Heating device with a temperature measuring device and method for measuring the temperature at the heating device and for manufacturing

Description

Area of ​​application and state of the art

[0001] The invention relates to a heating device with a temperature measuring device for this heating device as well as methods for temperature measurement on such a heating device and also methods for producing such a heating device.

[0002] It is known from EP 3 145 273 B1 to provide a heating device with a temperature measuring device. The heating device comprises a flat support, a heating conductor, and an electrically conductive connection surface in the manner of an electrode, with a dielectric layer provided between the two. A temperature-dependent leakage current through this dielectric layer can be detected by a measuring device and evaluated as a measure of a local temperature change at the heating device. However, experience has shown that such local temperature changes only occur near or directly at the heating conductor. Furthermore, they essentially measure the temperature influenced by the heating conductor.

[0003] US 2020 / 056811 A1 discloses another heating device that includes a temperature measuring device. Similar to the previously described method, a dielectric layer is provided between a heating conductor and an electrode, through which a temperature-dependent leakage current flows. This leakage current can be detected and used to evaluate a temperature change or temperature at the heating device.

[0004] WO 2006 / 083 162 A1 discloses another heating device with a temperature measuring device, which has an electrode between the insulation layer and the carrier, including electrical insulation. This electrode covers a surface and can be designed, for example, as a grid. It has a single connection for detecting a current flowing from a heating conductor through a dielectric layer. Therefore, a single connection is sufficient here. The flat design of the electrode allows the occurrence of a leakage current to be detected over the largest possible area. Area of ​​application and state of the art

[0005] The invention is based on the object of creating a heating device as mentioned above, as well as methods for measuring temperature therewith and methods for producing the same, with which problems of the prior art can be solved and in particular it is possible to advantageously produce or construct such a heating device and to advantageously detect a temperature thereon.

[0006] This object is achieved by a heating device having the features of claim 1, by a method for measuring the temperature of such a heating device having the features of claim 13, and by methods for producing such a heating device having the features of claims 14 or 15. Advantageous and preferred embodiments of the invention are the subject of the further claims and are explained in more detail below. Some of the features are explained only for the heating device itself or only for one of the methods mentioned. However, they should be able to apply independently and independently of one another to both the heating device and one of the methods. .

[0007] It is provided that the heating device has a flat carrier and at least one heating conductor on the flat carrier, wherein the heating conductor can optionally have several partial heating conductors or be divided into several such partial heating conductors. Furthermore, an elongated electrode is provided on the flat carrier, wherein here too either only a single elongated electrode can be provided or at least one further additional electrode can be provided. A layer structure is provided on the carrier with an insulating layer between the heating conductor and the electrode. This insulating layer advantageously has dielectric properties, as is known per se from the prior art. Furthermore, a measuring device for detecting locally high temperatures on the heating device is provided, which measuring device is connected to the electrode and to the heating conductor.The measuring device is designed to detect a temperature-dependent leakage current through the insulation layer between the heating conductor and the electrode, which can be in the range of a few mA. This temperature-dependent leakage current is evaluated as a measure of a local temperature or temperature change at the heating device. This mechanism is fundamentally known from the prior art, to which reference is made in this regard, so unnecessary repetition can be omitted here. This makes it possible, above all, to detect particularly high temperatures and, by taking countermeasures, to prevent them from damaging the heating device or an electrical device incorporating the heating device.

[0008] According to the invention, the electrode itself is made of a material with a temperature-dependent electrical resistance, so that it can itself be used directly for temperature measurement. It therefore not only conducts a current serving as a signal, but also detects the temperature itself, so to speak, as a type of sensor. For this purpose, the temperature dependence of the electrical resistance of the electrode material in a temperature range from 0°C to 500°C is between 0.0005 / °C and 0.01 / °C, or between 0.000500 = 500 ppm / K and 10,000 ppm / K, in particular based on room temperature as a reference. Furthermore, the temperature measuring device is connected to the electrode or to ends or terminals of the electrode in order to measure a temperature at the electrode using the temperature dependence of the electrical resistance of the electrode.Such a temperature measurement based on a temperature-dependent electrical resistance is also well known to those skilled in the art and can be implemented according to this prior art. The special feature of the invention lies in the fact that the electrode used for the aforementioned temperature detection based on the leakage current is now also used as a temperature sensor itself due to its specially designed temperature-dependent properties.

