CA1291228C - Stable metal-sheathed thermocouple cable - Google Patents
Stable metal-sheathed thermocouple cableInfo
- Publication number
- CA1291228C CA1291228C CA000546303A CA546303A CA1291228C CA 1291228 C CA1291228 C CA 1291228C CA 000546303 A CA000546303 A CA 000546303A CA 546303 A CA546303 A CA 546303A CA 1291228 C CA1291228 C CA 1291228C
- Authority
- CA
- Canada
- Prior art keywords
- alloy
- cable according
- nickel
- sheath
- silicon
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/851—Thermoelectric active materials comprising inorganic compositions
- H10N10/854—Thermoelectric active materials comprising inorganic compositions comprising only metals
Abstract
ABSTRACT
A thermocouple cable has a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath. The sheath comprises an oxidation-resistant alloy having a thermal coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300°C; the sheath preferably being formed from a nickel based alloy, such as a nickel-chromium alloy. The positive and negative thermoelements preferably also comprise nickel-based alloys.
A thermocouple cable has a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath. The sheath comprises an oxidation-resistant alloy having a thermal coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300°C; the sheath preferably being formed from a nickel based alloy, such as a nickel-chromium alloy. The positive and negative thermoelements preferably also comprise nickel-based alloys.
Description
~X9~2~3 STABL~ METAL-S~IEATHED THE~MOCOUPLE CABLE
This invention relates to a mineral-insulated, metal-sheathed (MIMS) thermocouple cable, and to thermocouples made from such cable.
The manufacture of ~IMS cable is well known. The components consist of a metallic sheath and two thermoelements (thermocouple conductors) insulated from each other, and the sheath, by a compacted ceramic-oxide-insulation material. The components are assembled under clean, dry conditions and by a process such as drawing, swaging or rolling, the sheath diameter is reduced to compact the ceramic and fill the - available space. The assembly is further reduced in diameter to the desired size, an overall reduction in diameter of 10 to 1 being common. Before diameter reduction the assembly may be evacuated, annealed and or back-filled with an inert gas.
Thermocouples are temperature-measuring sensors.
They are fabricated from MIMS cable by cutting to the required length, welding the thermoelements together at one end of the cable to form the 'hot junction' and welding extension leads to the other. Insulating powder is packed in around the hot junction to avoid an air pocket in the completed product, and the MIMS section of the thermocouple is then sealed by welding in some sheathing alloy over the hot junction and, for example, providing a suitable potting compound at the other.
Conventional base-metal MIMS cables are produced with sheaths of inconel or stainless steel and with thermoelements of one of the five internationally-standardised thermocouple types (types E,J,K, N and T: letter designations of the Instrument Society of ~merica).
O~ the tw~ types suitable ~or high-temperature use - ~29~28 (types N and K3 the t~pe N alloys have well-defined compositions whereas those for the type K alloys are not defined. The main requirement for the positive and negative type K thermoelements is that, as a matched pair, the relationship between their net emf and temperature should agree with the relevant internationally-accepted reference equations (such as BS4937, ASTM E230) within defined limits of error.
The present invention is directed to providing an improved M~MS thermocouple cable, and to thermocouples made ~rom such cable.
A thermocouple cable according to the invention has a positive and a negative thermoelement conforming to the standard emf-temperature specification for t~pe K
thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant alloy having a thermal coefficient substantially the same as that of the negative thermoelement and a melting point in excess o~ 1300C.
The alloy of which the sheath is ~ormed may be a nickel based alloy, although other alloys such as cobalt based alloys can be used. The nickel based alloy preferably is a nickel-chromium alloy, a particularly preferred alloy being one containing 13 to 15 wt.% chromium, 1 to 2 wt.% silicon with the balance most typically principally comprising ; nickel. The nickel-based alloy preferably contains substantially no manganese; while manganese, if present, shQuld be l~ss than 0.1 wt.%.
The nickel-based alloys for the sheath may contain FY _3_ -` ~29~2~3 elements such as magnesium to enhance their oxidation resistance, and refractory metals such as niobium, tungsten, tantalum or molybdenum to enhance physical properties of the sheath, such as its strength. Nicrosil (nominally 14.2 wt.%
chromium, 1.4 wt.% silicon and the balance essentially nickel) is an example of a suitable alloy for the sheath.
The positive and negative thermoelements are to be of alloys conforming to the standard emf-temperature specification of type K thermocouples. The thermoelements preferably are of respective alloys such that they conform to such specification to within -~ 0.75~ of temperature, most preferably to within + 0.375% of temperature. The thermoelements should be of alloys melting above 1300C; the alloys preferably comprising nickel-based alloys. In the case of the positive thermoelement, the alloy preferably comprises 9 to 10 wt.% chromium, with the balance substantially comprising nickel, although it may contain up to 1 wt.%
silicon and small quantities of other conventional alloy additions.
The negative thermoelement preferably contains 1 to 3 wt.% silicon in nickel. However, it typically will also contain other elements, preferably totalling less than 6 wt.%, such as manganese, cobalt, aluminium and copper. Such other elements preferably are added as required to adjust the emf-temperature relationship, of the positive thermoelement relative to the negative, to conform to the standard em~-temperature specification for type K thermocouples.
The insulating ceramic may be of any suitable rQEractory oxide or comhination oF oxides. Examples o~
3Q suitable oxides are those of magnesium, aluminium and FY ~4~
~L~91228 beryllium.
Another aspect of this invention is as follows:
A thermocouple cable having a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant nickel-based alloy containing chromium, silicon and less than 0.1 wt.% manganese, said nickel based alloy having a thermal expansion coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300C; the positive thermoelement comprising a nickel-based alloy containing chromium and the negative thermoelement comprising a nickel-based alloy containing silicon.
~29~L228 Advantages of the Invention Thermocouples fabricated from cable according to the invention, such as by the ~abrication procedure outlined above, are a considerable improvement over bare-wire type K
thermocouples and those produced from conventional base-metal MIMS cables. They have excellent stability, both thermoelectric and mechanical, at hi~h temperatures and the invention is an advance for the following reasons. Having the thermolements within a MIMS system avoids instabilities and premature failure at high temperatures (beyond about 900C), due to oxidation, that occur in 'bare-wire' thermocouples.
