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Title:
TEMPERATURE MEASURING DEVICE WITH MULTIPOINT THERMOCOUPLES
Document Type and Number:
WIPO Patent Application WO/2019/042529
Kind Code:
A1
Abstract:
A temperature measuring device (SC1-SC3) comprises a sheath (S) having an insulating material (IM) and a plurality of conductors (a1-d2) forming a plurality of conductor pairs (a-d) within the sheath (S), each of the conductor pairs (a-d) being formed of a first conductor (a1 -d1 ) and a second conductor (a2-d2) of different materials. The first conductor (a1-d1) and second conductor (a2-d2) of a respective conductor pair (a-d) are connected to one another at a respective unique longitudinal location along the sheath (S) so as to form a respective thermocouple (t1-t4) at the respective unique longitudinal location, the respective thermocouple (t1-t4) forming a respective temperature measurement point (m1 -m4). For each respective one of the conductor pairs (a-c), except for one of the conductor pairs (d), the second conductor (a2-c2) forms part of the first conductor (b1-d1) of an adjacent one of the conductor pairs (b-d) such that each of the conductors (a1-d2) of the plurality of conductors forms part of no more than two thermocouples (t1-t4).

Inventors:
REICHERT, Rudolf (Haselweg 5, Pleinfeld, 91785, DE)
Application Number:
EP2017/071616
Publication Date:
March 07, 2019
Filing Date:
August 29, 2017
Export Citation:
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Assignee:
W.L. GORE & ASSOCIATES GMBH (Hermann-Oberth-Straße 22, Putzbrunn, 85640, DE)
International Classes:
G01K1/02; G01K1/08; G01K7/02
Foreign References:
DE202014103008U12014-10-28
US4242907A1981-01-06
US6550963B22003-04-22
JP2003057120A2003-02-26
Attorney, Agent or Firm:
SCHMITT-NILSON SCHRAUD WAIBEL WOHLFROM PATENTANWÄLTE (Destouchesstraße 68, Munich, 80796, DE)
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Claims:
Claims

5 1 . A temperature measuring device (SC1 -SC3) comprising

- a sheath (S) having an insulating material (IM),

- a plurality of conductors (a1 -d2) forming a plurality of conductor pairs (a-d) within the sheath (S), each of the conductor pairs (a-d) being formed of a first conductor (a1 -d1 ) and a second conductor (a2-d2) which is of a different material than the o first conductor (a1 -d1 ),

- wherein the first conductor (a1 -d1 ) and second conductor (a2-d2) of a respective conductor pair (a-d) are connected to one another at a respective unique longitudinal location along the sheath (S) so as to form a respective thermocouple (†1 -t4) at the respective unique longitudinal location, the respective thermocouple (t1 -t4)

5 forming a respective temperature measurement point (m1 -m4),

- wherein for each respective one of the conductor pairs (a-c), except for one of the conductor pairs (d), the second conductor (a2-c2) forms part of the first conductor (b1 -d1 ) of an adjacent one of the conductor pairs (b-d) such that each of the conductors (a1 -d2) of the plurality of conductors forms part of no more than two thermocouples (t1 -t4).

2. The temperature measuring device according to claim 1 , comprising

- a first conductor pair (a) and a second conductor pair (b),

- the first conductor (a1 ) and second conductor (a2) of the first conductor pair (a) are connected to one another at a first unique longitudinal location along the sheath (S) so as to form a first thermocouple (t1 ) at the first unique longitudinal location,

- the first conductor (b1 ) and second conductor (b2) of the second conductor pair (b) are connected to one another at a second unique longitudinal location along the sheath (S) so as to form a second thermocouple (t2) at the second unique longitudinal location different from the first unique longitudinal location,

- wherein the second conductor (a2) of the first conductor pair (a) forms part of the first conductor (b1 ) of the second conductor pair (b), wherein the first conductor (b1 ) of the second conductor pair (b) is larger in length than the first conductor (a1 ) of the first conductor pair (a).