[0009] In an embodiment of the invention, the temperature dependence of the electrical resistance of the electrode or of the electrode material in the stated temperature range of 0°C to 200°C can be between 0.0015 / °C and 0.005 / °C or between 0.0015 = 1,500 ppm / K and 5,000 ppm / K, particularly advantageously at approximately 0.0035 / °C or 0.0035 = 3,500 ppm / K. The temperature-dependent resistance of the electrode can thus be determined, and the temperature can be precisely determined from the respective electrical resistance or its change.

[0010] Precious metals, such as silver, palladium, platinum, gold, or ruthenium, can advantageously be used for the electrode. A general electrode material with a PTC / NTC effect can also be used independently.

[0011] In an embodiment of the invention, it is possible for the electrode to be at least partially covered or overlapped by the heating conductor, in particular with regard to a projection onto the plane of the carrier. This carrier is generally advantageously flat or planar, but it can also be curved or tubular; in particular, the structure of the functional layers can be provided on the outside of the tube. The insulation layer runs between the heating conductor and the electrode, wherein the insulation layer advantageously has a larger area or a much larger area than the area covered by the heating conductor and / or electrode. It can be provided that a section of the electrode runs along a longitudinal extent of the heating conductor and is covered or overlapped by the heating conductor.In particular, the electrode or a section of the electrode can run along at least 70% or 90% of the length of the heating conductor, allowing temperature monitoring of the heating conductor in this area. Advantageously, an electrode or a section of the electrode runs along the entire length of the heating conductor, allowing temperature monitoring at any point along the heating conductor. This ensures maximum protection against damage to the heating device due to excessively high temperatures of the heating conductor.

[0012] In one embodiment of the invention, the electrode can have a narrow width compared to its length. Thus, the length can be at least twenty times the width, preferably at least fifty times the width. Thus, relatively little electrode material is required for the electrode, which is often expensive. For the task of detecting a leakage current through the insulation layer to the heating conductor, such a relatively narrow electrode width is sufficient. For temperature measurement directly using the electrode, a small conductor cross-section can be advantageous.

[0013] Advantageously, the insulation layer can have an electrical resistance between a top and bottom surface, or between the heating conductor and the electrode, of at least 1 MΩ in a temperature range of 100°C to 150°C. Advantageously, this can even be at least 10 MΩ. At a certain temperature, which is considered to be initially critical for the heating device with regard to a local temperature increase, the electrical resistance can drop significantly. The material composition can be selected accordingly. However, this is generally known from the aforementioned prior art.

[0014] In one embodiment of the invention, the electrode can be designed so that its total electrical resistance, i.e., between two electrode terminals, is between 50 Ω and 100 kΩ in a specified temperature range between 0°C and 500°C. In particular, the electrical resistance of the electrode can be between 5 kΩ and 20 kΩ in this temperature range. The change in this electrical resistance over temperature or with a change in temperature has been described above.

[0015] For precise and reliable temperature evaluation, the electrode can be provided with a consistent or constant width along its length. By varying the course of the electrode path, in particular by means of bends and / or straight sections, specific areas can be evaluated more precisely. The thickness of the electrode should also be consistent or constant, in particular to improve the manufacturability of the electrode. For example, a width can be in the range from 0.05 mm to 2 mm, and a thickness between 3 µm and 1 mm. Furthermore, designs with a series connection of different electrode path geometries are possible. One embodiment can, for example, be a series connection of an electrode network and a sensor electrode. This has the advantage that the position of the hot spot can be determined by evaluating the two evaluation options: leakage current and resistance measurement.

[0016] Preferably, the width of a heating conductor is considerably larger than its length and also, in absolute terms, than the electrode. In particular, a heating conductor can be five to one hundred times wider than an electrode, particularly the electrode overlapped by the heating conductor. The aforementioned combination of an electrode network and a sensor electrode is also advantageously possible here.

[0017] In yet another embodiment of the invention, the electrode material can have a variable temperature coefficient of its electrical resistance, advantageously a PTC material. This ensures that, in the case of very high temperatures, excessive currents do not flow through the electrode when measuring the temperature.

