JPH0548153A - Burnout detector circuit for thermocouple thermometer - Google Patents

Burnout detector circuit for thermocouple thermometer

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Publication number
JPH0548153A
JPH0548153A JP3224683A JP22468391A JPH0548153A JP H0548153 A JPH0548153 A JP H0548153A JP 3224683 A JP3224683 A JP 3224683A JP 22468391 A JP22468391 A JP 22468391A JP H0548153 A JPH0548153 A JP H0548153A
Authority
JP
Japan
Prior art keywords
voltage
thermocouple
burnout
vac
measuring unit
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.)
Granted
Application number
JP3224683A
Other languages
Japanese (ja)
Other versions
JP3217814B2 (en
Inventor
Atsushi Mizuno
厚 水野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hioki EE Corp
Original Assignee
Hioki EE Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hioki EE Corp filed Critical Hioki EE Corp
Priority to JP22468391A priority Critical patent/JP3217814B2/en
Publication of JPH0548153A publication Critical patent/JPH0548153A/en
Application granted granted Critical
Publication of JP3217814B2 publication Critical patent/JP3217814B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Arrangements For Transmission Of Measured Signals (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

PURPOSE:To obtain a burnout detector circuit in which a measuring error does not occur by superposing a burnout detecting AC voltage on a thermal electromotive force of a thermocouple, and removing the AC voltage by a filter after amplifying it. CONSTITUTION:An AC voltage VAC from an AC signal source 6 is applied to a thermal electromotive force Vt of a thermocouple 1 to a composite voltage VX. After this is amplified by A times by an amplifier 2, an AC voltage AVAC is removed by a low pass filter 8 in a temperature measuring unit 7, a DC voltage ACt is extracted, applied to an A/D converter 3, and digitally converted. A measuring unit 4 calculates a measured temperature from digital data AVt, and displays it on a display unit 9. On the other hand, the voltage AVx of the amplifier 2 is also applied to a burnout signal generator 10, and converted to a DC voltage Va through a capacitor C and a rectifier 11. When a burnout occurs, the voltage Va becomes larger than a threshold voltage Vvef, a comparator 12 is turned ON, and a disconnection of the thermocouple 1 is informed.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】この発明は熱電対温度計のバーン
アウト検出回路に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burnout detection circuit for a thermocouple thermometer.

【0002】[0002]

【従来の技術】熱電対温度計などに温度センサとして用
いられている熱電対素子は劣化して断線することがあ
り、この断線現象を一般にバーンアウトと称している。
そこでこの種の装置においては熱電対素子が断線してい
るか否かを監視するバーンアウト検出回路を設け、断線
の場合は素子を交換するようにしている。
2. Description of the Related Art A thermocouple element used as a temperature sensor in a thermocouple thermometer or the like may be deteriorated and disconnected, and this disconnection phenomenon is generally called burnout.
Therefore, in this type of device, a burnout detection circuit for monitoring whether or not the thermocouple element is disconnected is provided, and in the case of disconnection, the element is replaced.

【0003】図4に従来の熱電対温度計におけるバーン
アウト検出回路の一例が示されているが、例えば正の直
流電圧源+Vccから抵抗R3を介して熱電対1に電流
iを流し、その電圧降下Viを同熱電対1の熱起電力V
tに重畳するようにしている。その合成電圧Vxとする
と、 Vx=Vt+Vi (1) である。この電圧Vxは増幅器2に加えられる。
FIG. 4 shows an example of a burnout detection circuit in a conventional thermocouple thermometer. For example, a current i is caused to flow from a positive DC voltage source + Vcc to a thermocouple 1 through a resistor R3, and the voltage thereof is applied. The drop Vi is the thermoelectromotive force V of the thermocouple 1.
It overlaps with t. If the combined voltage is Vx, then Vx = Vt + Vi (1). This voltage Vx is applied to the amplifier 2.

