Title of Invention	A RESISTANCE THERMOMETER FOR ACCURATE THERMAL CONTACTING FOR TEMPERATURE MEASUREMENT IN EXTENSIVE AREAS
Abstract	The present invention relates to a resistance thermometer comprising at least one temperature- dependent electrical resistance element (1) which has at least two connection contacts (8), comprising a carrier (3) to which the resistance element can be fixed in such a manner that it can be brought into good thermal contact with an object whose temperature is to be measured, and comprising electrical leads (2, 5) which are provided for the purpose of connecting the electrical connection contacts (8) to a measuring instrument. In order to provide a resistance thermometer which is simple and inexpensive to produce, enables good thermal contact-connection, can be designed to measure more extensive areas and can be used, at least for simple applications, in an identical or similar manner to the more expensive thermometers which are provided with a platinum wire as the resistance element, the invention proposes that a heat- resistant plastic material which can be bent slightly in at least one direction and in which at least two electrical conductor tracks are embedded is provided as the carrier (3).

Title of Invention

A RESISTANCE THERMOMETER FOR ACCURATE THERMAL CONTACTING FOR TEMPERATURE MEASUREMENT IN EXTENSIVE AREAS

Abstract

The present invention relates to a resistance thermometer comprising at least one temperature- dependent electrical resistance element (1) which has at least two connection contacts (8), comprising a carrier (3) to which the resistance element can be fixed in such a manner that it can be brought into good thermal contact with an object whose temperature is to be measured, and comprising electrical leads (2, 5) which are provided for the purpose of connecting the electrical connection contacts (8) to a measuring instrument. In order to provide a resistance thermometer which is simple and inexpensive to produce, enables good thermal contact-connection, can be designed to measure more extensive areas and can be used, at least for simple applications, in an identical or similar manner to the more expensive thermometers which are provided with a platinum wire as the resistance element, the invention proposes that a heat- resistant plastic material which can be bent slightly in at least one direction and in which at least two electrical conductor tracks are embedded is provided as the carrier (3).

