JP4835207B2 - Temperature transmitter - Google Patents

Temperature transmitter Download PDF

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JP4835207B2
JP4835207B2 JP2006060513A JP2006060513A JP4835207B2 JP 4835207 B2 JP4835207 B2 JP 4835207B2 JP 2006060513 A JP2006060513 A JP 2006060513A JP 2006060513 A JP2006060513 A JP 2006060513A JP 4835207 B2 JP4835207 B2 JP 4835207B2
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resistance
wiring resistance
wiring
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temperature
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JP2007240230A (en
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誠 竹内
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Yokogawa Electric Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that any disconnection can not be detected when a wiring resistance line connecting a resistance thermometer sensor to a temperature transmitter is disconnected. <P>SOLUTION: The temperature transmitter for inputting voltage signals from the resistance thermometer sensor via two measurement wires and the wiring resistance line, converting the voltage signals into a temperature value by applying an arithmetic operation thereto and outputting a temperature signal, is equipped with a disconnection detecting means which detects the disconnection of the wiring resistance line by using the voltage signals. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

本発明は、測温抵抗体を用いて温度計測を行って温度出力として伝送する温度伝送器に係り、特に測温抵抗体と温度伝送器を結ぶ配線抵抗線の断線、または断線に至る不具合を検知して温度計測の信頼性を確保出来るように改良された温度伝送器に関する。   The present invention relates to a temperature transmitter that performs temperature measurement using a resistance temperature detector and transmits the temperature output as a temperature output, and in particular, a failure of a wiring resistance wire that connects the resistance temperature detector and the temperature transmitter, or a problem that leads to disconnection. The present invention relates to an improved temperature transmitter that can detect and ensure the reliability of temperature measurement.

図４は従来から一般に使用されている２本の計測配線を持つ２線式の温度伝送器である。温度伝送器１０は測温抵抗体１１の一方が計測配線１２により温度伝送器１０の主入力端子１３に接続され、測温抵抗体１１の他方は計測配線１４により温度伝送器１０のセンサグラウンド端子１５に接続されている。以上の構成において、測温抵抗体１１において温度が測温抵抗体１１の抵抗変化として測定され、温度伝送器１０はこの抵抗変化を温度換算して温度出力する。   FIG. 4 shows a two-wire temperature transmitter having two measurement wires generally used in the past. In the temperature transmitter 10, one end of the resistance temperature detector 11 is connected to the main input terminal 13 of the temperature transmitter 10 by the measurement wiring 12, and the other end of the resistance temperature detector 11 is connected to the sensor ground terminal of the temperature transmitter 10 by the measurement wiring 14. 15 is connected. In the above configuration, the temperature is measured as a resistance change of the resistance thermometer 11 in the resistance thermometer 11, and the temperature transmitter 10 converts the resistance change into a temperature and outputs a temperature.

図５は従来から一般に使用されている２本の計測配線の他に１本の配線抵抗線を持つ３線式の温度伝送器である。温度伝送器２０は測温抵抗体１１の一方が計測配線１２により温度伝送器２０の主入力端子１３に接続され、測温抵抗体１１の他方は計測配線１４により温度伝送器２０のセンサグラウンド端子１５に接続されると共に、配線抵抗線２１により温度伝送器２０の配線抵抗入力端子２２に接続されている。   FIG. 5 shows a three-wire temperature transmitter having one wiring resistance wire in addition to two measurement wires generally used conventionally. In the temperature transmitter 20, one end of the resistance temperature detector 11 is connected to the main input terminal 13 of the temperature transmitter 20 by the measurement wiring 12, and the other end of the resistance temperature detector 11 is connected to the sensor ground terminal of the temperature transmitter 20 by the measurement wiring 14. 15 and connected to the wiring resistance input terminal 22 of the temperature transmitter 20 by the wiring resistance wire 21.

以上の構成において、測温抵抗体１１において温度が測温抵抗体１１の抵抗変化として測定され、温度伝送器２０はこの抵抗変化を温度換算して温度出力するが、３線式では、配線抵抗入力端子２２を利用して計測配線の影響を補正して測定精度の向上が図られている。   In the above configuration, the temperature is measured by the resistance temperature detector 11 as a resistance change of the resistance temperature detector 11, and the temperature transmitter 20 converts the resistance change into a temperature and outputs a temperature. The measurement accuracy is improved by correcting the influence of the measurement wiring by using the input terminal 22.