【0004】いま、増幅器2の増幅度をAとすると、式
(1)の電圧は同増幅器2にてA倍され、その出力電圧
は A・Vx=A(Vt+Vi) となる。この電圧は例えばA/Dコンバータ3にてディ
ジタル変換され、測定部4に加えられる。測定部4は上
記A倍されたデータを例えば演算により1/Aにし、上
記式(1)の値を求めるようになっている。
Now, assuming that the amplification degree of the amplifier 2 is A, the voltage of the equation (1) is multiplied by A in the amplifier 2 and the output voltage becomes A · Vx = A (Vt + Vi). This voltage is digitally converted by, for example, the A / D converter 3 and applied to the measuring unit 4. The measuring unit 4 calculates the value of the above formula (1) by making the data multiplied by A into 1 / A, for example, by calculation.

【0005】ここで、熱電対1を構成する2つの異種金
属線とそのリード線が有する抵抗をR1,R2とする
と、上記電圧源+Vccから抵抗R3を介して流れる電
流iにより熱電対1に生じる電圧降下Viは Vi=i(R1+R2) ={Vcc/(R1+R2+R3)}(R1+R2) であるから、合成電圧Vxは Vx=Vt+Vcc(R1+R2)/(R1+R2+R3) (2) となる。この場合、抵抗R3の値は通常 R3》R1+R2 のように設定されているから、熱電対1が正常に動作し
ている場合は式(2)の右辺第2の項分母におけるR1
+R2を無視すると、 Vx〓Vt+Vcc(R1+R2)/R3 (3) とおくことができる。
Assuming that the resistances of the two dissimilar metal wires constituting the thermocouple 1 and their lead wires are R1 and R2, the current i flowing from the voltage source + Vcc through the resistance R3 causes the thermocouple 1 to generate. Since the voltage drop Vi is Vi = i (R1 + R2) = {Vcc / (R1 + R2 + R3)} (R1 + R2), the combined voltage Vx is Vx = Vt + Vcc (R1 + R2) / (R1 + R2 + R3) (2). In this case, the value of the resistor R3 is usually set as R3 >> R1 + R2, so when the thermocouple 1 is operating normally, R1 in the second term denominator on the right side of the equation (2) is
Ignoring + R2, it can be written as Vx = Vt + Vcc (R1 + R2) / R3 (3).

【0006】熱電対1が断線した場合には熱起電力Vt
が発生しないから、 Vt=0 である。よって式(2)より Vx=Vcc(R1+R2)/(R1+R2+R3) また、素子の抵抗の和R1+R2は断線により無限大と
みなせるから、上式のR3を無視すると Vx〓Vcc (4) となる。ここで、増幅器2の出力A・Vccが例えばA
/Dコンバータ3のフルスケール入力電圧以上となるよ
うにすると同A/Dコンバータは飽和し、測定部4から
はフルスケールデータ(11…1)が得られる。このデ
ータを図示しない表示部に表示すれば熱電対1のバーン
アウトを検出することができる。
When the thermocouple 1 is broken, the thermoelectromotive force Vt
Does not occur, Vt = 0. Therefore, from the formula (2), Vx = Vcc (R1 + R2) / (R1 + R2 + R3) Further, the sum R1 + R2 of the resistances of the elements can be regarded as infinity due to the disconnection, so that if R3 in the above formula is ignored, Vx = Vcc (4). Here, the output A · Vcc of the amplifier 2 is, for example, A
When the voltage is set to be equal to or higher than the full-scale input voltage of the / D converter 3, the same A / D converter is saturated and full-scale data (11 ... 1) is obtained from the measuring unit 4. If this data is displayed on a display unit (not shown), burnout of the thermocouple 1 can be detected.

【0007】図5には、上記増幅器2の代りに差動増幅
器5を用いた他の例が示されているが、動作は図4の例
と実質的に同じであるからその説明は省略する。
FIG. 5 shows another example in which the differential amplifier 5 is used in place of the above-mentioned amplifier 2, but the operation is substantially the same as the example in FIG. 4, and therefore its explanation is omitted. ..