Full Text	EPHY-MESS Gesellschaft fur elektro-physikalische Messgeräte mbH Resistance thermometer The present invention concerns a resistance thermometer comprising at least one temperature-dependent electrical resistance element which has at least two connection contacts, a carrier on which the resistance element can be fixed in such a way that it can be brought into good thermal contact with an object whose temperature is to be measured, and electrical supply lines provided for connecting the electrical connection contacts of the resistance element to a measuring instrument. Corresponding resistance thermometers are known in many different configurations in the state of the art. By way of example, known in the state of the art are what are referred to as slot thermometers which are provided for detecting temperatures on or in machines and installations and for the thermal protection thereof. Such thermometers are typically fitted in slots in electric motors and generators and are generally in the structural form of a thin elongate parallelepiped of up to 1 m in length, of a width of about 5 to 15 millimetres and of a thickness or height of between typically 1 and 5 mm, wherein deviations from those dimensions are readily possible. As a temperature-dependent resistance element, those known resistance thermometers include a thin platinum wire which is wound onto a bar-shaped carrier, wherein the length and diameter of such a wire are usually so selected that the resistance involves a given, fixedly predetermined resistance value such as for example 100  either at 0º C or at 300 K. Such resistance thermometers are admittedly highly reliable, accurate and also temperature-resistant but they are relatively complicated and expensive to manufacture. Platinum is relatively costly as a material so that very thin platinum wires must be worked as the resistance elements, to reduce material costs. Those wires however are very difficult in terms of handling and adjustment to given, fixedly predetermined resistance values at given temperatures is also difficult, complicated and expensive. The thin wire has to be fixed on a suitable carrier in a complicated procedure and the electrical supply lines generally require an arrangement for relieving a traction loading thereon. The flexibility of such thermometers is limited as, upon bending of the carrier, a certain tensile stress is exerted on the delicate, thin platinum wire. In addition other resistance thermometers are also known, which have for example a thin-layer resistance as the resistance element, which can also be a platinum resistance but which could also comprise other materials involving a temperature- dependent resistance, including semiconductor material, special alloys of semiconductor or metal contacts etc. It will be noted however that those resistance elements suffer from the disadvantage that they are relatively compact and can thus only implement laterally limited point measurement and they assume the ambient temperature more slowly than a thin platinum wire. In comparison with that state of the art the object of the present invention is to provide a resistance thermometer which is simple and inexpensive to produce, which permits good thermal contacting, which can be designed for the measurement of more extensive regions and which can be used, at least for simple situations of use, in the same or similar manner to the more complicated and expensive thermometers which are equipped with platinum wire as the resistance element. That object is attained in that the carrier is a plastic material which is easily bendable in at least one direction and in which at least two electrical conductor tracks are embedded, wherein a prefabricated resistance having at least two electrical connection contacts is used as the resistance element. In that respect, in the sense of the present invention, the term "embedded" is also intended to denote conductor tracks which are disposed in surface relationship on a plastic carrier material, for example which are applied in the form of a layer, in which respect it will be appreciated that it is preferable for the conductor tracks to be enclosed by the plastic material on at least three sides and in particular on all four sides. In accordance with the invention therefore the carrier on which a resistance element is fixed in such a way that it can be brought into good thermal contact with the measurement environment is provided with integrated conductor tracks, wherein moreover the carrier is a plastic material which is easily bendable in at least one direction. It will be appreciated that the carrier is accordingly also easily bendable in one direction together with the electrical conductor tracks embedded therein, and can thus be very easily and simply adapted to the geometry of given objects to be measured. The integrated configuration of the carrier and the electrical supply lines facilitates the procedure involved in fixing and contacting the resistance element as, instead of the previous three elements, namely the resistance element, the carrier and the supply lines which had to be jointly brought together and fixed to each other, now there are only two elements which are to be fixed to each other as the carrier and the conductor tracks are of an integrated nature. In a preferred embodiment of the invention the plastic material in which the conductor tracks are embedded or on which they are integrally disposed is an extrudable, temperature-resistant thermoplastic material such as for example a polyimide, in particular polyamideimide or a polyetherketone such as for example PEEK. PTFE is also suitable as the plastic carrier material. The plastic material should be heat-resistant to up to at least 180°C, preferably up to at least 200°C or above. The connection contacts of the electrical resistance element are easily connected or contacted to the at least two conductor tracks, for example by soldering, welding, or similar contacting procedures and are then automatically also at least provisionally fixed to the carrier. The integrated conductor tracks in turn have good thermal conductivity and, by way of the flexible carrier, can be easily brought into good thermal contact with the object whose temperature is to be determined, and they thus contribute to effectively transmitting to the resistance element, the temperature of a region which extends beyond the dimensions of the resistance element. The features of preferred embodiments of the invention, which are described hereinafter in part in conjunction with each other, are each to be considered as being disclosed individually and separately in themselves and can be combined with all other features in any combinations, insofar as a feature does not necessarily presuppose another feature or represents a more concrete form of another feature. In the preferred embodiment the carrier is a plastic material in strip form of a cross-section whose width is at least double, preferably at least four times and still more preferably at least six times or particularly preferably even more than eight times the height of the material in strip form. In that case, in relation to a non-circular cross- section for the material in strip form, the greatest cross-sectional extent is referred to here as the "width" and the dimension of the shortest extent is referred to as the "height". Desirably such a strip is of a width of at least 3 mm, preferably at least 5 mm. Elements in strip form which have been subjected to practical testing in preliminary investigations were for example of a width of the order of magnitude of 6 to 9 mm. In the preferred embodiment the maximum width is 25 mm, wherein maximum widths of 20 mm or 15 mm are still more preferred and particularly preferably the total width is below 12 mm. In specific terms, minimum widths of 6 mm or less can be achieved where that is required. The height or thickness of the carrier including the embedded electrical conductor tracks should preferably not be below 0.2 mm and is preferably at least 0.4 mm to be able to ensure sufficient thickness both of the conductor tracks and also the insulating carrier layers. The maximum height or thickness should if possible not exceed 3 mm, better 2 mm. The cross-sectional dimensions of the carrier overall determine the maximum possible cross-section of the conductor tracks. On the one hand there must be at least two electrical conductor tracks to be able to contact the at least two connection contacts of a resistance element, in order to measure therebetween the resistance of the resistance element. In addition those conductor tracks must be insulated from each other and they are preferably also insulated with respect to the environment by the carrier element and are preferably enclosed on all sides by the carrier element, wherein the carrier element is removed on one side of those conductor tracks only in the regions in which the connection contacts of the resistance element must be connected to the conductor tracks. In addition the electrical conductor tracks which are generally also good thermal conductors serve for thermally connecting the electrical resistance element to the environment to be measured, over a greater region which is adjacent to the resistance element, whereas the plastic material of the carrier is generally a poor conductor of heat, that is to say it was only intended to cover the electrical conductor tracks with a thin layer insofar as it is required for the desired insulation and also for mechanical integrity of the carrier. In addition the electrical conductor tracks overall were to involve a relatively low level of resistance as, at least in the case of a two-wire measurement operation, the resistance of the supply lines is also measured in addition to the resistance of the resistance element and as the resistance of the supply lines is also generally temperature-dependent, which makes the measurement correspondingly less accurate or requires additional corrections which can be correspondingly more disregarded, the lower the absolute resistance of the supply lines in relation to the resistance of the resistance element. The endeavour is therefore to make the cross- section of the conductor tracks sufficiently great and the cross-section of the carrier material enclosing the conductor tracks as small as possible, that is to say insofar as that is compatible with the insulation requirements and the mechanical demands as a carrier. For that reason the cross-section of the individual conductor track should not be less than a given minimum dimension and is preferably at least 0.1 and still more preferably 0.2 or indeed 0.3 mm2. On the other hand the cross-section both of the carrier material and also of the conductor tracks should not be excessively great, because that limits the bendability and mobility of the carrier. Good flexibility in at least one plane is achieved however inter alia by the above-mentioned preferred relationships between the width and the height of the cross-section. In the preferred embodiment of the invention the carrier material and the conductor tracks are rectangular in cross-section, the long sides of those cross-sections extending in parallel relationship with each other. The conductor tracks preferably comprise copper as copper is both a good thermal conductor and also a good electrical conductor and in addition is comparatively inexpensive. The carrier material is preferably produced with a constant cross-section, in the form of an endless material, and is cut to length as may be desired, in the lengths required for specific thermometers. It will be appreciated that the same consideration preferably also applies to the conductor tracks which are integrated into the carrier material. For many purposes of use it is desirable if the temperature is detected over a prolonged measurement distance or if a longer portion of an object whose temperature is to be determined is detected, which cannot be readily bridged over by the heat- conducting conductor tracks. For such a purpose it is provided in accordance with the invention that a plurality of resistance elements are distributed over a carrier portion of corresponding length, preferably at equal spacings. The resistance elements used are preferably thin-layer resistances, in particular PT thin-layer resistances, which are relatively