JP2008191131A - Thermometric resistor measuring circuit - Google Patents
Thermometric resistor measuring circuit Download PDFInfo
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- JP2008191131A JP2008191131A JP2007028989A JP2007028989A JP2008191131A JP 2008191131 A JP2008191131 A JP 2008191131A JP 2007028989 A JP2007028989 A JP 2007028989A JP 2007028989 A JP2007028989 A JP 2007028989A JP 2008191131 A JP2008191131 A JP 2008191131A
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Abstract
Description
本発明は、測温抵抗体測定回路に関し、詳しくは、測温抵抗体のどの導線が断線したのかを的確に識別できるようにしたものである。 The present invention relates to a resistance temperature detector measurement circuit, and more specifically, it is possible to accurately identify which conductor of a resistance temperature detector is broken.
測温抵抗体は、抵抗体の温度変化による抵抗値の変化に基づいて測定対象の温度を電気的に測定するものであり、各種工場プラントや研究分野における温度センサとして広く用いられている。 A resistance temperature detector is for electrically measuring the temperature of a measurement object based on a change in resistance value due to a temperature change of the resistor, and is widely used as a temperature sensor in various plant plants and research fields.
図2は、従来の3線式測温抵抗体の使用例を示す回路図である。図2において、抵抗値RTを有する測温抵抗体1の一端には抵抗値rAを有する導線Aが接続され、他端には抵抗値rBを有する導線Bおよび抵抗値rbを有する導線bが接続されている。導線Aには一定の電流iを出力する定電流源2が接続され、導線bは抵抗値RSを有する基準抵抗体3を介して共通電位点に接続されている。また、測温抵抗体1の各導線A,B,bの端部は演算回路4に接続されている。なお、導線Aと導線bの抵抗値はrA=rbになるように選定されている。
FIG. 2 is a circuit diagram showing an example of use of a conventional three-wire resistance thermometer. In FIG. 2, a resistance wire RT having a resistance value rA is connected to one end of a resistance temperature detector 1 having a resistance value RT, and a conductor wire B having a resistance value rB and a conductor wire b having a resistance value rb are connected to the other end. Has been. The conducting wire A is connected to a constant
このような構成において、定電流源2の出力電流iは、rA→RT→rb→RSの経路で共通電位点に流れる。演算回路4は十分高い入力インピーダンスを有するものであり、測温抵抗体1の各導線A,B,bの端部電圧VA,VB,Vbを測定して測温抵抗体1の抵抗値RTを求めるために以下の演算を行う。
RT=(VA−2VB+Vb)*RS/Vb (1)
In such a configuration, the output current i of the constant
RT = (VA−2VB + Vb) * RS / Vb (1)
ところで、測温抵抗体1は、特許文献1の段落0014にも記載されているように、測定対象の高温雰囲気や常温から高温までの大きな温度サイクル環境に曝される結果、導線A,B,bや測温抵抗体1の本体が断線して温度測定結果が異常値を示したままになり、温度測定不能状態に陥ることがある。 By the way, as described in paragraph 0014 of Patent Document 1, the resistance temperature detector 1 is exposed to a high temperature atmosphere to be measured and a large temperature cycle environment from room temperature to high temperature. b or the body of the resistance temperature detector 1 may be disconnected, and the temperature measurement result may remain abnormal, and the temperature measurement may be disabled.
温度測定不能状態の発生は、測温抵抗体1の温度測定結果に基づいて連続プロセスの温度制御を行うシステムにおいては安定動作を阻害することになり、迅速に検出して異常状態の原因を把握し、対策を講じることが求められる。 Occurrence of a temperature measurement impossible state impedes stable operation in a system that performs temperature control of a continuous process based on the temperature measurement result of the resistance temperature detector 1, and quickly detects and grasps the cause of the abnormal state Therefore, it is necessary to take measures.
図2の回路構成によれば、導線Aが断線すると端部電圧VAが定電流源2側の電位に振り切れることから導線Aの断線検出は可能であり、導線bが断線すると端部電圧Vbが共通電位点側の電位に振り切れることから導線bの断線検出も可能である。
According to the circuit configuration of FIG. 2, when the conducting wire A is disconnected, the end voltage VA can be completely shifted to the potential on the constant
しかし、導線Bが断線すると、演算回路4の入力インピーダンスが十分高いことから端部電圧VBは不定になり、導線Bの断線を検出することは不可能である。導線Bの断線を検出するためには、図2の回路の他に、付加回路や演算処理が必要になる。 However, if the conducting wire B is disconnected, the input voltage of the arithmetic circuit 4 is sufficiently high, so that the end voltage VB becomes indefinite, and it is impossible to detect the disconnection of the conducting wire B. In order to detect disconnection of the conducting wire B, an additional circuit and arithmetic processing are required in addition to the circuit of FIG.
