JPH0151134B2 - - Google Patents
Info
- Publication number
- JPH0151134B2 JPH0151134B2 JP23825883A JP23825883A JPH0151134B2 JP H0151134 B2 JPH0151134 B2 JP H0151134B2 JP 23825883 A JP23825883 A JP 23825883A JP 23825883 A JP23825883 A JP 23825883A JP H0151134 B2 JPH0151134 B2 JP H0151134B2
- Authority
- JP
- Japan
- Prior art keywords
- thermocouple
- insulating material
- sheath
- thermocouple wire
- inner sheath
- 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
Links
- 239000011810 insulating material Substances 0.000 claims description 18
- 238000009413 insulation Methods 0.000 claims description 15
- 238000009826 distribution Methods 0.000 claims description 6
- 239000007769 metal material Substances 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 2
- 230000007423 decrease Effects 0.000 description 6
- 229910000809 Alumel Inorganic materials 0.000 description 3
- 229910001179 chromel Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 238000009529 body temperature measurement Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
- G01K7/10—Arrangements for compensating for auxiliary variables, e.g. length of lead
Description
【発明の詳細な説明】
〔発明の分野〕
この発明は、シース型熱電対で温度を測定する
ときに、高温域で生じる絶縁材の絶縁抵抗の低下
を補償する方式に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for compensating for a decrease in insulation resistance of an insulating material that occurs in a high temperature range when measuring temperature with a sheathed thermocouple.
〔発明の背景〕
いわゆるシース型熱電対は、第１図及び第２図
で示すように、ステンレス管等のシース１の中に
クロメル線とアルメル線といつた異なる２種の金
属線からなる熱電対素線２，３を収納すると共
に、同シース１中にマグネシア、アルミナ等の絶
縁材４を充填し、熱電対素線２，３及びシース１
の間を互いに絶縁したものである。このシース型
熱電対で温度を測定する場合は、熱電対素線２，
３の端部を互いに接合して温接点５を設ける共
に、他端側の冷接点６，７を一定の温度に維持し
ながら、これら冷接点６，７間で熱起電力を測定
することにより、同温接点５の温度を求める。[Background of the Invention] As shown in Figs. 1 and 2, a so-called sheath type thermocouple is a thermocouple made of two different metal wires, a chromel wire and an alumel wire, inside a sheath 1 such as a stainless steel tube. In addition to housing the paired wires 2 and 3, the sheath 1 is filled with an insulating material 4 such as magnesia or alumina, and the thermocouple wires 2 and 3 and the sheath 1 are
The space between them is insulated from each other. When measuring temperature with this sheathed thermocouple, the thermocouple wire 2,
By joining the ends of 3 to each other to form a hot junction 5, and while maintaining the cold junctions 6 and 7 on the other end at a constant temperature, the thermoelectromotive force is measured between these cold junctions 6 and 7. , find the temperature of the isothermal junction 5.
しかしながら、上記絶縁材４は、温度が高くな
ると絶縁性が低下する性質を持つており、一般に
100℃上昇する毎に絶縁抵抗が１桁程度のオーダ
ーで低下するとされている。従つて、上記シース
型熱電対が高温にさらされると、絶縁材４の絶縁
抵抗が低下し、熱電対素線２と３の間にその間の
電位差に応じた電流が流れることになる。そうす
ると両熱電対素線２，３の間で電圧低下を生じ、
冷接点６，７では、温接点５に対応する熱起電力
を正確に示さなり、温度測定に誤差を生じること
になる。 However, the insulating material 4 has a property that its insulation properties decrease as the temperature increases, and generally
It is said that insulation resistance decreases by about one digit for every 100°C rise. Therefore, when the sheath type thermocouple is exposed to high temperatures, the insulation resistance of the insulating material 4 decreases, and a current flows between the thermocouple wires 2 and 3 in accordance with the potential difference therebetween. This will cause a voltage drop between both thermocouple wires 2 and 3,
The cold junctions 6 and 7 do not accurately indicate the thermoelectromotive force corresponding to the hot junction 5, resulting in an error in temperature measurement.