図６は従来から一般に使用されている２本の計測配線の他に２本の配線抵抗線を持つ４線式の温度伝送器である。温度伝送器３０は測温抵抗体１１の一方が計測配線１２により温度伝送器３０の主入力端子１３に接続されると共に、配線抵抗線３１により温度伝送器３０の配線抵抗入力端子３２に接続されている。また、温抵抗体１１の他方は計測配線１４により温度伝送器３０のセンサグラウンド端子１５に接続されると共に、配線抵抗線２１により温度伝送器３０の配線抵抗入力端子２２に接続されている。   FIG. 6 shows a four-wire temperature transmitter having two wiring resistance wires in addition to two measurement wires generally used conventionally. In the temperature transmitter 30, one of the resistance temperature detectors 11 is connected to the main input terminal 13 of the temperature transmitter 30 by the measurement wiring 12 and connected to the wiring resistance input terminal 32 of the temperature transmitter 30 by the wiring resistance wire 31. ing. The other end of the temperature resistor 11 is connected to the sensor ground terminal 15 of the temperature transmitter 30 by the measurement wiring 14 and is connected to the wiring resistance input terminal 22 of the temperature transmitter 30 by the wiring resistance wire 21.

以上の構成において、測温抵抗体１１において温度が測温抵抗体１１の抵抗変化として測定され、温度伝送器３０はこの抵抗変化を温度換算して温度出力するが、４線式では、配線抵抗入力端子２２、３２を利用して計測配線の影響を補正して更なる測定精度の向上が図られている。   In the above configuration, the temperature is measured by the resistance temperature detector 11 as a resistance change of the resistance temperature detector 11, and the temperature transmitter 30 converts the resistance change into a temperature and outputs a temperature. The measurement accuracy is further improved by correcting the influence of the measurement wiring using the input terminals 22 and 32.

下記特許文献１には、測温抵抗体を用いた３線あるいは４線の配線を持つ温度計測器が開示され、一般的にこれらの配線が断線したかどうかを診断し断線していれば配線切替回路によりこれらの配線を切り替える温度計測器が開示されている。   The following Patent Document 1 discloses a temperature measuring instrument having a three-wire or four-wire wiring using a resistance temperature detector, and generally diagnoses whether or not these wirings are disconnected, and wiring is performed if they are disconnected. A temperature measuring instrument that switches these wirings by a switching circuit is disclosed.

特開２００５−２３３７３７号公報JP 2005-233737 A

以上のように測温抵抗体１１を用いた温度計測には２線式、３線式および４線式など各種の方式あるが、どの方式においても配線のうち１つの配線が断線した場合は正しい計測が出来なくなる。   As described above, there are various methods such as 2-wire, 3-wire, and 4-wire methods for temperature measurement using the resistance temperature detector 11, but any method is correct when one of the wires is disconnected. Measurement cannot be performed.

測温抵抗体１１に電流を流す計測配線１２，１４が断線した場合は、主入力端子が高い電位に直ちに上昇するので、断線検知が可能であるが、配線抵抗線２１，３１が断線した場合は、断線検知が出来ない。   When the measurement wirings 12 and 14 for passing current to the resistance temperature detector 11 are disconnected, the main input terminal immediately rises to a high potential, so that the disconnection can be detected, but the wiring resistance lines 21 and 31 are disconnected. Cannot detect disconnection.

配線抵抗線２１，３１が断線した場合は、この配線抵抗線２１，３１の電位を計測する温度伝送器３０、４０内のＡ／Ｄ変換器の入力が開放電位となり、中途半端にふらついた電位がＡ／Ｄ変換される。   When the wiring resistance lines 21 and 31 are disconnected, the input of the A / D converter in the temperature transmitters 30 and 40 for measuring the potential of the wiring resistance lines 21 and 31 becomes an open potential, and the potential fluctuates halfway. Are A / D converted.

従って、この電位をパラメータとして演算された温度値は全く信用のない値となってしまう。この開放電位のふらつきが大きなものであれば温度演算値が大幅に変化するので異常を検知出来る可能性があるが、開放電位は不定となるので温度演算値も不定となる。 Therefore, the temperature value calculated using this potential as a parameter is a value that is not reliable at all. If the fluctuation of the open-circuit potential is large, the temperature calculation value changes significantly, so that an abnormality can be detected. However, since the open-circuit potential is indefinite, the temperature calculation value is also undefined.

そこで、本発明は測温抵抗体を用いた温度計測において、配線抵抗線の断線を正確に検知出来るように改良し、温度計測の信頼性を向上させることを目的とする。   In view of the above, an object of the present invention is to improve the reliability of temperature measurement by improving the temperature measurement using a resistance temperature detector so that the disconnection of the wiring resistance wire can be accurately detected.