3. The temperature measuring device according to claim 2, further comprising - a third conductor pair (c), wherein the first conductor (c1 ) and second conductor (c2) of the third conductor pair (c) are connected to one another at a third unique longitudinal location along the sheath (S) so as to form a third thermocouple (t3) at the third unique longitudinal location different from the second unique longitudinal

5 location,

- wherein the second conductor (b2) of the second conductor pair (b) forms part of the first conductor (c1 ) of the third conductor pair (c), wherein the first conductor (c1 ) of the third conductor pair (c) is larger in length than the first conductor (b1 ) of the second conductor pair (b).

o

4. The temperature measuring device according to claim 3, wherein the first conductor (a1 ) of the first conductor pair (a) and the first conductor (c1 ) of the third conductor pair (c) are of the same material, and the second conductor (a2) of the first conductor pair (a) and the second conductor (c2) of the third conductor pair

5 (c) are of the same material.

5. The temperature measuring device according to one of claims 1 to 4, wherein the sheath (S) forms a tapering section (ts) from a first diameter to a second, smaller diameter between one of the thermocouples (t1 ) and another one of the thermocouples (t4) along the sheath (S).

6. The temperature measuring device according to one of claims 1 to 5, wherein the sheath (S) comprises a filler material (f1 -f3) in continuation of the first conductor (a1 -c1 ) of one of the conductor pairs (a-c) between one of the thermocouples (t1 ) and another one of the thermocouples (t4) along the sheath (S).

7. The temperature measuring device according to one of claims 1 to 6, wherein the first conductor (c1 ) of one of the conductor pairs (c) comprises a greater diameter than the first conductor (a1 ) of another one of the conductor pairs (a).

8. The temperature measuring device according to claim 7, wherein

the first conductor (c1 ) of the one of the conductor pairs (c), which comprises the greater diameter, is larger in length than the first conductor (a1 ) of the another one of the conductor pairs (a).

9. The temperature measuring device according to one of claims 1 to 8, wherein at least some of the conductors (a1 -d2) are insulated with a material comprising at least one of fluoropolymer, fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA) and polytetrafluoroethylene (PTFE).

10. The temperature measuring device according to one of claims 1 to 9, wherein the sheath comprises at least one layer which comprises polytetrafluoroethylene (PTFE).

1 1 . The temperature measuring device according to one of claims 1 to 10, wherein the temperature measuring device (SC1 -SC3) is capable for operation at temperatures up to 300°C, particularly between -250°C and 260°C.

12. The temperature measuring device according to one of claims 1 to 1 1 , wherein the plurality of conductors (a1 -d2) form a number of up to approximately 200 thermocouples (t1 -t4), particularly between approximately 80 and 120 thermocouples (t1 -t4).

13. The temperature measuring device according to one of claims 1 to 12, further comprising terminals (T) for coupling to a voltage measuring device (MD) for measuring voltages (Ua, Ub) of opposite polarity at two successive conductor pairs (a, b).

14. A temperature measurement arrangement, comprising a temperature measuring device (SC1 -SC3) according to one of the preceding claims and a voltage measuring device (MD), wherein at least some of the conductors (a1 -d2) of the temperature measuring device (SC1 -SC3) are coupled to the voltage measuring device (MD) for measuring voltages (Ua, Ub) of opposite polarity at two successive conductor pairs (a, b).

Description:
Temperature measuring device with multipoint thermocouples

The present invention relates to a temperature measuring device which comprises a plurality of conductor pairs within a sheath, wherein each of the conductor pairs is formed of a first conductor and a second conductor which are of a different material, and the first conductor and second conductor of a respective conductor pair are connected to one another at a respective unique longitudinal location along the sheath so as to form a respective thermocouple which forms a respective temperature measurement point. The invention further relates to a temperature measurement arrangement using such temperature measuring device.

Generally, a thermocouple or thermocouple assembly is an electrical device comprising two dissimilar conductors which are connected to one another at a particular location. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature at or near the particular location. Thermocouples are widely used in temperature measurement devices, particularly in environments, such as wells, which demand for temperature measurement along distributed distinct locations.