The use of the sheath alloy specified for the invention avoids the main cause of thermoelectric instability in conventional MIMS systems, that due to the migration of Mn from the sheath. Also, use of the sheath of the invention avoids mechanical failures that occur in conventional MIMS systems because of the difference in thermal expansion between that of the sheath and that of the negative thermoelement. Further, the sheath specified o~ the inven~ion is more resistant to oxidation and can be used in air at higher temperatures and for longer periods than the conventional sheathing alloys inconel and stainless steel. Finally, the only standardised base-metal thermocouples with a practical life beyond 1000C
are the type K and type N thermocouples. Within a MIMS system having the sheath of the invention, the type K thermoelements of the invention are more thermoelectrically stable than the type N and are less likel~ to fail because of any mixmatch in the thermal expansion coefficient. A1SQ~ type K thermo-couples, includin~ thos~ made ~rom the ca~le of the inven~ion, . . . , ,. .. ,, . , . . ,: . .
.
~L~91~28 are of greater practical Yalue because there are two orders ofmagnitude more instruments, and associated items of equipment, available in the type K calibration than in the type N.
Development of the Invention In the following, experimental background to the invention is detailad. In this, reference is made to the accompanying drawings, in which:
Figure 1 shows a typical MIMS cable, illustrative of that used to produce thermocouples, the cable 10 having a sheath 12 in which two thermoelements 14 are insulated by compacted ceramic 16;
Figure 2 is a plot of reversible change in Seebeck coefficient after 200 hours at temperature; and Figure 3 is a plot of in situ temperature drift during 200 hours at temperature.
Our research into the thermoelectric behaviour of conventional nickel-based MIMS thermocouples showed that the main cause of instability at high temperatures was the migration of Mn from the sheath to the thermoelements. As a first step in developing a new, more stable MIMS system the alloy Nicrosil was considered by us as a sheath. Our subsequent work confirmed the importance of avoiding Mn.
High-nickel alloys such as Nicrosil have the added advantage of having a similar thermal e~pansion coefficient to that of the negative type N and type K thermoelements, both being high-nickel alloys. Relative to these thermoelements, the thermal expansion of stainless steel or inconel on heating to 900C is 0.2 to 0.4~ which is lar~e compared to that of Nicrosil, 0.05~. ~if~rential thermal e~pansion causes mechanical Eailure during thermal cycling in type ~ and type N
F~ -6-9~2~8 MIMS thermocouples having sheaths of inconel or stainless steel.
Nicrosil-sheathed MIMS thermocouples, comprising three (Kl, R2 and K3) type K thermocouples according to the invention and one type N thermocouple, each as described in Table 1, have been studied. What follows is a brief account of this work.
Table 1. Composition of thermoelements studied within Nicrosil-sheathed MIMS thermocouples, in weight percentO
Typ2 Thermox~ple ~ itive thermcelement N~ti~ thermce1a~nt . _ .
N N Ni 14.0Cr 1.SS~ Ni ~.4Si 0.~
K K1 Ni 9.2 Cr O.5Si Ni 1.6Si 1.6Mn 1.~ 0.6Co K K2 Ni-9,7 Cr 0.3Si Ni 2.0~i 0. ~ 0.~ O.~C0 K K3 Ni 9.1 Cr 0.4Sl ~ 2,~5i O.OMn 2,~ 1.0Co -- _, It is the integrated effect of local changes in Seebeck coefficient along the length of a thermocouple that dictates the extent of drift in its signal and thus of the temperature error it produces. For this reason the changes in Seebeck coefficient that occur at temperatures up to 1200C were measured as a function of time for the various thermoelements. Each thermocouple was heated either isothermally or in a 'gradient-annealing' furnace, the temperature within the latter being roughly linear with distance along much o~ its length. The resultant change in Seebeck coefficient, as a function of position along the - thermocouple, wa~ obtained with a horizontal, mQtor-driven 'scannin~ ~urnace' moving at Q.125 m~ s 1, This furnace had a wire wound ~.ubu~ar muÇfle, 1.2 m long, containing a 20 mm ID
FY ~7~
9~L~28 earthed Inconel tube, it had a relatively steep temperature-gradient region at the entrance port and its temperature was uniform at 500C to + 5C along most of its length. At any given time during a scan the emf produced by the temperature step, from ambient to 500C, occurred over a distance of 120 mm. If the thermocouple had just been heated in the gradient-annealing furnace this length of it would correspond to a range of annealing temperatures of typically +
30C about To at its centre. Hence the emf measured at this immersion in the scanning furnace would reflect the average effect of annealing at To + 30C.
The movement of the scanning furnace and the electrical measurements were controlled by a Hewlett Packard (HP) 86B computer interfaced to a HP 3456A DMM, having 0.1 ~V
resolution, and a low-thermal ( 0.1 ~uV) two-pole scanner. The cold junction ends of all thermocouples were connected to a set of temperature-monitored terminals at 20C uniorm to +
0.01C.
During the scan the tip temperature of each thermocouple was obtained with a PtlO~Rh versus Pt reference thermocouple whose tip was wire-wrapped to that of the thermocouple under test with Nichrome wire. The reference thermocouple has 0.5 mm diameter wires in a 1060 mm long twin-bore insulator of recrystallised alumina and its Seebeck coefficient varied by less than ~ 0.02% along its length.
Values of test thermocouple tip temperature ~about 500C) were converted to values o emf, Eo~ for each thermoelement relative to platinum. From measurements taken during the scan, the comput~r produced a thermQelectric signature for each thermoelement as a plot of E-Eo against position along 9~Z8 the specimen. E is the output of the thermoelement relative to the platinum leg of the re~erence thermocouple and corrected for the cold-junction temperature.
E was developed in the 480C temperature step at the entrance port of the scanning furnace and any difference, ~E, between repeated signatures represents a change in Seebeck coefficient of:
~ S - ~E/480 Here it is assumed that ~S is independent of temperature to at least 500C. This was found to be so for changes produced by 200 h at 350,700 and 1100C. The repeatability of the scanning facility is such that changes in signature of 10 pV
(0.02 ~VK 1~ or more are significant.
Studies were made of both reversible and irreversible changes in ~eebeck coefficient produced by heating for periods of 0.5 to 300 h. Preliminary measurements revealed that significant reversible changes did not occur above 1000C and that when such changes did occur, at lower temperatures, a heating at 1000 to 1100C reversed the process. There was no noticeable di~ference in the effects of heating perioas of 5 and 60 minutes. A~ter each such heating the specimen was 'air quenched' by withdrawing it in about 2 s from the furnace and holding it stationary in air at 20C
until cool. Hence a 10 minute heating at about 1020C
followed by an air quench was chosen as the defined 'recovery anneal'.