【0008】[0008]

【発明が解決しようとする課題】上記従来のバーンアウ
ト検出回路によると、熱電対の断線等は確実に検出でき
る。しかし、熱電対が正常であって通常の温度測定を行
っている場合には、式(3)に示すように温度測定値V
xに対して右辺第2項が誤差分として入り込む。そのた
め、一般にはR3に数百KΩ以上の高抵抗を用いて誤差
の減少を図っているが、この誤差は回路構成上必然的に
発生するので無くすることは困難である。また、高抵抗
を用いると誘導等による雑音を拾いやすく好ましくな
い。
According to the above-mentioned conventional burnout detection circuit, the disconnection of the thermocouple or the like can be surely detected. However, when the thermocouple is normal and the normal temperature measurement is performed, the temperature measurement value V is calculated as shown in equation (3).
The second term on the right side of x enters as an error component. Therefore, in general, a high resistance of several hundreds of KΩ or more is used for R3 to reduce the error, but this error is inevitably generated in the circuit configuration, and it is difficult to eliminate it. Further, if a high resistance is used, noise due to induction or the like tends to be picked up, which is not preferable.

【0009】この発明は上記の事情を考慮してなされた
もので、その目的は、測定誤差が本来発生しないように
構成したバーンアウト検出回路を提供することにある。
The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a burnout detection circuit configured so that a measurement error should not originally occur.

【0010】[0010]

【課題を解決するための手段】この発明の実施例が示さ
れている図1を参照すると、熱電対1、増幅器2、A/
Dコンバータ3、測定部4などは前記従来装置とほぼ同
様に構成され、したがって、同一の参照符号が付されて
いる。この実施例においては、上記課題を解決するため
下記ないしの手段を備えている。
Referring to FIG. 1, which illustrates an embodiment of the present invention, a thermocouple 1, an amplifier 2, an A /
The D converter 3, the measuring unit 4 and the like are configured in substantially the same manner as the above-mentioned conventional device, and are therefore provided with the same reference numerals. In this embodiment, the following means are provided to solve the above problems.

【0011】 例えば熱電対1の熱起電力Vtにバー
ンアウト検出用の交流電圧Vacを重畳する交流信号源
6を備えている。
For example, an AC signal source 6 that superimposes an AC voltage Vac for burnout detection on the thermoelectromotive force Vt of the thermocouple 1 is provided.

【0012】 例えば増幅器2の後段を温度測定部7
とバーンアウト信号発生部10の2つの系にて構成し、
温度測定部7は、上記交流電圧Vacを除去し熱起電力
Vtを通過させるローパスフィルタ8を備えている。
For example, the temperature measuring unit 7 is provided after the amplifier 2.
And a burnout signal generator 10
The temperature measuring unit 7 includes a low-pass filter 8 that removes the AC voltage Vac and passes the thermoelectromotive force Vt.

【0013】 上記バーンアウト信号発生部10は、
例えば熱起電力Vtの通過を阻止し交流電圧Vacを通
過させるコンデンサCと、同交流電圧Vacを直流に変
換する整流回路11と、その整流した直流電圧が所定の
しきい値レベルを超えたとき上記熱電対1の断線を知ら
せる信号を発するコンパレータ12及び基準電圧源13
とを備えている。
The burnout signal generator 10 is
For example, when a capacitor C that blocks passage of the thermoelectromotive force Vt and passes the AC voltage Vac, a rectifying circuit 11 that converts the AC voltage Vac into a DC, and the rectified DC voltage exceeds a predetermined threshold level. Comparator 12 and reference voltage source 13 for issuing a signal notifying the disconnection of the thermocouple 1
It has and.

【0014】[0014]

【作用】上記の手段により熱電対1の熱起電力Vtに
バーンアウト検出用の交流電圧Vacを重畳すると、増
幅器2に加わる電圧は直流電圧Vtと交流電圧Vacの
和の電圧となる。ここで増幅器2の増幅度をAとする
と、同増幅器2の出力側には入力電圧をA倍した電圧が
現れる。この場合、温度測定部7には上記の手段によ
りローパスフィルタ7を介して直流の熱起電力A・Vt
が取り込まれ、測定誤差の要因となる交流電圧が除かれ
る。
When the AC voltage Vac for burnout detection is superimposed on the thermoelectromotive force Vt of the thermocouple 1 by the above means, the voltage applied to the amplifier 2 becomes the sum of the DC voltage Vt and the AC voltage Vac. Here, when the amplification degree of the amplifier 2 is A, a voltage obtained by multiplying the input voltage by A appears on the output side of the amplifier 2. In this case, the temperature measuring unit 7 is connected to the DC thermoelectromotive force A · Vt via the low-pass filter 7 by the above means.
Is taken in and the AC voltage that causes the measurement error is removed.