本発明は、このような従来の問題点に着目したものであり、その目的は、測温抵抗体の各導線の断線を個別に検出できる測温抵抗体測定回路を提供することにある。 The present invention pays attention to such a conventional problem, and an object thereof is to provide a resistance temperature detector measurement circuit capable of individually detecting disconnection of each conductor of the resistance temperature detector.
このような課題を達成するために、請求項1の発明は、
一端側に2本の導線b,Bが接続され他端側に1本の導線Aが接続された測温抵抗体と、導線bに接続された第1の定電流源と、導線Bに接続された第2の定電流源と、導線Aを共通電位点に接続する基準抵抗と、導線Aと基準抵抗との接続点の電圧を測定する電圧測定手段を備え、
前記第1の定電流源と第2の定電流源の出力電流が異なる値に設定され、前記電圧測定手段の電圧測定値の変化に基づき断線した導線が特定されることを特徴とする。
In order to achieve such a problem, the invention of claim 1
A resistance temperature detector having two conductors b and B connected to one end and a conductor A connected to the other end, a first constant current source connected to the conductor b, and a conductor B A second constant current source, a reference resistor for connecting the conductor A to the common potential point, and a voltage measuring means for measuring the voltage at the connection point of the conductor A and the reference resistor,
The output currents of the first constant current source and the second constant current source are set to different values, and the disconnected conductor is specified based on the change in the voltage measurement value of the voltage measurement means.
請求項2の発明は、請求項1記載の測温抵抗体測定回路において、
前記電圧測定手段の電圧測定値の変化に応じて選択的に駆動され、断線した導線を可視化表示するアラーム手段を有することを特徴とする。
The invention of
It has an alarm means which is selectively driven according to a change in the voltage measurement value of the voltage measuring means, and visualizes and displays the disconnected conductor.
これらにより、電圧測定値の変化から、測温抵抗体の断線した導線を特定できる。 Thus, the disconnected conductor of the resistance temperature detector can be identified from the change in the voltage measurement value.
以下、本発明について、図面を用いて説明する。図1は本発明に基づく実施の形態の具体例を示す回路図であり、図2と共通する部分には同一の符号を付けている。図1と図2の異なる点は、測温抵抗体RTが上下を反対にして演算回路4に接続され、導線bには一定の電流4iを出力する定電流源2が接続され、導線Bには一定の電流iを出力する定電流源5が接続され、導線Aは抵抗値RSを有する基準抵抗体3を介して共通電位点に接続されていることである。
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a specific example of an embodiment according to the present invention, and the same reference numerals are given to portions common to FIG. The difference between FIG. 1 and FIG. 2 is that the resistance temperature detector RT is connected upside down to the arithmetic circuit 4, the constant
図1において、定電流源2の出力電流4iはrb→RT→rA→RSの経路で共通電位点に流れ、定電流源5の出力電流iはrB→RT→rA→RSの経路で共通電位点に流れることから、RT→rA→RSの経路には4i+i=5iの電流が流れることになる。なお、導線Aと導線Bと導線bの抵抗値はrA=rB=rbになるように選定されている。
In FIG. 1, the output current 4i of the constant
十分高い入力インピーダンスを有する演算回路4は、測温抵抗体1の各導線A,B,bの端部電圧VA,VB,Vbを測定して測温抵抗体1の抵抗値RTを求めるために以下の演算を行う。
RT=−(VA−3VB+2Vb)*RS/VA (2)
The arithmetic circuit 4 having a sufficiently high input impedance measures the end voltages VA, VB, Vb of the conductors A, B, b of the resistance temperature detector 1 to obtain the resistance value RT of the resistance temperature detector 1. The following calculation is performed.
RT = − (VA−3VB + 2Vb) * RS / VA (2)
ここで、導線Aの端部電圧VAに着目する。各導線A,B,bが断線していない正常状態ではVA=5i*RSで表されるが、各導線A,B,bが個別に断線すると、それぞれの断線に応じて、
1)導線A断線時:VA=0
2)導線B断線時:VA=4i*RS
3)導線b断線時:VA=i*RS
のように変化する。
Here, attention is paid to the end voltage VA of the conducting wire A. In a normal state where each conductor A, B, b is not disconnected, it is represented by VA = 5i * RS. However, when each conductor A, B, b is disconnected individually, according to each disconnection,
1) When conductor A is disconnected: VA = 0
2) Conductor B is disconnected: VA = 4i * RS
3) Conductor b is disconnected: VA = i * RS
It changes as follows.