[0018] In an advantageous embodiment of the invention, it can be provided that the heating device has a plurality of heating conductors or that one heating conductor has a plurality of partial heating conductors. These can be interconnected, for example and advantageously in series. A parallel connection and a combination of series connection and parallel connection are also possible in principle. Preferably, each of the partial heating conductors covers an electrode or an electrode section, in particular with the aforementioned advantageous specification that an overlap of at least 80% or 90%, in particular 100%. The individual partial heating conductors can be connected to one another by means of connecting sections, in particular in order to be able to avoid bends or curves in the partial heating conductor itself. These would be disadvantageous for current conduction for known reasons.An electrode or electrode section can be provided in the area of ​​these connecting sections, but this is not mandatory. However, the electrode should preferably follow the path of the heating conductor. The electrical resistance of these connecting sections should be significantly lower than that of the heating conductor material, preferably at least ten times lower.

[0019] In a further development of the invention, it can be provided that at least one additional electrode is provided which consists of the same material as the electrode. This additional electrode also serves to measure the temperature, but it is not covered or overlapped by a heating conductor. Preferably, a lateral distance of this additional electrode from a heating conductor or from any heating conductor in the surrounding area is provided which is twice the width of the electrode track or at least 1 mm or even at least 2 mm, advantageously at least 10 mm. In this way, it can be achieved that the temperature at the additional electrode is mainly or even exclusively influenced by the carrier or by a medium which the carrier is adjacent to or which the carrier contains, for example water.Temperature measurement at the additional electrode is advantageously carried out via a change in its electrical resistance over temperature, i.e., exactly as with the electrode described above. Thus, the additional electrode is also connected to the same temperature measuring device as the electrode covered or overlapped by the heating conductor.

[0020] The following layer structure can advantageously be provided for the heating device. A cover layer or a carrier insulation layer can be applied to the carrier, which can be made of ceramic or preferably of metal or steel. The at least one electrode is applied to this carrier insulation layer, preferably all of the electrodes or electrode sections, in particular also an aforementioned additional electrode. On top of this, in turn, the insulation layer according to the invention is applied, through which a leakage current can flow if the temperature is locally too high. On top of this insulation layer, in turn, the heating conductor or all of the heating conductors and partial heating conductors are applied. On top of this, in turn, a cover layer is applied to the outside, in particular to protect the heating conductor from the effects of the atmosphere or oxygen, i.e. primarily from oxidation.Electrical contact to the electrode and the heating conductor is made in a known manner, in particular by ensuring that they are not covered laterally by the respective insulation layers.

[0021] Alternatively, the order can also be carrier, carrier insulation layer or dielectric layer, heating conductor, insulation layer or dielectric layer, electrode(s), cover layer.

[0022] In a method according to the invention for measuring the temperature at such a heating device, this is provided in two different ways. On the one hand, temperature is detected via a temperature-dependent leakage current flowing through the insulation layer between the heating device and the electrode. In particular, it can be determined that the local temperature is too high if such a leakage current is flowing to any significant extent. On the other hand, temperature is measured at the heating device by measuring a temperature change at the electrode alone and determining this via the temperature-dependent electrical resistance of the electrode. For this purpose, a control of the heating device or for the heating device can be provided, in which this evaluation takes place as a temperature change over time.

[0023] In a first general method according to the invention for producing a heating device as described above, this heating device comprises several heating conductors. These can also be several partial heating conductors as described above. All heating conductors and, if applicable, all partial heating conductors of the heating device are applied in the same process section or in the same process step and from the same heating conductor material. If this takes place in several steps, this is also carried out identically for all heating conductors or partial heating conductors.

[0024] In a second method according to the invention for producing a heating device, as described above, the heating device has multiple electrodes. In particular, a previously described additional electrode is also provided. All electrodes or electrode sections, in particular also the aforementioned additional electrode, are applied in the same process step and from the same electrode material. Similar to what was previously described for the heating conductor, if multiple layers of the electrode material are applied, this also applies identically to all electrodes or electrode sections and also to any additional electrode that may be provided. Brief description of the drawings

[0025] Embodiments of the invention are shown schematically in the drawings and are described in more detail below. Fig. 1 a plan view of a first embodiment of a heating device according to the invention with a flat heating conductor and meander-shaped electrode, Fig. 2 a section through the heating device from Fig. 1 with the layer structure, Fig. 3 to Fig. 6 various modifications of heating devices similar Fig. 1 with different designs for heating conductor and electrode. Detailed description of the implementation examples

[0026] In the Fig. 1 A heating device 11 according to the invention is shown in plan view. It has a rectangular shape here, but can also have any desired shape. In addition to flat designs of a heating device 11, curved and tubular heating devices are also conceivable. In particular, the heating device 11 is manufactured using thick-film technology.