第３図は、シース型熱電対において、絶縁材４
の絶縁抵抗が低下した場合の等価モデルを示した
ものであり、さらに第４図は、この微少区間にお
ける等価モデルを示したものである。熱電対素線
２，３の間で発生する電圧の低下は、絶縁抵抗
RXの絶縁材４を介して一方の熱電対素線２から
他方の熱電対素線３へと電流が流れることによつ
て生じるものであり、一般にシヤントエラー
Eerrと呼ばれ、次式で表わされる。 Figure 3 shows the insulating material 4 in a sheath type thermocouple.
Fig. 4 shows an equivalent model in the case where the insulation resistance of is reduced, and Fig. 4 shows an equivalent model in this minute section. The voltage drop that occurs between the thermocouple wires 2 and 3 is due to the insulation resistance.
This is caused by current flowing from one thermocouple wire 2 to the other thermocouple wire 3 via the insulating material 4 of the R
It is called Eerr and is expressed by the following formula.
Eerr＝Eout−（Ein＋E1＋E2）
＝−（Ein＋E1）r1／（r1＋RX）
ここでEinは、或る位置で熱電対素線２，３間
に入力する電圧、Eoutは、これより温接点６，
７寄りの位置で出力される電圧、E1，E2は、そ
れぞれt1とt2，t2とt3の温度差によつて熱電対素
線２，３の微少区間に発生する熱起電力、RXは、
温度t2における絶縁材４の絶縁抵抗、r1，r2は、
各微少区間における熱電対素線２，３の抵抗であ
る。 Eerr=Eout-(Ein+ E1 + E2 ) =-(Ein+ E1 ) r1 /( r1 + Rx ) Here, Ein is the voltage input between thermocouple wires 2 and 3 at a certain position, and Eout is, From this, hot junction 6,
The voltages E 1 and E 2 output at the position near 7 are the thermal effects generated in the minute sections of the thermocouple wires 2 and 3 due to the temperature difference between t 1 and t 2 and between t 2 and t 3 , respectively. Power, R
The insulation resistance, r 1 , r 2 of the insulating material 4 at the temperature t 2 is,
This is the resistance of the thermocouple wires 2 and 3 in each minute section.
この式から明らかな通り、上記シヤントエラー
Eerrを低減するためには、(1)高温での絶縁抵抗
RXが高い絶縁材４を使用すること、(2)熱電対素
線２，３の抵抗r1を低くするため、適当な材料を
選択するか或いはその径を太くすることが必要と
なる。しかし、熱電対に要請される種々の条件か
ら、このような対策には限度があり、大きな効果
は期待できない。 As is clear from this formula, the above shunt error
In order to reduce Eerr, (1) Insulation resistance at high temperature
It is necessary to use an insulating material 4 with a high R X and (2) to select an appropriate material or increase the diameter in order to lower the resistance r 1 of the thermocouple wires 2 and 3. However, there are limits to such measures due to the various conditions required of thermocouples, and great effects cannot be expected.
この発明は、シース型熱電対を使用した高温域
での温度測定における上記のような問題を解決す
べくなされたものであつて、温接点と冷接点の間
で発生する電圧低下を解消することにより、温接
点と冷接点の間で発生した熱起電力が冷接点に正
確に現れるようにし、もつて高温域での正確な温
度測定を可能としたものである。以下、この発明
の構成を図示の実施例に基づき詳細に説明する。
This invention was made in order to solve the above-mentioned problems in temperature measurement in a high temperature range using a sheathed thermocouple. This allows the thermoelectromotive force generated between the hot and cold junctions to appear accurately at the cold junction, thereby making it possible to accurately measure temperature in high temperature ranges. EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention will be described in detail based on the illustrated embodiment.
この発明では、第５図で示すように、熱電対素
線１２，１３を絶縁材１４が充填された内シース
１８，１９にそれぞれ収納し、さらにこれを絶縁
材１４が充填された外シース１１に収納する。そ
して内シース１８，１９とこれらの中の熱電対素
線１２，１３または内シース１８と１９の少なく
とも何れか１組の部材の長手方向に亙つて互いに
等しい電位分布を与えながら、冷接点１６，１７
間で電圧を測定し、これにより温接点１５での温
度を求める。
In this invention, as shown in FIG. Store it in. The cold junction 16 and 17
The voltage at the hot junction 15 is measured, and the temperature at the hot junction 15 is determined from this.
