structural conditions or to optimize sensor integration. Material removal can reduce the bolt's mass while simultaneously improving specific mechanical properties.

[0031] Furthermore, the force-measuring bolt may have a polygonal cross-section. A polygonal cross-section, such as a hexagonal or square cross-section, can be advantageous in certain applications where additional anti-rotation or special mechanical anchoring is required. The polygonal cross-section allows the bolt to be fitted into a suitable socket or counterpart with appropriate geometric features, which can increase the stability and precision of the measurements.

[0032] The insulating layer can be in direct contact with the force-measuring surface of the force-measuring bolt. In this configuration, the insulating layer lies directly on the surface of the force-measuring bolt, without any intervening layers. This direct arrangement ensures effective electrical insulation and optimal transmission of mechanical deformations from the force-measuring surface to the overlying measuring layer.

[0033] Alternatively, additional layers can be present between the force-measuring surface of the force-measuring bolt and the insulating layer, as well as between the insulating layer and the measuring layer. These additional layers can fulfill various functions and further improve the performance of the force-measuring bolt.

[0034] A metallic adhesion promoter can be provided between the force-measuring surface and the insulating layer. An intermediate layer of a metallic adhesion promoter, for example based on Cr (chromium), Al (aluminum), and / or Zr (zirconium), can be applied to the force-measuring surface before the insulating layer is applied. This layer improves the adhesion of the insulating layer to the force-measuring surface and increases mechanical integrity and resistance to delamination.

[0035] Furthermore, a corrosion protection layer can be applied additionally or alternatively to protect the bolt from chemical influences and corrosion. This can be particularly useful in aggressive environments where the force-measuring bolt is used.

[0036] Additional layers can also be formed between the insulating layer and the measuring layer. For example, it would be conceivable to apply an intermediate layer between the insulating layer and the measuring layer to reduce mechanical stresses. This layer can consist of materials that allow for a gradual adjustment of the mechanical properties between the two main layers, thereby increasing the structural integrity and the lifespan of the sensor.

[0037] The functionality of the force-measuring bolt can be further optimized by combining and arranging these layers. The choice of specific layers and their sequence depends on the requirements of the respective application and the environmental conditions under which the force-measuring bolt is operated.

[0038] Finally, the object of the invention can also be achieved by a method for manufacturing a force measuring bolt for measuring forces and / or moments in components subjected to forces and / or moments, comprising the following steps:

[0039] - Applying an electrically insulating insulating layer directly to a force measuring surface of the force measuring bolt.

[0040] - Applying a deformation-sensitive measuring layer to the insulation layer,

[0041] - where the application of the insulating layer and / or the measuring layer takes place at a temperature of less than 250°C.

[0042] This inventive method for manufacturing a force-measuring bolt is carried out at a temperature of less than 250°C. This reduces thermal stresses and deformations during the manufacturing process and enables the use of temperature-sensitive materials. The low process temperature also contributes to energy savings and minimizes the risk of damage to the substrates and layers. This increases production quality and reduces costs.

[0043] The application of the sensor layer system to the force-measuring bolt is explained in more detail below. Advantageously, the force-measuring surface of the bolt is first thoroughly cleaned to remove all contaminants such as oil, grease, dust, and oxides. This can be done by chemical cleaning, plasma etching, or mechanical polishing.

[0044] The first layer applied to the force-measuring surface is the electrically insulating layer. This layer can be applied using various methods, including physical vapor deposition (PVD), such as sputtering, plasma-assisted chemical vapor deposition (PACVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). In sputtering, ions are accelerated toward a target material, knocking atoms out of the target and / or depositing them, in combination with gas atoms, onto the force-measuring surface. CVD utilizes gaseous precursor molecules that react on the surface of the force-measuring surface to form a solid layer. ALD builds layers at the atomic level through repeated, self-limiting reactions of gaseous precursor molecules.The insulating layer preferably consists of materials such as silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4) or various polymers that offer excellent insulating properties and chemical resistance.

