JP4209429B2

JP4209429B2 - Strain / temperature measurement method

Info

Publication number: JP4209429B2
Application number: JP2006064519A
Authority: JP
Inventors: 卓郎小澤
Original assignee: 株式会社東京測器研究所
Priority date: 2006-03-09
Filing date: 2006-03-09
Publication date: 2009-01-14
Anticipated expiration: 2026-03-09
Also published as: JP2007240378A

Description

本発明は、抵抗式ひずみゲージを使用してひずみ測定を行うと共に、リード線により構成した熱電対を用いて温度測定を行うひずみ・温度測定方法に関する。 The present invention relates to a strain / temperature measurement method in which strain measurement is performed using a resistance strain gauge and temperature measurement is performed using a thermocouple constituted by a lead wire.

従来、この種の測定手法としては、例えば特許文献１に記載されているものが知られている。 Conventionally, as this kind of measurement technique, for example, the one described in Patent Document 1 is known.

この測定手法を図２を参照して以下に説明する。測定対象物に貼着される抵抗式ひずみゲージ１００の一端に第１リード線１０１および第２リード線１０２の２本のリード線が接続され、他端には、第３リード線１０３および第４リード線１０４の２本リード線が接続されている。そして、抵抗式ひずみゲージ１００は、３個の固定抵抗値の抵抗体１０５，１０６，１０７を直列に接続してなる抵抗回路１０８に第１リード線１０１および第３リード線１０３を介して接続され、この接続により抵抗式ひずみゲージ１を一辺に有するブリッジ回路１０９（詳しくはホイートストンブリッジ回路）が構成される。なお、抵抗体１０５〜１０７の各抵抗値は、抵抗式ひずみゲージ１の無ひずみ状態での抵抗値（公称抵抗値）と同じである。また、図２中ｒ101〜ｒ104は、それぞれ第１〜第４リード線１０１〜１０４の抵抗値を示している。 This measurement technique will be described below with reference to FIG. Two lead wires of a first lead wire 101 and a second lead wire 102 are connected to one end of a resistance strain gauge 100 attached to the measurement object, and a third lead wire 103 and a fourth lead wire are connected to the other end. Two lead wires of the lead wire 104 are connected. The resistance strain gauge 100 is connected via a first lead wire 101 and a third lead wire 103 to a resistor circuit 108 formed by connecting three resistors 105, 106, 107 having fixed resistance values in series. By this connection, a bridge circuit 109 (specifically, a Wheatstone bridge circuit) having the resistive strain gauge 1 on one side is configured. The resistance values of the resistors 105 to 107 are the same as the resistance values (nominal resistance values) of the resistance strain gauge 1 in the unstrained state. Further, r101 to r104 in FIG. 2 indicate resistance values of the first to fourth lead wires 101 to 104, respectively.

このブリッジ回路１０９は、第３リード線１０３と抵抗回路１０８との接続部であるＡ点と、このＡ点に対してブリッジ回路１０９の対角点となるＣ点（抵抗体１０６と抵抗体１０７との接続部）とを一対の入力部とし、これらの入力部の間にブリッジ電源電圧Ｅが印加される。また、第１および第２リード線１０１，１０２が接続されたひずみゲージ１００の一端と、この一端に対してブリッジ回路１０９の対角点となるＤ点（抵抗体１０５と抵抗体１０６との接続部）とを一対の出力部とし、そららの出力部の間の電位差ｅがブリッジ回路１０９の出力電圧として計測される。この場合、出力電圧ｅの計測に際しては、ひずみゲージ１００の一端の電位は、前記第２リード線１０２を介して抽出される。すなわち、１ゲージ３線法に従って、第２リード線１０２を用いて出力電圧ｅが計測される。この出力電圧ｅは、ひずみゲージ１００の抵抗値変化に応じて変化するので、該出力電圧ｅを基に、ひずみゲージ１００のひずみ（ひずみゲージ１を貼着する測定対象物のひずみ）が測定される。 The bridge circuit 109 includes a point A which is a connection portion between the third lead wire 103 and the resistor circuit 108, and a point C (the resistor 106 and the resistor 107 which is a diagonal point of the bridge circuit 109 with respect to the point A. Are connected to each other), and a bridge power supply voltage E is applied between these input portions. Further, one end of the strain gauge 100 to which the first and second lead wires 101 and 102 are connected, and a point D (a connection between the resistor 105 and the resistor 106) that is a diagonal point of the bridge circuit 109 with respect to the one end. A pair of output units, and a potential difference e between the output units is measured as an output voltage of the bridge circuit 109. In this case, when measuring the output voltage e, the potential at one end of the strain gauge 100 is extracted via the second lead wire 102. That is, the output voltage e is measured using the second lead wire 102 in accordance with the 1-gauge 3-wire method. Since this output voltage e changes according to the change in the resistance value of the strain gauge 100, the strain of the strain gauge 100 (the strain of the measurement object to which the strain gauge 1 is attached) is measured based on the output voltage e. The