このような課題を達成するために、本発明のうち請求項１記載の発明は、
電源と主入力端子とセンサグラウンド端子と配線抵抗入力端子と演算処理手段を備え、
抵抗値Ｒｐｔを有する測温抵抗体の一方が配線抵抗Ｒ０を有する一方の計測配線を介して前記主入力端子に接続され、測温抵抗体の他方が配線抵抗Ｒ０を有する他方の計測配線を介して前記センサグラウンド端子に接続されると共に配線抵抗Ｒ０を有する配線抵抗線を介して前記配線抵抗入力端子に接続され、前記センサグラウンド端子は抵抗Ｒを介して共通電位点に接続され、
前記演算処理手段は、前記電源の電流Ｉが前記主入力端子に入力されて前記一方の計測配線と前記測温抵抗体と前記他方の計測配線と前記センサグラウンド端子と前記抵抗Ｒよりなる経路を経て前記共通電位点に流れることにより前記主入力端子に発生する主入力電圧Ｖ１と前記センサグラウンド端子に発生するセンサグラウンド電圧Ｖ０と前記配線抵抗入力端子に発生する配線抵抗電圧Ｖ２の測定値を取り込み、
Ｒｐｔ＝（Ｖ０＋Ｖ１−２Ｖ２）／Ｉ
の演算を行うことにより前記測温抵抗体の抵抗値Ｒｐｔを算出し、
Ｒ０＝（Ｖ２−Ｖ０）／Ｉ
の演算を行うことにより前記配線抵抗線の抵抗値Ｒ０を算出するように構成された温度伝送器において、
前記演算処理手段は、前記配線抵抗線の初期配線抵抗値Ｒ００を算出してメモリに格納した後、所定のタイミングで前記配線抵抗線の配線抵抗現在値ＲＸを算出して、
Ｒｄ＝ＲＸ−Ｒ００
の演算を行うことによりこれら初期配線抵抗値Ｒ００と現在配線抵抗値ＲＸとの差抵抗値Ｒｄを算出し、算出された差抵抗値Ｒｄが所定の設定閾値を超えたか否かにより前記配線抵抗線の断線検知を行うことを特徴とする。 In order to achieve such a problem, the invention according to claim 1 of the present invention is:
Power supply, main input terminal, sensor ground terminal, wiring resistance input terminal, and arithmetic processing means,
One of the resistance temperature detectors having a resistance value Rpt is connected to the main input terminal via one measurement wiring having a wiring resistance R0, and the other temperature measurement resistor is connected to the other measurement wiring having a wiring resistance R0. Connected to the sensor ground terminal and connected to the wiring resistance input terminal via a wiring resistance line having a wiring resistance R0, and the sensor ground terminal is connected to a common potential point via a resistor R,
The arithmetic processing means inputs a current I of the power source to the main input terminal, and makes a path formed by the one measurement wiring, the temperature measuring resistor, the other measurement wiring, the sensor ground terminal, and the resistance R. Then, the measured values of the main input voltage V1 generated at the main input terminal, the sensor ground voltage V0 generated at the sensor ground terminal, and the wiring resistance voltage V2 generated at the wiring resistance input terminal are captured by flowing to the common potential point. ,
Rpt = (V0 + V1-2V2) / I
By calculating the resistance value Rpt of the resistance temperature detector,
R0 = (V2-V0) / I
In the temperature transmitter configured to calculate the resistance value R0 of the wiring resistance line by performing the calculation of
The arithmetic processing means calculates an initial wiring resistance value R00 of the wiring resistance line and stores it in a memory, and then calculates a wiring resistance current value RX of the wiring resistance line at a predetermined timing,
Rd = RX-R00
By calculating the difference resistance value Rd between the initial wiring resistance value R00 and the current wiring resistance value RX, the wiring resistance line is determined depending on whether or not the calculated difference resistance value Rd exceeds a predetermined set threshold value. It is characterized by detecting disconnection.

請求項２記載の発明は、請求項１記載の発明において、
前記配線抵抗の現在値を読込む所定のタイミングは、一定値、または一定間隔、または入力手段からのユーザ設定値であることを特徴とする。 The invention according to claim 2 is the invention according to claim 1,
The predetermined timing for reading the current value of the wiring resistance is a fixed value, a fixed interval, or a user set value from an input means.

請求項３記載の発明は、請求項１記載の発明において、
前記差抵抗値Ｒｄが前記設定閾値を超えた場合に、前記配線抵抗線の断線、または断線に至る不具合を検知して警報することを特徴とする。 The invention according to claim 3 is the invention according to claim 1 ,
When the differential resistance value Rd exceeds the set threshold value, a disconnection of the wiring resistance line or a malfunction that leads to a disconnection is detected and an alarm is given.

請求項４記載の発明は、請求項１記載の発明において、
前記差抵抗値Ｒｄが前記設定閾値を超えた場合に、前記配線抵抗線の伝送構成を変更してバックアップするバックアップ手段を具備することを特徴とする。 The invention according to claim 4 is the invention according to claim 1 ,
When the differential resistance value Rd exceeds the set threshold value, backup means is provided for backing up by changing the transmission configuration of the wiring resistance line.