[0045] After the insulating layer, the deformation-sensitive measuring layer is applied. This layer can be applied using similar processes to the insulating layer, including PVD, PACVD, and CVD. PVD sputtering is particularly suitable for metallic and metal-alloyed materials such as NiCr, FeNi, FePt, FePd, FeMn, CoMn, FeNiPt, FeNiMn, CoMnFe, CrFe, CrMn, CoCr, and diamond-like carbon (DLC).

[0046] The applied layers are advantageously structured to form strain sensors and / or measuring grids. This can be achieved through photolithography and etching techniques. In photolithography, a light-sensitive photoresist is applied to the layer and structured with a specific pattern by exposure. In etching, chemical or physical processes are used to remove the material in the unexposed areas, thus creating the desired structures. Another possibility is to structure the measuring layer using laser ablation.

[0047] If required, a protective layer can be applied to the structured measuring layer to provide additional protection against mechanical and chemical influences. This protective layer can also be applied by sputtering, CVD, or ALD. Materials for the protective layer can be oxides, nitrates, or polymers that offer mechanical protection and chemical resistance. The described process offers several significant advantages. The layers are applied at temperatures below 250°C, which reduces thermal stresses and deformations during the manufacturing process and allows the use of temperature-sensitive materials such as unhardened or hardened steel and aluminum. The processes used (PVD, CVD, ALD) ensure high precision and adhesion of the layers to the force-measuring surface, resulting in a reliable and durable sensor technology.Low process temperatures and versatile coating methods allow for the use of various materials for the insulation and measuring layers, increasing the force-measuring bolt's adaptability to diverse applications. The sensor layer system enables the production of very small sensors with a total thickness of less than 200 µm, reducing installation space and weight and facilitating integration into compact and space-saving designs. Finally, the uniform layer distribution and large covered area of ​​the force-measuring surface ensure high measurement accuracy by minimizing the effects of geometric deviations.

[0048] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0049] It shows:

[0050] Figure 1 shows a force measuring bolt in a schematic representation,

[0051] Figure 2 shows a sectional view of a first embodiment of a sensor layer system,

[0052] Figure 3 shows a sectional view of a second embodiment of a sensor layer system,

[0053] Figure 4 shows a sectional view of a third embodiment of a sensor layer system. Figure 1 shows a force-measuring bolt 1 for measuring forces and / or moments in components subjected to forces and / or moments, comprising a force-measuring surface 2 on which a strain-based sensor 3 is applied.

[0054] In the embodiment of the force-measuring bolt 1 as shown in Figure 1, the sensor layer system 4 is arranged on the lateral surface of the force-measuring bolt 1. It is understood that the sensor layer system 4 can also be arranged on another surface of the force-measuring bolt 1, for example, on one of its end faces. Furthermore, a sensor layer system 4 can be positioned on an end face and on the lateral surface of the force-measuring bolt 1.

[0055] As can be clearly seen in Figure 2, the sensor 3 has a sensor layer system 4 with a layer thickness of less than 200 pm. The sensor layer system 4 has an electrically insulating insulating layer 5, which is in direct contact with the force-measuring surface 2, and a deformation-sensitive measuring layer 6, which is applied to the insulating layer 5. The total thickness of the layer sequence applied to the force-measuring surface 2, consisting of the measuring layer 6 and the insulating layer 5, is less than 50 pm.

[0056] The measuring layer 6 is structured such that strain sensors and / or measuring grids, in particular in the form of half- or full bridges, are formed, although this is not explicitly shown in the figures. The force measuring bolt 1 is made of aluminum and / or a composite material and / or unhardened or hardened steel.

[0057] As shown in Figure 3, the sensor layer system 4 can further comprise a protective layer 7 that covers the insulating layer 5 at least partially, preferably completely. The insulating layer 5 can comprise one or more oxides, in particular oxide layers, and / or oxynitrides and / or polymers.