For example, US 6 550 963 B2 describes a multipoint thermocouple for sensing temperature. The multipoint thermocouple comprises a sheath having a plurality of conductor pairs disposed within the sheath. Each conductor pair has two conductors of dissimilar materials joined at a unique junction point along the sheath. The unique junction points permit sensing of temperature at different locations along the length of the multipoint thermocouple. Thus, a multipoint thermocouple with a single sheath can be utilized to sense temperature at a plurality of distinct locations. The conductor pairs are electrically separated by an electrical insulation material disposed about the conductor pairs within the sheath. With increasing number of thermocouples to be formed, however, the number of conductors within the sheath increases so that the multipoint thermocouple becomes quite costly, heavy, and bulky. For example, for forming a multipoint thermocouple with 100 thermocouples, 200 conductors would have to be disposed within the sheath of such multipoint thermocouple. JP 2003-057120 A discloses a multipoint temperature measurement device in which for one of two metal wires constituting each of thermocouples 2A, 2B, 2C, 2D... , a common metal wire is used for each thermocouple. The number of necessary metal wires or conductors is reduced to approximately half of a multipoint 5 thermocouple as described above. The whole structure of the measurement system is simplified, and the cost is reduced. The number of metal wires of thermocouples does not increase as much even in a case in which a higher number of thermocouples is needed. On the other hand, however, if the common metal wire undergoes disruption or an error, such as wire break, the whole multipoint tem- i o perature measurement device may be affected by malfunction as each of the thermocouples is affected by a failure of the common metal wire, which significantly reduces reliability.

It would thus be beneficial to provide a temperature measuring device with multi- 15 point thermocouples which can be manufactured at lower cost and that provides a comparably high reliability.

The invention relates to a temperature measuring device and a temperature measurement arrangement according to the appended claims.

0

According to an aspect, there is provided a temperature measuring device comprising a sheath having an insulating material, a plurality of conductors forming a plurality of conductor pairs within the sheath, each of the conductor pairs being formed of a first conductor and a second conductor which is of a different material5 than the first conductor. The first conductor and second conductor of a respective conductor pair are connected to one another at a respective unique longitudinal location along the sheath so as to form a respective thermocouple at the respective unique longitudinal location, the respective thermocouple forming a respective temperature measurement point. For each respective one of the conductor pairs,0 except for one of the conductor pairs, the second conductor forms part of the first conductor of an adjacent one of the conductor pairs such that each of the conductors of the plurality of conductors forms part of no more than two thermocouples.

Advantageously, with such temperature measuring device, which may be imple-5 mented in the form of a temperature sensor cable, there can be provided a temperature measuring device with multipoint thermocouples which can be manufactured at lower cost, as a result of a reduced number of required conductors, and provides a comparably high reliability, since there is no common conductor used by all thermocouples which may affect in a case of an impact, such as wire break, the function of the whole multipoint temperature measurement device. Rather, according to the inventive multipoint temperature measurement device, in case of an impact, such as a wire break, two thermocouples may be affected at maximum, since each of the conductors forms part of no more than two thermocouples. At the same time, the number of conductors can be kept at a minimum. Particularly, a number of thermocouples TC may be formed which equals the number of conductors C minus 1 , i.e. the number of conductors C is: C = TC + 1.

More specifically, the temperature measuring device comprises a first conductor pair and a second conductor pair, the first conductor and second conductor of the first conductor pair are connected to one another at a first unique longitudinal location along the sheath so as to form a first thermocouple at the first unique longitudinal location, and the first conductor and second conductor of the second conductor pair are connected to one another at a second unique longitudinal location along the sheath so as to form a second thermocouple at the second unique longitudinal location different from the first unique longitudinal location. The second conductor of the first conductor pair forms part of the first conductor of the second conductor pair, wherein the first conductor of the second conductor pair is larger in length than the first conductor of the first conductor pair. In this way, the number of conductors can be kept at a minimum and the number of required conductors within the sheath decreases towards the thermocouples which are at greater distances.