一方、ひずみ測定に使用する前記第１〜第３リード線１０１〜１０３は、その材質（導線の材質）は同じであり、例えば銅である。また、第４リード線１０４の材質は、第１〜第３リード線１０１〜１０３と異なり、例えば、コンスタンタンである。この場合、第３リード線１０３と第４リード線１０４とにより、ひずみゲージ１００の他端を接点とする熱電対１１０が構成される。この熱電対１１０の出力電圧ｅt、すなわち、第３リード線１０３の先端（抵抗回路１０８側の端部）と、第４リード線１０４の先端（ひずみゲージ１と反対側の端部）との間の電位差ｅtが熱電対１１０の温度に応じた電圧となるので、該出力電圧ｅtが計測され、その計測された出力電圧ｅtを基に、熱電対１１０の温度、すなわち、ひずみ測定環境の温度が測定される。 On the other hand, the first to third lead wires 101 to 103 used for strain measurement have the same material (material of the conductive wire), for example, copper. The material of the fourth lead wire 104 is different from the first to third lead wires 101 to 103, for example, constantan. In this case, the third lead wire 103 and the fourth lead wire 104 constitute a thermocouple 110 having the other end of the strain gauge 100 as a contact. The output voltage et of the thermocouple 110, that is, between the tip of the third lead wire 103 (end on the resistance circuit 108 side) and the tip of the fourth lead wire 104 (end on the side opposite to the strain gauge 1). Is the voltage corresponding to the temperature of the thermocouple 110, the output voltage et is measured, and the temperature of the thermocouple 110, that is, the temperature of the strain measurement environment is determined based on the measured output voltage et. Measured.

このような測定手法によれば、ひずみ測定と、それに影響を及ぼす環境温度の測定とを同時に行なうことが可能となり、ブリッジ回路１０９の出力電圧ｅに基づくひずみ測定値を温度測定に応じて補正する（温度に応じたひずみゲージ１００の見かけひずみを補償する）などの処理を行なうことが可能となる。
実用新案登録第３０４６９７０号 According to such a measurement technique, it is possible to simultaneously perform strain measurement and measurement of the environmental temperature affecting the strain measurement, and correct the strain measurement value based on the output voltage e of the bridge circuit 109 according to the temperature measurement. It is possible to perform processing such as (compensates for the apparent strain of the strain gauge 100 according to temperature).
Utility model registration No. 3046970

前記特許文献１に見られる技術では、熱電対１１０を構成する第３および第４リード線１０３，１０４のうちの第３リード線１０３は、ブリッジ回路１０９に組み込まれているので、該ブリッジ回路１０９にブリッジ電源電圧Ｅを印加した状態で、第３リード線１０３に電流が流れ、その電流と第３リード線１０３の抵抗値ｒ103とに応じた電圧が該第３リード線１０３に発生する。そして、その電圧は、第３リード線１０３の長さやひずみゲージ１００の抵抗値変化などに応じて変化する。このため、熱電対１１０の出力電圧ｅtは、熱電対１１０の温度だけに依するものではなく、ひずみゲージ１００の抵抗値変化などの影響を受ける。従って、熱電対１１０の出力電圧ｅtから把握される温度に誤差が生じ、特にその誤差は、第１〜第４リード線１０１〜１０４の長さが長い場合に大きなものとなるという不都合があった。 In the technique found in Patent Document 1, the third lead wire 103 of the third and fourth lead wires 103 and 104 constituting the thermocouple 110 is incorporated in the bridge circuit 109. In the state where the bridge power supply voltage E is applied, a current flows through the third lead wire 103, and a voltage corresponding to the current and the resistance value r 103 of the third lead wire 103 is generated at the third lead wire 103. The voltage changes according to the length of the third lead wire 103, the resistance value change of the strain gauge 100, and the like. For this reason, the output voltage et of the thermocouple 110 does not depend only on the temperature of the thermocouple 110 but is affected by a change in the resistance value of the strain gauge 100 and the like. Therefore, there is an inconvenience that an error occurs in the temperature obtained from the output voltage et of the thermocouple 110, and that the error becomes particularly large when the first to fourth lead wires 101 to 104 are long. .

本発明はかかる背景に鑑み、ひずみ測定を行いつつ高精度の温度測定を可能とするひずみ・温度測定方法を提供することを目的とする。 In view of this background, an object of the present invention is to provide a strain / temperature measurement method that enables highly accurate temperature measurement while performing strain measurement.

かかる目的を達成するために、本発明のひずみ測定方法は、一端に、同一材質から成る第１リード線および第２リード線が接続されると共に、他端に、該第１および第２リード線と同一材質から成る第３リード線と、該第１〜第３リード線とは異なる材質から成り、該第３リード線と共に熱電対を構成する第４リード線とが接続された抵抗式ひずみゲージを用い、固定抵抗値の複数の抵抗体から成る抵抗回路に前記第１リード線および第３リード線を介して前記抵抗式ひずみゲージを接続することにより該抵抗式ひずみゲージを一辺に有するブリッジ回路を構成し、このブリッジ回路にブリッジ電源電圧を印加しつつ、該ブリッジ回路の出力電圧を１ゲージ３線法に従って前記第２リード線を用いて抽出すると共に、前記熱電対の出力電圧を前記第３リード線および第４リード線を介して抽出し、前記抽出したブリッジ回路の出力電圧を基に前記抵抗式ひずみゲージに生じるひずみを測定すると共に、前記抽出した熱電対の出力電圧を基に該熱電対の温度を測定するようにしたひずみ・温度測定方法において、前記ブリッジ回路にブリッジ電源電圧を印加した状態で前記第１リード線に生じる電圧を該第１リード線の前記抵抗回路への接続部と前記第２リード線とを介して抽出し、その抽出した第１リード線の発生電圧と前記抽出した熱電対の出力電圧との差に基づいて該熱電対の温度を測定するようにしたことを特徴とする。 In order to achieve this object, the strain measuring method of the present invention has a first lead wire and a second lead wire made of the same material connected to one end, and the first and second lead wires connected to the other end. A resistance strain gage in which a third lead wire made of the same material as that of the first lead wire and a fourth lead wire constituting a thermocouple together with the third lead wire are connected to the third lead wire. And connecting the resistance strain gauge through the first lead wire and the third lead wire to a resistance circuit composed of a plurality of resistors having a fixed resistance value, and having the resistance strain gauge on one side The bridge power supply voltage is applied to the bridge circuit, and the output voltage of the bridge circuit is extracted using the second lead wire according to the 1-gauge 3-wire method, and the output voltage of the thermocouple is Extracted via the third lead wire and the fourth lead wire, and measured strain generated in the resistance strain gauge based on the output voltage of the extracted bridge circuit, and based on the output voltage of the extracted thermocouple In the strain / temperature measurement method in which the temperature of the thermocouple is measured, a voltage generated in the first lead wire in a state where a bridge power supply voltage is applied to the bridge circuit is supplied to the resistance circuit of the first lead wire. And the temperature of the thermocouple is measured based on the difference between the extracted voltage of the first lead wire and the extracted output voltage of the thermocouple. It is characterized by that.

前記第１〜第４リード線の長さは、一般に、ほぼ同じ長さとされ、また、第１〜第３リード線の材質は、同一であるので、第１リード線の抵抗値と第３リード線の抵抗値とは、常にほぼ等しい値になる。そして、１ゲージ３線法では、ブリッジ回路のブリッジ電源電圧に対して、第１リード線および第３リード線は直列に接続されることとなるので、第１リード線と第３リード線とにそれぞれ流れる電流も等しい。従って、ブリッジ回路にブリッジ電源電圧を付与した状態で第１リード線に生じる電圧と第３リード線に生じる電圧とはほぼ等しくなる。さらに、１ゲージ３線法では、第１リード線の抵抗式ひずみゲージ側の端部の電位は、前記第２リード線を介して抽出でき、第１リード線の抵抗回路側の端部の電位は、該抵抗回路と第１リード線との接続部から抽出できる。従って、その接続部と前記第２リード線とを介して第１リード線に生じる電圧を抽出できる。なお、その抽出には、高入力インピーダンスの増幅器やバッファを使用すればよい。 In general, the first to fourth lead wires have substantially the same length, and the first to third lead wires are made of the same material. Therefore, the resistance value of the first lead wire and the third lead wire are the same. The resistance value of the wire is always almost equal. In the 1-gauge 3-wire method, the first lead wire and the third lead wire are connected in series with respect to the bridge power supply voltage of the bridge circuit, so that the first lead wire and the third lead wire are connected to each other. The currents flowing through each are the same. Therefore, the voltage generated in the first lead wire and the voltage generated in the third lead wire in a state where the bridge power supply voltage is applied to the bridge circuit are substantially equal. Furthermore, in the 1-gauge 3-wire method, the potential at the end of the first lead wire on the resistance strain gauge side can be extracted via the second lead wire, and the potential at the end of the first lead wire on the resistance circuit side. Can be extracted from the connection between the resistor circuit and the first lead wire. Therefore, it is possible to extract a voltage generated in the first lead wire through the connection portion and the second lead wire. For the extraction, a high input impedance amplifier or buffer may be used.

そこで、本発明のひずみ・温度測定方法では、前記第１リード線に生じる電圧を該第１リード線の前記抵抗回路への接続部と前記第２リード線とを介して抽出し、その抽出した第１リード線の電圧と前記抽出した熱電対の出力電圧との差に基づいて該熱電対の温度を測定するようにした。この場合、抽出される第１リード線の発生電圧は、前記第３リード線の発生電圧とほぼ等しいので、この発生電圧と熱電対との差の電圧は、熱電対の出力電圧から、第３リード線に流れる電流と該第３リード線の抵抗値とに応じて該第３リード線に発生する電圧を除去したものに相当する。従って、当該差の電圧に基づいて熱電対の温度を測定することで、該熱電対の温度を精度よく測定することができることとなる。 Therefore, in the strain / temperature measurement method of the present invention, the voltage generated in the first lead wire is extracted via the connection portion of the first lead wire to the resistance circuit and the second lead wire, and the extraction is performed. The temperature of the thermocouple was measured based on the difference between the voltage of the first lead wire and the output voltage of the extracted thermocouple. In this case, since the generated voltage of the extracted first lead wire is substantially equal to the generated voltage of the third lead wire, the difference voltage between the generated voltage and the thermocouple is calculated from the output voltage of the thermocouple as the third voltage. This corresponds to a voltage obtained by removing the voltage generated in the third lead wire in accordance with the current flowing in the lead wire and the resistance value of the third lead wire. Therefore, by measuring the temperature of the thermocouple based on the difference voltage, the temperature of the thermocouple can be accurately measured.

よって、本発明のひずみ・温度測定手法によれば、ひずみ測定を行いつつ高精度の温度測定を可能なる。 Therefore, according to the strain / temperature measurement method of the present invention, it is possible to perform temperature measurement with high accuracy while performing strain measurement.

本発明の一実施形態を図１を参照して説明する。図１は本発明を適用した測定系の要部構成を示す回路図である。 An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing a main configuration of a measurement system to which the present invention is applied.

図１を参照して、１はひずみを測定しようとする測定対象物（図示せず）に接着剤などを介して貼着される抵抗式ひずみゲージ（以下、単にひずみゲージという）、２はひずみゲージ１を接続する測定器である。 Referring to FIG. 1, reference numeral 1 is a resistance strain gauge (hereinafter simply referred to as a strain gauge) attached to an object to be measured (not shown) via an adhesive or the like, and 2 is a strain. A measuring instrument to which the gauge 1 is connected.

ひずみゲージ１の一端には、第１リード線１１および第２リード線１２が接続され、他端には、第３リード線１３および第４リード線１４が接続されている。そして、第１〜第４リード線１１〜１４は、それぞれ測定器２に設けられた接続端子２１，２２，２３，２４に接続される。 The first lead wire 11 and the second lead wire 12 are connected to one end of the strain gauge 1, and the third lead wire 13 and the fourth lead wire 14 are connected to the other end. The first to fourth lead wires 11 to 14 are connected to connection terminals 21, 22, 23, and 24 provided in the measuring instrument 2, respectively.

第１〜第４リード線１１〜１４は、ほぼ同じ長さである。また、第１〜第４リード線１１〜１４のうちの第１〜第３リード線１１〜１３は、その導線の径および材質がいずれも同一である。従って、第１〜第３リード線１１〜１３のそれぞれの抵抗値ｒ11，ｒ12，ｒ13は互いにほぼ同一である。なお、第１〜第３リード線１１〜１３の材質は例えば銅である。 The first to fourth lead wires 11 to 14 have substantially the same length. In addition, the first to third lead wires 11 to 13 of the first to fourth lead wires 11 to 14 have the same diameter and material. Accordingly, the resistance values r11, r12, r13 of the first to third lead wires 11-13 are substantially the same. The material of the first to third lead wires 11 to 13 is, for example, copper.

一方、第４リード１４はその導線の材質が第１〜第３リード線１１〜１３と相違しており、その材質は、例えばコンスタンタンである。従って、第４リード線１４と第３リード線１３とにより、ひずみゲージ１の他端を接点とする熱電対１５が構成されている。なお、第４リード線１４の導線の径は、第１〜第３リード線１１〜１３の径と同じでもよいが、異なっていてもよい。また、第４リード線１４の抵抗値ｒ14は、第１〜第３リード線１１〜１３のそれぞれの抵抗値ｒ11，ｒ12，ｒ13と同じでもよいが、異なっていてもよい。 On the other hand, the material of the lead wire of the fourth lead 14 is different from that of the first to third lead wires 11 to 13, and the material thereof is, for example, constantan. Accordingly, the fourth lead wire 14 and the third lead wire 13 constitute a thermocouple 15 having the other end of the strain gauge 1 as a contact. In addition, although the diameter of the conducting wire of the 4th lead wire 14 may be the same as the diameter of the 1st-3rd lead wires 11-13, it may differ. The resistance value r14 of the fourth lead wire 14 may be the same as or different from the respective resistance values r11, r12, r13 of the first to third lead wires 11-13.

測定器２には、３個の固定抵抗値の抵抗体２５，２６，２７を直列に接続してなる抵抗回路２８（抵抗体２５〜２７の直列回路）と、ブリッジ電源２９と、増幅器３０と、差動増幅器３１とが設けられている。 The measuring device 2 includes a resistor circuit 28 (series circuit of resistors 25 to 27) formed by connecting three resistors 25, 26, and 27 having fixed resistance values in series, a bridge power supply 29, an amplifier 30, and the like. The differential amplifier 31 is provided.

抵抗回路２８は、その両端がそれぞれ接続端子２１，２３に同電位に導通されており、これらの接続端子２１，２３に前記第１リード線１１および第３リード線１３を接続することで、ひずみゲージ１を１辺に有するブリッジ回路３２が構成されるようになっている。なお、抵抗回路２８の各抵抗体２５，２６，２７の抵抗値は、いずれもひずみゲージ１の無ひずみ状態での抵抗値（ひずみゲージ１の公称抵抗値）と同じである。各抵抗体２５〜２７としては、固定抵抗値の通常の抵抗素子を使用すればよいが、ひずみゲージ１と同じ特性のひずみゲージを使用してもよい。補足すると、ブリッジ回路３２の各辺（ひずみゲージ１を含む辺以外の辺）の固定抵抗値が複数の抵抗体の合成抵抗値になるように、より多くの抵抗体を組み合わせて抵抗回路２８を構成するようにしてもよい。 Both ends of the resistance circuit 28 are electrically connected to the connection terminals 21 and 23 at the same potential. By connecting the first lead wire 11 and the third lead wire 13 to the connection terminals 21 and 23, the resistance circuit 28 is strained. A bridge circuit 32 having the gauge 1 on one side is configured. The resistance values of the resistors 25, 26, and 27 of the resistance circuit 28 are all the same as the resistance value of the strain gauge 1 in the unstrained state (the nominal resistance value of the strain gauge 1). As each of the resistors 25 to 27, a normal resistance element having a fixed resistance value may be used, but a strain gauge having the same characteristics as the strain gauge 1 may be used. Supplementally, the resistor circuit 28 is configured by combining more resistors so that the fixed resistance value of each side of the bridge circuit 32 (side other than the side including the strain gauge 1) becomes the combined resistance value of the plurality of resistors. You may make it comprise.

ブリッジ電源２９は、ブリッジ回路３２の電源電圧として、一定のブリッジ電源電圧Ｅを出力するものである。この場合、第３リード線１３と抵抗回路２８の抵抗体２７との接続部であるＡ点（接続端子２３と同電位部分）と、抵抗体２５および抵抗体２６の接続部であるＣ点とがブリッジ回路３２の一対の電源入力部であるので、これらの電源入力部Ａ，Ｃに導体ライン３３ａ，３３ｂを介して接続されている。 The bridge power supply 29 outputs a constant bridge power supply voltage E as the power supply voltage of the bridge circuit 32. In this case, a point A that is a connection portion between the third lead wire 13 and the resistor 27 of the resistor circuit 28 (a portion having the same potential as the connection terminal 23), and a point C that is a connection portion between the resistor 25 and the resistor 26 Is a pair of power input portions of the bridge circuit 32, and is connected to these power input portions A and C via conductor lines 33a and 33b.

増幅器３０は、ブリッジ回路の出力電圧ｅを増幅して出力するものである。ここで、１ゲージ３線法のひずみ測定では、第１および第２リード線１１，１２が接続されたひずみゲージ１の一端と、抵抗体２６と抵抗体２７との接続部であるＤ点との間の電位差がブリッジ回路３２の検出すべき出力電圧ｅである。このため、増幅器３０は、その入力側が、ブリッジ回路３２のＤ点と第２リード線１２を接続する接続端子２２とにそれぞれ導体ライン３４ａ，３４ｂを介して接続されている。この場合、増幅器３０は、高入力インピーダンスのものであるため、ひずみゲージ１の一端およびブリッジ回路３２のＤ点と、増幅器３０の入力側との間に流れる電流は極めて微小である。従って、増幅器３０の入力側をＤ点と接続端子２２とに接続することで、ブリッジ回路３２に流れる電流に実質的な影響を及ぼすことなく、増幅器３０の入力側にひずみゲージ１の一端の電位が第２リード線１２を介して入力されると共に、ブリッジ回路３２のＤ点の電位が入力される。これにより、ブリッジ回路３２の検出すべき出力電圧ｅが適切に抽出されて増幅器３０に入力され、該出力電圧ｅに比例した電圧が増幅器３０から出力される。 The amplifier 30 amplifies and outputs the output voltage e of the bridge circuit. Here, in the strain measurement of the 1-gauge 3-wire method, one end of the strain gauge 1 to which the first and second lead wires 11 and 12 are connected, and a point D which is a connection portion between the resistor 26 and the resistor 27, Is the output voltage e to be detected by the bridge circuit 32. Therefore, the input side of the amplifier 30 is connected to the connection point 22 connecting the point D of the bridge circuit 32 and the second lead wire 12 via conductor lines 34a and 34b, respectively. In this case, since the amplifier 30 has a high input impedance, the current flowing between one end of the strain gauge 1 and the point D of the bridge circuit 32 and the input side of the amplifier 30 is extremely small. Therefore, by connecting the input side of the amplifier 30 to the point D and the connection terminal 22, the potential of one end of the strain gauge 1 on the input side of the amplifier 30 without substantially affecting the current flowing through the bridge circuit 32. Is input via the second lead wire 12 and the potential at the point D of the bridge circuit 32 is input. As a result, the output voltage e to be detected by the bridge circuit 32 is appropriately extracted and input to the amplifier 30, and a voltage proportional to the output voltage e is output from the amplifier 30.

差動増幅器３１は、熱電対１５の出力電圧ｅtと、第１リード線１１の発生電圧ｅrとを入力として、それらの差（ｅt−ｅr）の電圧を増幅して出力するものである。ここで、熱電対１５の出力電圧ｅtは、第３リード線１３の先端（接続端子２３への接続端）と、第４リード線１４の先端（接続端子２４への接続端）との間の電位差であるので、接続端子２３，２４がそれぞれ導体ライン３５ａ，３５ｂを介して差動増幅器３１の入力側に接続されている。また、第１リード線１１の発生電圧ｅrは、第１リード線１１の先端（接続端子２１との接続端）と、第１リード線１１の基端（ひずみゲージ１との接続端）との間の電位差であるので、第１リード線１１の基端に第２リード線１２を介して接続される接続端子２２と、第１リード線１１の先端を接続する接続端子２１とがそれぞれ導体ライン３６ａ，３６ｂを介して差動増幅器３１の入力側に接続されている。この場合、差動増幅器３１は、高入力インピーダンスのものであるため、接続端子２３，２４と差動増幅器３１の入力側との間に流れる電流、並びに、ひずみゲージ１の一端（第２リード線１２のひずみゲージ１への接続端）と接続端子２１（第１リード線１１の先端）と差動増幅器との間で流れる電流は極めて微小である。従って、差動増幅器３１の入力側を上記のように接続端子２１〜２４に接続することで、ブリッジ回路３２に流れる電流に実質的な影響を及ぼすことなく、第３リード線１３および第４リード線１４のそれぞれの先端の電位が差動増幅器３１に入力されると共に、第１リード線１１の先端および基端のそれぞれの電位が差動増幅器３１に入力される。これにより、熱電対１５の出力電圧ｅtと、第１リード線１１の発生電圧ｅrとが適切に抽出されて差動増幅器３１に入力され、それらの差分の電圧（ｅt−ｅr）に比例する電圧が差動増幅器３１から出力される。 The differential amplifier 31 receives the output voltage et of the thermocouple 15 and the generated voltage er of the first lead wire 11 and amplifies and outputs the difference voltage (et−er). Here, the output voltage et of the thermocouple 15 is between the tip of the third lead wire 13 (connection end to the connection terminal 23) and the tip of the fourth lead wire 14 (connection end to the connection terminal 24). Because of the potential difference, the connection terminals 23 and 24 are connected to the input side of the differential amplifier 31 via conductor lines 35a and 35b, respectively. The generated voltage er of the first lead wire 11 is the difference between the tip of the first lead wire 11 (connection end with the connection terminal 21) and the base end of the first lead wire 11 (connection end with the strain gauge 1). Therefore, the connection terminal 22 connected to the base end of the first lead wire 11 via the second lead wire 12 and the connection terminal 21 connecting the tip end of the first lead wire 11 are respectively conductor lines. The differential amplifier 31 is connected to the input side via 36a and 36b. In this case, since the differential amplifier 31 has a high input impedance, the current flowing between the connection terminals 23 and 24 and the input side of the differential amplifier 31 and one end of the strain gauge 1 (second lead wire) No. 12 connecting end to the strain gauge 1), the connecting terminal 21 (tip of the first lead wire 11), and the current flowing between the differential amplifier are extremely small. Therefore, by connecting the input side of the differential amplifier 31 to the connection terminals 21 to 24 as described above, the third lead wire 13 and the fourth lead are not substantially affected on the current flowing in the bridge circuit 32. The potential at each distal end of the line 14 is input to the differential amplifier 31, and the potential at each distal end and proximal end of the first lead wire 11 is input to the differential amplifier 31. As a result, the output voltage et of the thermocouple 15 and the generated voltage er of the first lead wire 11 are appropriately extracted and input to the differential amplifier 31, and the voltage proportional to the difference voltage (et-er) between them. Is output from the differential amplifier 31.

なお、増幅器３０および差動増幅器３１の出力は、ひずみ測定値や温度測定値を求める処理を実行する演算処理部（図示しない）などに入力される。 The outputs of the amplifier 30 and the differential amplifier 31 are input to an arithmetic processing unit (not shown) that executes processing for obtaining a strain measurement value and a temperature measurement value.

次にかかる測定系の作動を説明する。ひずみゲージ１を測定対象物に貼着し、前記リード線１１〜１４をそれぞれ測定器２の接続端子２１〜２４に接続した状態で、ブリッジ電源２９を起動する。これにより、ブリッジ電源２９からブリッジ電源電圧Ｅがブリッジ回路３２の入力部Ａ，Ｃの間に印加され、ブリッジ回路３２（第１および第３リード線１１，１３を含む）に電流が流れる。 Next, the operation of the measurement system will be described. The bridge power supply 29 is activated in a state where the strain gauge 1 is attached to the measurement object and the lead wires 11 to 14 are connected to the connection terminals 21 to 24 of the measuring instrument 2, respectively. Thereby, the bridge power supply voltage E is applied from the bridge power supply 29 between the input parts A and C of the bridge circuit 32, and a current flows through the bridge circuit 32 (including the first and third lead wires 11 and 13).

このとき、ブリッジ回路３２の出力電圧ｅは、ひずみゲージ１のひずみ（ひずみゲージ１を貼着した測定対象物のひずみ）に応じた値となり、その出力電圧ｅが前記したように増幅器３０に入力されて増幅され、該出力電圧ｅに比例した電圧が増幅器３０から出力される。 At this time, the output voltage e of the bridge circuit 32 becomes a value corresponding to the strain of the strain gauge 1 (the strain of the measurement object attached with the strain gauge 1), and the output voltage e is input to the amplifier 30 as described above. The amplifier 30 amplifies and outputs a voltage proportional to the output voltage e from the amplifier 30.

また、差動増幅器３１には、前記したように熱電対１５の出力電圧ｅtと第１リード線１１の発生電圧ｅrとが入力され、それらの差分の電圧（ｅt−ｅr）に比例した電圧が作動増幅器３１から出力される。ここで、熱電対１５の出力電圧ｅtには、該熱電対１５の温度に起因する電圧成分だけでなく、ブリッジ回路３２に含まれる第３リード線１３に流れる電流に起因して該第３リード線１３に発生する電圧成分も含まれる。 Further, as described above, the output voltage et of the thermocouple 15 and the generated voltage er of the first lead wire 11 are input to the differential amplifier 31, and a voltage proportional to the difference voltage (et−er) is obtained. Output from the operational amplifier 31. Here, the output voltage et of the thermocouple 15 includes not only the voltage component due to the temperature of the thermocouple 15 but also the third lead due to the current flowing through the third lead wire 13 included in the bridge circuit 32. A voltage component generated on the line 13 is also included.

一方、第１リード線１１に流れる電流と第３リード線１３に流れる電流は等しく、また、該第１および第３リード線１１，１３の抵抗値は、ほぼ同一である。従って、差動増幅器３１に入力される第１リード線１１の発生電圧ｅrは、第３リード線１３の発生電圧にほぼ等しい。このため、差動増幅器３１の出力は、熱電対１５の出力電圧ｅtから、第３リード線１３の発生電圧を除去してなる電圧、すなわち、該熱電対１５の温度に起因する電圧にほぼ比例するものとなる。これにより、差動増幅器３１から、熱電対１５の温度だけに依存する電圧信号が得られることとなる。 On the other hand, the current flowing through the first lead wire 11 and the current flowing through the third lead wire 13 are equal, and the resistance values of the first and third lead wires 11 and 13 are substantially the same. Therefore, the generated voltage er of the first lead wire 11 input to the differential amplifier 31 is substantially equal to the generated voltage of the third lead wire 13. For this reason, the output of the differential amplifier 31 is approximately proportional to the voltage obtained by removing the voltage generated by the third lead wire 13 from the output voltage et of the thermocouple 15, that is, the voltage resulting from the temperature of the thermocouple 15. To be. As a result, a voltage signal that depends only on the temperature of the thermocouple 15 is obtained from the differential amplifier 31.

そして、増幅器３０および差動増幅器３１の出力を入力する図示しない演算処理部では、差動増幅器３１の出力を基に熱電対１５の温度、すなわち、ひずみゲージ１によるひずみ測定箇所の環境温度を測定する（差動増幅器３１の出力電圧を温度値に換算する）。また、該演算処理部では、例えば増幅器３０の出力を基に、ひずみゲージ１のひずみを測定し（増幅器３０の出力電圧をひずみ値に換算する）、さらに、そのひずみ測定値を熱電対１５の温度測定値を基に補正することで、該ひずみ測定値の温度補償（環境温度の変化に応じたひずみゲージ１の見かけひずみの補償）を行なう。また、演算処理部は、その温度補償後のひずみ測定値や、温度測定値を記録保持したり、表示するなどの処理を実行する。なお、ひずみ測定値の温度補償は、補正換算表などを用いて作業者が行なうようにしてもよい。 An arithmetic processing unit (not shown) that inputs the outputs of the amplifier 30 and the differential amplifier 31 measures the temperature of the thermocouple 15 based on the output of the differential amplifier 31, that is, the environmental temperature of the strain measurement location by the strain gauge 1. (The output voltage of the differential amplifier 31 is converted into a temperature value). Further, in the arithmetic processing unit, for example, the strain of the strain gauge 1 is measured based on the output of the amplifier 30 (the output voltage of the amplifier 30 is converted into a strain value), and the strain measurement value of the thermocouple 15 is measured. By correcting based on the measured temperature value, temperature compensation of the measured strain value (compensation of the apparent strain of the strain gauge 1 according to the change of the environmental temperature) is performed. In addition, the arithmetic processing unit performs processing such as recording and holding the strain measurement value after temperature compensation and the temperature measurement value, and displaying the temperature measurement value. Note that the temperature compensation of the strain measurement value may be performed by an operator using a correction conversion table or the like.

この場合、差動増幅器３１の出力を基に、熱電対１５の温度（ひずみ測定時の環境温度）を精度よく測定できるので、ブリッジ回路３２の出力電圧ｅから得られるひずみ測定値の補正を適切に行なうことができる。 In this case, since the temperature of the thermocouple 15 (environment temperature at the time of strain measurement) can be accurately measured based on the output of the differential amplifier 31, correction of the strain measurement value obtained from the output voltage e of the bridge circuit 32 is appropriately performed. Can be done.

なお、以上説明した実施形態では、熱電対１５の出力電圧ｅtと第１リード線１１の発生電圧ｅrとの差分の電圧（ｅt−ｅr）を差動増幅器３１を使用して検出するようにしたが、熱電対１５の出力電圧ｅtと第１リード線１１の発生電圧ｅrとをそれぞれ各別に増幅したものをＡ／Ｄ変換し、それらの値の差を演算により求めるようにしてもよい。 In the embodiment described above, the differential voltage (et−er) between the output voltage et of the thermocouple 15 and the generated voltage er of the first lead wire 11 is detected using the differential amplifier 31. However, the output voltage et of the thermocouple 15 and the voltage er generated by the first lead wire 11 may be A / D converted and the difference between these values may be obtained by calculation.

また、前記実施形態では、１つのひずみゲージ１だけを使用する測定系を説明したが、複数のひずみゲージ１を使用して、多点測定を行なう測定系であってもよい。その場合、各ひずみゲージ１と測定器２との接続をスイッチを介して切り換えるようにしてもよい。 In the above embodiment, a measurement system using only one strain gauge 1 has been described. However, a measurement system that uses a plurality of strain gauges 1 to perform multipoint measurement may be used. In that case, you may make it switch the connection of each strain gauge 1 and the measuring device 2 via a switch.

本発明のひずみ・温度測定方法を適用した測定系の要部の回路構成図。The circuit block diagram of the principal part of the measuring system to which the strain / temperature measuring method of the present invention is applied. 従来のひずみ・温度測定手法を説明するための回路図。The circuit diagram for demonstrating the conventional strain and temperature measurement method.

Explanation of symbols

１…抵抗式ひずみゲージ、１１…第１リード線、１２…第２リード線、１３…第３リード線、１４…第４リード線、１５…熱電対、３２…ブリッジ回路。 DESCRIPTION OF SYMBOLS 1 ... Resistance strain gauge, 11 ... 1st lead wire, 12 ... 2nd lead wire, 13 ... 3rd lead wire, 14 ... 4th lead wire, 15 ... Thermocouple, 32 ... Bridge circuit.

Claims

A first lead wire and a second lead wire made of the same material are connected to one end, a third lead wire made of the same material as the first and second lead wires to the other end, and the first to first lead wires A resistance strain gage made of a material different from the three lead wire and connected to the fourth lead wire constituting the thermocouple together with the third lead wire is used to form a resistance circuit composed of a plurality of resistors having a fixed resistance value. By connecting the resistance strain gauge via the first lead wire and the third lead wire to form a bridge circuit having the resistance strain gauge on one side, while applying a bridge power supply voltage to the bridge circuit, Extracting the output voltage of the bridge circuit using the second lead wire according to the 1 gauge three wire method, extracting the output voltage of the thermocouple via the third lead wire and the fourth lead wire, A strain / temperature measuring method for measuring strain generated in the resistance strain gauge based on the output voltage of the bridge circuit and measuring the temperature of the thermocouple based on the output voltage of the extracted thermocouple In
The voltage generated in the first lead wire in a state where a bridge power supply voltage is applied to the bridge circuit is extracted via the connection portion of the first lead wire to the resistor circuit and the second lead wire, and the extraction is performed. A strain / temperature measuring method characterized in that the temperature of the thermocouple is measured based on the difference between the voltage generated by the first lead wire and the output voltage of the extracted thermocouple.