これらから明らかなように、導線Aの端部電圧VAを測定することによって、その電圧測定値の大きさの変化に基づいて、3本の導線A,B,bのうちいずれの導線が断線したかを的確に特定できる。 As is clear from these, by measuring the end voltage VA of the conductor A, any one of the three conductors A, B, and b was disconnected based on the change in the magnitude of the voltage measurement value. Can be accurately identified.
なお、演算回路4は、演算増幅器で構成してもよいし、測温抵抗体1の各導線A,B,bの端部電圧VA,VB,VbをA/D変換器でデジタル信号に変換した後、CPUで演算処理するようにしてもよい。 The arithmetic circuit 4 may be composed of an operational amplifier, or the end voltages VA, VB, Vb of the conductors A, B, b of the resistance temperature detector 1 are converted into digital signals by an A / D converter. After that, the CPU may perform arithmetic processing.
どの導線が断線したかを可視化表示したい場合には、例えば3本の導線に対応する3個のアラームランプを設けておき、導線Aの端部電圧VAの3段階の変化に応じて各導線に対応するアラームランプを選択的に点灯駆動させればよい。 In order to visualize which conductor has been disconnected, for example, three alarm lamps corresponding to the three conductors are provided, and each conductor is subjected to three stages of changes in the end voltage VA of the conductor A. The corresponding alarm lamp may be selectively turned on.
また、上記実施例では、定電流源2と定電流源5の各出力電流の比を4:1に設定する例を示したが、出力電流の比率はこれに限るものではなく、導線Aの端部電圧VAの変化に基づいて3本の導線A,B,bのうちいずれの導線が断線したかが識別できれば定電流源2と定電流源5の出力電流が等しくなければよい。
In the above-described embodiment, the example in which the ratio of the output currents of the constant
さらに、いずれかの導線が断線したか否かだけが検出できればよくて、断線した導線を特定する必要がない場合には、導線Aの端部電圧VAがVA<5i*RSになっているか否かだけを単純に比較判定するための所定の閾値を有する簡単なコンパレータを設ければよい。 Furthermore, it is only necessary to detect whether or not any one of the conductors is disconnected, and when it is not necessary to specify the disconnected conductor, the end voltage VA of the conductor A is VA <5i * RS. It is only necessary to provide a simple comparator having a predetermined threshold for simply comparing and determining whether or not.
以上説明したように、本発明によれば、測温抵抗体の各導線の断線を個別に検出できる測温抵抗体測定回路が実現でき、各種分野における温度測定に好適である。 As described above, according to the present invention, a resistance temperature detector measurement circuit capable of individually detecting disconnection of each lead wire of the resistance temperature detector can be realized, which is suitable for temperature measurement in various fields.
1 測温抵抗体
2 第1定電流源
3 基準抵抗体
4 演算回路
5 第2定電流源
DESCRIPTION OF SYMBOLS 1
Claims (2)
前記第1の定電流源と第2の定電流源の出力電流が異なる値に設定され、前記電圧測定手段の電圧測定値の変化に基づき断線した導線が特定されることを特徴とする測温抵抗体測定回路。 A resistance temperature detector having two conductors b and B connected to one end and one conductor A connected to the other end, a first constant current source connected to the conductor b, and a conductor B A second constant current source, a reference resistor for connecting the conductor A to the common potential point, and a voltage measuring means for measuring the voltage at the connection point of the conductor A and the reference resistor,
The temperature measurement is characterized in that the output currents of the first constant current source and the second constant current source are set to different values, and a broken wire is specified based on a change in a voltage measurement value of the voltage measuring means. Resistor measurement circuit.
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101074599B1 (en) * | 2008-12-31 | 2011-10-17 | 엘에스산전 주식회사 | Temperature Detector and Measurement Method Of The Same |
US20150198486A1 (en) * | 2014-01-16 | 2015-07-16 | Azbil Corporation | Temperature measuring system and temperature measuring instrument |
WO2016166901A1 (en) * | 2015-04-17 | 2016-10-20 | 三菱電機株式会社 | Temperature measurement device |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101074599B1 (en) * | 2008-12-31 | 2011-10-17 | 엘에스산전 주식회사 | Temperature Detector and Measurement Method Of The Same |
US20150198486A1 (en) * | 2014-01-16 | 2015-07-16 | Azbil Corporation | Temperature measuring system and temperature measuring instrument |
JP2015135238A (en) * | 2014-01-16 | 2015-07-27 | アズビル株式会社 | Temperature measurement system, and temperature measurement instrument |
US9683900B2 (en) * | 2014-01-16 | 2017-06-20 | Azbil Corporation | Temperature measuring system and temperature measuring instrument |
WO2016166901A1 (en) * | 2015-04-17 | 2016-10-20 | 三菱電機株式会社 | Temperature measurement device |
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