According to an embodiment, the temperature measuring device further comprises a third conductor pair, wherein the first conductor and second conductor of the third conductor pair are connected to one another at a third unique longitudinal location along the sheath so as to form a third thermocouple at the third unique longitudinal location different from the second unique longitudinal location. The second conductor of the second conductor pair forms part of the first conductor of the third conductor pair, wherein the first conductor of the third conductor pair is larger in length than the first conductor of the second conductor pair.

According to an embodiment, the first conductor of the first conductor pair and the first conductor of the third conductor pair are of the same material, and the second conductor of the first conductor pair and the second conductor of the third conduc- tor pair are of the same material, e.g. metal material. Thus, the temperature measurement device comprises conductors of pairwise alternating and distinct materials. However, there may also be embodiments in which the materials of the conductors within the sheath are chosen from more than two types of materials.

According to an embodiment, the sheath may have a tapering section from a first diameter to a second, smaller diameter between one of the thermocouples and another one of the thermocouples along the sheath. This takes account of the fact that the number of required conductors within the sheath decreases towards the thermocouples which are at greater distances, which advantageously may be used to decrease the size of the sheath at greater distances, so that the temperature sensor cable is less bulky at greater distances and can be moved more easily, e.g. , along curved paths in a well.

According to an embodiment, the sheath comprises a filler material in continuation of the first conductor of one of the conductor pairs between one of the thermocouples and another one of the thermocouples along the sheath. Such configuration may be preferred if the sheath diameter shall not change towards greater distances, but shall be kept substantially uniform, and any hollow spaces within the sheath shall be avoided.

According to an embodiment, the first conductor of one of the conductor pairs comprises a greater diameter than the first conductor of another one of the conductor pairs. Advantageously, the first conductor which comprises the greater diameter is larger in length than the first conductor of the other conductor pair. This provides the advantage that a measurement resistance of the temperature sensor cable can be adapted for each or some of the conductors to a particular measurement distance.

According to an embodiment, at least some of the conductors, either individually and/or as a conductor compound, are insulated with a material comprising at least one of fluoropolymer, fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA) and polytetrafluoroethylene (PTFE). Particularly, insulation material comprising PTFE enables that the temperature measuring device may be employed at high temperature sites. The whole temperature measuring device may be protected against high temperatures in that the sheath is provided with at least one layer comprising polytetra- fluoroethylene (PTFE), i.e. the whole conductor composite is sheathed with PTFE. However, other materials, such as FEP, PFA, and derivates thereof, or PL) and PE are also possible, depending on the respective application conditions.

Advantageously, the temperature measuring device is capable for operation at temperatures of up to 300°C, particularly between -250°C and 260°C.

According to an embodiment, the plurality of conductors form a number of up to approximately 200 thermocouples, preferably between approximately 80 and 120 thermocouples.

According to another aspect, the invention relates to a temperature measurement arrangement comprising a temperature measuring device according to the aspects and embodiments as described herein, and a voltage measuring device. At least some of the conductors of the temperature measuring device are coupled to the voltage measuring device for measuring voltages of opposite polarity at two successive conductor pairs. To this end, the temperature measuring device further comprises terminals for coupling to such voltage measuring device for measuring the voltages of opposite polarity at two successive conductor pairs.

Further aspects and embodiments of the invention will now be described with respect to the accompanying drawings, in which

Fig. 1 shows a schematically illustrated temperature measuring device according to an embodiment of the invention,

Fig. 2 shows a schematically illustrated temperature measuring device according to a further embodiment of the invention,

Fig. 3 shows a schematically illustrated temperature measuring device according to a further embodiment of the invention.