Since the gradient-annealing furnace covers only a limited range of temperature, about 350C ~or a peak ann~aling temperature o~ 1000C, the 200 to 1~00C
interval considered in this study was examined in Çour FY _9_ ~ 29~28 overlapping zones. For each zone a different set of specimens was used and each set consisted of three MIMS specimens, one of each of the three diameters 1.5, 3 and 6 mm. This enabled any diameter-dependence to be observed.
To distinguish between reversible and irreversible changes the following sequence was followed for each specimen:
(a) reco~ery anneal (b) scan (c) recovery anneal (d) gradient anneal (period to) (e) scan (f) repeat of steps (a) to (e) with different to~
The effect of heating for a period to at any temperature To, within the range of the gradient-annealing furnace, was indicated by the dif~erence between the signatures obtained before and after the gradient anneal.
This change has two components, the irreversible and the reversible. The irreversible component was determined from the signature measured after the subsequent recovery anneal and was cumulative. The reversible component was then calculated by substraction.
Thus, it was found that changes in coefficient are of two types. The irst is a reversible one i.e. after the Seebeck coefficient changes on heating, it will return to its former value on a brief heating at a higher temperature (such as 1000C) and the process is repeatable. This process is a consequence o changes throughout the alloy structure and ~hus occurs e~ually in bare-wire and MIM~ thermocouples~ Further, the change in ~oe~icient is inde~endent Q~ thermoelement diameter. The second t~pc o~ change is irreversible and F~ -10--`` 1.29~
occurs because of changes at the surface of each thermoelement. It is therefore diameter dependent. Its cause and degree of change is different from those that would have occurred had the wires been exposed to air, i.e. had they been a bare-wire thermocouple. Since there is no relationship between the two sets of processes the behaviour of a particular pair of thermoelements in a ~IMS system is not predictable from data obtained for the same thermoelements as bare wires e~posed to air.
The reversible changes in Seebeck coefficient for each thermocouple pair tested is indicated in Figure 2 and clearly the change in each of the 3 type K thermocouples is similar yet considerably less than that in the type N therm-ocouple. It was also found that reversible change at any one temperature occurs rapidly at first and then levels off in the long term. For e~ample, there is little change beyond that at 200 hours and half this change occurs in less than 10 hours.
In the MIMS configuration, irreversible change in ! the coeficient is minimised if the manganese content of the sheath is negligible, as is the case or a Nicrosil sheath.
Indeed it was ~ound that the irreversible change in 200 hours in all 4 thermocouple examples studied (Table 1) was insigniicant below 800C and less than about 0.2 /uV/K at 1100C. Beyond this temperature the change becomes increasingly negative reaching -0.9+ 2~ fK at 1200C for all specimens. The variation in behaviour between the three type K thermocouples was similar to the diEerence between their mean behaviour and that oE the type N thermocouple. Hence the irrevQrsible ~hancJes occurring in the type K and type N
thermocouples are not ~ignificantly di~erent.
~l2'91228 , ~
The integrated effect of reversible and irreversible changes in the Seebeck coefficient is evident in the in situ drift of a thermocouple. This is the drift in signal that occurs ~or a thermocouple whilst the temperature of its tip and its temperature profile are held fixed. Figure 3 shows the in situ drift in 200 hours at any given temperature for the 4 examples. For temperatures to about 1000C the main contributor to drift is the reversible effect and hence the type K combinations performed better than the type N.
10 Furthermore, for periods of use beyond ~00 hours the contribution from reversible change in the coefficient will change little and it is only at temperatures approaching 1200C that the long-term irreversible changes would have a significant effect. For example, for type N thermoelements in a Nicrosil MIMS sheath at 1100C the in situ drift for 2000 hours was not significantly different ~rom that at 200 hours.
There was a barely-measurable decrease in signal in the long term, as e~pected, because of irreversible chan~es occurring in that part o~ the thermocouple at 100 to 1100C, Hence, the ~ situ drift for all 4 types of specimen (Table 1) over long periods o~ time, such as 2000 h or so, is little different from that indicated in Figure 3 for 20Q h.
Below 1000C the drift would be marginally higher than indicated and beyond 1000C it would be less and eventually become negative. Overall, the type K varieties perform better than the type N (Figure 3) and for this reason they were selected as thermoelements for this invention.
The Invention compared with Conventional ~hermocouple~
For variable-ir~mersion applica~ions at high 30 temperatures requiring a short-term use of small-diameter FY -1~-~LZ9~ ~28 probes, the conventional alternatives are:
(a) 24 AWG ~0.5 mm wires) bare-wire t~ermocouples in woven insulation or ceramic beads. For comparison purposes the type N thermocouple was chos~n for this study because it is the most stable base-metal type for bare-wire use in air.
(b~ MIMS probes with 1.5 mm diameter sheaths. Samples of the stainless-steel-sheathed type K MIMS system were chosen to represent this group since it is the most commonly used MIMS system.
Errors at high temperatures are greatest when p~obes are moved to a lesser immersion depth and are proportional to the changes in 5eebeck coefficient that occur on he~ating at these temperatures, e.g. 64 h at 1100C. These changes were measured by the above mentioned method and the results ara given in Table 2. The changes found for examples of this invention (1.5 mm OD Nicrosil sheath and the thermoelements Xl, K2 and K3) are an order of magnitude smaller than those for the conventional probes).
Z0 Table 2. Change in Seebeck coef~icient of small-diameter probes ~described above~ for 64 h of heating at 1100C.
, Prob~ ohU~ in Coefficient ~Y/K
Bare-w~re typ~ N 3.3 5tainless-steel-sheathed type K MIMS -3.2 ~xample~ of inv~ntion:
Kl -0.40 K3 -O,48 The most common use oE thermocouples is in long-term 3Q fixed-immersion applications. In such cases, probe ~and wire) 9~ Z2 ~
diameters are larger for longer life and to minimise _n situ drift at high temperatures. The most commonly used is the bare-wire type K thermocouple with each wire 1.5 to 3.3 mm in diameter. With insulating beads and a separate protection sheath the overall probe diameter becomes 12 to 25 mm.
Some high-temperature in situ-drift data for such probes are as follows:
(a) 15 AWG ~1.5 mm wires) thermocouples at 1000C
drifted 5C in 300 h and 20C in 5000 h.
(b) 8 AWG (3.3 mm wires) thermocouples at 1100C
drifted 12C in 800 h.
(c) 8 AWG (3.3 mm wires) thermocouples at 1200C
drifted 27C in 700 h.
~d) 15 AWG (1.5 mm wires) thermocouples at 1200C
drifted 66C in about 500 h and mechanically failed by 1000 h.