inexpensive in comparison with platinum wires. In that case, a plurality of such resistances which are distributed over the length of the carrier portion can be connected in parallel. It will be noted however that it is also possible for a plurality of resistances to be connected in series in succession on a single conductor track, by that conductor track being respectively interrupted between the two connection legs, which are contacted in succession with the conductor track, of each of the resistances. In a preferred embodiment of the invention the carrier material has at least three conductor tracks, which makes it possible for a plurality of resistances arranged thereon to be selectively connected in parallel or in series. In particular, with at least three resistances, two of those resistances can be connected in series and a third can be connected in parallel with the two or in parallel with one of the series-connected resistances. With four resistances it is for example possible for two resistances to be connected in parallel in pairs in each case and for those parallel-connected pairs to be connected in turn in series in succession, or vice-versa. If in such a situation four nominally identical resistances are used, that combined parallel and series connection also has the same resistance value as each individual resistance, wherein, when using resistances involving tolerance, the resistances can be measured prior to contacting and can be arranged in the series and parallel circuit in accordance with the specific tolerance deviations found, so that the overall resistance of the interconnected resistances has a lower tolerance deviation from the reference or target value than one or other of the individual resistances. The connection contacts or connection wires of the resistance elements, particularly in the case of thin-layer resistances, contribute to the resistance value, in which respect the lengths of those connection contacts or contact wires can be so adapted, that is to say shortened, that as a result the resistance of the conductor tracks can be compensated and also any tolerance deviations can be reduced. A further advantage of using at least three conductor tracks is that it is possible to provide a third measurement tapping on the third conductor track so that it is possible for a respective one of the series-connected groups of parallel resistors to be measured separately by a procedure whereby the third measurement tapping is used instead of a respective one of the other two, minimally present measurement tappings. That permits additional differentiation and positional resolution of the measured temperature if the resistance elements are arranged group-wise in succession along the thermometer section (wherein the resistance elements of a group are respectively connected in parallel). In the preferred embodiment of the present invention in which the carrier for example is of a width of about 6 or at a maximum 8 mm, a thickness of less than 1 mm and for example has three embedded flat conductor tracks of cross-sections of each 1.5 x 0.2 mm2, applying resistance elements to one of the longer cross-sectional sides of the carrier makes it possible to manufacture thermometers whose maximum thickness is between 2 and 4 mm while the width approximately corresponds to the width of the carrier and the length of the carrier and thus of the thermometer can be selected as desired to correspond to the purpose of use. When using a single resistance element typical overall lengths of such a resistance thermometer are for example 50 mm while when using a plurality of resistance elements overall lengths of up to 1 mm or also thereabove are readily possible. The spacing of adjacent resistance elements should preferably be not more than 10 cm. Preferably the electrical thin-layer resistances are applied flat to the flat top side of the carrier, the connection contacts are contacted with two of the embedded flat conductors and then the carrier with the resistance which is placed flat thereon or which is pressed flat thereon in specifically targeted fashion can be cast around for example with silicone. Preferably all resistance elements are applied on only one side of the carrier although for many purposes of use an alternate arrangement or an arrangement which changes in accordance with another scheme, on both sides of the carrier, can also be appropriate. The carrier material is preferably heat-resistant and flexible so that it can be fitted into narrow slots or gaps in a machine and for example can also be placed around curved or cylindrical parts of a machine or other objects to be measured, wherein the resistance elements are brought into good contact with the surface of the object to be measured, even if only the side of the carrier, that is remote from the applied resistances, can be brought into direct contact with the object to be measured. The conductor tracks and the relatively thin insulating layer on the conductor tracks, as well as the flat cross-sectional shape of the carrier and the conductor tracks, then always still provide for relatively good thermal contact between the object to be measured and the resistance element. Preferably the carrier with the resistance or resistances which is enclosed by casting with silicone and/or a heat-conducting paste is also encased with a shrink tube extending over the entire length of the carrier. The carrier can additionally be embedded into a suitable plastic housing or at least an end portion thereof, or can be connected to an end portion which accommodates external supply lines connected to the electrical conductor tracks of the carrier, for example being soldered or welded or bonded thereto, wherein an end of the carrier material in question is supported at the end portion which thus serves as a means for relieving traction loadings thereon when the supply lines are fixed thereto. A particular advantage is that, in the preferred variant of the present invention, the carrier material with the embedded conductor tracks is produced in a constant cross- section, in the form of endless material. The carrier can thus be easily adapted to any desired length, it guarantees good thermal coupling of the resistance elements and at the same time it is very inexpensive. Further advantages, features and possible uses of the present invention will be clearly apparent from the description hereinafter of a preferred embodiment and the accompanying drawings in which: Figure 1 shows a plan view of a resistance thermometer according to the invention, wherein a covering shrink tube and the silicone casting material are shown as being removed from the surface, Figure 2 shows a portion from Figure 1 on an enlarged scale, Figure 3 shows a cross-section along line A-A in Figure 2 but without the housing 15, and Figure 4 shows a cross-section through a carrier material according to the invention with partially removed insulation of two conductor tracks. As can be seen from Figure 4 the carrier 3 of the resistance thermometer which is generally identified by reference 10 comprises a plastic strip which is rectangular in cross-section, with three flat conductors which are also rectangular in cross-section and which are denoted by references 2a, 2b and 2c. The height of the carrier material is for example 0.5 to 0.8 mm and the width is between 6 and 8 mm. The cross-section of the individual conductor tracks 2a, 2b and 2c is for example 0.2 mm x 1.5 mm, that is to say about 0.3 mm2. The spacing of adjacent conductor tracks is for example about 0.2 to 0.5 mm and the thickness of the insulating layer on the upper and lower long sides of the cross-section is preferably 0.1 to 0.3 mm but can also be thicker when extreme demands are made in terms of high-voltage dielectric strength. The outer lateral insulations along the longitudinal edges of the carrier 3 should also be at least 0.1 to 0.5 mm or more. The insulating limbs 6 between the conductor tracks are preferably of a width of at least 0.2, preferably at least 0.5 mm. In the illustrated version the insulating limbs 6 are almost 0.5 mm wide. The plastic material is insulating and flexible and very easily bendable about an axis parallel to the longitudinal side of the cross-section. In Figure 4 the plastic material 6 is removed on the top side from two of the conductor tracks 2b, 2c in order there to be able to contact a resistance element 1 or the connection contacts 8 thereof, as shown in Figure 3. It is also possible to see solder beads 12 with which the connection contacts 8 are electrically connected to the conductor tracks 2b, 2c. It is also possible to see a heat-conducting paste 13, by means of which the actual resistance element 1 which has a PT thin-layer resistance is fixed on the surface of the carrier 3 and in good surface contact in relation to the surface of the carrier 3. The resistance element 1 is only separated from the subjacent conductor tracks 2b, 2c by a relatively thin layer of the insulating material so that the conductor tracks 2b, 2c can transport heat out of regions which are adjacent to the resistance element 1 to the resistance element 1 or can conduct excess heat therefrom. Optionally the resistance thermometer can be brought into contact with the object whose temperature is to be measured, either with the rear side which is opposite the resistance element or however with the side on which the resistance element 1 is disposed. Optionally the resistance thermometer can also be fitted into a groove in the object in question and can be clamped or cast therein so that heat transfer to the resistance element 1 can take place from both sides. Figure 1 shows the resistance thermometer which is generally identified by reference 10 and which in principle can be produced in any length as the carrier 3 is an endless material which is cut to length in accordance with the specific requirement for a thermometer. In the present example in Figure 1 which shows a resistance thermometer almost in its natural size or on a slightly increased scale the carrier 3 has three parallel conductor tracks 2a, 2b and 2c of constant cross-section, which extend over the entire length of the carrier 3 and with which a total of four resistance elements 1 are contacted. Shown at the right-hand end are two electrical supply lines 5 which are in contact with the two outer conductor tracks 2a and 2c. The resistances 1a, 1b and 1c and 1d are connected in parallel in pairs between the lines 2b, 2c and 2a, 2b respectively and, by virtue of the connection to the central conductor track 2b which is not in direct contact with the outer supply lines 5, effectively have a series connection of the two pairs shown at the right and the left respectively. The resistances however can equally well be arranged in such a way that a resistor is connected alternately to the conductor tracks 2b, 2c and 2a and 2b respectively, which in this embodiment would not in any way alter the effective parallel and series connection. It would also be possible for all resistances to be connected in parallel, in which case only two conductor tracks would be required, and the outer connecting lines 5 could either contact the conductor tracks 2a and 2b or 2b and 2c, instead of the conductor tracks 2a and 2c as shown here. As already mentioned the resistances can also be connected in series, in which case then, if the number of the resistances is equal to or greater than the number of available conductor tracks, the series connection can be implemented inter alia by at least a portion of the resistances being contact with both respective connections on the same conductor track, with the conductor track being interrupted between the connections of the resistance in question. In order to implement a series connection with the carrier material according to the invention however it is alternatively also possible for the two connections of each of the resistances to be respectively connected to another conductor track if a respective one of the conductor tracks is alternately interrupted between successive resistances. It is then advantageously possible to use a third conductor track as the return conductor in order to have all connections of the thermometer jointly at one end of the carrier. The length of the electrical connection wires 8 which make up a part of the measurement resistance is