２つの部材に等しい電位分布を与える手段とし
ては、両部材を同種の金属材料で製作し、熱電対
素線１２，１３の冷接点１６，１７側でこれらに
等しい電位を与えるのが適当である。 As a means of giving equal potential distribution to the two members, it is appropriate to make both members from the same type of metal material and to give them equal potentials on the cold junctions 16 and 17 sides of the thermocouple wires 12 and 13. .
この発明の構成を図示の実施例によりさらに具
体的に説明する。
The configuration of the present invention will be explained in more detail with reference to illustrated embodiments.
第６図の実施例は、内シース１８，１９とこれ
らにそれぞれ収納された熱電対素線１２，１３に
等しい電位分布を与える場合の実施例である。こ
の場合、内シース１８，１９には、それぞれこれ
らに収納される熱電対素線１２，１３と同種の材
料、例えば熱電対素線１２，１３がそれぞれクロ
メル線とアルメル線であるときは、内シース１
８，１９にもそれぞれクロメル管とアルメル管を
使用する。そしてこれにより温度測定をするとき
は、温接点１５を目的の個所に配置すると共に、
冷接点１６，１７を一定の温度に維持しながら、
計器２０によつてその間で電圧を測定する。この
場合に、内シース１８，１９の端部には、電源回
路２１，２２を接続し、上記冷接点１６，１７で
測定されるのと等しい電位を与える。 The embodiment shown in FIG. 6 is an embodiment in which an equal potential distribution is applied to the inner sheaths 18 and 19 and the thermocouple wires 12 and 13 housed therein, respectively. In this case, the inner sheaths 18 and 19 are made of the same material as the thermocouple wires 12 and 13 housed therein, for example, when the thermocouple wires 12 and 13 are made of chromel wire and alumel wire, respectively, sheath 1
8 and 19 also use chromel tubes and alumel tubes, respectively. When measuring temperature using this method, place the hot junction 15 at the desired location, and
While maintaining the cold junctions 16 and 17 at a constant temperature,
A meter 20 measures the voltage therebetween. In this case, power supply circuits 21 and 22 are connected to the ends of the inner sheaths 18 and 19 to provide a potential equal to that measured at the cold contacts 16 and 17.
いまここで各熱電対素線１２，１３の冷接点１
６，１７で測定される電位がそれぞれV12，V22
とし、これと等しい電位を内シース１８，１９の
端部にそれぞれ与えたとした場合において、熱電
対素線１２，１３上の一点P11とP21、及びこれら
の点に対応する内シース１８，１９上の一点PS11
とPS21の電位V11，V21，VS11，VS21は、それぞれ
次の式で表される。 Now here, cold junction 1 of each thermocouple wire 12, 13
The potentials measured at 6 and 17 are V 12 and V 22 respectively.
If the same potential is applied to the ends of the inner sheaths 18 and 19, points P 11 and P 21 on the thermocouple wires 12 and 13, and the inner sheath 18 corresponding to these points, One point on 19 P S11
The potentials V 11 , V 21 , V S11 , and V S21 of PS21 are respectively expressed by the following equations.
V11＝V12−E12
VS11＝V12−ES12
V21＝V22−E22
VS21＝V22−ES22
ここでE12，E22は、熱電対素線１２，１３にお
いて冷接点１６，１７から上記P11，P21点までの
区間に発生する熱起電力であり、ES12，ES22は、
内シース１８，１９においてその端部から上記
PS11，PS21までの区間に発生する熱起電力であ
る。 V 11 = V 12 −E 12 V S11 = V 12 −E S12 V 21 = V 22 − E 22 V S21 = V 22 − E S22 where E 12 and E 22 are This is the thermoelectromotive force generated in the area from the contacts 16 and 17 to the above points P 11 and P 21 , and E S12 and E S22 are:
From the ends of the inner sheaths 18 and 19,
This is the thermoelectromotive force generated in the section between P S11 and P S21 .
