JP2006105902A - Resistance measuring device - Google Patents

Resistance measuring device Download PDF

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JP2006105902A
JP2006105902A JP2004296175A JP2004296175A JP2006105902A JP 2006105902 A JP2006105902 A JP 2006105902A JP 2004296175 A JP2004296175 A JP 2004296175A JP 2004296175 A JP2004296175 A JP 2004296175A JP 2006105902 A JP2006105902 A JP 2006105902A
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circuit
constant current
current
overvoltage
resistor
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Eiji Sannomaru
英二 山王丸
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ADC KK
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ADC KK
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Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power capacity of an active element for overvoltage protection provided in a resistance-measuring device. <P>SOLUTION: This device is equipped with a constant-current generation circuit for applying a prescribed constant current to a resistor to be measured that is connected between input terminals, and allowing a resistance measuring circuit to measure the voltage generated in the resistor to be measured; the active element for overvoltage protection connected in series to a current passage of the constant current applied to the resistor to be measured, for protecting the constant-current generation circuit, by absorbing the overvoltage when an excessive voltage is applied between the input terminals; and a current suppression circuit for detecting the state where the excessive voltage is applied between the input terminals, and suppressing the constant current generated in the constant-current generation circuit to small current. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明はデジタルボルトメータ（デジボル）等に組込まれて実用される抵抗測定装置に関し、特に被測定抵抗器を抵抗測定回路に接続するための入力端子に誤って過大な電圧を印加してしまった場合でも、抵抗測定装置の破損を防ぐ保護機能を付加しようとするものである。   The present invention relates to a resistance measuring device incorporated in a digital voltmeter (Digibol) or the like, and in particular, an excessive voltage is erroneously applied to an input terminal for connecting a resistor to be measured to a resistance measuring circuit. Even in such a case, it is intended to add a protection function for preventing the resistance measuring device from being damaged.

図２に従来の抵抗測定装置の概略の構成を示す。図中１１Ａ、１１Ｂは被測定抵抗器１２を抵抗測定回路１０に電気的に接続するための入力端子を示す。入力端子１１Ａと１１Ｂは一方１１Ｂが共通電位に接続され、他方１１Ａが抵抗測定回路１０に接続される。
定電流発生回路２０はこの例では演算増幅器２１と、電界効果トランジスタ２２と、レンジ切替回路２３と、電圧源２４とによって構成される。電圧源２４は所定の電圧、例えば１Ｖを発生し、その電圧を演算増幅器２１の非反転入力端子に印加する。演算増幅器２１の出力端子に電界効果トランジスタ２２のゲートを接続し、電界効果トランジスタ２２のソースと負電源２５の間にレンジ切替回路２３を接続し、電界効果トランジスタ２２のソースに発生する電圧を演算増幅器２１の反転入力端子に帰還させる。 FIG. 2 shows a schematic configuration of a conventional resistance measuring apparatus. In the figure, reference numerals 11A and 11B denote input terminals for electrically connecting the measured resistor 12 to the resistance measuring circuit 10. One of input terminals 11 </ b> A and 11 </ b> B is connected to a common potential, and the other 11 </ b> A is connected to the resistance measurement circuit 10.
In this example, the constant current generating circuit 20 includes an operational amplifier 21, a field effect transistor 22, a range switching circuit 23, and a voltage source 24. The voltage source 24 generates a predetermined voltage, for example, 1 V, and applies the voltage to the non-inverting input terminal of the operational amplifier 21. The gate of the field effect transistor 22 is connected to the output terminal of the operational amplifier 21, and the range switching circuit 23 is connected between the source of the field effect transistor 22 and the negative power source 25 to calculate the voltage generated at the source of the field effect transistor 22. Feedback is made to the inverting input terminal of the amplifier 21.

この回路構造によれば演算増幅器２１の出力端子の電圧が常時０となる状態に安定する。つまり、レンジ切替回路２３に常に１Ｖが発生する状態に安定する。従って、レンジ切替回路２３を構成する抵抗器Ｒ１、Ｒ２、Ｒ３、Ｒ４の値を例えば１００Ω、１ｋΩ、１０ｋΩ、１００ｋΩに設定しておくことにより定電流発生回路２０で発生する電圧ＩＳを１０ｍＡ、１ｍＡ、０．１ｍＡ、０．０１ｍＡのように切替えることができる。この電流ＩＳが被測定抵抗器１２に印加され、被測定抵抗器１２に発生する電圧ＶＸ＝ＩＳ・ＲＸを抵抗測定回路１０を構成する電圧測定回路で測定し、被測定抵抗器１２の抵抗値ＲＸを算出する。 According to this circuit structure, the voltage at the output terminal of the operational amplifier 21 is stabilized in a state where it is always zero. That is, the range switching circuit 23 is always stable in a state where 1 V is generated. Therefore, the voltage I generated in the constant current generation circuit 20 is set by setting the values of the resistors R 1 , R 2 , R 3 , and R 4 constituting the range switching circuit 23 to, for example, 100Ω, 1 kΩ, 10 kΩ, and 100 kΩ. S can be switched to 10 mA, 1 mA, 0.1 mA, and 0.01 mA. This current I S is applied to the resistor 12 to be measured, and the voltage V X = I S · R X generated in the resistor 12 to be measured is measured by the voltage measuring circuit constituting the resistance measuring circuit 10, calculating a resistance value R X 12.

尚、レンジ切替回路２３はコントローラ３０から送られて来るロジック信号ＡとＢによってマルチプレクサ２３Ａが切替制御され、抵抗器Ｒ１〜Ｒ４の中の何れか一つの抵抗器が選択されて電界効果トランジスタ２２のソースと負電源２５との間に接続され、測定レンジが切替えられる。
ここで被測定抵抗器１２と定電流発生回路２０との間に過電圧保護用能動素子２６が介挿される。この過電圧保護用能動素子２６は特に耐圧（コレクタ−エミッタ間の耐圧）が大きいトランジスタを適用し、入力端子１１Ａ、１１Ｂ間に誤まって過大な電圧、例えば１０００Ｖ程度が印加されても、この過大電圧を吸収し、定電流発生回路２０が破損することを防止するために設けられる。 Incidentally, range switching circuit 23 is a multiplexer 23A is switched controlled by logic signals A and B transmitted from the controller 30, the resistors R 1 one of the resistor selected by the field effect transistor in to R 4 Connected between the 22 sources and the negative power supply 25, the measurement range is switched.
Here, an overvoltage protection active element 26 is interposed between the resistor 12 to be measured and the constant current generation circuit 20. The overvoltage protection active element 26 uses a transistor having a particularly high withstand voltage (collector-emitter withstand voltage), and even if an excessive voltage, for example, about 1000 V is erroneously applied between the input terminals 11A and 11B, It is provided to absorb the voltage and prevent the constant current generating circuit 20 from being damaged.

過電圧保護用能動素子２６はダイオード２７の電圧降下で発生する順方向バイアスにより常時オンの状態に維持されている。従って、定電流発生回路２０が発生する電流ＩＳは過電圧保護用能動素子２６を通じて被測定抵抗器１２に印加される。この状態で入力端子１１Ａに正極性の過大電圧が印加されると、この過大電圧が過電圧保護用能動素子２６のコレクタ−エミッタ間に印加され、コレクタ−エミッタ間を過大電圧に維持する。この結果として、定電流発生回路２０には過大電圧が印加されることはなく、定電流発生回路２０は過大電圧から保護される。 The overvoltage protection active element 26 is always kept on by a forward bias generated by a voltage drop of the diode 27. Accordingly, the current I S that constant current generating circuit 20 generates is applied to the measurement resistor 12 through the overvoltage protection for an active element 26. In this state, when a positive overvoltage is applied to the input terminal 11A, this overvoltage is applied between the collector and the emitter of the overvoltage protection active element 26, and the overvoltage is maintained between the collector and the emitter. As a result, an excessive voltage is not applied to the constant current generating circuit 20, and the constant current generating circuit 20 is protected from the excessive voltage.

尚、抵抗測定回路１０にも入力端子１１Ａに印加された過大電圧が入力されるが、抵抗測定回路１０にも電圧保護回路が設けられており、この電圧保護回路により抵抗測定回路１０は保護される。本発明は定電流発生回路２０を過大電圧から保護することを目的とするから、抵抗測定回路１０の保護回路については特に言及しないことにする。   Note that an excessive voltage applied to the input terminal 11A is also input to the resistance measurement circuit 10. However, the resistance measurement circuit 10 is also provided with a voltage protection circuit, and the resistance measurement circuit 10 is protected by this voltage protection circuit. The Since the present invention aims to protect the constant current generation circuit 20 from an excessive voltage, the protection circuit of the resistance measurement circuit 10 will not be specifically mentioned.

入力端子１１Ａに過大電圧が印加される理由としてはデジタルボルトメータの分野では抵抗測定用の入力端子１１Ａと１１Ｂを直流の電圧測定の入力端子として流用する例が多いことにある。このために、直流電圧測定モードに切替られているものと思い違いをして抵抗測定モードに設定されているにも係わらず直流の高電圧を印加してしまう事例がある。
尚、抵抗測定用の定電流発生回路２０にはリレー接点ＲＬが直列に接続され、入力端子１１Ａと１１Ｂを電圧測定端子として用いる場合はこのリレー接点ＲＬをオフとし、定電流発生回路２０を切離すように構成される。またダイオードＤは抵抗測定モードで入力端子１１Ａが負極性となる過電流が印加された場合に、この過電圧から定電流発生回路２０を保護するためのダイオードである。 The reason why an excessive voltage is applied to the input terminal 11A is that, in the field of digital voltmeters, there are many examples in which the input terminals 11A and 11B for resistance measurement are used as input terminals for DC voltage measurement. For this reason, there is an example in which a high DC voltage is applied despite the fact that the resistance measurement mode is set, as if it is switched to the DC voltage measurement mode.
In addition, a relay contact RL is connected in series to the resistance measuring constant current generating circuit 20, and when the input terminals 11A and 11B are used as voltage measuring terminals, the relay contact RL is turned off and the constant current generating circuit 20 is turned off. Configured to separate. The diode D is a diode for protecting the constant current generating circuit 20 from this overvoltage when an overcurrent that causes the input terminal 11A to have a negative polarity is applied in the resistance measurement mode.

このような理由から抵抗測定モードで過大電圧が入力される機会が多発するので従来より、定電流発生回路２０と直列に過電圧保護用能動素子２６を設けているが、抵抗測定レンジが微小抵抗を分解能よく測定するレンジに設定されている状態で、入力端子１１Ａと１１Ｂの間に正極性の過大電圧が印加されたとすると、この状態では定電流発生回路２０が発生する定電流Ｉｓは比較的大きい電流値に設定されているため、過電圧保護用能動素子２６はコレクタ及びエミッタ間の耐圧はともかくとして、電力容量も大きい容量が要求されることになる。 For this reason, there are many occasions when an excessive voltage is input in the resistance measurement mode. Therefore, an active element 26 for overvoltage protection has been provided in series with the constant current generation circuit 20, but the resistance measurement range has a very small resistance. When set to the range of measurement resolution well, the overvoltage of the positive polarity and is applied between the input terminals 11A and 11B, the constant current I s of the constant current generating circuit 20 is generated in this state is relatively Since the large current value is set, the overvoltage protection active element 26 is required to have a large power capacity regardless of the breakdown voltage between the collector and the emitter.

つまり、例えばレンジ切替回路２３に用いる抵抗器Ｒ１、Ｒ２、Ｒ３、Ｒ４の抵抗値がそれぞれ１００Ω、１ｋΩ、１０ｋΩ、１００ｋΩとした場合、抵抗器Ｒ１を選択した場合は定電流Ｉｓは１０ｍＡとなり、Ｒ２を選択した場合はＩＳ＝１ｍＡ、Ｒ３を選択した場合はＩｓ＝０．１ｍＡ、Ｒ４を選択した場合はＩｓ＝０．０１ｍＡとなる。過電圧保護用能動素子２６のコレクタ−エミッタ間に印加される可能性がある過電圧が仮に１０００Ｖとした場合、定電流ＩS＝１０ｍＡである場合には過電圧保護用能動素子２６には電力容量ＷＰとしてＷＰ＝１０Ｗが要求される。更にＩS＝１ｍＡの場合はＷＰ＝１Ｗ、ＩＳ＝０．１ｍＡの場合はＷＰ＝０．１Ｗ、ＩＳ＝０．０１ｍＡの場合はＷＰ＝０．０１Ｗとなる。耐圧が１０００Ｖで電力容量が１０Ｗ乃至１Ｗ程度の能動素子はかなり高値であり、また形状も大きいため抵抗測定装置に実装することはコストの点と、小型化を達することに反するため、実装はむずかしい。 That is, for example, when the resistance values of the resistors R 1 , R 2 , R 3 , and R 4 used in the range switching circuit 23 are 100Ω, 1 kΩ, 10 kΩ, and 100 kΩ, respectively, the constant current I is selected when the resistor R 1 is selected. s is 10 mA. When R 2 is selected, I S = 1 mA, when R 3 is selected, I s = 0.1 mA, and when R 4 is selected, I s = 0.01 mA. If the overvoltage that can be applied between the collector and the emitter of the overvoltage protection active element 26 is 1000 V, and if the constant current I S = 10 mA, the overvoltage protection active element 26 has a power capacity W P W P = 10 W is required. Further, when I S = 1 mA, W P = 1 W, when I S = 0.1 mA, W P = 0.1 W, and when I S = 0.01 mA, W P = 0.01 W. An active element having a withstand voltage of 1000 V and a power capacity of about 10 W to 1 W has a fairly high value and has a large shape, so mounting on a resistance measuring device is contrary to cost and downsizing, so mounting is difficult. .

このため、一般的には定電流発生回路２０で発生する定電流を１ｍＡ〜０．０１ｍＡ程度の範囲に抑制し、過電圧保護用能動素子２６に要求される電力容量を小さい値で済むようにしている。然し乍ら、このように定電流発生回路２０で発生する電流ＩSの値を小さい値に制限してしまうと、小さい抵抗値の測定を分解能よく行なうことができなくなる不都合が生じる。
この発明の目的は微小抵抗の抵抗値を分解能よく測定することができ、然も過電圧保護用能動素子の電力容量も小さい容量に制限することができる抵抗測定装置を提供しようとするものである。 Therefore, generally, the constant current generated by the constant current generating circuit 20 is suppressed to a range of about 1 mA to 0.01 mA so that the power capacity required for the overvoltage protection active element 26 can be reduced. However, if the value of the current I S generated in the constant current generation circuit 20 is limited to a small value in this way, there is a disadvantage that measurement of a small resistance value cannot be performed with high resolution.
An object of the present invention is to provide a resistance measuring apparatus that can measure the resistance value of a minute resistance with high resolution and can limit the power capacity of an active element for overvoltage protection to a small capacity.

本発明では、抵抗値を測定すべき被測定抵抗器を抵抗測定回路に接続するための一対の端子と、この一対の端子で構成される入力端子間に接続された被測定抵抗器に所定の定電流を印加し、被測定抵抗器に発生する電圧を抵抗測定回路に測定させる定電流発生回路と、被測定抵抗器に印加される定電流の電流通路に直列接続され、入力端子間に過大電圧が印加された場合に、その過大電圧を吸収し、上記定電流発生回路を保護する過電圧保護用能動素子と、入力端子間に過大電圧が印加された状態を検出し、上記定電流発生回路で発生する定電流を小電流に抑制する電流抑制回路とを備える抵抗測定装置を提案する。   In the present invention, a predetermined resistor is connected to a pair of terminals for connecting a resistor to be measured whose resistance value is to be measured to the resistance measuring circuit, and a resistor to be measured connected between input terminals constituted by the pair of terminals. A constant current generation circuit that applies a constant current and causes the resistance measurement circuit to measure the voltage generated at the resistor under test is connected in series with the current path of the constant current applied to the resistor under test. When a voltage is applied, the overvoltage protection active element that absorbs the overvoltage and protects the constant current generation circuit and the state where the overvoltage is applied between the input terminals are detected, and the constant current generation circuit A resistance measuring device including a current suppression circuit that suppresses the constant current generated in the above to a small current is proposed.

この発明では更に、定電流発生回路は発生する定電流の値を切替えるレンジ切替回路を備え、電流抑制回路は入力端子間に過電圧が印加された場合、その検出出力によりレンジ切替回路のレンジを小電流レンジに切替えて過電圧保護用能動素子に流れる電流を抑制する抵抗測定装置を提案する。   According to the present invention, the constant current generation circuit further includes a range switching circuit for switching a value of the generated constant current, and the current suppression circuit reduces the range of the range switching circuit by the detection output when an overvoltage is applied between the input terminals. A resistance measuring device is proposed that suppresses the current flowing in the overvoltage protection active element by switching to the current range.

この発明による抵抗測定装置によれば入力端子に過電圧が印加されると、この過電圧の印加を電流抑制回路が検出し、その検出出力によって定電流発生回路で発生する定電流を小レンジ側に切替える制御を実行する。この結果、被測定抵抗器に大きい電流を印加する測定モードで動作している状態で過電圧が印加されても、過電圧の印加と同時に電流抑制回路が動作し、定電流発生回路が発生する定電流を小さいレンジ側に切り替えるため、これに伴なって過電圧保護用能動素子を流れる電流も抑制される。従って過電圧保護用能動素子は電力容量の小さい素子を用いることができる。   According to the resistance measuring apparatus of the present invention, when an overvoltage is applied to the input terminal, the current suppression circuit detects the application of the overvoltage, and the constant current generated in the constant current generation circuit is switched to the small range side by the detection output. Execute control. As a result, even if an overvoltage is applied while operating in a measurement mode that applies a large current to the resistor under test, the current suppression circuit operates simultaneously with the application of the overvoltage, and the constant current generating circuit generates a constant current. Therefore, the current flowing through the overvoltage protection active element is also suppressed. Therefore, an element having a small power capacity can be used as the overvoltage protection active element.

本発明を実施する場合、過電圧保護用能動素子のバイアス電圧発生回路から、過電圧が印加されたことを検出する検出信号を発生させ、この検出信号で電流抑制回路を構成する能動素子を制御し、ロジック信号を発信させる。このロジック信号により定電流発生回路を構成するレンジ切替回路の状態を切替制御し、レンジ切替回路の切替状態を小電流発生状態に切替え、過電圧保護用能動素子を流れる電流を抑制する動作を実行させる。   When carrying out the present invention, a detection signal for detecting that an overvoltage is applied is generated from the bias voltage generation circuit of the active element for overvoltage protection, and the active element constituting the current suppression circuit is controlled by this detection signal, Send a logic signal. With this logic signal, the state of the range switching circuit that constitutes the constant current generation circuit is controlled to be switched, the switching state of the range switching circuit is switched to the small current generation state, and the operation of suppressing the current flowing through the overvoltage protection active element is executed. .

図１に本発明による抵抗測定装置の実施例を示す。図２と対応する部分には同一符号を付し、その重複説明は省略するが、この発明ではダイオード２７と共通電位との間に抵抗値の小さい過電圧検出用抵抗器４１を接続し、この過電圧検出用抵抗器４１に発生する電圧をダイオード４２で取り出すことによって電流抑制回路４０の起動制御を実行させる。
つまり、定常状態では過電圧検出用抵抗器４１に発生する電圧はダイオード４２の導通電圧（例えば０．６Ｖ程度）以下となるように過電圧検出用抵抗器４１の抵抗値を選定する。入力端子１１Ａ、１１Ｂ間に過電圧（例えば１００Ｖ以上）が印加された場合は過電圧検出用抵抗器４１に発生する電圧がダイオード４２の導電電圧を超えるように構成し、ダイオード４２の導通によって過電圧の印加状態を検出し、電流抑制回路４０を起動させる。 FIG. 1 shows an embodiment of a resistance measuring apparatus according to the present invention. The parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and repeated description thereof is omitted. In the present invention, an overvoltage detection resistor 41 having a small resistance value is connected between the diode 27 and the common potential. The start-up control of the current suppression circuit 40 is executed by taking out the voltage generated in the detection resistor 41 by the diode 42.
That is, the resistance value of the overvoltage detection resistor 41 is selected so that the voltage generated in the overvoltage detection resistor 41 in the steady state is equal to or lower than the conduction voltage of the diode 42 (for example, about 0.6 V). When an overvoltage (for example, 100 V or more) is applied between the input terminals 11A and 11B, the voltage generated in the overvoltage detection resistor 41 exceeds the conductive voltage of the diode 42, and the overvoltage is applied by the conduction of the diode 42. The state is detected, and the current suppression circuit 40 is activated.

電流抑制回路４０は過電圧検出用抵抗器４１とダイオード４２とから成る過電圧検出回路に加えて能動素子４４と抵抗器４５とから成るロジック信号発生回路とによって構成することができる。ダイオード４２の検出信号を能動素子４４のベースに入力し、ダイオード４２の導通電流により能動素子４４をオンの状態に制御する。能動素子４４がオンの状態に制御されることにより、能動素子４４のコレクタから「１」論理から「０」論理に立下がるロジック信号が発信される。このロジック信号をワイヤードオアの形態でレンジ切替回路２３へ入力するように構成する。   The current suppression circuit 40 can be configured by a logic signal generation circuit including an active element 44 and a resistor 45 in addition to an overvoltage detection circuit including an overvoltage detection resistor 41 and a diode 42. The detection signal of the diode 42 is input to the base of the active element 44, and the active element 44 is controlled to be in an ON state by the conduction current of the diode 42. When the active element 44 is controlled to be in the ON state, a logic signal that falls from “1” logic to “0” logic is transmitted from the collector of the active element 44. The logic signal is input to the range switching circuit 23 in the form of wired OR.

ここでコントローラ３０からレンジ切替回路２３へ入力されるロジック信号とレンジ切替状態との関係について下表を用いて説明する。表中Ａ、Ｂはコントローラ３０からレンジ切替回路２３へ入力されるロジック信号を示すＡは制御信号線３１を通じてレンジ切替回路２３へ入力されるロジック信号を示す。


表１
Ａ Ｂ ＲS ＩS 電力容量
――――――――――――――――――――――――――――――
１ １ Ｒ１（１００Ω） １０ｍＡ １０Ｗ
１ ０ Ｒ２（１ｋΩ） １ｍＡ １Ｗ
０ １ Ｒ３（１０ｋΩ） １００μＡ ０．１Ｗ
０ ０ Ｒ４（１００ｋΩ） １０μＡ ０．０１Ｗ
ロジック信号ＡとＢが共に「１」論理である場合、マルチプレクサ２３Ａはスイッチ０がオンの状態に制御され、抵抗器Ｒ１が選択される。抵抗器Ｒ１は抵抗値が１００Ωに設定されている。演算増幅器２１の反転入力端子の電位は電圧源２４と同じ電位に維持されるから、電圧源２４の起電圧が１（Ｖ）であるとすると、定電流発生回路２０で発生する定電流ＩＳはＩＳ＝１Ｖ／１００Ω＝１０ｍＡとなる。この状態で入力端子１１Ａと１１Ｂに正極性の過大電圧例えば１０００Ｖが印加されたとすると、過電圧保護用能動素子２６に要求される電力容量は１０Ｗとなる。 Here, the relationship between the logic signal input from the controller 30 to the range switching circuit 23 and the range switching state will be described with reference to the following table. In the table, A and B indicate logic signals input from the controller 30 to the range switching circuit 23, and A indicates a logic signal input to the range switching circuit 23 through the control signal line 31.


Table 1
A B R S I S Power Capacity ――――――――――――――――――――――――――――――
1 1 R 1 (100Ω) 10 mA 10 W
1 0 R 2 (1 kΩ) 1 mA 1 W
0 1 R 3 (10 kΩ) 100 μA 0.1 W
0 0 R 4 (100 kΩ) 10 μA 0.01 W
If the logic signals A and B are both "1" logic, the multiplexer 23A is controlled to switch 0 is on, resistor R 1 is selected. Resistor R 1 is the resistance value is set to 100 [Omega. Since the potential of the inverting input terminal of the operational amplifier 21 is maintained at the same potential as that of the voltage source 24, assuming that the electromotive voltage of the voltage source 24 is 1 (V), the constant current I S generated by the constant current generation circuit 20. Is I S = 1V / 100Ω = 10 mA. If a positive overvoltage, for example, 1000 V is applied to the input terminals 11A and 11B in this state, the power capacity required for the overvoltage protection active element 26 is 10W.

ロジック回路Ａ、Ｂが「１」「０」の場合はマルチプレクサ２３Ａはスイッチ１がオンに制御され、抵抗器Ｒ２が選択される。抵抗器Ｒ２の抵抗値が１ｋΩに設定されているものとすると、定電流発生回路２０が発生する定電流ＩＳはＩＳ＝１ｍＡとなる。過電圧保護用能動素子２６に１ｍＡが流されている状態で入力端子１１Ａに１０００Ｖの過電圧が印加されたとすると、この状態で過電圧保護用能動素子２６に要求される電力容量は１Ｗとなる。
ロジック信号Ａ、Ｂが「０」、「１」の場合はマルチプレクサ２３Ａはスイッチ２がオンとなり、抵抗器Ｒ３が選択される。抵抗器Ｒ３は１０ｋΩに設定されているものとすると、定電流発生回路２０が発生する定電流ＩＳは１００μＡとなる。この状態で１０００Ｖの過電圧が印加されたとすると、この状態で過電圧保護用能動素子２６に要求される電力容量は０．１Ｗとなる。 Logic circuits A, B multiplexer 23A in the case of "1", "0" is the control switch 1 is turned on, the resistor R 2 is selected. When the resistance value of the resistor R 2 is assumed to be set to 1 k [Omega, the constant current I S that constant current generating circuit 20 generates becomes I S = 1 mA. Assuming that an overvoltage of 1000 V is applied to the input terminal 11A in a state where 1 mA is passed through the overvoltage protection active element 26, the power capacity required for the overvoltage protection active element 26 in this state is 1W.
Logic signals A, B is "0", the multiplexer 23A in the case of "1" will switch 2 is turned on, the resistor R 3 is selected. If the resistor R 3 is assumed to be set to 10 k.OMEGA, a constant current I S that constant current generating circuit 20 generates becomes 100 .mu.A. If an overvoltage of 1000 V is applied in this state, the power capacity required for the overvoltage protection active element 26 in this state is 0.1 W.

ロジック信号Ａ、Ｂが「０」、「０」の場合はマルチプレクサ２３Ａはスイッチ３がオンに制御され、抵抗器Ｒ４が選択される。抵抗器Ｒ４の抵抗値が１００ｋΩに設定されているものとすると、定電流発生回路２０が発生する定電流ＩＳは１０μＡとなる。この状態で入力端子１１Ａに１０００Ｖの過電圧が印加されると過電圧保護用能動素子２６に要求される電力容量は０．０１Ｗとなる。
以上の説明から明らかなように、ロジック信号Ａ、Ｂが「０」、「１」か「０」、「０」の状態で過電圧が印加された場合は過電圧保護用能動素子２６に要求される電力容量は０．１Ｗか０．０１Ｗのように小さい容量でよいことが解る。従って、この発明ではロジック信号Ａをレンジ切替回路２３に伝える制御信号線３１にワイヤードオアの形態でロジック信号発生用の能動素子４４が発生するロジック信号をレンジ切替回路２３に入力する構成とする。つまり、能動素子４４は過電圧検出時にオンの状態に制御され、このオン動作により「１」から「０」となるロジック信号を発信する。このロジック信号の発信によりコントローラ３０からレンジ切替回路２３に印加されるロジック信号Ａが「１」の状態であっても能動素子４４がオンの状態になることにより強制的に「０」に反転されるから、表１から明らかなように、ロジック信号Ａが「０」であれば過電圧保護用能動素子２６に要求される電力容量は０．１Ｗか或は０．０１Ｗに制限され小さい容量に制御される。この結果、過電圧保護用能動素子２６を電力容量の小さい素子を用いることができる利点が得られる。 Logic signals A, B is "0", the multiplexer 23A in the case of "0" is the control switch 3 is turned on, the resistor R 4 is selected. When the resistance value of the resistor R 4 is assumed to be set to 100 k.OMEGA, a constant current I S that constant current generating circuit 20 generates becomes 10 .mu.A. When an overvoltage of 1000 V is applied to the input terminal 11A in this state, the power capacity required for the overvoltage protection active element 26 is 0.01W.
As is clear from the above description, when an overvoltage is applied when the logic signals A and B are “0”, “1”, “0”, and “0”, the overvoltage protection active element 26 is required. It can be seen that the power capacity may be as small as 0.1 W or 0.01 W. Therefore, according to the present invention, a logic signal generated by the active element 44 for generating a logic signal is input to the range switching circuit 23 in a wired OR form on the control signal line 31 that transmits the logic signal A to the range switching circuit 23. That is, the active element 44 is controlled to be in an on state when an overvoltage is detected, and a logic signal that changes from “1” to “0” is transmitted by this on operation. Even if the logic signal A applied from the controller 30 to the range switching circuit 23 is “1” by the transmission of this logic signal, it is forcibly inverted to “0” when the active element 44 is turned on. Therefore, as is clear from Table 1, if the logic signal A is “0”, the power capacity required for the overvoltage protection active element 26 is limited to 0.1 W or 0.01 W and controlled to a small capacity. Is done. As a result, an advantage that an element having a small power capacity can be used as the overvoltage protection active element 26 is obtained.

つまり、本発明によれば定電流発生回路２０が比較的大きい電流例えば１０ｍＡを発生し、抵抗値の小さい抵抗器の抵抗値を分解能よく測定できる優れた特性を持ちながら、過電圧保護用能動素子２６の電力容量を１０Ｗより小さくできる利点が得られる。つまり、従来は過電圧保護用能動素子２６の定電流発生回路２０で発生する電流が最大で１ｍＡに制限した場合に電力容量は１Ｗ程度を必要としたが、本発明によれば定電流発生回路２０の発生電流をそれより大きく採るにも係わらず更に小さい電力容量の能動素子を用いることができる利点が得られる。   In other words, according to the present invention, the constant current generating circuit 20 generates a relatively large current, for example, 10 mA, and has an excellent characteristic capable of measuring the resistance value of a resistor having a small resistance value with good resolution, while overvoltage protection active element 26. The advantage is that the power capacity can be made smaller than 10 W. That is, conventionally, when the current generated in the constant current generating circuit 20 of the overvoltage protection active element 26 is limited to 1 mA at maximum, the power capacity is required to be about 1 W. However, according to the present invention, the constant current generating circuit 20 is required. However, it is possible to use an active element having a smaller power capacity in spite of the fact that a larger current is generated.

本発明による抵抗測定装置はデジタルボルトメータのような電圧、電流測定器に組込まれて各種の用途に実用される。   The resistance measuring apparatus according to the present invention is incorporated in a voltage / current measuring instrument such as a digital voltmeter and is practically used for various applications.

本発明の一実施例を説明するための接続図。The connection diagram for demonstrating one Example of this invention. 従来の技術を説明するための接続図。The connection diagram for demonstrating the prior art.

符号の説明Explanation of symbols

１０ 抵抗測定回路 ４４ 能動素子
１１Ａ、１１Ｂ 入力端子
１２ 被測定抵抗器
２０ 定電流発生回路
２３ レンジ切替回路
２６ 過電圧保護用能動素子
３０ コントローラ
４１ 過電圧検出用抵抗器








10 Resistance measurement circuit 44 Active element 11A, 11B Input terminal
12 Resistor to be measured
20 Constant current generator
23 Range switching circuit
26 Active element for overvoltage protection
30 controller
41 Resistor for overvoltage detection








Claims (2)

抵抗値を測定すべき被測定抵抗器を抵抗測定回路に接続するための一対の端子と、
この一対の端子で構成される入力端子間に接続された被測定抵抗器に所定の定電流を印加し、被測定抵抗器に発生する電圧を上記抵抗測定回路に測定させる定電流発生回路と、
被測定抵抗器に印加される定電流の電流通路に直列接続され、上記入力端子間に過大電圧が印加された場合に、その過大電圧を吸収し、上記定電流発生回路を保護する過電圧保護用能動素子と、
上記入力端子間に過大電圧が印加された状態を検出し、上記定電流発生回路で発生する定電流を小電流に抑制する電流抑制回路と、
を備えることを特徴とする抵抗測定装置。 A pair of terminals for connecting the resistor under test whose resistance value is to be measured to the resistance measurement circuit;
A constant current generating circuit that applies a predetermined constant current to a resistor to be measured connected between the input terminals constituted by the pair of terminals, and causes the resistance measuring circuit to measure a voltage generated in the resistor to be measured;
For overvoltage protection that is connected in series to the current path of the constant current applied to the resistor under test and absorbs the overvoltage and protects the constant current generation circuit when an overvoltage is applied between the input terminals. An active element;
A current suppression circuit that detects a state in which an excessive voltage is applied between the input terminals and suppresses the constant current generated by the constant current generation circuit to a small current;
A resistance measuring device comprising: 請求項１記載の抵抗測定装置において、上記定電流発生回路は発生する定電流の値を切替えるレンジ切替回路を備え、上記電流抑制回路は上記入力端子間に過電圧が印加された場合、その検出出力により上記レンジ切替回路のレンジを小電流レンジに切替えて上記過電圧保護用能動素子に流れる電流を抑制することを特徴とする抵抗測定装置。








2. The resistance measuring apparatus according to claim 1, wherein the constant current generating circuit includes a range switching circuit that switches a value of the generated constant current, and the current suppressing circuit detects a detection output when an overvoltage is applied between the input terminals. The resistance measuring device according to claim 1, wherein the range switching circuit is switched to a small current range to suppress a current flowing through the overvoltage protection active element.








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JP2012068023A (en) * 2010-09-21 2012-04-05 Hioki Ee Corp Ground resistance meter
RU2451297C1 (en) * 2011-03-25 2012-05-20 Вячеслав Николаевич Козубов Method to measure low resistances, including drain-source resistance of field transistor open channel
JP2018009828A (en) * 2016-07-12 2018-01-18 日置電機株式会社 Measurement device
CN110927465A (en) * 2019-11-26 2020-03-27 深圳供电局有限公司 Direct current resistance measuring circuit and device
JPWO2021149175A1 (en) * 2020-01-22 2021-07-29
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012068023A (en) * 2010-09-21 2012-04-05 Hioki Ee Corp Ground resistance meter
RU2451297C1 (en) * 2011-03-25 2012-05-20 Вячеслав Николаевич Козубов Method to measure low resistances, including drain-source resistance of field transistor open channel
US10928428B2 (en) 2016-07-12 2021-02-23 Hioki Denki Kabushiki Kaisha Measuring apparatus
WO2018012388A1 (en) * 2016-07-12 2018-01-18 日置電機株式会社 Measuring device
CN109328305A (en) * 2016-07-12 2019-02-12 日置电机株式会社 Measurement device
JP2018009828A (en) * 2016-07-12 2018-01-18 日置電機株式会社 Measurement device
CN109328305B (en) * 2016-07-12 2021-06-15 日置电机株式会社 Measuring apparatus
JP2022509820A (en) * 2018-12-03 2022-01-24 アステック インターナショナル リミテッド Switched mode power supply with configurable communication address
US11557917B2 (en) 2018-12-03 2023-01-17 Astec International Limited Switched mode power supplies with configurable communication addresses
CN110927465A (en) * 2019-11-26 2020-03-27 深圳供电局有限公司 Direct current resistance measuring circuit and device
JPWO2021149175A1 (en) * 2020-01-22 2021-07-29
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