suitably adapted to possibly compensate for the supply line resistance of the supply lines and the conductor tracks 2a, 2b and 2c respectively. In other words the connection wires 8 of the resistance elements (for example la) which are further away from the outer connection cables 5 or the outer connection contacts 4 respectively can be shortened more greatly than the resistance elements (for example 1d) which are closer to the cables 5. The outer supply lines or connection cables 5 can in particular also have double the number (that is to say 4) of electrical conductors in order to go over to 4-point measurement of the resistance as closely as possible to the conductor tracks 2a, 2b, 2c. In the illustrated combined series and parallel connection of the four resistances and on the assumption that all four resistances are of the same nominal value, the totality of the four resistance elements 1 connected in that fashion also have the same nominal value as each individual resistance. As already mentioned, by means of a skilful combination of the individual resistances which can each in itself have certain tolerance deviations, it then becomes possible in comparison to reduce the tolerance deviation of the combined resistance. The maximum number of resistance elements 1 on a carrier 3 is not limited and depends only on the space available on a given carrier portion, in which respect however there is generally no need for the resistance elements to be arranged at a very close spacing as in any case a certain temperature detection is achieved over a relatively large region which amounts to a multiple of the thermal contact surface of the individual resistance element 1, by way of the conductor tracks but also by way of any adjacent machine components or the like. As can also be seen from Figure 3 the resistance elements 1 are substantially fiat parallelepipedic elements, the width of which at any event is less than the width of the carrier 3 and the thickness of which is preferably less than 1 mm, for example 0.9 mm. For good thermal contact, the external contact surfaces of the thin-layer resistances should preferably be at least 2 mm2, preferably at least 3 to 4 mm2. The carrier 3 with the applied and contacted resistance elements 1a, 1b, 1c, 1d can possibly either be restricted to the individual resistance elements or it can be encased by casting over its entire length with a heat-contacting paste 13, a silicone adhesive or another protective and binding material so that the finished resistance thermometer is then overall of a thickness which is scarcely more than the total of the thickness of the carrier 3 and one of the resistance elements 1. Finally the entire carrier with the resistance elements cast therein can also be encased in a shrink tube 14 or in a preferably thin-walled, insulating housing, wherein Figure 1 also shows the shrink tube version at the upper and lower edges of the carrier 3 and at the left-hand and right-hand ends of the thermometer 10. It is also possible to provide a housing in the form of a non-insulating housing, for example comprising a soft or thin-walled metal material which is pressed to the carrier and the resistances and which ensures good temperature distribution and thermal contact in relation to the resistance elements, which however presupposes that the conductor tracks and the resistance elements are well insulated in relation to the housing. That could be ensured for example by the combination of an inner insulating shrink tube and an outer metal housing surrounding the shrink tube. Figure 2 shows an enlargement of the right-hand end of the resistance thermometer 10 but with a modification insofar as the shrink tube 14 of Figure 1 is replaced by a housing 15 which however can also be provided in addition to a shrink tube 14. The housing 15 is also a flat housing of rectangular cross-section, with an opening which fairly precisely corresponds to the width and height of the carrier material, possibly additionally with the resistance elements 1 cast therein. The end 9, which can be seen at the right, of the carrier 3 is supported against the right-hand end of the corresponding opening in the housing 15 and the supply lines 5 are passed through two gaps or bores in the right-hand end of the housing 15 and contacted with the tracks 2a and 2c. Because the end 9 of the carrier 3 is supported in the housing that effectively forms a mean for relieving traction loadings on the connection wires or cables 5 which can also be fixed in the housing, although that is not shown here. The housing can also be only in the form of a short end portion which receives only a short end part of the thermometer 10, which only includes for example the connection contacts for the supply lines 5. That avoids the housing 15 adversely affecting the thermal contact of the most closely adjacent resistance element 1 with the surroundings. Each of the cables 5 can have two connection wires which are insulated relative to each other and which for the purposes of 4-point measurement are jointly connected to the contact locations 4. Alternatively the housing 15 can also comprise a metal, preferably a soft metal and in particular a metal foil or a metal braid or mesh and can be pressed to the resistance thermometer for good thermal contact, in which case then however the thermometer 10 must be insulated in relation to the housing 15, for example by a shrink tube 14 within the housing 15. The resistance thermometers according to the invention are relatively simple and inexpensive to produce, they are extremely flexible in the preferred variant and they are therefore suitable for very many different purposes of use. CLAIMS 1. A resistance thermometer comprising at least one temperature-dependent electrical resistance element (1) which has at least two connection contacts (8), a carrier (3) on which the resistance element can be fixed in such a way that it can be brought into good thermal contact with an object whose temperature is to be measured, and electrical supply lines (2, 5) provided for connecting the electrical connection contacts (8) to a measuring instrument, characterised in that provided as the carrier (3) is a heat-resistant plastic material which is easily bendable in at least one direction and in which at least two electrical conductor tracks are embedded. 2. A resistance thermometer according to claim 1 characterised in that the carrier is in strip form of a cross-section whose width is at least double the height. 3. A resistance thermometer according to claim 2 characterised in that the cross-sectional material in strip form is of a width which is at least four times and preferably at least six times and particularly preferably more than eight times the height or thickness of the material in strip form. 4. A resistance thermometer according to one of claims 1 to 3 characterised in that its width is at least 3 and preferably at least 5 mm. 5. A resistance thermometer according to one of claims 1 to 4 characterised in that the width of the material in strip form is at a maximum 25 mm, preferably at a maximum 20 or 15 mm and particularly preferably at a maximum 12 mm. 6. A resistance thermometer according to one of claims 1 to 5 characterised in that the electrical conductor tracks in turn are of a strip-shaped configuration and are each of a cross-section whose width is more double and preferably more than four times the cross-sectional height. 7. A resistance thermometer according to one of claims 1 to 6 characterised in that the cross-section of the carrier and preferably also the cross-section of the electrical conductors is substantially right-angled, wherein the long sides of the cross- section of the carrier and the electrical conductors extend parallel. 8. A resistance thermometer according to one of claims 1 to 7 characterised in that the at least one resistance element is placed on one side of the carrier and its connection contacts are respectively connected to another of the at least two electrical conductors, wherein for a series connection the conductor tracks are alternately interrupted between successive resistances and for a parallel connection the conductor tracks do not have any interruption between successive resistances. 9. A resistance thermometer according to one of claims 1 to 8 characterised in that the at least one resistance element is placed on one side of the carrier and its connection contacts are respectively connected to one and the same of the at least two electrical conductors, wherein the electrical conductor is interrupted between the connection contacts of the resistance element. 10. A resistance thermometer according to one of claims 1 to 9 characterised in that the conductor tracks comprise copper of a cross-section of at least 0.1 mm2, preferably at least 0.2 mm2. 11. A resistance thermometer according to one of claims 1 to 10 characterised in that three parallel conductor tracks are provided on the material in strip form. 12. A resistance thermometer according to one of claims 1 to 11 characterised in that the conductor tracks extend in a common plane in the carrier material. 13. A resistance thermometer according to one of claims 1 to 12 characterised in that at least two resistances are arranged at a spacing relative to each other on the carrier material and are contacted. 14. A resistance thermometer according to claim 13 characterised in that the resistances are connected in parallel. 15. A resistance thermometer according to claim 13 characterised in that the resistances are connected in series. 16. A resistance thermometer according to one of claims 1 to 15 characterised in that there are provided at least three resistances, wherein the resistances are connected in part in parallel and in part in series. 17. A resistance thermometer according to one of claims 1 to 16 characterised in that there are provided at least three conductor tracks (2a, 2b, 2c) with which resistances (1a, 1b, 1c, 1d) are directly or indirectly contacted. 18. A resistance thermometer according to one of claims 1 to 17 characterised in that the at least one resistance element is a platinum thin-layer resistance. 19. A resistance thermometer according to one of claims 1 to 18 characterised in that the resistance element is encased by casting jointly with the carrier with silicone and/or heat-conducting paste (13). 20. A resistance thermometer according to one of claims 1 to 19 characterised in that the carrier and the resistance element are encased by a shrink tube or housing. 21. A resistance thermometer according to one of claims 1 to 20 characterised in that the electrical resistance caused by the length of the conductor tracks (2a, 2b, 2c) to the connection wires of the resistances is compensated by the corresponding reduction in the length of the connection wires of the resistance. 22. A resistance thermometer according to one of claims 1 to 21 characterised in that the carrier material including the conductor tracks integrated into the carrier material is produced with a constant cross-section in the form of endless material, preferably by extrusion. 23. A resistance thermometer according to claim 22 characterised in that the carrier material is cut to the length required for the specific thermometer. The present invention relates to a resistance thermometer comprising at least one temperature- dependent electrical resistance element (1) which has at least two connection contacts (8), comprising a carrier (3) to which the resistance element can be fixed in such a manner that it can be brought into good thermal contact with an object whose temperature is to be measured, and comprising electrical leads (2, 5) which are provided for the purpose of connecting the electrical connection contacts (8) to a measuring instrument. In order to provide a resistance thermometer which is simple and inexpensive to produce, enables good thermal contact-connection, can be designed to measure more extensive areas and can be used, at least for simple applications, in an identical or similar manner to the more expensive thermometers which are provided with a platinum wire as the resistance element, the invention proposes that a heat- resistant plastic material which can be bent slightly in at least one direction and in which at least two electrical conductor tracks are embedded is provided as the carrier (3).