(e) high-temperature drift rates for bare-wire thermocouples vary considerably because of differences in composition and thus dif~erences in the oxidation mechanisms,.
In the Nicrosil-sheathed MIMS system, type K thermoelements specified for the invention will suffer less drift. For example, at 1100C the change over a 2000 h period would reach a maximum of about 3C in 200 to 500 h and then decrease slightly. The overall change would not exceed 5C. Notice also that the probe diameter for this example ; is only 6mm ~Figure 3), 2 to 4 times smaller than conventional probes.
.. . .
This invention relates to a mineral-insulated, metal-sheathed (MIMS) thermocouple cable, and to thermocouples made from such cable.
The manufacture of ~IMS cable is well known. The components consist of a metallic sheath and two thermoelements (thermocouple conductors) insulated from each other, and the sheath, by a compacted ceramic-oxide-insulation material. The components are assembled under clean, dry conditions and by a process such as drawing, swaging or rolling, the sheath diameter is reduced to compact the ceramic and fill the - available space. The assembly is further reduced in diameter to the desired size, an overall reduction in diameter of 10 to 1 being common. Before diameter reduction the assembly may be evacuated, annealed and or back-filled with an inert gas.
Thermocouples are temperature-measuring sensors.
They are fabricated from MIMS cable by cutting to the required length, welding the thermoelements together at one end of the cable to form the 'hot junction' and welding extension leads to the other. Insulating powder is packed in around the hot junction to avoid an air pocket in the completed product, and the MIMS section of the thermocouple is then sealed by welding in some sheathing alloy over the hot junction and, for example, providing a suitable potting compound at the other.
Conventional base-metal MIMS cables are produced with sheaths of inconel or stainless steel and with thermoelements of one of the five internationally-standardised thermocouple types (types E,J,K, N and T: letter designations of the Instrument Society of ~merica).
O~ the tw~ types suitable ~or high-temperature use - ~29~28 (types N and K3 the t~pe N alloys have well-defined compositions whereas those for the type K alloys are not defined. The main requirement for the positive and negative type K thermoelements is that, as a matched pair, the relationship between their net emf and temperature should agree with the relevant internationally-accepted reference equations (such as BS4937, ASTM E230) within defined limits of error.
The present invention is directed to providing an improved M~MS thermocouple cable, and to thermocouples made ~rom such cable.
A thermocouple cable according to the invention has a positive and a negative thermoelement conforming to the standard emf-temperature specification for t~pe K
thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant alloy having a thermal coefficient substantially the same as that of the negative thermoelement and a melting point in excess o~ 1300C.
The alloy of which the sheath is ~ormed may be a nickel based alloy, although other alloys such as cobalt based alloys can be used. The nickel based alloy preferably is a nickel-chromium alloy, a particularly preferred alloy being one containing 13 to 15 wt.% chromium, 1 to 2 wt.% silicon with the balance most typically principally comprising ; nickel. The nickel-based alloy preferably contains substantially no manganese; while manganese, if present, shQuld be l~ss than 0.1 wt.%.
The nickel-based alloys for the sheath may contain FY _3_ -` ~29~2~3 elements such as magnesium to enhance their oxidation resistance, and refractory metals such as niobium, tungsten, tantalum or molybdenum to enhance physical properties of the sheath, such as its strength. Nicrosil (nominally 14.2 wt.%
chromium, 1.4 wt.% silicon and the balance essentially nickel) is an example of a suitable alloy for the sheath.
The positive and negative thermoelements are to be of alloys conforming to the standard emf-temperature specification of type K thermocouples. The thermoelements preferably are of respective alloys such that they conform to such specification to within -~ 0.75~ of temperature, most preferably to within + 0.375% of temperature. The thermoelements should be of alloys melting above 1300C; the alloys preferably comprising nickel-based alloys. In the case of the positive thermoelement, the alloy preferably comprises 9 to 10 wt.% chromium, with the balance substantially comprising nickel, although it may contain up to 1 wt.%
silicon and small quantities of other conventional alloy additions.
The negative thermoelement preferably contains 1 to 3 wt.% silicon in nickel. However, it typically will also contain other elements, preferably totalling less than 6 wt.%, such as manganese, cobalt, aluminium and copper. Such other elements preferably are added as required to adjust the emf-temperature relationship, of the positive thermoelement relative to the negative, to conform to the standard em~-temperature specification for type K thermocouples.
The insulating ceramic may be of any suitable rQEractory oxide or comhination oF oxides. Examples o~
3Q suitable oxides are those of magnesium, aluminium and FY ~4~
~L~91228 beryllium.
Another aspect of this invention is as follows:
A thermocouple cable having a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant nickel-based alloy containing chromium, silicon and less than 0.1 wt.% manganese, said nickel based alloy having a thermal expansion coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300C; the positive thermoelement comprising a nickel-based alloy containing chromium and the negative thermoelement comprising a nickel-based alloy containing silicon.
~29~L228 Advantages of the Invention Thermocouples fabricated from cable according to the invention, such as by the ~abrication procedure outlined above, are a considerable improvement over bare-wire type K
thermocouples and those produced from conventional base-metal MIMS cables. They have excellent stability, both thermoelectric and mechanical, at hi~h temperatures and the invention is an advance for the following reasons. Having the thermolements within a MIMS system avoids instabilities and premature failure at high temperatures (beyond about 900C), due to oxidation, that occur in 'bare-wire' thermocouples.
The use of the sheath alloy specified for the invention avoids the main cause of thermoelectric instability in conventional MIMS systems, that due to the migration of Mn from the sheath. Also, use of the sheath of the invention avoids mechanical failures that occur in conventional MIMS systems because of the difference in thermal expansion between that of the sheath and that of the negative thermoelement. Further, the sheath specified o~ the inven~ion is more resistant to oxidation and can be used in air at higher temperatures and for longer periods than the conventional sheathing alloys inconel and stainless steel. Finally, the only standardised base-metal thermocouples with a practical life beyond 1000C
are the type K and type N thermocouples. Within a MIMS system having the sheath of the invention, the type K thermoelements of the invention are more thermoelectrically stable than the type N and are less likel~ to fail because of any mixmatch in the thermal expansion coefficient. A1SQ~ type K thermo-couples, includin~ thos~ made ~rom the ca~le of the inven~ion, . . . , ,. .. ,, . , . . ,: . .
.
~L~91~28 are of greater practical Yalue because there are two orders ofmagnitude more instruments, and associated items of equipment, available in the type K calibration than in the type N.