【0015】また、バーンアウト信号発生部10には、
上記の手段によりコンデンサCを介して交流電圧A・
Vacが取り込まれる。熱電対1が正常に動作している
場合には取り込んだ交流電圧A・Vacは比較的小さい
値であるから、その整流電圧もそれに対応した大きさの
電圧となる。熱電対1が断線した場合には、上記交流電
圧Vacは交流信号源6の信号源電圧Vとほぼ等しくな
り、コンデンサCを介して取り込まれる電圧はA・Vと
なる。この電圧は比較的大きい値であり、その整流電圧
もそれに対応した大きさの電圧となる。
Further, the burnout signal generator 10 includes
By the above means, the AC voltage A
Vac is taken in. When the thermocouple 1 is operating normally, the taken-in AC voltage A · Vac has a relatively small value, so the rectified voltage also has a voltage corresponding to it. When the thermocouple 1 is broken, the AC voltage Vac becomes substantially equal to the signal source voltage V of the AC signal source 6, and the voltage taken in via the capacitor C becomes A · V. This voltage has a relatively large value, and the rectified voltage also has a magnitude corresponding thereto.

【0016】よって、基準電圧源13のしきい値電圧V
refを交流電圧A・Vacの整流電圧より大きく、か
つ、交流電圧A・Vの整流電圧より小さい適当な値に設
定すると、熱電対1が断線した場合にはコンパレータ1
2の出力がONとなり、このON出力を測定部4へ送る
ことによりバーンアウトを知らせることができる。
Therefore, the threshold voltage V of the reference voltage source 13
If ref is set to an appropriate value that is greater than the rectified voltage of the AC voltage A · Vac and smaller than the rectified voltage of the AC voltage A · V, the comparator 1 will operate when the thermocouple 1 is disconnected.
The output of No. 2 is turned ON, and the burnout can be notified by sending this ON output to the measuring unit 4.

【0017】[0017]

【実施例】上記図1において、熱電対1の熱起電力をV
t、交流信号源6の信号源電圧をV、同信号源6から上
記熱電対1に加える交流電圧をVacとすると、熱起電
力Vtと加えられた交流電圧Vacとの合成電圧Vx
は、 Vx=Vt+Vac (5) となる。この場合、加えられた交流電圧Vacの大きさ
は Vac=V(R1+R2)/(R1+R2+R3) であるから、この値を式(5)に代入すると合成電圧V
xは Vx=Vt+V(R1+R2)/(R1+R2+R3) (6) となる。
EXAMPLE In FIG. 1, the thermoelectromotive force of the thermocouple 1 is V
where t is the signal source voltage of the AC signal source 6 and VAC is the AC voltage applied from the signal source 6 to the thermocouple 1, a combined voltage Vx of the thermoelectromotive force Vt and the applied AC voltage Vac
Becomes Vx = Vt + Vac (5). In this case, since the magnitude of the applied AC voltage Vac is Vac = V (R1 + R2) / (R1 + R2 + R3), substituting this value into the equation (5) results in the combined voltage Vac.
x becomes Vx = Vt + V (R1 + R2) / (R1 + R2 + R3) (6).