この場合、内シース１８，１９とその中の熱電
対素線１２，１３はそれぞれ同種の金属材料で製
作されており、それらの熱電能が互いに等しいこ
とから、E12＝ES12，E22＝ES22となり、この結果
V11＝VS11，V21＝VS21となる。この関係は、当該
熱電対の何れの点でも成立することから、内シー
ス１８，１９とその中の熱電対素線１２，１３
は、その長手方向に亙つて互いに等しい電位分布
を持つ。従つてこれらの間には何れの点でも電位
差が発生せず、高温によりこの間の絶縁材１４の
絶縁抵抗RXが低下しても同絶縁材１４を介して
この間に電流が生じることがない。従つて熱電対
素線１２と１３の間にも電流が発生せず、絶縁材
１４の絶縁抵抗RXの低下による電圧低下、即ち
シヤントエラーが防止され、温接点１５と冷接点
１６，１７の間で発生した熱起電力が冷接点１
６，１７の間に正確に現れる。 In this case, the inner sheaths 18 and 19 and the thermocouple wires 12 and 13 therein are each made of the same kind of metal material, and their thermoelectric powers are equal to each other, so that E 12 = E S12 , E 22 = E S22 , and this result
V 11 =V S11 and V 21 =V S21 . Since this relationship holds true at any point of the thermocouple, the inner sheaths 18 and 19 and the thermocouple wires 12 and 13 therein are
have equal potential distribution over their longitudinal direction. Therefore, no potential difference is generated between them at any point, and even if the insulation resistance R X of the insulating material 14 between them is reduced due to high temperature, no current is generated between them through the insulating material 14. Therefore, no current is generated between the thermocouple wires 12 and 13, and a voltage drop due to a decrease in the insulation resistance RX of the insulating material 14, that is, a shunt error, is prevented, and the current is not generated between the hot junction 15 and the cold junctions 16, 17. The thermoelectromotive force generated at cold junction 1
Appears exactly between 6 and 17.
次ぎに第７図の実施例は、内シース１８と１９
に等しい電位分布を与える場合の実施例である。
この場合、両内シース１８，１９には、同種の金
属材料を使用し、かつ電源回路２１，２２により
その端部に等しい電位を与える。 Next, the embodiment of FIG. 7 has inner sheaths 18 and 19.
This is an example in which a potential distribution equal to is given.
In this case, both inner sheaths 18 and 19 are made of the same type of metal material, and power supply circuits 21 and 22 apply equal potential to their ends.
この場合も、上記第６図の実施例の場合と同じ
く内シース１８と１９の電位分布が等しくなり、
その間の絶縁材１４の絶縁抵抗RXが低下しても、
同絶縁材１４を介して電流が流れない。従つて、
この場合もまた熱電対素線１２と１３の中間部で
の電流の発生が防止され、いわゆるシヤントエラ
ーを防止することができる。 In this case as well, the potential distributions of the inner sheaths 18 and 19 are equal, as in the embodiment shown in FIG.
Even if the insulation resistance R X of the insulating material 14 between them decreases,
No current flows through the insulating material 14. Therefore,
In this case as well, generation of current at the intermediate portion between the thermocouple wires 12 and 13 is prevented, and so-called shunt errors can be prevented.
以上のようにこの発明によれば、高温域におい
て絶縁材１４の絶縁抵抗RXが低下したときも、
熱電対素線１２と１３の間の絶縁状態をほゞ完全
な状態で維持することができることから、温接点
１５と冷接点１６，１７の間での電圧低下を防止
することができる。このため、温接点１５と冷接
点１６，１７の間で発生した熱起電力が冷接点１
６，１７に正確に現れることになり、温度の測定
を正確に行うことができるようになる。
As described above, according to the present invention, even when the insulation resistance R
Since the insulation state between the thermocouple wires 12 and 13 can be maintained in an almost perfect state, a voltage drop between the hot junction 15 and the cold junctions 16 and 17 can be prevented. Therefore, the thermoelectromotive force generated between the hot junction 15 and the cold junctions 16 and 17 is transferred to the cold junction 1.
6 and 17, and the temperature can be measured accurately.