Referring to the illustration as shown in Fig. 1 , an exemplary temperature measuring device SC1 is illustrated according to one embodiment of the present invention. For example, the temperature measuring device SC1 takes the form of a mul- tipoint temperature sensor cable. The temperature measuring device SC1 comprises a sheath S in which a plurality of conductors a1 -d2 forming a plurality of conductor pairs a-d extend. Each conductor pair a-d is formed by a pair of conductors of dissimilar materials, typically metals, that are joined at a respective junction point to form a respective thermocouple t1 -t4. For example, the conductors of a respective conductor pair may be welded together to form the junction. Other techniques may also be applied, such as ultrasound welding, soft-soldering, hard- soldering, wire wrap, crimping, clamping, cold welding, and/or glueing, e.g with an electrically conductive adhesive. Within the sheath S, an insulation material IM, such as an electrical insulation material, is disposed between and/or about the individual conductors a1 -d2 of conductor pairs a-d. Various electrical insulation materials may be used.

For measuring temperatures at the locations of the respective thermocouples t1 - t4, the terminals T of the conductor pairs a-d may be coupled with terminals VT of a voltage measuring device MD, e.g. a voltmeter, that measures the difference in potential created at the respective junction of the two metals of a conductor pair. This difference in potential corresponds to a given temperature. In the present case, voltages Ua at conductor pair a, Ub at conductor pair b, Uc at conductor pair c, and Ud at conductor pair c are measured with the voltage measuring device MD. The voltages Ua and Ub (which are voltages at two successive conductor pairs a and b) are of opposite polarity, and voltages Uc and Ud (which are voltages at two successive conductor pairs c and d) are of opposite polarity with respect to one another.

In principle, the temperature measuring device SC1 (i.e. multipoint temperature sensor cable) may comprise any number of conductors and conductor pairs appropriate for the respective application depending on space constraints and the desired application. In the present embodiment, four conductor pairs a-d are shown for explanation reasons, which are only exemplary in number without any limiting effect on structure and/or function of the invention.

More specifically, as shown in Fig. 1 , each of the conductor pairs a-d is formed of a first conductor a1 -d1 and a second conductor a2-d2 which is of a different material than the first conductor a1 -d1. For example, the conductor pair a is formed of a first conductor a1 and a second conductor a2 which is of a different material than the first conductor a1 . Likewise, the conductor pair b is formed of a first conductor b1 and a second conductor b2 which is of a different material than the first conductor b1 . Analogously, conductor pairs c and d are formed.

The respective first conductor a1 -d1 and second conductor a2-d2 of a respective conductor pair a-d are connected to one another at a respective unique longitudinal location along the sheath S so as to form a respective thermocouple t1 -t4 at the respective unique longitudinal location. The thermocouples t1 -t4 each form a respective temperature measurement point m1 -m4 for measuring a temperature at a particular unique location along the sheath. For example, the first conductor a1 and second conductor a2 of the conductor pair a are connected to one another at a first unique longitudinal location along the sheath S to form the thermocouple t1 at this unique longitudinal location. Thus, a first temperature measurement point ml is formed at this location. Likewise, the first conductor b1 and second conductor b2 of the conductor pair b are connected to one another at a second unique longitudinal location along the sheath S to form the thermocouple t2 at this unique longitudinal location which corresponds to a second temperature measurement point m2.

Generally, for each of the conductor pairs (in the present example: conductor pairs a-c), except for one of the conductor pairs (in the present example: the conductor pair d), the second conductor a2-c2 forms part of the first conductor b1 -d1 of an adjacent conductor pair (in the present example: conductor pairs b-d).

For example, as illustrated for conductor pairs a and b, first conductor a1 and second conductor a2 of conductor pair a are connected to one another at a first unique longitudinal location along the sheath S forming first thermocouple t1 , and the first conductor b1 and second conductor b2 of the conductor pair b are connected to one another at a second unique longitudinal location along the sheath S forming second thermocouple t2 at the second unique longitudinal location which is different from the first unique longitudinal location. Unique location shall mean that the conductor pairs are each having its own unique junction point so that the thermocouples are respectively distributed at distinct (unique) locations along the sheath, thus forming a multipoint thermocouple measurement device having distinct temperature measurement points.