Development of the Invention In the following, experimental background to the invention is detailad. In this, reference is made to the accompanying drawings, in which:
Figure 1 shows a typical MIMS cable, illustrative of that used to produce thermocouples, the cable 10 having a sheath 12 in which two thermoelements 14 are insulated by compacted ceramic 16;
Figure 2 is a plot of reversible change in Seebeck coefficient after 200 hours at temperature; and Figure 3 is a plot of in situ temperature drift during 200 hours at temperature.
Our research into the thermoelectric behaviour of conventional nickel-based MIMS thermocouples showed that the main cause of instability at high temperatures was the migration of Mn from the sheath to the thermoelements. As a first step in developing a new, more stable MIMS system the alloy Nicrosil was considered by us as a sheath. Our subsequent work confirmed the importance of avoiding Mn.
High-nickel alloys such as Nicrosil have the added advantage of having a similar thermal e~pansion coefficient to that of the negative type N and type K thermoelements, both being high-nickel alloys. Relative to these thermoelements, the thermal expansion of stainless steel or inconel on heating to 900C is 0.2 to 0.4~ which is lar~e compared to that of Nicrosil, 0.05~. ~if~rential thermal e~pansion causes mechanical Eailure during thermal cycling in type ~ and type N
F~ -6-9~2~8 MIMS thermocouples having sheaths of inconel or stainless steel.
Nicrosil-sheathed MIMS thermocouples, comprising three (Kl, R2 and K3) type K thermocouples according to the invention and one type N thermocouple, each as described in Table 1, have been studied. What follows is a brief account of this work.
Table 1. Composition of thermoelements studied within Nicrosil-sheathed MIMS thermocouples, in weight percentO
Typ2 Thermox~ple ~ itive thermcelement N~ti~ thermce1a~nt . _ .
N N Ni 14.0Cr 1.SS~ Ni ~.4Si 0.~
K K1 Ni 9.2 Cr O.5Si Ni 1.6Si 1.6Mn 1.~ 0.6Co K K2 Ni-9,7 Cr 0.3Si Ni 2.0~i 0. ~ 0.~ O.~C0 K K3 Ni 9.1 Cr 0.4Sl ~ 2,~5i O.OMn 2,~ 1.0Co -- _, It is the integrated effect of local changes in Seebeck coefficient along the length of a thermocouple that dictates the extent of drift in its signal and thus of the temperature error it produces. For this reason the changes in Seebeck coefficient that occur at temperatures up to 1200C were measured as a function of time for the various thermoelements. Each thermocouple was heated either isothermally or in a 'gradient-annealing' furnace, the temperature within the latter being roughly linear with distance along much o~ its length. The resultant change in Seebeck coefficient, as a function of position along the - thermocouple, wa~ obtained with a horizontal, mQtor-driven 'scannin~ ~urnace' moving at Q.125 m~ s 1, This furnace had a wire wound ~.ubu~ar muÇfle, 1.2 m long, containing a 20 mm ID
FY ~7~
9~L~28 earthed Inconel tube, it had a relatively steep temperature-gradient region at the entrance port and its temperature was uniform at 500C to + 5C along most of its length. At any given time during a scan the emf produced by the temperature step, from ambient to 500C, occurred over a distance of 120 mm. If the thermocouple had just been heated in the gradient-annealing furnace this length of it would correspond to a range of annealing temperatures of typically +
30C about To at its centre. Hence the emf measured at this immersion in the scanning furnace would reflect the average effect of annealing at To + 30C.
The movement of the scanning furnace and the electrical measurements were controlled by a Hewlett Packard (HP) 86B computer interfaced to a HP 3456A DMM, having 0.1 ~V
resolution, and a low-thermal ( 0.1 ~uV) two-pole scanner. The cold junction ends of all thermocouples were connected to a set of temperature-monitored terminals at 20C uniorm to +
0.01C.
During the scan the tip temperature of each thermocouple was obtained with a PtlO~Rh versus Pt reference thermocouple whose tip was wire-wrapped to that of the thermocouple under test with Nichrome wire. The reference thermocouple has 0.5 mm diameter wires in a 1060 mm long twin-bore insulator of recrystallised alumina and its Seebeck coefficient varied by less than ~ 0.02% along its length.
Values of test thermocouple tip temperature ~about 500C) were converted to values o emf, Eo~ for each thermoelement relative to platinum. From measurements taken during the scan, the comput~r produced a thermQelectric signature for each thermoelement as a plot of E-Eo against position along 9~Z8 the specimen. E is the output of the thermoelement relative to the platinum leg of the re~erence thermocouple and corrected for the cold-junction temperature.
E was developed in the 480C temperature step at the entrance port of the scanning furnace and any difference, ~E, between repeated signatures represents a change in Seebeck coefficient of:
~ S - ~E/480 Here it is assumed that ~S is independent of temperature to at least 500C. This was found to be so for changes produced by 200 h at 350,700 and 1100C. The repeatability of the scanning facility is such that changes in signature of 10 pV
(0.02 ~VK 1~ or more are significant.
Studies were made of both reversible and irreversible changes in ~eebeck coefficient produced by heating for periods of 0.5 to 300 h. Preliminary measurements revealed that significant reversible changes did not occur above 1000C and that when such changes did occur, at lower temperatures, a heating at 1000 to 1100C reversed the process. There was no noticeable di~ference in the effects of heating perioas of 5 and 60 minutes. A~ter each such heating the specimen was 'air quenched' by withdrawing it in about 2 s from the furnace and holding it stationary in air at 20C
until cool. Hence a 10 minute heating at about 1020C
followed by an air quench was chosen as the defined 'recovery anneal'.
Since the gradient-annealing furnace covers only a limited range of temperature, about 350C ~or a peak ann~aling temperature o~ 1000C, the 200 to 1~00C
interval considered in this study was examined in Çour FY _9_ ~ 29~28 overlapping zones. For each zone a different set of specimens was used and each set consisted of three MIMS specimens, one of each of the three diameters 1.5, 3 and 6 mm. This enabled any diameter-dependence to be observed.
To distinguish between reversible and irreversible changes the following sequence was followed for each specimen:
(a) reco~ery anneal (b) scan (c) recovery anneal (d) gradient anneal (period to) (e) scan (f) repeat of steps (a) to (e) with different to~
The effect of heating for a period to at any temperature To, within the range of the gradient-annealing furnace, was indicated by the dif~erence between the signatures obtained before and after the gradient anneal.
This change has two components, the irreversible and the reversible. The irreversible component was determined from the signature measured after the subsequent recovery anneal and was cumulative. The reversible component was then calculated by substraction.