第１図は、従来のシース型熱電対を示す縦断側
面図、第２図は、同縦断正面図、第３図は、同熱
電対において絶縁材の絶縁抵抗が低下したときの
等価モデルを示す説明図、第４図は、同モデルの
微少区間のモデルを示す説明図、第５図は、この
発明において使用する熱電対の構造を示す縦断正
面図、第６図及び第７図は、この発明の各実施例
を示す説明図である。
１１……外シース、１２，１３……熱電対素
線、１４……絶縁材、１５……温接点、１６，１
７……冷接点、１８，１９……内シース。
Figure 1 is a vertical side view of a conventional sheathed thermocouple, Figure 2 is a front view of the same, and Figure 3 is an equivalent model of the same thermocouple when the insulation resistance of the insulating material is reduced. An explanatory diagram, FIG. 4 is an explanatory diagram showing a minute section model of the same model, FIG. 5 is a longitudinal sectional front view showing the structure of the thermocouple used in this invention, and FIGS. It is an explanatory view showing each example of the invention. 11... Outer sheath, 12, 13... Thermocouple wire, 14... Insulating material, 15... Hot junction, 16, 1
7... Cold junction, 18, 19... Inner sheath.
Claims (1)
属線からなる熱電対素線を収納したシース型熱電
対において、各熱電対素線を絶縁材が充填された
内シースにそれぞれ収め、さらにこれら内シース
を絶縁材が充填された外シースに収納し、内シー
スと内シースまたは内シースとこの中の熱電対素
線の少なくとも一組の部材に長手方向に沿つて互
いに等しい電位分布を与えながら、上記熱電対素
線の冷接点側で電圧を測定し、これにより温接点
における温度を求めるようにしたことを特徴とす
るシース型熱電対における絶縁低下補償方式。 ２ 内シースとこの中の熱電対素線を同種の金属
材料で製作し、冷接点側で内シースに熱電対素線
と等しい電位を与えるようにした特許請求の範囲
第１項記載の補償方式。 ３ 複数の内シースを同種の金属材料で製作し、
熱電対素線の冷接点側でこれら内シースに等しい
電位を与えるようにした特許請求の範囲第１項記
載の補償方式。[Scope of Claims] 1. In a sheathed thermocouple in which thermocouple wires made of two different metal wires are housed in a sheath filled with an insulating material, each thermocouple wire is housed in an inner sheath filled with an insulating material. These inner sheaths are housed in an outer sheath filled with an insulating material, and at least one pair of the inner sheath and the inner sheath or the inner sheath and the thermocouple wire therein are connected to each other along the longitudinal direction. A method for compensating insulation loss in a sheathed thermocouple, characterized in that voltage is measured on the cold junction side of the thermocouple wire while giving an equal potential distribution, and the temperature at the hot junction is determined from this. 2. The compensation system according to claim 1, wherein the inner sheath and the thermocouple wire therein are made of the same kind of metal material, and the inner sheath is given a potential equal to that of the thermocouple wire on the cold junction side. . 3.Make multiple inner sheaths from the same kind of metal material,
2. The compensation system according to claim 1, wherein an equal potential is applied to the inner sheaths on the cold junction side of the thermocouple wire.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23825883A JPS60129631A (en) | 1983-12-17 | 1983-12-17 | Insulation degradation compensation in sheath-type thermocouple |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23825883A JPS60129631A (en) | 1983-12-17 | 1983-12-17 | Insulation degradation compensation in sheath-type thermocouple |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60129631A JPS60129631A (en) | 1985-07-10 |
| JPH0151134B2 true JPH0151134B2 (en) | 1989-11-01 |
Family
ID=17027503
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23825883A Granted JPS60129631A (en) | 1983-12-17 | 1983-12-17 | Insulation degradation compensation in sheath-type thermocouple |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60129631A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3348977B1 (en) * | 2017-01-13 | 2020-05-27 | IDT Europe GmbH | Failure tolerant thermovoltage acquisition for thermocouple applications |
-
1983
- 1983-12-17 JP JP23825883A patent/JPS60129631A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60129631A (en) | 1985-07-10 |
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