【0018】ここで、図2を併せて参照すると、同図
(A)は熱電対1が正常動作の場合で、同図(B)は断
線の場合である。いま、熱電対1は正常動作をしている
ものとし、上記式(5)の電圧Vxを図2(A)のイに
示す。この合成電圧Vxは例えば増幅器2にてA倍に増
幅され、同図2(A)のロに示すようになる。すなわ
ち、 AVx=AVt+AVac (7) 温度測定部7においては、ローパスフィルタ8がこの増
幅出力AVxから上記したように交流電圧AVacを除
去し、直流電圧AVtを抽出してA/Dコンバータ3に
加える。その状態を同図2(A)のハに示す。A/Dコ
ンバータ3はローパスフィルタ8から加わる電圧AVt
を同図(A)のニに示すようにディジタル変換する。た
だし、ニはディジタル変換データをアナログ電圧値に換
算して示してある。測定部4は例えばこのディジタルデ
ータAVtを上記増幅器2の増幅度Aにより割り算して
熱起電力Vtを求め、この電圧Vtに対応する測定温度
を算出して表示部9に表示する。
Referring to FIG. 2 together, FIG. 2A shows the case where the thermocouple 1 is operating normally, and FIG. 2B shows the case where the thermocouple 1 is broken. Now, it is assumed that the thermocouple 1 is operating normally, and the voltage Vx of the above formula (5) is shown in (a) of FIG. This combined voltage Vx is amplified by A times, for example, by the amplifier 2 and becomes as shown in B of FIG. That is, AVx = AVt + AVac (7) In the temperature measuring unit 7, the low-pass filter 8 removes the AC voltage AVac from the amplified output AVx as described above, extracts the DC voltage AVt, and applies it to the A / D converter 3. The state is shown in C of FIG. The A / D converter 3 receives the voltage AVt applied from the low-pass filter 8.
Is digitally converted as shown in D of FIG. However, D is shown by converting the digital conversion data into an analog voltage value. The measuring unit 4 divides this digital data AVt by the amplification degree A of the amplifier 2 to obtain the thermoelectromotive force Vt, calculates the measured temperature corresponding to this voltage Vt, and displays it on the display unit 9.

【0019】式(7)に示す増幅器2の出力電圧AVx
は、バーンアウト信号発生部10にも加えられる。この
場合、その直流電圧AVtはコンデンサCにより阻止さ
れ、交流電圧AVacが同コンデンサCを通過して図2
(A)のホに示すように整流回路11へ加えられる。整
流回路11はこの交流電圧AVacを整流して例えば平
均値を表す直流電圧Vaに変換する。それを図2(A)
のヘに示す。ここで、基準電圧源13のしきい値電圧V
refを同図への点線で示すように上記電圧Vaより大
きく設定すると、コンパレータ12の出力は図2(A)
のトに示すようにオフの状態となる。
Output voltage AVx of the amplifier 2 shown in equation (7)
Are also added to the burnout signal generator 10. In this case, the direct-current voltage AVt is blocked by the capacitor C, and the alternating-current voltage AVac passes through the same capacitor C so that the voltage of FIG.
It is added to the rectifier circuit 11 as shown in (A) -e. The rectifier circuit 11 rectifies this AC voltage AVac and converts it into a DC voltage Va representing an average value, for example. Figure 2 (A)
It is shown in F. Here, the threshold voltage V of the reference voltage source 13
When ref is set higher than the voltage Va as shown by the dotted line in the figure, the output of the comparator 12 is as shown in FIG.
It will be in the off state as shown in FIG.

【0020】次に、熱電対1が断線した場合を説明す
る。この場合、熱起電力Vtはゼロであるから、式
(5)より Vx〓Vac また、式(6)は Vx=V(R1+R2)/(R1+R2+R3) となるが、前記従来例と同様に R1+R2 → ∞ とみなしてR3を無視すると Vx〓V となる。よって Vx=V=Vac を得る。すなわち、増幅器2の入力電圧Vxは信号源6
の電圧Vとなる。この状態を図2(B)のイに示す。
Next, the case where the thermocouple 1 is broken will be described. In this case, since the thermoelectromotive force Vt is zero, Vx = Vac from the formula (5) and Vx = V (R1 + R2) / (R1 + R2 + R3) from the formula (6), but R1 + R2 → If it is regarded as ∞ and R3 is ignored, it becomes Vx〓V. Therefore, Vx = V = Vac is obtained. That is, the input voltage Vx of the amplifier 2 is the signal source 6
Voltage V. This state is shown in (a) of FIG.