Full Text

EPHY-MESS Gesellschaft fur elektro-physikalische Messgeräte mbH
Resistance thermometer
The present invention concerns a resistance thermometer comprising at least
one temperature-dependent electrical resistance element which has at least two
connection contacts, a carrier on which the resistance element can be fixed in such a
way that it can be brought into good thermal contact with an object whose temperature
is to be measured, and electrical supply lines provided for connecting the electrical
connection contacts of the resistance element to a measuring instrument.
Corresponding resistance thermometers are known in many different
configurations in the state of the art. By way of example, known in the state of the art
are what are referred to as slot thermometers which are provided for detecting
temperatures on or in machines and installations and for the thermal protection thereof.
Such thermometers are typically fitted in slots in electric motors and generators and are
generally in the structural form of a thin elongate parallelepiped of up to 1 m in length,
of a width of about 5 to 15 millimetres and of a thickness or height of between typically
1 and 5 mm, wherein deviations from those dimensions are readily possible.
As a temperature-dependent resistance element, those known resistance
thermometers include a thin platinum wire which is wound onto a bar-shaped carrier,
wherein the length and diameter of such a wire are usually so selected that the
resistance involves a given, fixedly predetermined resistance value such as for example
100  either at 0º C or at 300 K. Such resistance thermometers are admittedly highly
reliable, accurate and also temperature-resistant but they are relatively complicated and
expensive to manufacture. Platinum is relatively costly as a material so that very thin
platinum wires must be worked as the resistance elements, to reduce material costs.
Those wires however are very difficult in terms of handling and adjustment to given,
fixedly predetermined resistance values at given temperatures is also difficult,
complicated and expensive. The thin wire has to be fixed on a suitable carrier in a
complicated procedure and the electrical supply lines generally require an arrangement
for relieving a traction loading thereon. The flexibility of such thermometers is limited

as, upon bending of the carrier, a certain tensile stress is exerted on the delicate, thin
platinum wire.
In addition other resistance thermometers are also known, which have for
example a thin-layer resistance as the resistance element, which can also be a platinum
resistance but which could also comprise other materials involving a temperature-
dependent resistance, including semiconductor material, special alloys of
semiconductor or metal contacts etc. It will be noted however that those resistance
elements suffer from the disadvantage that they are relatively compact and can thus
only implement laterally limited point measurement and they assume the ambient
temperature more slowly than a thin platinum wire.
In comparison with that state of the art the object of the present invention is to
provide a resistance thermometer which is simple and inexpensive to produce, which
permits good thermal contacting, which can be designed for the measurement of more
extensive regions and which can be used, at least for simple situations of use, in the
same or similar manner to the more complicated and expensive thermometers which are
equipped with platinum wire as the resistance element.
That object is attained in that the carrier is a plastic material which is easily
bendable in at least one direction and in which at least two electrical conductor tracks
are embedded, wherein a prefabricated resistance having at least two electrical
connection contacts is used as the resistance element.
In that respect, in the sense of the present invention, the term "embedded" is
also intended to denote conductor tracks which are disposed in surface relationship on a
plastic carrier material, for example which are applied in the form of a layer, in which
respect it will be appreciated that it is preferable for the conductor tracks to be enclosed
by the plastic material on at least three sides and in particular on all four sides.
In accordance with the invention therefore the carrier on which a resistance
element is fixed in such a way that it can be brought into good thermal contact with the
measurement environment is provided with integrated conductor tracks, wherein
moreover the carrier is a plastic material which is easily bendable in at least one
direction. It will be appreciated that the carrier is accordingly also easily bendable in
one direction together with the electrical conductor tracks embedded therein, and can
thus be very easily and simply adapted to the geometry of given objects to be measured.

The integrated configuration of the carrier and the electrical supply lines
facilitates the procedure involved in fixing and contacting the resistance element as,
instead of the previous three elements, namely the resistance element, the carrier and
the supply lines which had to be jointly brought together and fixed to each other, now
there are only two elements which are to be fixed to each other as the carrier and the
conductor tracks are of an integrated nature.
In a preferred embodiment of the invention the plastic material in which the
conductor tracks are embedded or on which they are integrally disposed is an
extrudable, temperature-resistant thermoplastic material such as for example a
polyimide, in particular polyamideimide or a polyetherketone such as for example
PEEK. PTFE is also suitable as the plastic carrier material. The plastic material should
be heat-resistant to up to at least 180°C, preferably up to at least 200°C or above.
The connection contacts of the electrical resistance element are easily connected
or contacted to the at least two conductor tracks, for example by soldering, welding, or
similar contacting procedures and are then automatically also at least provisionally
fixed to the carrier.
The integrated conductor tracks in turn have good thermal conductivity and, by
way of the flexible carrier, can be easily brought into good thermal contact with the
object whose temperature is to be determined, and they thus contribute to effectively
transmitting to the resistance element, the temperature of a region which extends
beyond the dimensions of the resistance element.
The features of preferred embodiments of the invention, which are described
hereinafter in part in conjunction with each other, are each to be considered as being
disclosed individually and separately in themselves and can be combined with all other
features in any combinations, insofar as a feature does not necessarily presuppose
another feature or represents a more concrete form of another feature.
In the preferred embodiment the carrier is a plastic material in strip form of a
cross-section whose width is at least double, preferably at least four times and still
more preferably at least six times or particularly preferably even more than eight times
the height of the material in strip form. In that case, in relation to a non-circular cross-
section for the material in strip form, the greatest cross-sectional extent is referred to
here as the "width" and the dimension of the shortest extent is referred to as the

"height". Desirably such a strip is of a width of at least 3 mm, preferably at least 5 mm.
Elements in strip form which have been subjected to practical testing in preliminary
investigations were for example of a width of the order of magnitude of 6 to 9 mm. In
the preferred embodiment the maximum width is 25 mm, wherein maximum widths of
20 mm or 15 mm are still more preferred and particularly preferably the total width is
below 12 mm. In specific terms, minimum widths of 6 mm or less can be achieved
where that is required. The height or thickness of the carrier including the embedded
electrical conductor tracks should preferably not be below 0.2 mm and is preferably at
least 0.4 mm to be able to ensure sufficient thickness both of the conductor tracks and
also the insulating carrier layers. The maximum height or thickness should if possible
not exceed 3 mm, better 2 mm.
The cross-sectional dimensions of the carrier overall determine the maximum
possible cross-section of the conductor tracks. On the one hand there must be at least
two electrical conductor tracks to be able to contact the at least two connection contacts
of a resistance element, in order to measure therebetween the resistance of the
resistance element. In addition those conductor tracks must be insulated from each
other and they are preferably also insulated with respect to the environment by the
carrier element and are preferably enclosed on all sides by the carrier element, wherein
the carrier element is removed on one side of those conductor tracks only in the regions
in which the connection contacts of the resistance element must be connected to the
conductor tracks.
In addition the electrical conductor tracks which are generally also good thermal
conductors serve for thermally connecting the electrical resistance element to the
environment to be measured, over a greater region which is adjacent to the resistance
element, whereas the plastic material of the carrier is generally a poor conductor of
heat, that is to say it was only intended to cover the electrical conductor tracks with a
thin layer insofar as it is required for the desired insulation and also for mechanical
integrity of the carrier. In addition the electrical conductor tracks overall were to
involve a relatively low level of resistance as, at least in the case of a two-wire
measurement operation, the resistance of the supply lines is also measured in addition
to the resistance of the resistance element and as the resistance of the supply lines is
also generally temperature-dependent, which makes the measurement correspondingly

less accurate or requires additional corrections which can be correspondingly more
disregarded, the lower the absolute resistance of the supply lines in relation to the
resistance of the resistance element. The endeavour is therefore to make the cross-
section of the conductor tracks sufficiently great and the cross-section of the carrier
material enclosing the conductor tracks as small as possible, that is to say insofar as that
is compatible with the insulation requirements and the mechanical demands as a carrier.
For that reason the cross-section of the individual conductor track should not be
less than a given minimum dimension and is preferably at least 0.1 and still more
preferably 0.2 or indeed 0.3 mm2. On the other hand the cross-section both of the
carrier material and also of the conductor tracks should not be excessively great,
because that limits the bendability and mobility of the carrier. Good flexibility in at
least one plane is achieved however inter alia by the above-mentioned preferred
relationships between the width and the height of the cross-section.
In the preferred embodiment of the invention the carrier material and the
conductor tracks are rectangular in cross-section, the long sides of those cross-sections
extending in parallel relationship with each other. The conductor tracks preferably
comprise copper as copper is both a good thermal conductor and also a good electrical
conductor and in addition is comparatively inexpensive.
The carrier material is preferably produced with a constant cross-section, in the
form of an endless material, and is cut to length as may be desired, in the lengths
required for specific thermometers. It will be appreciated that the same consideration
preferably also applies to the conductor tracks which are integrated into the carrier
material.
For many purposes of use it is desirable if the temperature is detected over a
prolonged measurement distance or if a longer portion of an object whose temperature
is to be determined is detected, which cannot be readily bridged over by the heat-
conducting conductor tracks. For such a purpose it is provided in accordance with the
invention that a plurality of resistance elements are distributed over a carrier portion of
corresponding length, preferably at equal spacings. The resistance elements used are
preferably thin-layer resistances, in particular PT thin-layer resistances, which are
relatively inexpensive in comparison with platinum wires. In that case, a plurality of
such resistances which are distributed over the length of the carrier portion can be

connected in parallel. It will be noted however that it is also possible for a plurality of
resistances to be connected in series in succession on a single conductor track, by that
conductor track being respectively interrupted between the two connection legs, which
are contacted in succession with the conductor track, of each of the resistances.
In a preferred embodiment of the invention the carrier material has at least three
conductor tracks, which makes it possible for a plurality of resistances arranged thereon
to be selectively connected in parallel or in series. In particular, with at least three
resistances, two of those resistances can be connected in series and a third can be
connected in parallel with the two or in parallel with one of the series-connected
resistances. With four resistances it is for example possible for two resistances to be
connected in parallel in pairs in each case and for those parallel-connected pairs to be
connected in turn in series in succession, or vice-versa. If in such a situation four
nominally identical resistances are used, that combined parallel and series connection
also has the same resistance value as each individual resistance, wherein, when using
resistances involving tolerance, the resistances can be measured prior to contacting and
can be arranged in the series and parallel circuit in accordance with the specific
tolerance deviations found, so that the overall resistance of the interconnected
resistances has a lower tolerance deviation from the reference or target value than one
or other of the individual resistances.
The connection contacts or connection wires of the resistance elements,
particularly in the case of thin-layer resistances, contribute to the resistance value, in
which respect the lengths of those connection contacts or contact wires can be so
adapted, that is to say shortened, that as a result the resistance of the conductor tracks
can be compensated and also any tolerance deviations can be reduced.
A further advantage of using at least three conductor tracks is that it is possible
to provide a third measurement tapping on the third conductor track so that it is
possible for a respective one of the series-connected groups of parallel resistors to be
measured separately by a procedure whereby the third measurement tapping is used
instead of a respective one of the other two, minimally present measurement tappings.
That permits additional differentiation and positional resolution of the measured
temperature if the resistance elements are arranged group-wise in succession along the

thermometer section (wherein the resistance elements of a group are respectively
connected in parallel).
In the preferred embodiment of the present invention in which the carrier for
example is of a width of about 6 or at a maximum 8 mm, a thickness of less than 1 mm
and for example has three embedded flat conductor tracks of cross-sections of each 1.5
x 0.2 mm2, applying resistance elements to one of the longer cross-sectional sides of the
carrier makes it possible to manufacture thermometers whose maximum thickness is
between 2 and 4 mm while the width approximately corresponds to the width of the
carrier and the length of the carrier and thus of the thermometer can be selected as
desired to correspond to the purpose of use. When using a single resistance element
typical overall lengths of such a resistance thermometer are for example 50 mm while
when using a plurality of resistance elements overall lengths of up to 1 mm or also
thereabove are readily possible. The spacing of adjacent resistance elements should
preferably be not more than 10 cm.
Preferably the electrical thin-layer resistances are applied flat to the flat top side
of the carrier, the connection contacts are contacted with two of the embedded flat
conductors and then the carrier with the resistance which is placed flat thereon or which
is pressed flat thereon in specifically targeted fashion can be cast around for example
with silicone. Preferably all resistance elements are applied on only one side of the
carrier although for many purposes of use an alternate arrangement or an arrangement
which changes in accordance with another scheme, on both sides of the carrier, can also
be appropriate. The carrier material is preferably heat-resistant and flexible so that it
can be fitted into narrow slots or gaps in a machine and for example can also be placed
around curved or cylindrical parts of a machine or other objects to be measured,
wherein the resistance elements are brought into good contact with the surface of the
object to be measured, even if only the side of the carrier, that is remote from the
applied resistances, can be brought into direct contact with the object to be measured.
The conductor tracks and the relatively thin insulating layer on the conductor tracks, as
well as the flat cross-sectional shape of the carrier and the conductor tracks, then
always still provide for relatively good thermal contact between the object to be
measured and the resistance element.

Preferably the carrier with the resistance or resistances which is enclosed by
casting with silicone and/or a heat-conducting paste is also encased with a shrink tube
extending over the entire length of the carrier. The carrier can additionally be
embedded into a suitable plastic housing or at least an end portion thereof, or can be
connected to an end portion which accommodates external supply lines connected to
the electrical conductor tracks of the carrier, for example being soldered or welded or
bonded thereto, wherein an end of the carrier material in question is supported at the
end portion which thus serves as a means for relieving traction loadings thereon when
the supply lines are fixed thereto.
A particular advantage is that, in the preferred variant of the present invention,
the carrier material with the embedded conductor tracks is produced in a constant cross-
section, in the form of endless material. The carrier can thus be easily adapted to any
desired length, it guarantees good thermal coupling of the resistance elements and at the
same time it is very inexpensive.
Further advantages, features and possible uses of the present invention will be
clearly apparent from the description hereinafter of a preferred embodiment and the
accompanying drawings in which:
Figure 1 shows a plan view of a resistance thermometer according to the
invention, wherein a covering shrink tube and the silicone casting material are shown as
being removed from the surface,
Figure 2 shows a portion from Figure 1 on an enlarged scale,
Figure 3 shows a cross-section along line A-A in Figure 2 but without the
housing 15, and
Figure 4 shows a cross-section through a carrier material according to the
invention with partially removed insulation of two conductor tracks.
As can be seen from Figure 4 the carrier 3 of the resistance thermometer which
is generally identified by reference 10 comprises a plastic strip which is rectangular in
cross-section, with three flat conductors which are also rectangular in cross-section and
which are denoted by references 2a, 2b and 2c. The height of the carrier material is for
example 0.5 to 0.8 mm and the width is between 6 and 8 mm. The cross-section of the
individual conductor tracks 2a, 2b and 2c is for example 0.2 mm x 1.5 mm, that is to
say about 0.3 mm2. The spacing of adjacent conductor tracks is for example about 0.2