[0027] The heating device 11 has a carrier 12 made either of electrically insulating ceramic or of metal. The aforementioned layer structure is located on a carrier top side 13, which, in the case of a metal carrier 12, is provided with functional insulation 27. On the carrier top side 13, two contact tracks 15a and 15b made of highly electrically conductive material are arranged parallel and spaced from one another. They merge to the left into contact surfaces 16a and 16b. The contact tracks 15a and 15b contact a wide, flat heating conductor 18 between them. Reference is made, for example, to EP 3250003 A1. The current flow direction through the heating conductor 18 is perpendicular to the longitudinal extent of the contact tracks 15a and 15b.

[0028] A supply voltage source 20 is connected to the contact surfaces 16a and 16b via contact lines 17a and 17b. This is known from the prior art. The supply voltage source is advantageously the 230 V household mains voltage as an AC voltage. Use in the automotive sector or in a car is also possible, i.e., with a DC voltage of 12 V or 48 V or even higher.

[0029] An electrode 22 runs meandering across the surface of the heating conductor 18 in six parallel tracks. The tracks can be approximately equally spaced from one another, but they can also be spaced at different distances, for example, for different power densities or to enable more precise analysis of defined areas. The top and bottom tracks can also run even closer to the contact tracks 15a and 15b. The electrode 22 has two electrode connections 23a and 23b on the left. A resistance measuring device 25 is connected via electrode leads 24a and 24b. This allows the electrical resistance of the electrode 22 to be measured, and based on its temperature dependence, the temperature can be determined. For this purpose, the electrode 22 consists of a material mentioned above with a silver content of 10% to 90% or 80% to 90%. However, a material mentioned above can also be used for the electrode.

[0030] It can be seen that, due to the temperature-dependent, variable electrical resistance of electrode 22, the temperature measurement does not allow for local temperature measurement at a single point, but rather a temperature measurement that is distributed or averaged across the area covered by electrode 22. For local temperature measurement, in particular for detecting dangerous local excess temperatures, a leakage current detector is used, as known from the prior art mentioned above. It is then connected via contact lines 17a and 17b and electrode lines 24a and 24b.

[0031] For an explanation, please refer to the Fig. 2 and, above all, explicitly referred to the aforementioned state of the art. According to Fig. 2The carrier 12 has a carrier top side 13 with the layer structure and a carrier bottom side 14. The carrier bottom side 14 is in contact with water W, which is to be heated by the heating device 11. The layer structure on the carrier top side 13, produced using thick-film technology, has the aforementioned functional insulation 27 of the carrier 12 as its bottom layer. The electrode 22 is applied to the functional insulation 27 in the desired shape. Variations of this shape have been explained above and will be described below with reference to the Fig. 4 to 5 still shown. Electrode 22 has an electron terminal 23 on the right, to which an electrode lead 24 is connected, for example, welded here. It can also be soldered; alternatively, contact can be made using pressed-on contacts or a clamp connector.

[0032] The electrode 22 is covered by an insulating layer 29, which exhibits the dielectric properties mentioned above. This includes the fact that at a certain elevated temperature, for example, 350°C to 400°C, the electrical resistance drops significantly, allowing a leakage current to flow. This leakage current can flow from the heating conductor 18 applied to the insulating layer 29 to the electrode 22. The heating conductor 18, in turn, has a contact surface 16 applied to the right, which can be connected via a contact line 17. At this temperature, there is a risk of permanent damage if it persists for a period of more than 1 minute or more than 20 seconds.

[0033] A covering layer 31 is applied to the heating conductor 18. It leaves the contact surface 16 exposed for the subsequent attachment of the contact line 17, similar to how the electrode connection 23 remains exposed when the insulating layer 29 is applied. The covering layer 31 serves to protect the structure of the support device 11 from the outside, in particular to protect the heating conductor 18 from the ambient atmosphere and, in particular, from oxidation.