以上説明したことから明らかなように、本発明によれば次のような効果がある。
請求項１に記載した発明によれば、演算処理手段により測温抵抗体から２本の計測配線と共に配線抵抗線を介して入力された電圧信号を用いて先の配線抵抗線の断線検知をするようにしたので、この電圧信号の電圧変化を用いて断線検知をする場合だけでなく、この電圧信号を演算して断線検知をすることもでき、多様な形で配線抵抗線の断線検知をすることができ、温度計測の信頼性を向上させることができる。
さらに、配線抵抗線の配線抵抗の初期値と現在値との差抵抗値が設定閾値を超えたか否かにより断線検知を行うようにしたので、配線抵抗線の断線だけでなく、断線に至る経過も知ることができ、正確に断線検出が出来る効果がある。 As is apparent from the above description, the present invention has the following effects.
According to the first aspect of the invention, the disconnection of the previous wiring resistance line is detected by the arithmetic processing means using the voltage signal input from the resistance temperature detector through the wiring resistance line together with the two measurement wirings. As a result, it is possible not only to detect disconnection using the voltage change of this voltage signal, but also to detect disconnection by computing this voltage signal, and detect disconnection of wiring resistance lines in various forms. And the reliability of temperature measurement can be improved.
Furthermore, since the disconnection detection is performed based on whether the difference resistance value between the initial value and the current value of the wiring resistance line exceeds the set threshold, not only the disconnection of the wiring resistance line but also the process leading to the disconnection There is an effect that disconnection can be accurately detected.

請求項２に記載した発明によれば、配線抵抗の現在値の読込みタイミングを、一定値、または一定間隔、または入力手段からのユーザ設定値で行うようにしたので、断線の場合だけでなく定期的に診断することで配線抵抗が徐々に増加するような不具合について検知が可能になる効果がある。 According to the second aspect of the present invention, since the reading timing of the current value of the wiring resistance is performed at a constant value, a constant interval, or a user set value from the input means, not only in the case of disconnection, but also periodically By performing the diagnosis, it is possible to detect a malfunction in which the wiring resistance gradually increases.

また、測定した配線抵抗値を時系列で保存しそのトレンドをとることで抵抗値が次第に増加してきた等の断線予測をすることが出来る効果もある。さらに、入力手段によりユーザが読込みタイミングを任意に設定出来るので、現場の状況に応じて配線抵抗値を計測することが出来る。 In addition, there is an effect that it is possible to predict the disconnection such as the resistance value gradually increasing by storing the measured wiring resistance value in time series and taking the trend. Furthermore, since the user can arbitrarily set the read timing by the input means, the wiring resistance value can be measured according to the situation at the site.

請求項３に記載した発明によれば、差抵抗値が設定閾値を超えた場合に、配線抵抗線の断線、または断線に至る不具合を検知して外部に警報することにより、異常状態を外部に速やかに知らせることができ、早期のトラブル処理が可能になる。 According to the third aspect of the present invention, when the differential resistance value exceeds the set threshold value, an abnormal state can be externally detected by detecting a disconnection of the wiring resistance line or a failure leading to the disconnection. Notification can be made promptly and early troubleshooting can be performed.

請求項４に記載した発明によれば、バックアップ手段により、差抵抗値が設定閾値を超えた場合に、配線抵抗線の数を減らして精度の低下を最小限にしながらも温度計測を確保することができる効果がある。
According to the fourth aspect of the present invention, when the differential resistance value exceeds the set threshold value, the backup unit can ensure temperature measurement while reducing the number of wiring resistance lines and minimizing a decrease in accuracy. There is an effect that can.

以下、本発明について図面を用いて詳細に説明する。図２は本発明に係る温度伝送器の１実施例を示すブロック図である。図１はこの温度伝送器で演算実行する配線抵抗線の断線検知をする断線検知手段の手順を示すフローチャート図である。 Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of a temperature transmitter according to the present invention. FIG. 1 is a flow chart showing the procedure of a disconnection detecting means for detecting disconnection of a wiring resistance wire that is executed by the temperature transmitter.

先ず、図２を用いて本発明に係る温度伝送器４０の構成について説明する。ここでは、温度伝送器４０として３線式の場合の実施例を示している。なお、以下の説明においては、従来の温度伝送器に示す構成要素と同一の機能を持つ構成要素については同一の符号を付して適宜にその説明を省略する。 First, the structure of the temperature transmitter 40 according to the present invention will be described with reference to FIG. Here, an example in which the temperature transmitter 40 is a three-wire type is shown. In the following description, components having the same functions as those shown in the conventional temperature transmitter are denoted by the same reference numerals, and description thereof is omitted as appropriate.