【0021】増幅器2はこの電圧VacをA倍して温度
測定部7とバーンアウト信号発生部10へ送出する。こ
のA倍した電圧を同図2(B)のロに示す。温度測定部
7のローパスフィルタ8はこの増幅電圧AVacを除去
するからその出力はゼロ、したがってA/Dコンバータ
3のディジタルデータもゼロとなる。この状態をそれぞ
れ図2(B)のハとニに示す。
The amplifier 2 multiplies this voltage Vac by A and sends it to the temperature measuring section 7 and the burnout signal generating section 10. The voltage multiplied by A is shown in B of FIG. 2 (B). Since the low-pass filter 8 of the temperature measuring unit 7 removes this amplified voltage AVac, its output is zero, and therefore the digital data of the A / D converter 3 is also zero. This state is shown in FIGS. 2B and 2C, respectively.

【0022】バーンアウト信号発生部10においては、
上記交流電圧AVacがコンデンサCを通って整流回路
11に加えられ、例えば平均値を表す直流電圧Vaに変
換される。この状態を図2(B)のホ,ヘに示す。同図
ヘにおいて、直流電圧Vaはしきい値電圧Vrefより
十分大きいのでコンパレータ12はオンとなり、図2
(B)のトに示すようにその出力側にはHレベルの電圧
が発生する。このHレベルの電圧は熱電対1の断線を知
らせるバーンアウト信号として測定部4へ送られ、測定
部4はこの信号を受けると例えば表示部9の図示しない
表示器に熱電対1が断線であることを表示させるように
なっている。あるいはバーンアウト表示用のランプなど
を点灯させるようにしてもよい。
In the burnout signal generator 10,
The AC voltage AVac is applied to the rectifier circuit 11 through the capacitor C and converted into, for example, a DC voltage Va representing an average value. This state is shown in FIGS. In the figure, since the DC voltage Va is sufficiently higher than the threshold voltage Vref, the comparator 12 is turned on, and
As shown in (B) -G, an H-level voltage is generated on the output side. This H-level voltage is sent to the measuring unit 4 as a burnout signal indicating the disconnection of the thermocouple 1, and when the measuring unit 4 receives this signal, the thermocouple 1 is broken in the display (not shown) of the display unit 9, for example. It is supposed to be displayed. Alternatively, a burnout display lamp or the like may be turned on.

【0023】図3には、前記図5の従来例にならって差
動増幅器5を用いた他の実施例が示されているが、各部
の動作は上記図1の場合と同様であるからその説明は省
略する。
FIG. 3 shows another embodiment using the differential amplifier 5 in accordance with the conventional example of FIG. 5, but the operation of each part is the same as in the case of FIG. 1 described above. The description is omitted.

【0024】[0024]

【発明の効果】以上、詳細に説明したようにこの発明に
おいては、熱電対1の断線等を検出するため例えば交流
信号源6から上記熱電対1へ所定レベルの交流電圧Va
cを加え、同熱電対1の直流熱起電力Vtと加えた交流
電圧Vacとの合成電圧Vxから一方の上記直流電圧V
tを分離抽出して測定する温度測定部7と、上記合成電
圧Vxから他方の上記交流電圧Vacを分離抽出してそ
のレベルが所定のしきい値電圧以下であるか否かを監視
し、該しきい値電圧を超えると上記温度測定部7へ警告
の出力を発するバーンアウト信号発生部10とを備えて
いる。
As described above in detail, in the present invention, in order to detect the disconnection or the like of the thermocouple 1, for example, from the AC signal source 6 to the thermocouple 1, an AC voltage Va of a predetermined level is obtained.
One of the above DC voltage V from the combined voltage Vx of the DC thermoelectromotive force Vt of the thermocouple 1 and the added AC voltage Vac.
The temperature measuring unit 7 that separates and extracts t and measures the other alternating voltage Vac from the combined voltage Vx that is separated and extracted to monitor whether the level is equal to or lower than a predetermined threshold voltage. A burnout signal generating unit 10 is provided for outputting a warning to the temperature measuring unit 7 when the threshold voltage is exceeded.

【0025】したがって、この発明によると、温度測定
部7内は熱起電力Vtのみに関連した信号となり、誤差
要因となる他の信号成分が入り込まないため高精度で温
度を測定することができる。また、バーンアウト信号発
生部10内は上記交流電圧Vacのみに関連した信号と
なるので、熱電対1の断線等により交流電圧Vacが増
大した場合にはそれを確実に検出してバーンアウト信号
を送出することができる。
Therefore, according to the present invention, the temperature measuring section 7 has a signal related only to the thermoelectromotive force Vt, and other signal components that cause an error do not enter, so that the temperature can be measured with high accuracy. Further, since the signal inside the burnout signal generator 10 is related only to the AC voltage Vac, when the AC voltage Vac increases due to the disconnection of the thermocouple 1 or the like, it is surely detected and the burnout signal is generated. Can be sent out.

【図面の簡単な説明】[Brief description of drawings]

【図1】この発明を適用した装置例の電気的構成を示す
ブロック線図。
FIG. 1 is a block diagram showing an electrical configuration of a device example to which the present invention is applied.

【図2】上記装置例における各部の動作説明用信号波形
図。
FIG. 2 is a signal waveform diagram for explaining the operation of each unit in the above device example.

【図3】この発明を適用した他の装置例の電気的構成を
示すブロック線図。
FIG. 3 is a block diagram showing an electrical configuration of another device example to which the present invention is applied.

【図4】従来装置の電気的構成を示すブロック線図。FIG. 4 is a block diagram showing an electrical configuration of a conventional device.

【図5】従来装置の他の例における電気的構成を示すブ
ロック線図。
FIG. 5 is a block diagram showing an electrical configuration in another example of the conventional device.

【符号の説明】[Explanation of symbols]

1 熱電対 3 A/Dコンバータ 4 測定部 6 交流信号源 7 温度測定部 8 ローパスフィルタ 9 表示部 10 バーンアウト信号発生部 11 整流回路 12 コンパレータ 13 基準電圧源 C コンデンサ Va 整流直流電圧 Vac 分圧交流電圧 Vref しきい値電圧 Vt 熱起電力 1 Thermocouple 3 A / D Converter 4 Measuring Section 6 AC Signal Source 7 Temperature Measuring Section 8 Low Pass Filter 9 Display Section 10 Burnout Signal Generation Section 11 Rectifier Circuit 12 Comparator 13 Reference Voltage Source C Capacitor Va Rectified DC Voltage Vac Partial AC Voltage Vref Threshold voltage Vt Thermoelectromotive force

Claims (1)

【特許請求の範囲】[Claims] 【請求項1】 熱電対1を温度センサとし、その発生す
る熱起電力Vtのディジタル変換データに基づいて温度
を測定するとともに、一定電圧を有する電圧源から上記
熱電対1の出力側端子に所定の分圧電圧を加え、同端子
間の電圧増大により上記熱電対1の断線等を検出して表
示する熱電対温度計のバーンアウト検出回路において、 上記熱電対1に抵抗R3を介して交流の分圧電圧Vac
を加える交流信号源6と、 上記熱電対1の熱起電力Vtと上記交流信号源6から加
えた交流電圧Vacとの合成電圧から、ローパスフィル
タ8を含み上記直流の熱起電力Vtを分離抽出してディ
ジタル変換し温度を測定するA/Dコンバータ3及び測
定部4を有する温度測定部7と、 上記熱起電力Vtと交流電圧Vacとの合成電圧からそ
の交流電圧Vacを分離抽出するコンデンサCと、該抽
出した交流電圧Vacを整流して直流電圧Vaに変換す
る整流回路11と、所定のしきい値電圧Vrefを有
し、上記整流直流電圧Vaを同しきい値電圧Vrefと
比較して直流電圧Vaがしきい値電圧Vrefを超えた
とき上記測定部4へ出力を送出するコンパレータ12と
を備えたバーンアウト信号発生部10と、 上記測定部4がコンパレータ12からの出力を受けて発
する指令信号により上記熱電対1の断線を表示する表示
部9とを備えていることを特徴とする熱電対温度計のバ
ーンアウト検出回路。
1. A thermocouple 1 is used as a temperature sensor, the temperature is measured based on digital conversion data of thermoelectromotive force Vt generated by the temperature sensor, and a predetermined voltage is applied to an output side terminal of the thermocouple 1 from a voltage source having a constant voltage. In the burnout detection circuit of the thermocouple thermometer, which detects a disconnection or the like of the thermocouple 1 by increasing the voltage between the terminals and displays the voltage, the burnout detection circuit of the thermocouple 1 detects the AC Divided voltage Vac
Is added, and the thermoelectric power Vt of the thermocouple 1 and the AC voltage Vac applied from the AC signal source 6 are combined and extracted, and the DC thermoelectromotive force Vt including the low-pass filter 8 is separated and extracted. A temperature measuring section 7 having an A / D converter 3 and a measuring section 4 for digitally converting and measuring the temperature, and a capacitor C for separating and extracting the AC voltage Vac from the combined voltage of the thermoelectromotive force Vt and the AC voltage Vac. A rectifying circuit 11 for rectifying the extracted AC voltage Vac to convert it into a DC voltage Va; and a predetermined threshold voltage Vref, and comparing the rectified DC voltage Va with the threshold voltage Vref. The burnout signal generator 10 including a comparator 12 that outputs an output to the measuring unit 4 when the DC voltage Va exceeds the threshold voltage Vref, and the measuring unit 4 includes a comparator. Burnout detection circuit of thermocouple, characterized in that a display unit 9 for displaying the disconnection of the thermocouple 1 by a command signal originating receiving an output from the 12.
JP22468391A 1991-08-09 1991-08-09 Burnout detection circuit of thermocouple thermometer Expired - Fee Related JP3217814B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP22468391A JP3217814B2 (en) 1991-08-09 1991-08-09 Burnout detection circuit of thermocouple thermometer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP22468391A JP3217814B2 (en) 1991-08-09 1991-08-09 Burnout detection circuit of thermocouple thermometer

Publications (2)

Publication Number Publication Date
JPH0548153A true JPH0548153A (en) 1993-02-26
JP3217814B2 JP3217814B2 (en) 2001-10-15

Family

ID=16817592

Family Applications (1)

Application Number Title Priority Date Filing Date
JP22468391A Expired - Fee Related JP3217814B2 (en) 1991-08-09 1991-08-09 Burnout detection circuit of thermocouple thermometer

Country Status (1)

Country Link
JP (1) JP3217814B2 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007087343A (en) * 2005-09-26 2007-04-05 Teac Corp Abnormality detection device of sensor
GB2498370A (en) * 2012-01-12 2013-07-17 Rolls Royce Engine Control Systems Ltd Thermocouple fault detection
JP2015116383A (en) * 2013-12-19 2015-06-25 株式会社テクノリンク Ultrasonic living body stimulation device
CN106370319A (en) * 2016-09-05 2017-02-01 珠海格力电器股份有限公司 Temperature detection circuit
EP3719464A1 (en) * 2019-04-02 2020-10-07 Hamilton Sundstrand Corporation Reduced error sensor fault detection

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007087343A (en) * 2005-09-26 2007-04-05 Teac Corp Abnormality detection device of sensor
GB2498370A (en) * 2012-01-12 2013-07-17 Rolls Royce Engine Control Systems Ltd Thermocouple fault detection
JP2015116383A (en) * 2013-12-19 2015-06-25 株式会社テクノリンク Ultrasonic living body stimulation device
CN106370319A (en) * 2016-09-05 2017-02-01 珠海格力电器股份有限公司 Temperature detection circuit
EP3719464A1 (en) * 2019-04-02 2020-10-07 Hamilton Sundstrand Corporation Reduced error sensor fault detection
US11112444B2 (en) 2019-04-02 2021-09-07 Hamilton Sundstrand Corporation Reduced error sensor fault detection

Also Published As

Publication number Publication date
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