In the present example, the second conductor a2 of the conductor pair a forms part of the first conductor b1 of the conductor pair b. The first conductor b1 of the conductor pair b is larger in length than the first conductor a1 of the conductor pair a, since it forms a different thermocouple t2 at a different, more distant location. Likewise, the second conductor b2 of the conductor pair b forms part of the first conductor c1 of the conductor pair c. Again, the first conductor c1 of the conductor pair c is larger in length than the first conductor b1 of the conductor pair b, since it forms a different thermocouple t3 at a different, more distant location.

As described above, for e.g. the conductor pair a, the second conductor a2 forms part of the first conductor b1 of adjacent conductor pair b. That is, one common wire can be used to form the second conductor of conductor pair a and the first conductor of adjacent conductor pair b. The first thermocouple t1 is formed along the length of the first conductor b1 of the second conductor pair b. Likewise, for the conductor pair b, the second conductor b2 forms part of the first conductor c1 of adjacent conductor pair c, and for the conductor pair c, the second conductor c2 forms part of the first conductor d1 of adjacent conductor pair d. An exception is the conductor pair d, in which the second conductor d2 is not shared with an adjacent conductor pair, as it is the outermost conductor pair.

Accordingly, each of the conductors a1 -d2 within the sheath S forms part of no more than two thermocouples. The plurality of conductors a1 -d2 forms a number of thermocouples t1 -t4 which equals the number of conductors minus 1. In the present embodiment, five conductors form four thermocouples. Thus, for example, with 61 conductors, 60 thermocouples can be formed

According to the embodiment as shown in Fig. 1 , the first conductor a1 of the conductor pair a and the first conductor c1 of the conductor pair c are of the same material, and the second conductor a2 of the conductor pair a and the second conductor c2 of the conductor pair c are of the same materia!. Thus, the temperature measurement device SC1 comprises conductors of alternating and distinct materials. However, there may also be embodiments in which the materials of the conductors change over a broader variety of materials to form various kinds of thermocouples. Typical thermocouple materials often used are Nickel-alloy thermocouples, Platinum/rhodium-alloy thermocouples, or Tungsten/rhenium-alloy thermocouples.

Thus, in summary and as illustrated in Fig. 1 , temperature may be determined at a plurality of temperature measurement points m1 -m4 along the length of sheath S by forming junction points at selected locations along the sheath. The embodiment of Fig. 1 illustrates four conductor pairs a-d each having its own unique junction point (thermocouple) t1 -t4, respectively. The junction points are formed at unique longitudinal locations along sheath 22 to permit the sensing of temperature at those unique locations.

Advantageously, in case of an impact, such as wire break of one of the conductors a1 -d2, at maximum two thermocouples may be affected, since each of the conductors forms part of no more than two thermocouples. For example, if the conductor b1 is affected by a wire break, only the thermocouples t1 and t2 are affected by malfunction, whereas the thermocouples t3 and t4 are still operable. This advantage scales up with the number of thermocouples: For example, in a temperature sensor cable with 120 thermocouples, in case of a wire break of one of the conductors, 1 18 thermocouples are still operable so that reliability of the whole temperature measurement arrangement is affected only at two temperature measurement points out of 120 measurement points, thus at a very low scale. At the same time, the number of conductors can be kept at a minimum, e.g. at a number of 121 conductors.

Fig. 2 shows a schematically illustrated temperature measuring device according to a further embodiment of the invention. The embodiment according to Fig. 2 corresponds widely to the embodiment according to Fig. 1 . Insofar, the same reference numerals are used. Different from the embodiment according to Fig. 1 , the embodiment of Fig. 2 shows a temperature measuring device SC2 in which the sheath S comprises a respective filler material f1 -f3 in continuation of the first conductors a1 -c1 of each one of the conductor pairs a-c between one of the thermocouples t1 and another one of the thermocouples t4 along the sheath S. For example, filler material f1 is provided in continuation of the first conductor a1 of the conductor pair a between the thermocouple t1 and the thermocouple t4. Likewise, filler material f2 is provided in continuation of the first conductor b1 of the conductor pair b between the thermocouple t2 and the thermocouple t4. In this way, the sheath S and insulation material IM does not comprise any hollow spaces as a result that the respective conductors have different length, and the sheath can keep an approximately uniform outer diameter.