温度伝送器４０の入力端側には、主入力端子１３、センサグラウンド端子１５、配線抵抗入力端子２２が設けられている。主入力端子１３は測温抵抗体１１の一端に計測配線１２で接続され、センサグラウンド端子１５は測温抵抗体１１の他端に計測配線１４で接続されている。さらに、配線抵抗入力端子２２は測温抵抗体１１の他端に配線抵抗線２１で接続されている。 On the input end side of the temperature transmitter 40, a main input terminal 13, a sensor ground terminal 15, and a wiring resistance input terminal 22 are provided. The main input terminal 13 is connected to one end of the resistance temperature detector 11 via a measurement wiring 12, and the sensor ground terminal 15 is connected to the other end of the resistance temperature detector 11 via a measurement wiring 14. Further, the wiring resistance input terminal 22 is connected to the other end of the resistance temperature detector 11 by a wiring resistance wire 21.

そして、測温抵抗体１１は抵抗値Ｒｐｔを、計測配線１２、１４，および配線抵抗線２１はいずれも等しい配線抵抗Ｒ０を有している。温度伝送器４０の電源ＶＤＤからは、電流Ｉが主入力端子１３、計測配線１２、測温抵抗体１１、計測配線１４、センサグラウンド端子１５、抵抗Ｒを順次に介して共通電位点ＣＯＭに流されている。 The resistance temperature detector 11 is the resistance value R pt, measurement lines 12, 14, and the wiring resistance wire 21 has a wire resistance R0 both equal. From the power supply VDD of the temperature transmitter 40, the current I flows to the common potential point COM through the main input terminal 13, the measurement wiring 12, the resistance temperature detector 11, the measurement wiring 14, the sensor ground terminal 15, and the resistance R sequentially. Has been.

その結果として、主入力端子１３には主入力電圧Ｖ１が、センサグラウンド端子１５にはセンサグラウンド電圧Ｖ０が、配線抵抗線２１には配線抵抗電圧Ｖ２が発生している。これらの主入力電圧Ｖ１、センサグラウンド電圧Ｖ０、および配線抵抗電圧Ｖ２は温度伝送器４０内のＡ／Ｄ変換器４１に入力され、ここでこれらの電圧はデジタルデータＤＤに変換される。 As a result, the main input voltage V1 is generated at the main input terminal 13, the sensor ground voltage V0 is generated at the sensor ground terminal 15, and the wiring resistance voltage V2 is generated at the wiring resistance line 21. These main input voltage V1, sensor ground voltage V0, and wiring resistance voltage V2 are input to an A / D converter 41 in the temperature transmitter 40, where these voltages are converted into digital data DD.

各電圧のデジタルデータＤＤは、演算処理手段４２に入力され、ここでＲＯＭ（Read-Only Memory）等のメモリ４３を用いながらＣＰＵ( Central Processing Unit )により温度演算、配線抵抗線の断線検知等の演算がなされる。さらに、キーボードなどの入力手段４６から入力されたデータも加味して断線検知等の演算処理がなされる。そして、これらの演算結果は温度出力４４、警報出力４５として外部に出力される。   The digital data DD of each voltage is input to the arithmetic processing means 42. Here, the CPU (Central Processing Unit) performs temperature calculation, detection of disconnection of the wiring resistance line, etc. using a memory 43 such as ROM (Read-Only Memory). An operation is performed. Further, calculation processing such as disconnection detection is performed in consideration of data input from the input means 46 such as a keyboard. These calculation results are output to the outside as a temperature output 44 and an alarm output 45.

次に、本発明が温度伝送器４０で演算実行する配線抵抗線の断線検知をする断線検知手段４７について図１に示すフローチャート図を用いてその手順を説明する。   Next, the procedure of the disconnection detecting means 47 for detecting disconnection of the wiring resistance wire, which is executed by the temperature transmitter 40 according to the present invention, will be described with reference to the flowchart shown in FIG.

ステップ１は、配線抵抗断線検知ＯＮとして、正常に配線抵抗線の断線検知が出来ると共に温度計測も行える初期状態にする。   Step 1 sets the wiring resistance disconnection detection ON to an initial state in which the disconnection of the wiring resistance line can be normally detected and the temperature can also be measured.

次に、ステップ２に移行して、配線抵抗値Ｒ０を測定して、配線抵抗の初期値Ｒ００を算出する。この後、ステップ３で測定した配線抵抗の初期値Ｒ００をメモリ４３に格納する。 Then control proceeds to step 2, by measuring the wiring resistance value R0, calculated by the wiring resistance of the initial value R 00. Thereafter, the initial value R 00 of the wiring resistance measured in step 3 is stored in the memory 43.