[0034] The functional principle of leakage current measurement and the temperatures at which it can be carried out will not be discussed further here, as this is sufficiently evident from the state of the art. Fig. 1 In this context, this means that the leakage current flows from the heating conductor 18 to the electrode 22 at a particularly hot spot on the insulation layer 29 between the two. In the range significantly below the critical temperature mentioned, no leakage current or no significant leakage current flows.

[0035] The temperature of the heating device 11 can be measured at any time using the temperature-dependent electrical resistance of the electrode 22. Advantageously, this can also be done simultaneously with the leakage current monitoring.

[0036] In the Fig. 3 An alternative structure is shown. The heating device 111 with a carrier 112 has three parallel contact tracks 115a, 115ab and 115b on the carrier's upper side. They each have contact surfaces 116a, 116ab and 116b on the left. This is similar to the Fig. 1A continuous surface can be covered by the heating conductor 118, i.e., from the upper contact track 115a to the lower contact track 115b. The middle contact track 115ab runs centrally and forms a type of intermediate tap. Depending on the supply voltage applied to the contact surfaces 116a, 116ab, and 116b, the two heating conductors 118a and 118b can be connected in series or parallel to each other as partial heating conductors, possibly even to different supply voltages.

[0037] An upper electrode 122a runs in a single loop above the upper heating conductor section 118a between contact track 115a and contact track 115ab. It can be electrically contacted on the left via two electrode terminals 123a and can, for example, be Fig. 1be connected to a resistance measuring device, which is not shown here. Likewise, a leakage current detector can be connected in the aforementioned manner. An identically designed lower electrode 122b runs above the lower heating conductor section 118b between contact track 115ab and contact track 115b. It can be electrically contacted in the aforementioned manner via electrode connections 123b provided on the left. This not only enables leakage current detection across both heating conductor sections 118a and 118b, but also the respective absolute temperature detection.

[0038] Another alternative construction of a heating device 211 according to the invention is shown in Fig. 4shown. Here, four parallel, strip-shaped partial heating conductors 218a, 218b, 218c, and 218d are provided. They are connected in series with one another by means of contact tracks 215 and have two contact surfaces 216a and 216b. Two electrodes are again provided, namely an upper electrode 222a and a lower electrode 222b. The upper electrode 222a runs, so to speak, in a loop almost entirely centrally along the two partial heating conductors 218a and 218b. It can be electrically contacted via electrode connections 223a at its ends. In a similar form, the lower electrode 222b runs along almost the entire length of the two lower partial heating conductors 218c and 218d. It is electrically contacted via electrode connections 223b at its ends. Leakage current detection is thus possible in two areas, since there are two separate electrodes 222a and 222b.Likewise, although the four partial heating conductors are always operated in series in the same way, a temperature measurement can be carried out separately in both the upper half and the lower half via the temperature-dependent electrical resistance of the electrodes 222a and 222b.

[0039] Yet another alternative construction of a heating device 311 is shown in Fig. 5 On a carrier 312 with a carrier top 313, in a simplified manner, Fig. 4 Two spaced and parallel partial heating conductors 318a and 318b are provided. They are connected on the right by a contact track 315. At the left ends, they are electrically connected in the aforementioned manner by means of a short contact track 315 and contact surfaces 316a and 316b. Their spacing is relatively large, but can also be smaller, in particular only two to four times the width of a single partial heating conductor.

[0040] An outer electrode 322a runs similarly to Fig. 4 over almost the entire length of both the upper heating conductor section 318a and the lower heating conductor section 318b. It also runs below the right contact track 315, where, however, no leakage current is to be expected. Nevertheless, a temperature measurement can also be performed here. This outer electrode 322a can be electrically contacted via contact surfaces 323a.

[0041] Within the free area between the two partial heating conductors 318a and 318b, an inner electrode 322b with two electrode terminals 323b runs in a loop. It can also be used for leakage current measurement, although it is unlikely that a leakage current will occur at the inner electrode 322b given the large distance to the partial heating conductors 318a and 318b. The outer electrode 322a is ultimately intended for this purpose. The inner electrode 323b can be intended exclusively for temperature measurement. It can advantageously be applied in the same manufacturing step as the outer electrode 322a, so that a temperature measuring device or a type of temperature sensor can be created in the same step in which the outer electrode 322a required for leakage current detection is applied. Advantageously, all layers, such as those from Fig. 2can be seen, applied by thick-film processes, in particular by screen printing. Thus, the process complexity is very low, and the cost essentially consists only of the additional electrode material. Furthermore, this inner electrode 322b enables temperature measurement at a certain distance from the partial heating conductors 318a and 318b, which is considered advantageous. Thus, a falsification of a temperature, for example a temperature of the water heated by the heating device 311, similar to the Fig. 2 , reduced or even eliminated by the higher temperature of the heating conductor itself.