Thus, it was found that changes in coefficient are of two types. The irst is a reversible one i.e. after the Seebeck coefficient changes on heating, it will return to its former value on a brief heating at a higher temperature (such as 1000C) and the process is repeatable. This process is a consequence o changes throughout the alloy structure and ~hus occurs e~ually in bare-wire and MIM~ thermocouples~ Further, the change in ~oe~icient is inde~endent Q~ thermoelement diameter. The second t~pc o~ change is irreversible and F~ -10--`` 1.29~
occurs because of changes at the surface of each thermoelement. It is therefore diameter dependent. Its cause and degree of change is different from those that would have occurred had the wires been exposed to air, i.e. had they been a bare-wire thermocouple. Since there is no relationship between the two sets of processes the behaviour of a particular pair of thermoelements in a ~IMS system is not predictable from data obtained for the same thermoelements as bare wires e~posed to air.
The reversible changes in Seebeck coefficient for each thermocouple pair tested is indicated in Figure 2 and clearly the change in each of the 3 type K thermocouples is similar yet considerably less than that in the type N therm-ocouple. It was also found that reversible change at any one temperature occurs rapidly at first and then levels off in the long term. For e~ample, there is little change beyond that at 200 hours and half this change occurs in less than 10 hours.
In the MIMS configuration, irreversible change in ! the coeficient is minimised if the manganese content of the sheath is negligible, as is the case or a Nicrosil sheath.
Indeed it was ~ound that the irreversible change in 200 hours in all 4 thermocouple examples studied (Table 1) was insigniicant below 800C and less than about 0.2 /uV/K at 1100C. Beyond this temperature the change becomes increasingly negative reaching -0.9+ 2~ fK at 1200C for all specimens. The variation in behaviour between the three type K thermocouples was similar to the diEerence between their mean behaviour and that oE the type N thermocouple. Hence the irrevQrsible ~hancJes occurring in the type K and type N
thermocouples are not ~ignificantly di~erent.
~l2'91228 , ~
The integrated effect of reversible and irreversible changes in the Seebeck coefficient is evident in the in situ drift of a thermocouple. This is the drift in signal that occurs ~or a thermocouple whilst the temperature of its tip and its temperature profile are held fixed. Figure 3 shows the in situ drift in 200 hours at any given temperature for the 4 examples. For temperatures to about 1000C the main contributor to drift is the reversible effect and hence the type K combinations performed better than the type N.
10 Furthermore, for periods of use beyond ~00 hours the contribution from reversible change in the coefficient will change little and it is only at temperatures approaching 1200C that the long-term irreversible changes would have a significant effect. For example, for type N thermoelements in a Nicrosil MIMS sheath at 1100C the in situ drift for 2000 hours was not significantly different ~rom that at 200 hours.
There was a barely-measurable decrease in signal in the long term, as e~pected, because of irreversible chan~es occurring in that part o~ the thermocouple at 100 to 1100C, Hence, the ~ situ drift for all 4 types of specimen (Table 1) over long periods o~ time, such as 2000 h or so, is little different from that indicated in Figure 3 for 20Q h.
Below 1000C the drift would be marginally higher than indicated and beyond 1000C it would be less and eventually become negative. Overall, the type K varieties perform better than the type N (Figure 3) and for this reason they were selected as thermoelements for this invention.
The Invention compared with Conventional ~hermocouple~
For variable-ir~mersion applica~ions at high 30 temperatures requiring a short-term use of small-diameter FY -1~-~LZ9~ ~28 probes, the conventional alternatives are:
(a) 24 AWG ~0.5 mm wires) bare-wire t~ermocouples in woven insulation or ceramic beads. For comparison purposes the type N thermocouple was chos~n for this study because it is the most stable base-metal type for bare-wire use in air.
(b~ MIMS probes with 1.5 mm diameter sheaths. Samples of the stainless-steel-sheathed type K MIMS system were chosen to represent this group since it is the most commonly used MIMS system.
Errors at high temperatures are greatest when p~obes are moved to a lesser immersion depth and are proportional to the changes in 5eebeck coefficient that occur on he~ating at these temperatures, e.g. 64 h at 1100C. These changes were measured by the above mentioned method and the results ara given in Table 2. The changes found for examples of this invention (1.5 mm OD Nicrosil sheath and the thermoelements Xl, K2 and K3) are an order of magnitude smaller than those for the conventional probes).
Z0 Table 2. Change in Seebeck coef~icient of small-diameter probes ~described above~ for 64 h of heating at 1100C.
, Prob~ ohU~ in Coefficient ~Y/K
Bare-w~re typ~ N 3.3 5tainless-steel-sheathed type K MIMS -3.2 ~xample~ of inv~ntion:
Kl -0.40 K3 -O,48 The most common use oE thermocouples is in long-term 3Q fixed-immersion applications. In such cases, probe ~and wire) 9~ Z2 ~
diameters are larger for longer life and to minimise _n situ drift at high temperatures. The most commonly used is the bare-wire type K thermocouple with each wire 1.5 to 3.3 mm in diameter. With insulating beads and a separate protection sheath the overall probe diameter becomes 12 to 25 mm.
Some high-temperature in situ-drift data for such probes are as follows:
(a) 15 AWG ~1.5 mm wires) thermocouples at 1000C
drifted 5C in 300 h and 20C in 5000 h.
(b) 8 AWG (3.3 mm wires) thermocouples at 1100C
drifted 12C in 800 h.
(c) 8 AWG (3.3 mm wires) thermocouples at 1200C
drifted 27C in 700 h.
~d) 15 AWG (1.5 mm wires) thermocouples at 1200C
drifted 66C in about 500 h and mechanically failed by 1000 h.
(e) high-temperature drift rates for bare-wire thermocouples vary considerably because of differences in composition and thus dif~erences in the oxidation mechanisms,.
In the Nicrosil-sheathed MIMS system, type K thermoelements specified for the invention will suffer less drift. For example, at 1100C the change over a 2000 h period would reach a maximum of about 3C in 200 to 500 h and then decrease slightly. The overall change would not exceed 5C. Notice also that the probe diameter for this example ; is only 6mm ~Figure 3), 2 to 4 times smaller than conventional probes.
.. . .
Claims (19)
1. A thermocouple cable having a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant nickel-based alloy containing chromium, silicon and less than 0.1 wt.% manganese, said nickel based alloy having a thermal expansion coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300°C; the positive thermoelement comprising a nickel-based alloy containing chromium and the negative thermoelement comprising a nickel-based alloy containing silicon.