ステップ４では、温度計測を行なう。温度計測に当たっては、先ず、測温抵抗体１１の抵抗値Ｒｐｔの演算を、測温抵抗体１１に電流Ｉを流して生じる主入力電圧Ｖ１、センサグラウンド電圧Ｖ０、配線抵抗電圧Ｖ２を用いて下式（１）に基づいて行う。
Ｒｐｔ＝（Ｖ０＋Ｖ１−２Ｖ２）／Ｉ （１）
この後、温度伝送器４０に内蔵された国際規格等で定められた抵抗値−温度変換表に基づいて温度が演算され、ステップ５で温度出力４４として出力される。

In step 4, temperature measurement is performed. In the temperature measurement, first, the resistance value Rpt of the resistance temperature detector 11 is calculated using the main input voltage V1, the sensor ground voltage V0, and the wiring resistance voltage V2 generated by passing the current I through the resistance temperature detector 11. This is performed based on equation (1).
Rpt = (V0 + V1-2V2) / I (1)
Thereafter, the temperature is calculated based on a resistance value-temperature conversion table defined by an international standard or the like built in the temperature transmitter 40, and is output as a temperature output 44 in step 5.

この後、ステップ６に移行する。通常は、配線抵抗Ｒ０は抵抗値演算に現れないが、配線抵抗Ｒ０は下式（２）に基づいて測定される。
Ｒ０＝（Ｖ２−Ｖ０）／Ｉ （２） Thereafter, the process proceeds to step 6. Normally, the wiring resistance R0 does not appear in the resistance value calculation, but the wiring resistance R0 is measured based on the following equation (2).
R0 = (V2-V0) / I (2)

そこで、現在配線抵抗値ＲＸを（２）式に基づいて適当なタイミングで測定する。この配線抵抗の現在値の読込みタイミングは、例えば１時間などの一定値としても良いし、３０分毎等の一定間隔として定期的に行っても良いし、ユーザが入力手段４６で設定出来るようにしても良い。更に、入力手段４６によりユーザが読込みタイミングを設定する場合は、現場の状況に合わせて配線抵抗値を計測することが出来る。 Therefore, it measured at an appropriate timing based on the current wiring resistance R X (2) expression. The reading timing of the current value of the wiring resistance may be a constant value such as 1 hour, or may be periodically performed at regular intervals such as every 30 minutes, or may be set by the user through the input means 46. May be. Furthermore, when the user sets the read timing by the input means 46, the wiring resistance value can be measured according to the situation at the site.

次に、ステップ７に移行する。ステップ７では、初期配線抵抗値Ｒ００と現在の現在配線抵抗値ＲＸの差である差抵抗値Ｒｄ（＝ＲＸ−Ｒ００）を所定の演算プログラムにより演算処理手段４２が演算する。 Next, the process proceeds to step 7. In step 7, the arithmetic processing means 42 calculates a difference resistance value Rd (= R X −R 00 ), which is a difference between the initial wiring resistance value R 00 and the current current wiring resistance value R X , using a predetermined calculation program.

ステップ８では、差抵抗値Ｒｄが予め決められた設定閾値ＳＳを超えたかどうかの判断を所定の演算プログラムにより演算処理手段４２が判断する。差抵抗値Ｒｄが設定閾値ＳＳを超えた場合（Ｙｅｓ）は、ステップ９に移行して配線抵抗線が断線したものして断線検知を行いステップ１０で断線警報出力を出す。ステップ８で差抵抗値Ｒｄが設定閾値ＳＳを超えない場合（Ｎｏ）は、ステップ４に戻りステップ６〜８を繰り返す。 In step 8, the arithmetic processing means 42 determines whether or not the differential resistance value Rd has exceeded a predetermined threshold value SS by using a predetermined arithmetic program. When the differential resistance value Rd exceeds the set threshold value SS (Yes), the process proceeds to step 9 where the wiring resistance line is disconnected and disconnection is detected, and a disconnection alarm output is output at step 10. When the differential resistance value Rd does not exceed the set threshold value SS in step 8 (No), the process returns to step 4 and steps 6 to 8 are repeated.

この設定閾値ＳＳについては、例えば０．１℃の精度の場合は、４０ｍΩ程度の抵抗測定精度があるので、設定閾値ＳＳを１Ωとした場合は、配線抵抗値が１Ω以上に増加した場合に断線を検知することになる。 With regard to the set threshold SS, for example, when the accuracy is 0.1 ° C., there is a resistance measurement accuracy of about 40 mΩ. Therefore, when the set threshold SS is set to 1Ω, disconnection occurs when the wiring resistance value increases to 1Ω or more. Will be detected.

また、この設定閾値ＳＳは、例えば１Ω等の固定値としても良いし、ユーザが入力手段４４で設定出来るようにしても良い。ただし、配線材料は周囲温度により抵抗値が変化するので、長距離配線をする場合には配線材による配線抵抗値の変化を考慮する必要がある。   The setting threshold SS may be a fixed value such as 1Ω or may be set by the user using the input unit 44. However, since the resistance value of the wiring material varies depending on the ambient temperature, it is necessary to consider the variation of the wiring resistance value due to the wiring material when performing long distance wiring.