[0042] In the Fig. 6 a heating device 11 with support 12 is shown in simplified form, in which similar to the Fig. 1A large-area heating conductor 18 runs between two contact tracks 15. Various possible designs of electrodes 22A to 22E are applied in the area between the contact tracks 15. They are shown in reduced form and as examples for illustrative purposes. They have two electrode terminals 23. There could also be at least two electrode terminals, meaning that an additional center tap might be present.

[0043] The electrode 22A is flat. Even though it is depicted here as only a small area, in particular covering a smaller area than the area of ​​the heating conductor 18 between the two contact tracks 15, it can be considerably larger in practice. In particular, it can occupy almost the entire area of ​​the semiconductor 18 between the two contact tracks 15. The electrode 22A is therefore an example of a flat or large-area design.

[0044] The electrode 22B is designed similarly to that in the Fig. 1 It is relatively narrow, meandering, and long. Electrode 22C is similar to electrode 22A in its flat design and slightly larger.

[0045] Although electrode 22D is elongated, it is considerably wider than electrode 22B and the narrow electrode 22E above it. It is intended to illustrate that even an elongated electrode configured as an electrode track can have a certain width. The width can be provided so that the electrode covers a certain area or so that it has a certain amount of resistance material at a defined or predetermined thickness, thus exhibiting a certain electrical resistance. Thus, the width of the electrode can be used as a parameter to achieve a specific electrical resistance for a given resistance material.

Claims

1. Heating device (11, 111, 211, 311) having a temperature measuring device (25) for the heating device, the heating device (11, 111, 211, 311) having: - a flat carrier (12, 112, 212, 312), - at least one heating conductor (18, 118, 218, 318) on the flat carrier (12, 112, 212, 312), - an electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) on the flat carrier (12, 112, 212, 312), - a layer structure on the carrier (12, 112, 212, 312) with an insulation layer (29) between the heating conductor (18, 118, 21 8, 318) and the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b), - a measuring device for detecting local high temperatures at the heating device (11, 111, 211, 311), the measuring device being connected to the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) and to the heating conductor (18, 118, 218, 318) and is designed to detect a temperature-dependent leakage current through the insulation layer (29) between the heating conductor (18, 118, 218, 318) and the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) and to evaluate it as a measure of a local temperature change at the heating device (11, 111, 211, 311), wherein: - the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) consists of a material with a temperature dependence of its electrical resistance, the temperature dependency is between 0.0005 / °C and 0.01 / °C or between 500 ppm / K and 10,000 ppm / K in a temperature range between 0°C and 500°C, - the temperature measuring device (25) is connected to the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) for measuring a temperature at the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) using the temperature dependence of the electrical resistance of the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b), characterized in that: - the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) is elongated, - the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) has two electrode connections (23, 23a, 23b, 123a, 123b, 223a, 223b, 323a, 323b) and is connected to the temperature measuring device (25) by means of the latter.

2. Heating device according to claim 1, characterized in that the temperature dependence of the electrical resistance of the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) is between 0.0015 / °C and 0.005 / °C or between 1500 ppm / K and 5000 ppm / K in a temperature range between 0°C and 500°C.

3. Heating device according to claim 1 or 2, characterized in that the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) is at least partially covered by the heating conductor (18, 118, 218, 318) with the insulation layer (29) in between, wherein a section of the electrode (22, 122a, 122b, 222a, 222 b, 322a, 322b) extends from the heating conductor (18, 118, 218, 318), in particular along at least 70% or 90% of the longitudinal extent of the heating conductor (18, 118, 218, 318).

4. Heating device according to one of the preceding claims, characterized in that the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) has a small width compared to its length, in particular the length being at least 20 times as large as the width, preferably at least 50 times as large as the width.