to 0.5 mm and the thickness of the insulating layer on the upper and lower long sides of
the cross-section is preferably 0.1 to 0.3 mm but can also be thicker when extreme
demands are made in terms of high-voltage dielectric strength. The outer lateral
insulations along the longitudinal edges of the carrier 3 should also be at least 0.1 to 0.5
mm or more. The insulating limbs 6 between the conductor tracks are preferably of a
width of at least 0.2, preferably at least 0.5 mm. In the illustrated version the insulating
limbs 6 are almost 0.5 mm wide. The plastic material is insulating and flexible and
very easily bendable about an axis parallel to the longitudinal side of the cross-section.
In Figure 4 the plastic material 6 is removed on the top side from two of the conductor
tracks 2b, 2c in order there to be able to contact a resistance element 1 or the
connection contacts 8 thereof, as shown in Figure 3. It is also possible to see solder
beads 12 with which the connection contacts 8 are electrically connected to the
conductor tracks 2b, 2c. It is also possible to see a heat-conducting paste 13, by means
of which the actual resistance element 1 which has a PT thin-layer resistance is fixed on
the surface of the carrier 3 and in good surface contact in relation to the surface of the
carrier 3. The resistance element 1 is only separated from the subjacent conductor
tracks 2b, 2c by a relatively thin layer of the insulating material so that the conductor
tracks 2b, 2c can transport heat out of regions which are adjacent to the resistance
element 1 to the resistance element 1 or can conduct excess heat therefrom. Optionally
the resistance thermometer can be brought into contact with the object whose
temperature is to be measured, either with the rear side which is opposite the resistance
element or however with the side on which the resistance element 1 is disposed.
Optionally the resistance thermometer can also be fitted into a groove in the object in
question and can be clamped or cast therein so that heat transfer to the resistance
element 1 can take place from both sides.
Figure 1 shows the resistance thermometer which is generally identified by
reference 10 and which in principle can be produced in any length as the carrier 3 is an
endless material which is cut to length in accordance with the specific requirement for a
thermometer. In the present example in Figure 1 which shows a resistance
thermometer almost in its natural size or on a slightly increased scale the carrier 3 has
three parallel conductor tracks 2a, 2b and 2c of constant cross-section, which extend
over the entire length of the carrier 3 and with which a total of four resistance elements

1 are contacted. Shown at the right-hand end are two electrical supply lines 5 which
are in contact with the two outer conductor tracks 2a and 2c. The resistances 1a, 1b and
1c and 1d are connected in parallel in pairs between the lines 2b, 2c and 2a, 2b
respectively and, by virtue of the connection to the central conductor track 2b which is
not in direct contact with the outer supply lines 5, effectively have a series connection
of the two pairs shown at the right and the left respectively. The resistances however
can equally well be arranged in such a way that a resistor is connected alternately to the
conductor tracks 2b, 2c and 2a and 2b respectively, which in this embodiment would
not in any way alter the effective parallel and series connection. It would also be
possible for all resistances to be connected in parallel, in which case only two
conductor tracks would be required, and the outer connecting lines 5 could either
contact the conductor tracks 2a and 2b or 2b and 2c, instead of the conductor tracks 2a
and 2c as shown here.
As already mentioned the resistances can also be connected in series, in which
case then, if the number of the resistances is equal to or greater than the number of
available conductor tracks, the series connection can be implemented inter alia by at
least a portion of the resistances being contact with both respective connections on the
same conductor track, with the conductor track being interrupted between the
connections of the resistance in question. In order to implement a series connection
with the carrier material according to the invention however it is alternatively also
possible for the two connections of each of the resistances to be respectively connected
to another conductor track if a respective one of the conductor tracks is alternately
interrupted between successive resistances. It is then advantageously possible to use a
third conductor track as the return conductor in order to have all connections of the
thermometer jointly at one end of the carrier.
The length of the electrical connection wires 8 which make up a part of the
measurement resistance is suitably adapted to possibly compensate for the supply line
resistance of the supply lines and the conductor tracks 2a, 2b and 2c respectively. In
other words the connection wires 8 of the resistance elements (for example la) which
are further away from the outer connection cables 5 or the outer connection contacts 4
respectively can be shortened more greatly than the resistance elements (for example
1d) which are closer to the cables 5. The outer supply lines or connection cables 5 can

in particular also have double the number (that is to say 4) of electrical conductors in
order to go over to 4-point measurement of the resistance as closely as possible to the
conductor tracks 2a, 2b, 2c. In the illustrated combined series and parallel connection
of the four resistances and on the assumption that all four resistances are of the same
nominal value, the totality of the four resistance elements 1 connected in that fashion
also have the same nominal value as each individual resistance. As already mentioned,
by means of a skilful combination of the individual resistances which can each in itself
have certain tolerance deviations, it then becomes possible in comparison to reduce the
tolerance deviation of the combined resistance. The maximum number of resistance
elements 1 on a carrier 3 is not limited and depends only on the space available on a
given carrier portion, in which respect however there is generally no need for the
resistance elements to be arranged at a very close spacing as in any case a certain
temperature detection is achieved over a relatively large region which amounts to a
multiple of the thermal contact surface of the individual resistance element 1, by way of
the conductor tracks but also by way of any adjacent machine components or the like.
As can also be seen from Figure 3 the resistance elements 1 are substantially fiat
parallelepipedic elements, the width of which at any event is less than the width of the
carrier 3 and the thickness of which is preferably less than 1 mm, for example 0.9 mm.
For good thermal contact, the external contact surfaces of the thin-layer resistances
should preferably be at least 2 mm2, preferably at least 3 to 4 mm2.
The carrier 3 with the applied and contacted resistance elements 1a, 1b, 1c, 1d
can possibly either be restricted to the individual resistance elements or it can be
encased by casting over its entire length with a heat-contacting paste 13, a silicone
adhesive or another protective and binding material so that the finished resistance
thermometer is then overall of a thickness which is scarcely more than the total of the
thickness of the carrier 3 and one of the resistance elements 1. Finally the entire carrier
with the resistance elements cast therein can also be encased in a shrink tube 14 or in a
preferably thin-walled, insulating housing, wherein Figure 1 also shows the shrink tube
version at the upper and lower edges of the carrier 3 and at the left-hand and right-hand
ends of the thermometer 10. It is also possible to provide a housing in the form of a
non-insulating housing, for example comprising a soft or thin-walled metal material
which is pressed to the carrier and the resistances and which ensures good temperature

distribution and thermal contact in relation to the resistance elements, which however
presupposes that the conductor tracks and the resistance elements are well insulated in
relation to the housing. That could be ensured for example by the combination of an
inner insulating shrink tube and an outer metal housing surrounding the shrink tube.
Figure 2 shows an enlargement of the right-hand end of the resistance
thermometer 10 but with a modification insofar as the shrink tube 14 of Figure 1 is
replaced by a housing 15 which however can also be provided in addition to a shrink
tube 14. The housing 15 is also a flat housing of rectangular cross-section, with an
opening which fairly precisely corresponds to the width and height of the carrier
material, possibly additionally with the resistance elements 1 cast therein. The end 9,
which can be seen at the right, of the carrier 3 is supported against the right-hand end of
the corresponding opening in the housing 15 and the supply lines 5 are passed through
two gaps or bores in the right-hand end of the housing 15 and contacted with the tracks
2a and 2c. Because the end 9 of the carrier 3 is supported in the housing that
effectively forms a mean for relieving traction loadings on the connection wires or
cables 5 which can also be fixed in the housing, although that is not shown here. The
housing can also be only in the form of a short end portion which receives only a short
end part of the thermometer 10, which only includes for example the connection
contacts for the supply lines 5. That avoids the housing 15 adversely affecting the
thermal contact of the most closely adjacent resistance element 1 with the surroundings.
Each of the cables 5 can have two connection wires which are insulated relative to each
other and which for the purposes of 4-point measurement are jointly connected to the
contact locations 4.
Alternatively the housing 15 can also comprise a metal, preferably a soft metal
and in particular a metal foil or a metal braid or mesh and can be pressed to the
resistance thermometer for good thermal contact, in which case then however the
thermometer 10 must be insulated in relation to the housing 15, for example by a shrink
tube 14 within the housing 15.
The resistance thermometers according to the invention are relatively simple
and inexpensive to produce, they are extremely flexible in the preferred variant and
they are therefore suitable for very many different purposes of use.

CLAIMS
1. A resistance thermometer comprising at least one temperature-dependent
electrical resistance element (1) which has at least two connection contacts (8), a
carrier (3) on which the resistance element can be fixed in such a way that it can be
brought into good thermal contact with an object whose temperature is to be
measured, and electrical supply lines (2, 5) provided for connecting the electrical
connection contacts (8) to a measuring instrument, characterised in that provided as
the carrier (3) is a heat-resistant plastic material which is easily bendable in at least
one direction and in which at least two electrical conductor tracks are embedded.
2. A resistance thermometer according to claim 1 characterised in that the
carrier is in strip form of a cross-section whose width is at least double the height.
3. A resistance thermometer according to claim 2 characterised in that the
cross-sectional material in strip form is of a width which is at least four times and
preferably at least six times and particularly preferably more than eight times the
height or thickness of the material in strip form.
4. A resistance thermometer according to one of claims 1 to 3 characterised in
that its width is at least 3 and preferably at least 5 mm.
5. A resistance thermometer according to one of claims 1 to 4 characterised in
that the width of the material in strip form is at a maximum 25 mm, preferably at a
maximum 20 or 15 mm and particularly preferably at a maximum 12 mm.
6. A resistance thermometer according to one of claims 1 to 5 characterised in
that the electrical conductor tracks in turn are of a strip-shaped configuration and are
each of a cross-section whose width is more double and preferably more than four
times the cross-sectional height.
7. A resistance thermometer according to one of claims 1 to 6 characterised in
that the cross-section of the carrier and preferably also the cross-section of the
electrical conductors is substantially right-angled, wherein the long sides of the cross-
section of the carrier and the electrical conductors extend parallel.

8. A resistance thermometer according to one of claims 1 to 7 characterised in
that the at least one resistance element is placed on one side of the carrier and its
connection contacts are respectively connected to another of the at least two electrical
conductors, wherein for a series connection the conductor tracks are alternately
interrupted between successive resistances and for a parallel connection the conductor
tracks do not have any interruption between successive resistances.
9. A resistance thermometer according to one of claims 1 to 8 characterised in
that the at least one resistance element is placed on one side of the carrier and its
connection contacts are respectively connected to one and the same of the at least two
electrical conductors, wherein the electrical conductor is interrupted between the
connection contacts of the resistance element.

10. A resistance thermometer according to one of claims 1 to 9 characterised
in that the conductor tracks comprise copper of a cross-section of at least 0.1 mm2,
preferably at least 0.2 mm2.
11. A resistance thermometer according to one of claims 1 to 10 characterised
in that three parallel conductor tracks are provided on the material in strip form.
12. A resistance thermometer according to one of claims 1 to 11 characterised
in that the conductor tracks extend in a common plane in the carrier material.
13. A resistance thermometer according to one of claims 1 to 12 characterised
in that at least two resistances are arranged at a spacing relative to each other on the
carrier material and are contacted.
14. A resistance thermometer according to claim 13 characterised in that the
resistances are connected in parallel.
15. A resistance thermometer according to claim 13 characterised in that the
resistances are connected in series.
16. A resistance thermometer according to one of claims 1 to 15 characterised
in that there are provided at least three resistances, wherein the resistances are
connected in part in parallel and in part in series.

17. A resistance thermometer according to one of claims 1 to 16 characterised
in that there are provided at least three conductor tracks (2a, 2b, 2c) with which
resistances (1a, 1b, 1c, 1d) are directly or indirectly contacted.
18. A resistance thermometer according to one of claims 1 to 17 characterised
in that the at least one resistance element is a platinum thin-layer resistance.
19. A resistance thermometer according to one of claims 1 to 18 characterised
in that the resistance element is encased by casting jointly with the carrier with
silicone and/or heat-conducting paste (13).
20. A resistance thermometer according to one of claims 1 to 19 characterised
in that the carrier and the resistance element are encased by a shrink tube or housing.
21. A resistance thermometer according to one of claims 1 to 20 characterised
in that the electrical resistance caused by the length of the conductor tracks (2a, 2b,
2c) to the connection wires of the resistances is compensated by the corresponding
reduction in the length of the connection wires of the resistance.
22. A resistance thermometer according to one of claims 1 to 21 characterised
in that the carrier material including the conductor tracks integrated into the carrier
material is produced with a constant cross-section in the form of endless material,
preferably by extrusion.
23. A resistance thermometer according to claim 22 characterised in that the
carrier material is cut to the length required for the specific thermometer.

The present invention relates to a resistance
thermometer comprising at least one temperature-
dependent electrical resistance element (1) which has
at least two connection contacts (8), comprising a
carrier (3) to which the resistance element can be
fixed in such a manner that it can be brought into
good thermal contact with an object whose temperature
is to be measured, and comprising electrical leads (2,
5) which are provided for the purpose of connecting the
electrical connection contacts (8) to a measuring
instrument. In order to provide a resistance
thermometer which is simple and inexpensive to produce,
enables good thermal contact-connection, can be
designed to measure more extensive areas and can be
used, at least for simple applications, in an identical
or similar manner to the more expensive thermometers
which are provided with a platinum wire as the
resistance element, the invention proposes that a heat-
resistant plastic material which can be bent slightly
in at least one direction and in which at least two
electrical conductor tracks are embedded is provided as
the carrier (3).

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=br6NKNapajMkYWk/JjtpUQ==&loc=wDBSZCsAt7zoiVrqcFJsRw==

« Previous Patent

Next Patent »

Patent Number

272926

Indian Patent Application Number

3034/KOLNP/2008

PG Journal Number

19/2016

Publication Date

06-May-2016

Grant Date

03-May-2016

Date of Filing

25-Jul-2008

Name of Patentee

EPHY-MESS GESELLSCHAFT FUR ELEKTRO-PHYSIKALISCHE MESSGERATE MBH

Applicant Address

BERTA-CRAMER-RING 1 65205 WIESBADEN-DELKENHEIM

Inventors:

#	Inventor's Name	Inventor's Address
1	ANDREAS H. G. BECKER	BRUNNENSTRASSE 3A, 65191 WIESBADEN
2	GERHARD HERDT	C.-SCHNEIDER-STR.9, 35510 BUTZBACH
3	VOLKER SCHARFENBERG	STOLBERGER STR. 77, 65205 WIESBADEN

PCT International Classification Number

G01K 1/08,G01K 7/18

PCT International Application Number

PCT/EP2007/051051

PCT International Filing date

2007-02-02

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	20 2006 001 883.2	2006-02-03	Germany