図１のフローチャート図に示す配線抵抗線の断線検知は、配線抵抗線の抵抗測定値の変化により検出するものであるが、これを配線抵抗電圧Ｖ２の変化に置き換えて検出させることも出来る。   The disconnection detection of the wiring resistance line shown in the flowchart of FIG. 1 is detected by a change in the resistance measurement value of the wiring resistance line, but it can be detected by replacing this with a change in the wiring resistance voltage V2.

また、断線の場合だけでなく、定期的に診断することにより配線抵抗が徐々に増加する不具合について検知が可能になる。この場合は、測定した配線抵抗値を時系列で保存しトレンドをとることで、抵抗値が次第に増えてきた等の検出が可能になる。   Further, not only in the case of disconnection, but also by detecting periodically, it is possible to detect a problem that the wiring resistance gradually increases. In this case, it is possible to detect that the resistance value has gradually increased by storing the measured wiring resistance value in time series and taking a trend.

図３は本発明の他の実施例の要部構成説明図であり、４線式の温度伝送器の例である。この場合の温度伝送器５０は、測温抵抗体１１と温度伝送器５０の間に配線切替回路５１が配置され、温度伝送器５０からの配線切替信号ＳＴにより配線抵抗線が断線を検知したときに配線抵抗線２１，３１が切り替えられる。   FIG. 3 is an explanatory view of the main part configuration of another embodiment of the present invention, and is an example of a four-wire temperature transmitter. In the temperature transmitter 50 in this case, when the wiring switching circuit 51 is disposed between the resistance temperature detector 11 and the temperature transmitter 50 and the wiring resistance wire detects the disconnection by the wiring switching signal ST from the temperature transmitter 50. The wiring resistance lines 21 and 31 are switched to each other.

このように４線式で配線抵抗線２１，３１が断線した場合は、３線式に切り替えて、バックアップ計測を行うことにより、温度計測の中断が防止でき、温度計測の信頼性が向上する。また、図示していないが、同様にして、３線式で配線抵抗線２１が断線した場合は、２線式に切り替えて同様にバックアップして温度計測の信頼性を向上させることができる。   Thus, when the wiring resistance lines 21 and 31 are disconnected in the 4-wire system, the temperature measurement can be prevented from being interrupted by switching to the 3-wire system and performing the backup measurement, and the reliability of the temperature measurement is improved. Although not shown in the figure, similarly, when the wiring resistance wire 21 is disconnected in a three-wire system, it is possible to improve the reliability of temperature measurement by switching to the two-wire system and backing up in the same manner.

本発明の断線検知手段の手順を示す要部フロ−チャート図である。It is a principal part flowchart which shows the procedure of the disconnection detection means of this invention. 本発明に係る温度伝送器の１実施例を示すブロック図である。It is a block diagram which shows one Example of the temperature transmitter which concerns on this invention. 本発明の他の実施例を示す構成図である。It is a block diagram which shows the other Example of this invention. 従来より一般に使用されている温度伝送器の構成説明図である。It is composition explanatory drawing of the temperature transmitter generally used conventionally. 従来より一般に使用されている温度伝送器の他の構成説明図である。It is another structure explanatory drawing of the temperature transmitter generally used conventionally. 従来より一般に使用されている温度伝送器の更に他の構成説明図である。It is further another structure explanatory drawing of the temperature transmitter generally used conventionally.

符号の説明Explanation of symbols

１０、２０、３０、４０ 温度変換器
１１ 測温抵抗体
１２、１４ 計測配線
１３ 主入力端子
１５ センサグランド端子
２１、３１ 配線抵抗線
２２、３２ 配線入力端子
４１ Ａ／Ｄ変換器
４２ 演算処理手段
４３ メモリ
４４ 温度出力
４５ 警報出力
４６ 入力手段
４７ 断線検知手段
Ｒ０ 配線抵抗
ＲＸ 現在配線抵抗値
Ｒ００ 初期配線抵抗値
Ｒｄ 差抵抗値
ＳＳ 設定閾値
Ｖ１ 主入力電圧
Ｖ２ 配線抵抗電圧
Ｖ０ センサグラウンド電圧

DESCRIPTION OF SYMBOLS 10, 20, 30, 40 Temperature converter 11 Resistance thermometer 12, 14 Measurement wiring 13 Main input terminal 15 Sensor ground terminal 21, 31 Wiring resistance wire 22, 32 Wiring input terminal 41 A / D converter 42 Arithmetic processing means 43 Memory 44 Temperature output 45 Alarm output 46 Input means 47 Disconnection detection means R0 Wiring resistance R X Current wiring resistance value R 00 Initial wiring resistance value Rd Differential resistance value SS Setting threshold V1 Main input voltage V2 Wiring resistance voltage V0 Sensor ground voltage

Claims (4)