5. Heating device according to one of the preceding claims, characterized in that the insulation layer (29) has an electrical resistance between a top side and an underside or between heating conductor (18, 118, 218, 318) and electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) of at least 1 MΩ in a temperature range between 0°C and 150°C, preferably at least 10 MΩ.

6. Heating device according to one of the preceding claims, characterized in that the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) has a total electrical resistance between 50 Ω and 100 kΩ in a temperature range between 0°C and 500°C, in particular between 5 kΩ and 20 kΩ.

7. Heating device according to one of the preceding claims, characterized in that the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) has a constant width along its longitudinal extent, in particular also a constant thickness.

8. Heating device according to one of the preceding claims, characterized in that the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) has a silver content as electrode material, in particular up to a maximum of 95%, preferably between 80% and 90%.

9. Heating device according to one of the preceding claims, characterized in that the electrode material has a variable temperature coefficient of electrical resistance, preferably a positive temperature coefficient of electrical resistance.

10. Heating device according to one of the preceding claims, characterized in that the heating conductor (118, 218, 318) has a plurality of sub-heating conductors (118a, 118b, 218a-d, 318a, 318b) which are connected to one another, preferably each of the sub-heating conductors (118a, 118b, 218a-d, 318a, 318b) covers an electrode (122a, 122b, 222a, 222b, 322a, 322b) or an electrode section, in particular connecting sections (115ab, 215, 315) being provided between the individual sub-heating conductors (118a, 118b, 218a-d, 318a, 318b) are provided connecting sections (115ab, 215, 315) made of a conductor material with a specific electrical resistance which is lower, by a factor of at least 10, than that of the heating conductor (118, 218, 318).

11. Heating device according to one of the preceding claims, characterized in that at least one additional electrode (323a, 323b) made of the same material as the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) is provided, which is not covered or overlapped by any heating conductor (18, 118, 218, 318), wherein preferably a lateral distance of the additional electrode from a heating conductor (18, 118, 218, 318) is at least 1 mm or at least 2 mm or is twice the width of the electrode web, in particular the additional electrode (323a, 323b) also being connected to the temperature measuring device (25).

12. Heating device according to one of the preceding claims, characterized in that a carrier insulation layer (27) is applied to the carrier (12, 112, 212, 312), wherein onto this carrier insulation layer (27) either the at least one electrode (22, 122a, 122b, 222a, 222b, 322a, 322b), on this electrode (22, 122a, 122b, 222a, 222b, 322a, 322b), the insulation layer (29) is applied to this electrode (22, 122a, 122b, 222a, 222b, 322a 322b), on the insulation layer (29) the heating conductor (18, 118, 218, 318) and on this the heating conductor (18, 118, 218, 318) the covering layer (31) are applied, or the heating conductor (18, 118, 218, 318), on this an insulation layer (29) or dielectric layer, onto this an electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) and onto this a covering layer (31) are applied to it.

13. Method for measuring the temperature at a heating device (11, 111, 211, 311) according to one of the preceding claims, characterized in that, on the one hand, a temperature is detected via a current flowing through the insulation layer (29) between the heating device (11, 111, 211, 311) and electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) and, on the other hand, a temperature measurement (25) is carried out on the heating device (11, 111, 211, 311) by measuring a temperature change at the electrode (22, 122a, 122b, 222a, 222b, 322a, 322b) alone and preferably evaluating it as a temperature change over time.

14. Method for producing a heating device (11, 111, 211, 311) according to one of the claims 1 to 12, characterized in that the heating device (11, 111, 211, 311) has a plurality of heating conductors (18, 118, 218, 318), in particular also the partial heating conductors (118a, 118b, 218a-d, 318a, 318b) according to claim 10, wherein all heating conductors (18, 118, 218, 318) and, if appropriate, also partial heating conductors (118a, 118b, 218a-d, 318a, 318b) of the heating device (11, 111, 211, 311) are applied in the same process step and from the same heating conductor material.

15. Method for producing a heating device (11, 111, 211, 311) according to one of the claims 1 to 12, characterized in that the heating device (11, 111, 211, 311) has a plurality of electrodes (22, 122a, 122b, 222a, 222b, 322a, 322b), in particular also the additional electrode (323a, 323b) according to claim 11, wherein all the electrodes (22, 122a, 122b, 222a, 222b, 322a, 322b, 323a, 323b) of the heating device (11, 111, 211, 311) are applied in the same process step and from the same electrode material.