2. A cable according to claim 1, wherein said alloy of said sheath contains 13 to 15 wt.% chromium and 1 to 2 wt.% silicon with the balance principally comprising nickel.
3. A cable according to claim 1, wherein said alloy of said sheath contains substantially no manganese.
4. A cable according to claim 2, wherein said alloy of said sheath contains substantially no manganese.
5. A cable according to claim 1, wherein said alloy of said sheath contains magnesium to enhance its oxidation resistance.
6. A cable according to claim 2, wherein said alloy of said sheath contains magnesium to enhance its oxidation resistance.
7. A cable according to claim 4, wherein said alloy of said sheath contains magnesium to enhance its oxidation resistance.
8. A cable according to claim 1, wherein the alloy of said sheath contains at least one refractory metal to enhance physical properties of the sheath.
9. A cable according to claim 5, wherein said at least one refractory metal is selected from niobium, tungsten, tantalum and molybdenum.
10. A cable according to claim 1, wherein the alloy of said positive thermoelement comprises 9 to 10 wt.%
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
11. A cable according to claim 2, wherein the alloy of said positive thermoelement comprises 9 to 10 wt.%
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
12. A cable according to claim 4, wherein the alloy of said positive thermoelement comprises 9 to 10 wt.%
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
chromium, with the balance substantially comprising nickel with optionally up to 1 wt.% silicon and small quantities of other conventional alloy additions.
13. A cable according to claim 1, wherein the alloy of said negative thermoelement comprises 1 to 3 wt.% silicon in nickel, and optionally other elements totalling less than 6 wt.%, including at least one of manganese, cobalt, aluminium and copper.
14. A cable according to claim 2, wherein the alloy of said negative thermoelement comprises 1 to 3 wt.% silicon in nickel, and optionally other elements totalling less than 6 wt.%, including at least one of manganese, cobalt, aluminium and copper.
15. A cable according to claim 4, wherein the alloy of said negative thermoelement comprises 1 to 3 wt.% silicon in nickel, and optionally other elements totalling less than 6 wt.%, including at least one of manganese, cohalt, aluminium and copper.
16. A cable according to claim 10, wherein the alloy of said negative thermoelement comprises 1 to 3 wt.% silicon is nickel, and optionally other elements totalling less than 6 wt.%, including at least one of manganese, cobalt, aluminium and copper.
17. A thermocouple fabricated from cable according to claim 1.
18. A thermocouple fabricated from cable according to claim 2.
19. A thermocouple fabricated from cable according to claim 16.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPH787886 | 1986-09-08 | ||
| AUPH07878 | 1986-09-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1291228C true CA1291228C (en) | 1991-10-22 |
Family
ID=3771802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000546303A Expired - Fee Related CA1291228C (en) | 1986-09-08 | 1987-09-08 | Stable metal-sheathed thermocouple cable |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5043023A (en) |
| EP (1) | EP0281606B1 (en) |
| JP (1) | JPH01501108A (en) |
| AT (1) | ATE139336T1 (en) |
| CA (1) | CA1291228C (en) |
| DE (1) | DE3751832D1 (en) |
| WO (1) | WO1988002106A1 (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4521639A (en) * | 1983-10-31 | 1985-06-04 | Falk Richard A | Repeating thermocouple |
| AU610527B2 (en) * | 1986-11-10 | 1991-05-23 | Nicrobell Pty Limited | Thermocouples of enhanced stability |
| EP0435963A4 (en) * | 1989-02-17 | 1991-08-28 | Nicrobell Pty Limited | Pyrometric thermoelectric sensor |
| EP0393264A1 (en) * | 1989-04-18 | 1990-10-24 | Inco Alloys Limited | Method for making mineral insulated metal sheathed cables |
| WO1993004504A1 (en) * | 1991-08-16 | 1993-03-04 | Nicrobell Pty. Limited | Thermocouple temperature sensor |
| US5230745A (en) * | 1991-12-06 | 1993-07-27 | Alcan International Limited | Thermocouple housing |
| US5368659A (en) | 1993-04-07 | 1994-11-29 | California Institute Of Technology | Method of forming berryllium bearing metallic glass |
| US5275670A (en) * | 1993-07-06 | 1994-01-04 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | High temperature, oxidation resistant noble metal-Al alloy thermocouple |
| US6830374B1 (en) * | 1999-08-16 | 2004-12-14 | Temperature Management Systems (Proprietary) Limited | Metallurgical thermocouple |
| JP2001201403A (en) * | 2000-01-18 | 2001-07-27 | Chubu Sukegawa Kogyo Kk | Thermocouple protection tube |
| JP2003535214A (en) | 2000-01-24 | 2003-11-25 | ハンチントン、アロイス、コーポレーション | High temperature heat treated alloy |
| US6455781B1 (en) | 2001-08-23 | 2002-09-24 | Chartered Semiconductor Manufacturing Ltd. | Thermocouple ceramic bead insulator |
| US6850859B1 (en) | 2003-12-03 | 2005-02-01 | Watlow Electric Manufacturing Company | Sensor drift compensation by lot |
| US7447607B2 (en) * | 2004-08-31 | 2008-11-04 | Watow Electric Manufacturing | System and method of compensation for device mounting and thermal transfer error |
| US7585166B2 (en) * | 2005-05-02 | 2009-09-08 | Buja Frederick J | System for monitoring temperature and pressure during a molding process |
| WO2008022122A2 (en) | 2006-08-14 | 2008-02-21 | Buja Frederick J | System and method employing a thermocouple junction for monitoring of physiological parameters |
| GB201005509D0 (en) * | 2010-03-31 | 2010-05-19 | Cambridge Entpr Ltd | Thermocouple apparatus and method |
| US8986205B2 (en) | 2010-05-14 | 2015-03-24 | Frederick J. Buja | Sensor for measurement of temperature and pressure for a cyclic process |
| BR112013010016A2 (en) | 2010-10-28 | 2016-08-02 | Heraeus Electro Nite Int | system for wireless measurement and method for transmitting at least one characteristic of a molten metal |