電源と主入力端子とセンサグラウンド端子と配線抵抗入力端子と演算処理手段を備え、
抵抗値Ｒｐｔを有する測温抵抗体の一方が配線抵抗Ｒ０を有する一方の計測配線を介して前記主入力端子に接続され、測温抵抗体の他方が配線抵抗Ｒ０を有する他方の計測配線を介して前記センサグラウンド端子に接続されると共に配線抵抗Ｒ０を有する配線抵抗線を介して前記配線抵抗入力端子に接続され、前記センサグラウンド端子は抵抗Ｒを介して共通電位点に接続され、
前記演算処理手段は、前記電源の電流Ｉが前記主入力端子に入力されて前記一方の計測配線と前記測温抵抗体と前記他方の計測配線と前記センサグラウンド端子と前記抵抗Ｒよりなる経路を経て前記共通電位点に流れることにより前記主入力端子に発生する主入力電圧Ｖ１と前記センサグラウンド端子に発生するセンサグラウンド電圧Ｖ０と前記配線抵抗入力端子に発生する配線抵抗電圧Ｖ２の測定値を取り込み、
Ｒｐｔ＝（Ｖ０＋Ｖ１−２Ｖ２）／Ｉ
の演算を行うことにより前記測温抵抗体の抵抗値Ｒｐｔを算出し、
Ｒ０＝（Ｖ２−Ｖ０）／Ｉ
の演算を行うことにより前記配線抵抗線の抵抗値Ｒ０を算出するように構成された温度伝送器において、
前記演算処理手段は、前記配線抵抗線の初期配線抵抗値Ｒ００を算出してメモリに格納した後、所定のタイミングで前記配線抵抗線の配線抵抗現在値ＲＸを算出して、
Ｒｄ＝ＲＸ−Ｒ００
の演算を行うことによりこれら初期配線抵抗値Ｒ００と現在配線抵抗値ＲＸとの差抵抗値Ｒｄを算出し、算出された差抵抗値Ｒｄが所定の設定閾値を超えたか否かにより前記配線抵抗線の断線検知を行うことを特徴とする温度伝送器。 Power supply, main input terminal, sensor ground terminal, wiring resistance input terminal, and arithmetic processing means,
One of the resistance temperature detectors having a resistance value Rpt is connected to the main input terminal via one measurement wiring having a wiring resistance R0, and the other temperature measurement resistor is connected to the other measurement wiring having a wiring resistance R0. Connected to the sensor ground terminal and connected to the wiring resistance input terminal via a wiring resistance line having a wiring resistance R0, and the sensor ground terminal is connected to a common potential point via a resistor R,
The arithmetic processing means inputs a current I of the power source to the main input terminal, and makes a path formed by the one measurement wiring, the temperature measuring resistor, the other measurement wiring, the sensor ground terminal, and the resistance R. Then, the measured values of the main input voltage V1 generated at the main input terminal, the sensor ground voltage V0 generated at the sensor ground terminal, and the wiring resistance voltage V2 generated at the wiring resistance input terminal are captured by flowing to the common potential point. ,
Rpt = (V0 + V1-2V2) / I
By calculating the resistance value Rpt of the resistance temperature detector,
R0 = (V2-V0) / I
In the temperature transmitter configured to calculate the resistance value R0 of the wiring resistance line by performing the calculation of
The arithmetic processing means calculates an initial wiring resistance value R00 of the wiring resistance line and stores it in a memory, and then calculates a wiring resistance current value RX of the wiring resistance line at a predetermined timing,
Rd = RX-R00
By calculating the difference resistance value Rd between the initial wiring resistance value R00 and the current wiring resistance value RX, the wiring resistance line is determined depending on whether or not the calculated difference resistance value Rd exceeds a predetermined set threshold value. A temperature transmitter characterized by detecting disconnection. 前記配線抵抗の現在値を読込む所定のタイミングは、一定値、または一定間隔、または入力手段からのユーザ設定値であることを特徴とする請求項１に記載の温度伝送器。   2. The temperature transmitter according to claim 1, wherein the predetermined timing for reading the current value of the wiring resistance is a constant value, a constant interval, or a user set value from an input means. 前記差抵抗値Ｒｄが前記設定閾値を超えた場合に、前記配線抵抗線の断線、または断線に至る不具合を検知して警報することを特徴とする請求項１に記載の温度伝送器。   2. The temperature transmitter according to claim 1, wherein when the differential resistance value Rd exceeds the set threshold value, a disconnection of the wiring resistance line or a failure leading to the disconnection is detected and alarmed. 前記差抵抗値Ｒｄが前記設定閾値を超えた場合に、前記配線抵抗線の伝送構成を変更してバックアップするバックアップ手段を具備することを特徴とする請求項１に記載の温度伝送器。   The temperature transmitter according to claim 1, further comprising backup means for changing and backing up the transmission configuration of the wiring resistance line when the differential resistance value Rd exceeds the set threshold value.
JP2006060513A 2006-03-07 2006-03-07 Temperature transmitter Active JP4835207B2 (en)

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