According to other embodiments, the filler material f1 -f3 can be formed of a respective blind conductor in continuation of and electrically separated from the re- spective sensing conductor. There is no specific constriction for a particular filler material which may be used.

Fig. 3 shows a schematically illustrated temperature measuring device according to a further embodiment of the invention. Again, the embodiment according to Fig. 3 corresponds widely to the embodiment according to Fig. 1. Insofar, the same reference numerals are used. Different from the embodiment according to Fig. 1 and Fig. 2, the embodiment of Fig. 3 shows a temperature measuring device SC3 in which the sheath S forms a tapering section ts from a first diameter (here: between thermocouples t1 and t2) to a second, smaller diameter (here: between thermocouples t3 and t4), the tapering section ts formed between the thermocouple t1 and thermocouple t4 along the sheath S. As such, the cross-section of the sheath reduces, so that weight and dimensions of the temperature sensor cable may be reduced with increasing distance. For example, the sheath S tapers at or after each of the thermocouples t1 -t4 towards a smaller diameter.

According to another embodiment, not explicitly shown in the Figures, the first conductor (such as conductor c1 ) of one of the conductor pairs, e.g. conductor pair c, comprises a greater diameter than the first conductor (such as conductor a1 ) of another one of the conductor pairs, e.g. conductor pair a. Advantageously, a respective conductor, which comprises the greater diameter, is larger in length than the conductor of the other conductor pair. Generally, conductors for shorter measurement distances can be provided with smaller diameters than conductors for larger measurement distances, which can be provided with large diameters taking account of the long distances, but without increasing the overall diameter of the sheath.

In this way, a measurement resistance of the temperature sensor cable can be adapted for each or some of the conductors to a particular measurement distance. Advantageously the technical maximum length of a temperature sensor cable can be further increased without increasing the overall diameter of the sheath, since conductor cross-section can be increased for conductors with large measurement distances, and conductor cross-section can be decreased for conductors with short measurement distances, thus without increasing the overall diameter of the sheath. That is, the outer diameter of the sheath may be kept substantially uniform along the length of the sheath. The conductors a1 -d2, or at least some of the conductors a1 -d2, may be insulated with a material comprising fluoropolymer, fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA) and/or polytetrafluoroethylene (PTFE). Especially the use of PTFE enables that the sensor cable may be used in rather extreme environments up to 300°C while, at the same time, providing accurate, high-resolution temperature data over the length of a well and a precise thermal profile of the well with a high number of measurement points.

In a potential implementation, the temperature sensor cable comprises a number of up to approximately 200 thermocouples (and measurement points, respectively). A typical temperature sensor cable preferably comprises between approximately 80 and 120 thermocouples. The term "approximately" shall mean that a number of thermocouples slightly exceeding or falling below the cited numbers (such as 79, 121 or 201 thermocouples) shall still be encompassed, since no "hard" structural or physical border for any number of conductors exists. In this regard, for example, a range of +/- 5% shall be encompassed.

According to embodiments, the temperature measuring device has a length of up to 500m (such as for observation wells), or a length of up to 2000m (such as for producer or injector wells). In other embodiments, the temperature measuring device has a length of up to 3500m.

According to embodiments, the temperature measuring device is capable for operation at temperatures up to 300°C. A typical temperature measuring device is capable for operation preferably at temperatures between -250°C and 260°C.

Measurement tests showed proper functionality of a temperature sensor cable sample with no cross talk of the temperature reading by small distance of the measurement points (~30cm). A first temperature measurement test included 4 different temperatures which were applied on the junctions with a heat gun. For each temperature the measurement sequence was the same. All measurement points worked and showed the same behavior in terms of response time and measured temperature without negative impact on the accuracy, response time and cross talk behavior as compared to prior art samples.