[0058] Figure 4 shows a further embodiment of a sensor layer system 4 in which a metallic adhesion promoter 8 is applied between the insulating layer 5 and the force measuring surface 2, in particular based on Cr and / or Al and / or Zr.

[0059] The force measuring bolt can be manufactured, for example, as follows: First, an electrically insulating insulating layer 5 is applied directly to a force measuring surface 2 of the force measuring bolt 1, followed by the application of a deformation-sensitive measuring layer 6 onto the insulating layer 5. The application of the insulating layer 5 and the measuring layer 6 takes place at a temperature of less than 250°C.

[0060] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Insofar as the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy.

[0061] List of reference signs

[0062] 1 force measuring bolt

[0063] 2 Force measuring surface 3 Sensor

[0064] 4 Sensor layer system

[0065] 5 Insulation layer

[0066] 6 measuring layer

[0067] 7 Protective layer 8 Adhesion promoter

Claims

Claims 1. Force measuring bolt (1) for measuring forces and / or moments in components subjected to forces and / or moments, comprising a force measuring surface (2) on which a strain-based sensor (3) is applied, characterized in that the sensor (3) has a sensor layer system (4) having a layer thickness of less than 200 pm, wherein the sensor layer system (4) has an electrically insulating insulating layer (5) which is directly adjacent to the force measuring surface (2), and a deformation-sensitive measuring layer (6) which is applied to the insulating layer (5).

2. Force measuring bolt (1 ) according to claim 1 , characterized in that the sensor layer system (4) comprises a protective layer (7) which covers the sensor layer system (4) at least partially, preferably completely.

3. Force measuring bolt (1 ) according to claim 1 or 2, characterized in that the insulating layer (5) comprises one or more oxides, in particular oxide layers, and / or oxynitrides and / or polymers and / or lacquers.

4. Force measuring bolt (1 ) according to one of the preceding claims, characterized in that the force measuring surface (2) which is covered with the sensor layer system (4) comprises at least 5%, preferably at least 10%, particularly preferably at least 20% of the active area of ​​the force measuring bolt (1 ).

5. Force measuring bolt (1) according to one of the preceding claims, characterized in that the total thickness of the layer sequence applied to the force measuring surface (2), comprising the measuring layer (6) and the insulating layer (5), is less than 50 pm.

6. Force measuring bolt (1 ) according to one of the preceding claims, characterized in that the measuring layer (6) comprises a metallic or metallic-alloyed layer, preferably selected from a group comprising NiCr, FeNi, FePt, FePd, FeMn, CoMn, FeNiPt, FeNiMn, CoMnFe, CrFe, CrMn, CoCr and / or diamond-like carbon layers.

7. Force measuring bolt (1 ) according to one of the preceding claims, characterized in that the measuring layer (6) is structured in such a way that strain sensors and / or measuring grids, in particular in the form of half or full bridges, are formed.

8. Force measuring bolt (1 ) according to one of the preceding claims, characterized in that the force measuring bolt is made of aluminium and / or a composite material and / or an unhardened or hardened steel.

9. Force measuring bolt (1 ) according to one of the preceding claims, characterized in that the force measuring bolt (1 ) comprises at least one further component selected from the group consisting of measuring amplifiers, temperature sensors, evaluation electronics.

10. Force measuring bolt (1) according to one of the preceding claims, characterized in that a metallic adhesion promoter (8) is applied between the insulating layer (5) and the force measuring surface (2), in particular based on Cr and / or Al and / or Zr. Method for manufacturing a force measuring bolt (1 ) for measuring forces and / or moments in components subjected to forces and / or moments, comprising the following steps: - Applying an electrically insulating insulating layer (5) directly to a force measuring surface (2) of the force measuring bolt (1 ) - Applying a deformation-sensitive measuring layer (6) to the insulating layer (5), - wherein the application of the insulating layer (5) and / or the measuring layer (6) takes place at a temperature of less than 250°C.

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