| JP5547117B2 (en) * | 2011-03-03 | 2014-07-09 | 株式会社神戸製鋼所 | Refractory remaining thickness evaluation method |
| TWI456201B (en) * | 2011-11-29 | 2014-10-11 | Univ Chung Hua | Wireless thermal bubble type accelerometer and method of manufacturing the same |
| DE102014116051A1 (en) * | 2014-11-04 | 2016-05-04 | Endress + Hauser Wetzer Gmbh + Co. Kg | Measuring arrangement comprising a first and a second pair of thermal wires |
| DE102014017157B3 (en) * | 2014-11-20 | 2016-01-28 | Caetec Gmbh | Thermo cable and module block for connection to a thermo-measuring system |
Family Cites Families (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB746274A (en) * | 1950-12-08 | 1956-03-14 | Kanthal Ab | Improvements in thermo-electric alloys |
| NL86228C (en) * | 1952-08-22 | |||
| US2691690A (en) * | 1952-08-22 | 1954-10-12 | Driver Harris Co | Thermocouple element composition |
| US2757221A (en) * | 1954-07-06 | 1956-07-31 | Driver Harris Co | Thermocouple element composition |
| BE540358A (en) * | 1954-08-06 | |||
| US2909428A (en) * | 1957-10-10 | 1959-10-20 | Hoskins Mfg Company | Thermocouple element |
| GB1037049A (en) * | 1962-11-09 | 1966-07-27 | Engelhard Ind Inc | Improvements in or relating to thermocouple assemblies |
| US3673003A (en) * | 1969-09-18 | 1972-06-27 | Driver Co Wilbur B | Thermocouple for nuclear environment |
| GB1347236A (en) * | 1970-01-30 | 1974-02-20 | Central Electr Generat Board | Thermocouples |
| US3820983A (en) * | 1971-08-20 | 1974-06-28 | Driver W Co | Nickel silicon magnesium alloy |
| JPS5132766B2 (en) * | 1972-07-25 | 1976-09-14 | ||
| US3776781A (en) * | 1973-04-12 | 1973-12-04 | Driver W Co | Thermocouple with nickel-silicon-magnesium alloy negative element |
| US3942242A (en) * | 1973-08-22 | 1976-03-09 | Engelhard Minerals & Chemicals Corporation | Thermocouple structure and method of manufacturing same |
| US4018624A (en) * | 1973-08-22 | 1977-04-19 | Engelhard Minerals & Chemicals Corporation | Thermocouple structure and method of manufacturing same |
| US3972740A (en) * | 1975-07-31 | 1976-08-03 | Wilbur B. Driver Company | Thermocouple with improved EMF stability |
| DE2547262C3 (en) * | 1975-10-22 | 1981-07-16 | Reinhard Dr. 7101 Flein Dahlberg | Thermoelectric arrangement with large temperature gradients and use |
| FR2469807A1 (en) * | 1979-11-07 | 1981-05-22 | Commissariat Energie Atomique | METHOD FOR PRODUCING A JUNCTION BETWEEN TWO VERY REDUCED METAL WIRES AND MEASURING DEVICES MADE FROM THIS JUNCTION |
| AU4167585A (en) * | 1984-05-07 | 1985-11-14 | Bell-Irh Limited | High temperature sheathed thermocouple |
| JPS60262377A (en) * | 1984-05-07 | 1985-12-25 | ニクロベル プロプライエタリー リミテッド | Stable high temperature cable and device formed therefrom |
| DE3636468C1 (en) * | 1986-10-25 | 1987-09-17 | Heraeus Gmbh W C | Sheathed wire thermocouple |
| US4834807A (en) * | 1986-11-10 | 1989-05-30 | Bell-Irh Limited | Thermocouples of enhanced stability |
-
1987
- 1987-09-08 EP EP87906050A patent/EP0281606B1/en not_active Expired - Lifetime
- 1987-09-08 AT AT87906050T patent/ATE139336T1/en not_active IP Right Cessation
- 1987-09-08 JP JP62505573A patent/JPH01501108A/en active Pending
- 1987-09-08 WO PCT/AU1987/000306 patent/WO1988002106A1/en active IP Right Grant
- 1987-09-08 DE DE3751832T patent/DE3751832D1/en not_active Expired - Lifetime
- 1987-09-08 US US07/237,304 patent/US5043023A/en not_active Expired - Lifetime
- 1987-09-08 CA CA000546303A patent/CA1291228C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01501108A (en) | 1989-04-13 |
| ATE139336T1 (en) | 1996-06-15 |
| WO1988002106A1 (en) | 1988-03-24 |
| DE3751832D1 (en) | 1996-07-18 |
| EP0281606A4 (en) | 1989-04-12 |
| US5043023A (en) | 1991-08-27 |
| EP0281606B1 (en) | 1996-06-12 |
| EP0281606A1 (en) | 1988-09-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1291228C (en) | Stable metal-sheathed thermocouple cable | |
| EP0292095B1 (en) | High-temperature mineral insulated metal-sheathed cable | |
| Bentley | Handbook of temperature measurement Vol. 3: the theory and practice of thermoelectric thermometry | |
| EP0322992A2 (en) | Thermocouples of enhanced stability | |
| EP0291187B1 (en) | Stable high-temperature thermocouple cable | |
| US4834807A (en) | Thermocouples of enhanced stability | |
| CA1238116A (en) | Stable high temperature cables and devices made therefrom | |
| AU610527B2 (en) | Thermocouples of enhanced stability | |
| AU592896B2 (en) | Stable metal-sheathed thermocouple cable | |
| Bentley | Long-term drift in mineral-insulated Nicrosil-sheathed type K thermocouples | |
| US7611280B2 (en) | EMF sensor with protective sheath | |
| Burley | Advanced integrally sheathed type N thermocouple of ultra-high thermoelectric stability | |
| US7131768B2 (en) | Extended temperature range EMF device | |
| Bentley | Thermoelectric hysteresis in Nicrosil and Nisil | |
| Starr et al. | A new stable nickel-base thermocouple | |
| EP0161986B1 (en) | Stable high temperature cables and devices made therefrom | |
| Anderson et al. | Problems in High Temperature Thermometry: Writing of this review was sponsored by the Energy Research and Development Administration under contract with the Union Carbide Corporation. | |
| AU602942B2 (en) | Stable high temperature cables and devices made therefrom | |
| Potts | Thermocouple Research to 10000C: Final Report November 1, 1957, Through June 30, 1959 | |
| NIST–Gaithersburg | I. Temperature Scales, Uncertainty, and Traceability II. Thermocouples and Thermocouple Wires | |
| EP1571432A1 (en) | EMF sensor with protective sheath | |
| Brooks et al. | High-temperature Sensors for BORAX-V Boiling Fuel Rods | |
| Carlson et al. | LEAD TELLURIDE RESEARCH PROGRAM. Final Report. | |
| CLARK et al. | High-Output Noble-Metal Thermocouples and Matching Lead Wire | |
| Davis | Metals Handbook Desk Edition |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |