JPH056670B2 - - Google Patents
Info
- Publication number
- JPH056670B2 JPH056670B2 JP23576784A JP23576784A JPH056670B2 JP H056670 B2 JPH056670 B2 JP H056670B2 JP 23576784 A JP23576784 A JP 23576784A JP 23576784 A JP23576784 A JP 23576784A JP H056670 B2 JPH056670 B2 JP H056670B2
- Authority
- JP
- Japan
- Prior art keywords
- measured
- resistance
- resistor
- amplifier
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000001514 detection method Methods 0.000 claims description 52
- 238000005259 measurement Methods 0.000 claims description 17
- 230000003071 parasitic effect Effects 0.000 description 17
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 11
- 238000000034 method Methods 0.000 description 9
- 238000002955 isolation Methods 0.000 description 7
- 238000007599 discharging Methods 0.000 description 6
- 238000009413 insulation Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Measurement Of Resistance Or Impedance (AREA)
- Measurement Of Current Or Voltage (AREA)
Description
【発明の詳細な説明】
「産業上の利用分野」
この発明は高い抵抗値を持つ抵抗に流れる電流
を測定する電流測定回路に関する。DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a current measuring circuit that measures a current flowing through a resistor having a high resistance value.
「従来の技術」
従来、特に高い抵抗、例えば絶縁抵抗を測定す
る方法として、その被測定抵抗に電圧を印加し、
その時流れる電流を測定する電圧電流法と、被測
定抵抗を含むブリツジ回路を平衡させた時の抵抗
を測定するゼロ位法とがあつた。高速度に測定を
行う場合は電圧電流法が用いられていた。これは
ブリツジによるゼロ位法はブリツジ回路の性質上
高い抵抗によりブリツジを構成することになり、
高抵抗のために必然的に寄生容量が発生し、それ
が小さな容量でも抵抗値が高いため時定数が大き
くなり、早い速度で測定をすることが困難となる
ためである。"Prior Art" Conventionally, as a method for measuring particularly high resistance, such as insulation resistance, a voltage is applied to the resistance to be measured.
There were two methods: the voltage-current method, which measured the current flowing at that time, and the zero-position method, which measured the resistance when the bridge circuit containing the resistance to be measured was balanced. For high-speed measurements, the voltage-current method was used. This is because in the zero position method using a bridge, the bridge is constructed with high resistance due to the nature of the bridge circuit.
This is because parasitic capacitance is inevitably generated due to high resistance, and even if the capacitance is small, the resistance value is high and the time constant becomes large, making it difficult to perform measurements at high speed.
これら電圧電流法及びゼロ位法はいずれにおい
ても微少電流を扱うため誘導雑音の影響を大きく
受ける。このため従来の絶縁計においては第３図
に示すようにされていた。即ち電源１１より被測
定抵抗１２の一端に電圧を印加し、被測定抵抗１
２の他端を検出抵抗器１３を通じて接地し、その
検出抵抗器１３の被測定抵抗１２側に得られた検
出電圧を増幅器１４で増幅して指示計１５に供給
する。この指示計１５の指示により被測定抵抗１
２を流れる電流値を知り、更に被測定抵抗１２の
抵抗値を知る。この場合被測定抵抗１２と検出抵
抗器１３との間のリード線１６上にシールド１７
を被せ、シールド１７を接地してリード線１６に
外部からの誘導雑音が乗らないようにしていた。
しかしこのシールド１７による遮蔽を完全にする
ことは困難であり、測定システムによつては実質
的にシールドを施すことができない場合がある。
このため従来の測定回路は雑音の影響を受け易い
ものであつた。 Both the voltage-current method and the zero-position method deal with minute currents and are therefore greatly affected by inductive noise. For this reason, the conventional insulation meter was constructed as shown in FIG. 3. That is, a voltage is applied from the power supply 11 to one end of the resistance to be measured 12, and the resistance to be measured 1 is
The other end of 2 is grounded through a detection resistor 13, and the detection voltage obtained at the resistance to be measured 12 side of the detection resistor 13 is amplified by an amplifier 14 and supplied to an indicator 15. According to the instruction of this indicator 15, the resistance to be measured 1
2, and also the resistance value of the resistor 12 to be measured. In this case, a shield 17 is placed on the lead wire 16 between the resistance to be measured 12 and the detection resistor 13.
The shield 17 was grounded to prevent induced noise from the outside from getting onto the lead wire 16.
However, it is difficult to achieve complete shielding by the shield 17, and depending on the measurement system, it may not be possible to provide substantial shielding.
For this reason, conventional measurement circuits have been susceptible to noise.
更に被測定抵抗の一般的な問題を述べれば、測
定器と被測定抵抗とを接続するケーブルの絶縁抵
抗は、被測定抵抗、例えば絶縁抵抗と同程度の抵
抗値となるため、その測定対象が被測定抵抗とケ
ーブルの絶縁抵抗との並列回路となつてしまう。
また被測定抵抗はその構造上必ず寄生容量が存在
し、その寄生容量が僅かの値であつても絶縁抵抗
のような大きな抵抗値の被測定抵抗の場合はその
寄生容量に対する充放電の時定数はかなり長いも
のとなる。また被測定抵抗に化学変化による電流
（吸収電流）が流れ、この電流は時間と共にゆる
やかに減少する特性を示す。 Furthermore, to discuss the general problem of resistance under test, the insulation resistance of the cable that connects the measuring instrument and the resistance under test is about the same resistance value as the resistance under test, for example, the insulation resistance. This results in a parallel circuit between the resistance to be measured and the insulation resistance of the cable.
Furthermore, due to the structure of the resistor to be measured, parasitic capacitance always exists, and even if the parasitic capacitance is small, in the case of a resistor to be measured with a large resistance value such as insulation resistance, the charging/discharging time constant for the parasitic capacitance is will be quite long. Further, a current (absorption current) due to a chemical change flows through the resistance to be measured, and this current exhibits a characteristic of gradually decreasing over time.
これらの問題のため先の電流電圧法によると、
被測定抵抗に流れる電流の他に接続ケーブルに流
れる電流、つまりケーブルの漏洩電流をも測定し
てしまいケーブルの漏洩電流以下の測定電流を測
定することはできない。また被測定抵抗に寄生す
る容量に対して急速な充電をすれば測定時間を早
めることができるが、一般に微小電流を測定する
電流計においては電流検出用の検出抵抗器の抵抗
値をあまり小さくすると、検出される電圧（検出
抵抗器における降下電圧）が小さくなり、増幅器
の雑音限界などから検出抵抗器の抵抗値を小さく
設定することはできない。このため検出抵抗器が
前記寄生容量に対する充電抵抗となつている場
合、高速度の測定が困難となる。 Due to these problems, according to the previous current-voltage method,
In addition to the current flowing through the resistance to be measured, the current flowing through the connecting cable, that is, the leakage current of the cable, is also measured, making it impossible to measure a measurement current that is less than the leakage current of the cable. In addition, the measurement time can be shortened by quickly charging the capacitance parasitic to the resistance being measured, but in general, in ammeters that measure minute currents, if the resistance value of the detection resistor for current detection is too small, , the detected voltage (voltage drop across the detection resistor) becomes small, and the resistance value of the detection resistor cannot be set to a small value due to the noise limit of the amplifier. Therefore, if the detection resistor serves as a charging resistor for the parasitic capacitance, high-speed measurement becomes difficult.
この発明の目的は高い抵抗に並列に容量が負荷
される場合でもその抵抗に流れる電流を高速度に
測定することができ、また誘導ハムなどの外部か
らの雑音に影響され難い電流測定回路を提供する
ものである。 The purpose of this invention is to provide a current measurement circuit that can measure the current flowing through a high resistance at high speed even when a capacitance is loaded in parallel with the resistance, and is not easily affected by external noise such as induced hum. It is something to do.
「問題点を解決するための手段」
この発明によれば被測定抵抗の電流入力側と電
流出力側とにそれぞれ第１、第２検出抵抗器が直
列に挿入され、その第１、第２検出抵抗器に得ら
れた各検出電圧は第１、第２増幅器でそれぞれ増
幅されるが、その増幅出力は互に逆極性となるよ
うにされる。第１、第２検出抵抗器の被測定抵抗
側にそれぞれ利得が１のバツフア回路が接続さ
れ、上記第１、第２増幅器の出力側と上記第２、
第１バツフア回路の出力側との間にそれぞれ第
１、第２の抵抗分割回路が接続される。これら抵
抗分割回路の分割比は同一とされる。これら第
１、第２抵抗分割回路の各分割点と上記第１、第
２検出抵抗器の被測定抵抗側との間にそれぞれ第
１、第２帰還増幅器が接続される。"Means for Solving the Problem" According to the present invention, first and second detection resistors are inserted in series on the current input side and current output side of the resistance to be measured, respectively, and the first and second detection resistors Each detection voltage obtained at the resistor is amplified by the first and second amplifiers, and the amplified outputs thereof are made to have opposite polarities. Buffer circuits each having a gain of 1 are connected to the resistor sides to be measured of the first and second detection resistors, and the output sides of the first and second amplifiers and the second,
First and second resistance divider circuits are respectively connected between the output side of the first buffer circuit and the output side of the first buffer circuit. The division ratios of these resistance divider circuits are the same. First and second feedback amplifiers are connected between each dividing point of the first and second resistance dividing circuits and the resistance-to-be-measured sides of the first and second detection resistors, respectively.
このように構成されているので被測定抵抗の抵
抗値が見掛上小さく、つまり寄生容量が多く存在
していると第１、第２検出抵抗器にそれだけ大き
な電流が流れ、これに応じて上記帰還増幅器を通
じて増幅器の出力が帰還されて上記被測定抵抗に
大きい電流を流し、寄生容量が存在すればこれに
対する充電が急速に行われる。逆に次の測定に移
り、つまり被測定抵抗を変えた場合においてそれ
までの寄生容量に充電されていた電圧が大きかつ
たり、或は何らかの理由により被測定抵抗の容量
に電荷が充電されている場合で、しかもその電圧
が高い場合には上記帰還増幅器を逆方向に電流が
流れて放電が行われる。このようにして高い抵抗
値の被測定抵抗で、しかも寄生容量が存在しても
その寄生容量に対して高速の充放電を行うことが
でき、高速度に測定を行うことが可能となる。 Because of this configuration, if the resistance value of the resistor to be measured is apparently small, that is, if there is a large amount of parasitic capacitance, a correspondingly large current will flow through the first and second detection resistors, and accordingly, the above-mentioned The output of the amplifier is fed back through the feedback amplifier, causing a large current to flow through the resistor to be measured, and if a parasitic capacitance exists, it is rapidly charged. Conversely, when moving on to the next measurement, that is, changing the resistance to be measured, the voltage charged in the parasitic capacitance up to that point may be large, or the capacitance of the resistance to be measured may be charged for some reason. If the voltage is high, current flows in the opposite direction through the feedback amplifier, causing discharge. In this way, even if a resistor to be measured has a high resistance value and a parasitic capacitance exists, the parasitic capacitance can be charged and discharged at high speed, and measurement can be performed at high speed.
この被測定抵抗の抵抗値が所定値以上か否か、
或は被測定抵抗に流れる電流が所定以下か否かを
判定するには、上記第１、第２抵抗分割回路の分
割点の電圧の差を取出して、その差が所定値以上
か否かによつて被測定抵抗に流れる電流の大小が
所定値以上か否かを測定することができる。また
被測定抵抗に流れる電流自体を測定する場合は被
測定抵抗に流れる電流が定常状態になつた状態で
上記第１、第２帰還増幅器の帰還回路を遮断して
この状態で上記第１、第２増幅器の出力を差動的
に取出し、その出力を指示計で測定すればよい。
このように電流値が基準より大か否かの測定、或
は電流の大きさの絶対的な測定も差動的に取出し
て行うため、第１、第２検出抵抗器に流れる電流
に外部から誘導雑音が重畳してもこれは同位相で
あつて上部差動的に取出す際に互に打消されてこ
の雑音によつて影響されるおそれはない。 Whether the resistance value of this resistor to be measured is greater than or equal to a predetermined value,
Alternatively, to determine whether the current flowing through the resistor to be measured is below a predetermined value, extract the difference in voltage between the dividing points of the first and second resistor divider circuits, and check whether the difference is greater than or equal to a predetermined value. Therefore, it is possible to measure whether the magnitude of the current flowing through the resistance to be measured is greater than or equal to a predetermined value. In addition, when measuring the current flowing through the resistor to be measured, the feedback circuits of the first and second feedback amplifiers are cut off when the current flowing through the resistor to be measured reaches a steady state. It is sufficient to extract the outputs of the two amplifiers differentially and measure the outputs with an indicator.
In this way, the measurement of whether the current value is larger than the reference or the absolute measurement of the current size is performed by differentially extracting the current, so the current flowing through the first and second detection resistors can be detected from the outside. Even if induced noise is superimposed, this noise is in the same phase and is canceled out when taken out differentially from the top, so there is no risk of being affected by this noise.
「実施例」
次にこの発明による電流測定回路の実施例を第
１図を参照して説明する。被測定抵抗１２はリー
ド線２１を通じて検出抵抗器２２の一端に接続さ
れ、検出抵抗器２２の他端は測定用電源１１の一
端、この例では正側に接続される。被測定抵抗１
２の他端はリード線２３を通じて検出抵抗器２４
の一端に接続され、検出抵抗器２４の他端は電源
１１の他端（負側）に接続される。リード線２１
及び検出抵抗器２２の接続点２５は被測定抵抗１
２の電流流入側であり、リード線２３及び検出抵
抗器２４の接続点２６は被測定抵抗１２の電流流
出側である。"Embodiment" Next, an embodiment of the current measuring circuit according to the present invention will be described with reference to FIG. The resistor 12 to be measured is connected to one end of a detection resistor 22 through a lead wire 21, and the other end of the detection resistor 22 is connected to one end of the measurement power supply 11, which is the positive side in this example. Resistance to be measured 1
The other end of 2 is connected to a detection resistor 24 through a lead wire 23.
The other end of the detection resistor 24 is connected to the other end (negative side) of the power supply 11. Lead wire 21
and the connection point 25 of the detection resistor 22 is the resistance to be measured 1
The connection point 26 between the lead wire 23 and the detection resistor 24 is the current outflow side of the resistor 12 to be measured.
検出抵抗器２２，２４に検出された電圧（降下
電圧）は増幅器２７，２８でそれぞれ増幅され、
その増幅出力として検出電圧が逆極性で得られる
ようにする。即ち検出抵抗器２２の接続点２５側
は増幅器２７の反転入力側に接続され、他端は非
反転入力側に接続される。一方検出抵抗器２４の
接続点２６側は増幅器２８の反転入力側に接続さ
れ、他端は非反転入力側に接続される。被測定抵
抗１２に流れる電流に基づく検出抵抗器２２，２
４を通る電流は矢印で示す通りであつて、増幅器
２７においては非反転入力側が正側となり、増幅
器２８においては反転入力側が正側となり、従つ
て増幅器２７，２８の出力は互に逆極性となる。
なお検出抵抗器２２，２４の抵抗値は互に等しく
しておく。また電源１１の負側は接地されてい
る。 The voltages (dropped voltages) detected by the detection resistors 22 and 24 are amplified by amplifiers 27 and 28, respectively.
The detected voltage is made to have a reverse polarity as its amplified output. That is, the connection point 25 side of the detection resistor 22 is connected to the inverting input side of the amplifier 27, and the other end is connected to the non-inverting input side. On the other hand, the connection point 26 side of the detection resistor 24 is connected to the inverting input side of the amplifier 28, and the other end is connected to the non-inverting input side. Detection resistor 22, 2 based on the current flowing through the resistance to be measured 12
The current flowing through the amplifier 27 is as shown by the arrow, and the non-inverting input side of the amplifier 27 is the positive side, and the inverting input side of the amplifier 28 is the positive side, so the outputs of the amplifiers 27 and 28 have opposite polarities. Become.
Note that the resistance values of the detection resistors 22 and 24 are made equal to each other. Further, the negative side of the power supply 11 is grounded.
接続点２５，２６にはそれぞれ利得が１のバツ
フア回路３１，３２の入力側が接続される。増幅
器２７の出力側は抵抗器３３，３４よりなる抵抗
分割回路３５を通じてバツフア回路３２の出力側
に接続される。増幅器２８の出力側は抵抗器３
６，３７よりなる抵抗分割回路３８を通じてバツ
フア回路３１の出力側に接続される。抵抗器３
３，３４の接続点、つまり抵抗分割回路３５の分
割点３９は帰還増幅器４１、更に必要に応じて帰
還抵抗器４２及びスイツチ４３の直列回路を通じ
て接続点２５に接続される。また抵抗分割回路３
８の分割点４４は帰還増幅器４５、必要に応じて
帰還抵抗器４６、スイツチ４７の直列回路を通じ
て接続点２６に接続される。 The input sides of buffer circuits 31 and 32 having a gain of 1 are connected to the connection points 25 and 26, respectively. The output side of the amplifier 27 is connected to the output side of the buffer circuit 32 through a resistance divider circuit 35 made up of resistors 33 and 34. The output side of the amplifier 28 is connected to the resistor 3.
It is connected to the output side of the buffer circuit 31 through a resistor divider circuit 38 consisting of 6 and 37. Resistor 3
The connection point 3 and 34, that is, the division point 39 of the resistance divider circuit 35, is connected to the connection point 25 through a feedback amplifier 41 and, if necessary, a series circuit of a feedback resistor 42 and a switch 43. Also, the resistance divider circuit 3
The dividing point 44 of 8 is connected to the connection point 26 through a series circuit of a feedback amplifier 45, a feedback resistor 46 as necessary, and a switch 47.
更にこの実施例においてリード線２１，２３に
それぞれシールド４８，４９が施される。電源１
１の正側は利得１のバツフア増幅器５１を通じて
シールド４８に接続される。増幅器２７の出力側
及びバツフア増幅器５１の出力側はそれぞれ電源
をアイソレーシヨンするアイソレーシヨン増幅器
５２の非反転入力側及び反転入力側に接続され
る。アイソレーシヨン増幅器５２の出力側は差動
増幅器５３の非反転入力側に接続される。差動増
幅器５３の反転入力側は増幅器２８の出力側に接
続され、出力側は指示計５４に接続される。 Further, in this embodiment, the lead wires 21 and 23 are provided with shields 48 and 49, respectively. Power supply 1
The positive side of 1 is connected to the shield 48 through a buffer amplifier 51 with a gain of 1. The output side of the amplifier 27 and the output side of the buffer amplifier 51 are respectively connected to the non-inverting input side and the inverting input side of an isolation amplifier 52 for isolating the power supply. The output side of isolation amplifier 52 is connected to the non-inverting input side of differential amplifier 53. The inverting input side of the differential amplifier 53 is connected to the output side of the amplifier 28, and the output side is connected to the indicator 54.
また抵抗分割回路３５の分割点３９はアイソレ
ーシヨン増幅器５５の非反転入力側に接続され、
アイソレーシヨン増幅器５５の反転入力側はバツ
フア回路３１の出力側に接続され、出力側は差動
増幅器５６の非反転入力側に接続される。抵抗分
割回路３８の分割点４４は増幅器５７の非反転入
力側に接続され、バツフア回路３２の出力側は増
幅器５７の反転入力側に接続され、増幅器５７の
出力側は差動増幅器５６の反転入力側に接続され
る。差動増幅器５６の出力は比較器５８に供給さ
れ、基準値に対する大小の測定結果が端子５９よ
り出力される。なお増幅器２７，４１，５１，５
２，５５、バツフ回路３１の共通電位点は電源１
１の正側、つまり高電位側となつており、これら
の高電位点６１はシールド４８に接続される。ま
たシールド４９は接地される。 Further, the dividing point 39 of the resistance dividing circuit 35 is connected to the non-inverting input side of the isolation amplifier 55,
The inverting input side of the isolation amplifier 55 is connected to the output side of the buffer circuit 31, and the output side is connected to the non-inverting input side of the differential amplifier 56. The dividing point 44 of the resistance divider circuit 38 is connected to the non-inverting input side of the amplifier 57, the output side of the buffer circuit 32 is connected to the inverting input side of the amplifier 57, and the output side of the amplifier 57 is connected to the inverting input side of the differential amplifier 56. connected to the side. The output of the differential amplifier 56 is supplied to a comparator 58, and the measurement result relative to the reference value is output from a terminal 59. Note that the amplifiers 27, 41, 51, 5
2, 55, the common potential point of the buffer circuit 31 is the power supply 1
1, that is, the high potential side, and these high potential points 61 are connected to the shield 48. Further, the shield 49 is grounded.
この構成において電源１１から被測定抵抗１２
にその被測定抵抗値に応じた電流が流れ、この電
流は検出抵抗器２２，２４に流れ、これらの検出
抵抗器２２，２４において被測定抵抗１２に流れ
た電源に対応した検出電圧がそれぞれ発生し、こ
れら検出電圧はそれぞれ増幅器２７，２８におい
て増幅される。増幅器２７の出力はアイソレーシ
ヨン増幅器５２により、それ迄の電源１１の高電
位側を基準としたレベルが接地を基準としたレベ
ルに変換されて差動増幅器５３に供給される。こ
の場合検出抵抗器２２，２４に得られた各検出電
圧が増幅器２７，２８の出力側に互に逆極性の増
幅出力として得られるため、差動増幅器５３の出
力は増幅器２７，２８の出力が加算されたものと
なり、増幅器５３の出力は被測定抵抗１２に流れ
る電流と対応し、これが指示計５４に指示され
る。 In this configuration, from the power supply 11 to the resistance to be measured 12
A current corresponding to the resistance value to be measured flows through the resistor 12, this current flows to the detection resistors 22 and 24, and a detection voltage corresponding to the power supply flowing to the resistance to be measured 12 is generated in these detection resistors 22 and 24, respectively. However, these detection voltages are amplified by amplifiers 27 and 28, respectively. The output of the amplifier 27 is converted by the isolation amplifier 52 from a level based on the high potential side of the power supply 11 to a level based on the ground, and is supplied to the differential amplifier 53. In this case, the detection voltages obtained at the detection resistors 22 and 24 are obtained as amplified outputs of opposite polarity to the output sides of the amplifiers 27 and 28, so the output of the differential amplifier 53 is different from the output of the amplifiers 27 and 28. The output of the amplifier 53 corresponds to the current flowing through the resistor 12 to be measured, and this is indicated to the indicator 54.
第１図において検出抵抗器２２の検出電圧の増
幅部分及び検出器２４の検出電圧の増幅部分は同
様な回路となつており、例えば検出抵抗器２２の
検出電圧を増幅する部分のみを取出してみると第
２図に示すようになる。即ち被測定抵抗１２の検
出抵抗器２２と反対側は接地され、また増幅器２
７は抵抗分割回路３５を通じて接地されたことに
なる。電源１１の電圧をＥ、被測定抵抗１２、検
出抵抗器２２、抵抗器３３，３４の各抵抗値を
Rx，Rs，Ra，Rbとし、増幅器２７の利得をＧと
すると、被測定抵抗１２に得られる電圧Exは
Ｅ×Rx／Rx＋Rs
であり、抵抗器３４に得られる電圧Esは
Ｅ×（１＋Ｇ×Rs／Rx＋Rs）×Rb／Ra＋Rb
となる。従つてこれら接続点２５に得られる電圧
Exと、分割点３９に得られる電圧Esとが等しい
と帰還増幅器４１に電流が流れない。この平衡状
態におけるRxよりも被測定抵抗１２の抵抗値Rx
は小さく、接続点２５の電圧Exが分割点３９の
電圧Esよりも小さくなると、帰還増幅器４１を通
じて電流が被測定抵抗１２へ供給される。逆に被
測定抵抗値Rxが前記平衡状態におけるRxが大き
くなるとExがEsより大きくなつて帰還増幅器４
１を逆流して分割点３９側に電流が流れる。即ち
この回路は分割点３９と接続点２５とがブリツジ
の一対の対角を構成し、一種のブリツジ回路を構
成し、ExとEsとが等しくなる条件を外れるとブ
リツジが不平衡となり帰還増幅器４１に電流が流
れ、この不平衡の大きさは分割点３９の電圧から
検出することができる。つまり分割点３９の電圧
Esが接続点２５の電圧Exより大きい場合は被測
定抵抗１２の抵抗値Rxブリツジの平衡条件で決
まる値よりも小さなものとなる。従つて基準電圧
Esよりも高いか低いかにより被測定抵抗値Rx、
つまり被測定電流（被測定抵抗１２を流れる電
流）の大小を測定することができる。 In FIG. 1, the detection voltage amplification part of the detection resistor 22 and the detection voltage amplification part of the detector 24 are similar circuits. For example, let's take out only the part that amplifies the detection voltage of the detection resistor 22. and as shown in Figure 2. That is, the opposite side of the resistance to be measured 12 from the detection resistor 22 is grounded, and the side opposite to the detection resistor 22 is connected to the ground.
7 is grounded through the resistor divider circuit 35. The voltage of the power supply 11 is E, and the resistance values of the resistor to be measured 12, the detection resistor 22, and the resistors 33 and 34 are
R x , R s , R a , R b and the gain of the amplifier 27 is G, the voltage Ex obtained at the resistor 12 to be measured is E×R x /R x +R s , and the voltage obtained at the resistor 34 is The resulting voltage Es is E×(1+G×R s /R x +R s )×R b /R a +R b . Therefore, the voltage obtained at these connection points 25
If E x and the voltage E s obtained at the dividing point 39 are equal, no current flows through the feedback amplifier 41 . The resistance value R x of the resistor to be measured 12 is higher than R x in this equilibrium state.
is small, and when the voltage E x at the connection point 25 becomes smaller than the voltage E s at the dividing point 39, a current is supplied to the resistor 12 through the feedback amplifier 41. Conversely, when the measured resistance value R x becomes larger than R x in the above-mentioned equilibrium state, E x becomes larger than E s and the feedback amplifier 4
1 flows backwards to the dividing point 39 side. In other words, in this circuit, the dividing point 39 and the connecting point 25 constitute a pair of diagonals of the bridge, forming a kind of bridge circuit, and when the condition that E x and E s are not equal is removed, the bridge becomes unbalanced and feedback A current flows through the amplifier 41, and the magnitude of this unbalance can be detected from the voltage at the dividing point 39. In other words, the voltage at dividing point 39
When E s is larger than the voltage E x at the connection point 25, the resistance value R x of the resistor 12 to be measured is smaller than the value determined by the equilibrium condition of the bridge. Therefore the reference voltage
The measured resistance value R x depends on whether it is higher or lower than E s .
In other words, it is possible to measure the magnitude of the current to be measured (the current flowing through the resistance to be measured 12).
第１図の例においては分割点３９の電圧Esと接
続点２５の電圧Ex（バツフア回路３１の出力）と
の差がアイソレーシヨン増幅器５５で増幅される
と共にその基準電位点が接地電位に下げられて差
動増幅器５６に供給される。また同様にして分割
点４４と接続点２６との電圧差が増幅器５７で増
幅されて差動増幅器５６へ供給される。この場合
増幅器５５，５７の利得は等しくされ、かつ増幅
出力は互に逆極性である。接続点２５と分割点３
９との電位差の絶対値と、接続点２６と分割点４
４の電位差の絶対値とは等しいが逆極性であり、
従つて差動増幅器５６の出力側でこれら電位差が
加算されて出力され、つまり基準に対する大小関
係がそれだけ大きな値となつて出力され、この出
力は比較器５８において例えば接地電位と比較さ
れる。被測定抵抗１２の抵抗値Rxが基準値より
も小さく、電流値は基準電流値よりも大きいと比
較器５８の出力が高レベルとなり、基準値より抵
抗値Rxが大きく、電流が基準値よりも小さけれ
ば比較器５８の出力は低レベルとなる。このよう
にして基準値に対する大小の判定を測定すること
ができる。 In the example of FIG. 1, the difference between the voltage E s at the dividing point 39 and the voltage E and is supplied to the differential amplifier 56. Similarly, the voltage difference between the dividing point 44 and the connecting point 26 is amplified by the amplifier 57 and supplied to the differential amplifier 56. In this case, the gains of amplifiers 55 and 57 are made equal, and the amplified outputs have opposite polarities. Connection point 25 and division point 3
9 and the absolute value of the potential difference between connection point 26 and division point 4
It is equal to the absolute value of the potential difference of 4 but has opposite polarity,
Therefore, on the output side of the differential amplifier 56, these potential differences are added and outputted, that is, the magnitude relation with respect to the reference becomes a correspondingly larger value, and this output is compared with, for example, a ground potential in the comparator 58. When the resistance value R x of the resistor to be measured 12 is smaller than the reference value and the current value is larger than the reference current value, the output of the comparator 58 becomes a high level, and the resistance value R x is larger than the reference value and the current becomes the reference value. If it is smaller than , the output of comparator 58 will be at a low level. In this way, it is possible to determine the magnitude relative to the reference value.
「発明の効果」
先に述べたように第２図の説明において被測定
抵抗１２を流れる電流が基準よりも大きいと帰還
増幅器４１を通じて電流が被測定抵抗１２へ供給
される。従つて被測定抵抗１２に比較的大きな寄
生容量が存在していると、この被測定抵抗値Rx
が見かけ上小さくなり、つまり検出抵抗器２２を
流れる電流が大きくなるため、先の作用によつて
帰還増幅器４１を通じて被測定抵抗１２へ電流が
供給され、寄生容量に対する充電が急速に行われ
る。また例えばリード線２１，２３の容量に電荷
が充電され、高い電圧となつている場合において
被測定抵抗１２を接続すると接続点２５の電位が
分割点３９の電位よりも高くなり、被測定抵抗１
２やリード線２１などの寄生容量の電荷が帰還増
幅器４１を逆流してその電荷を急速に吸収する。
同様に検出抵抗器２４側においても接続点２６と
分割点４４との電位関係によつて帰還増幅器４５
を通じて電流が流れて被測定抵抗１２の寄生容量
に対する充放電が急速に行われる。このため測定
をそれだけ速く行うことができる。"Effects of the Invention" As described above, in the description of FIG. 2, when the current flowing through the resistor 12 under test is larger than the reference, the current is supplied to the resistor 12 through the feedback amplifier 41. Therefore, if a relatively large parasitic capacitance exists in the resistance to be measured 12, this resistance to be measured R x
appears to be smaller, that is, the current flowing through the detection resistor 22 becomes larger, so that current is supplied to the resistor 12 to be measured through the feedback amplifier 41 due to the above action, and the parasitic capacitance is rapidly charged. Further, for example, when the capacitors of the lead wires 21 and 23 are charged with electric charge and are at a high voltage, when the resistor to be measured 12 is connected, the potential at the connection point 25 becomes higher than the potential at the dividing point 39, and the resistor to be measured 1
The charges of parasitic capacitances such as 2 and the lead wire 21 flow backward through the feedback amplifier 41, and the charges are rapidly absorbed.
Similarly, on the detection resistor 24 side, the feedback amplifier 45 is
A current flows through the resistor 12, and the parasitic capacitance of the resistor 12 to be measured is rapidly charged and discharged. Therefore, measurements can be made that much faster.
増幅器２７の利得をＧ、帰還増幅器４１の利得
をG1、帰還抵抗器４０の抵抗値をRfとすると、
接続点２５から測定器側を見た等価抵抗は
Rf／１＋Ｇ＋G1となる。これが被測定抵抗１２の寄
生容量に対する充電抵抗となり、この充電抵抗値
を検出抵抗器２２の抵抗値の例えば１／10以下とす
ることができ、そのようにすることにより帰還増
幅器４１，４５を通じて被測定抵抗１２に対する
寄生容量に対する充放電を行うことにより、検出
抵抗器２２，２４を通じて行う場合よりも急速に
行うことが可能となる。 Assuming that the gain of the amplifier 27 is G, the gain of the feedback amplifier 41 is G1 , and the resistance value of the feedback resistor 40 is Rf ,
The equivalent resistance when looking at the measuring device side from connection point 25 is
Rf/1+G+ G1 . This becomes a charging resistance for the parasitic capacitance of the resistance to be measured 12, and the charging resistance value can be set to, for example, 1/10 or less of the resistance value of the detection resistor 22. Charging and discharging the parasitic capacitance of the measuring resistor 12 can be performed more rapidly than through the sensing resistors 22 and 24.
なおこれら充放電に対する電流が安定化した後
にスイツチ４３，４７をオフとして増幅器５３の
出力によつて被測定抵抗１２を流れる電流値の測
定を行う。このため例えば差動増幅器５６の出力
の値の変化状態を表示し、これを見て安定化した
状態になつたのを判定してスイツチ４３，４７を
手動でオフにし、又は前記安定化を検出して自動
的にスイツチ４３，４７をオフとしてその時の差
動増幅器５３の出力から被測定抵抗１２の抵抗
値、或はこれを流れる電流を測定する。 Note that after the currents for charging and discharging are stabilized, the switches 43 and 47 are turned off, and the value of the current flowing through the resistance to be measured 12 is measured using the output of the amplifier 53. For this purpose, for example, the state of change in the output value of the differential amplifier 56 is displayed, and by looking at this, it is determined that the state has become stable, and the switches 43 and 47 are manually turned off, or the stabilization is detected. Then, the switches 43 and 47 are automatically turned off, and the resistance value of the resistor 12 to be measured or the current flowing through it is measured from the output of the differential amplifier 53 at that time.
二つの検出抵抗器２２，２４を使用し、しかも
これらに得られる検出電圧を逆極性で取出し、差
動増幅器５３にて差動的に加算し、或は比較測定
の場合は接続点２５，２６と分割点３９，４４と
の各電位差を差動増幅器５６で差動的に加算して
いる。リード線２１，２３に誘起される雑音は同
位相であるから、これら雑音は増幅器２７，２８
の出力側に同位相で現われるため各差動増幅器５
３，５６においてこれら雑音は互に打消されて差
動増幅器５３，５６の出力側には雑音は現われな
い。つまり外部からの誘導雑音に影響されない。 Two detection resistors 22 and 24 are used, and the detection voltages obtained from these are taken out with opposite polarities and added differentially in a differential amplifier 53, or in the case of comparative measurement, at connection points 25 and 26. A differential amplifier 56 differentially adds the potential differences between and the dividing points 39 and 44. Since the noise induced in the lead wires 21 and 23 is in the same phase, these noises are absorbed by the amplifiers 27 and 28.
appear in the same phase on the output side of each differential amplifier 5.
3 and 56, these noises are mutually canceled and no noise appears on the output side of the differential amplifiers 53 and 56. In other words, it is not affected by external induced noise.
更にこの例ではバツフア増幅器５１の出力をシ
ールド４８に接続してシールド４８の電位を電源
１１の高圧側に保持し、シールド４９を接地して
いるためシールド４８からシールド４９に通じる
漏洩電流が存在していてもバツフア増幅器５１か
らこの漏洩電流が供給され、この漏洩電流は被測
定抵抗１２へ流れない。またシールド４８は電源
１１の高圧側の電位とされ、また検出抵抗器２２
における電圧降下は僅かであるためシールド４８
及びリード線２１間の容量の充放電はごく僅かで
あり、殆んど無視できる。同様にシールド４９は
接地されており、これとリード線２３との間の充
放電はごく僅かである。この場合これらシールド
４８，４９をそれぞれ二重シールドとし、例えば
シールド４８側についてはその内側のシールドを
バツフア回路３１の出力側と接続し、外側のシー
ルドをバツフア増幅器５１の出力側と接続する
と、シールドとリード線との間の充放電の影響も
なくなる。 Furthermore, in this example, the output of the buffer amplifier 51 is connected to the shield 48 to maintain the potential of the shield 48 on the high voltage side of the power supply 11, and the shield 49 is grounded, so there is a leakage current flowing from the shield 48 to the shield 49. However, this leakage current is supplied from the buffer amplifier 51, and this leakage current does not flow to the resistor 12 to be measured. Further, the shield 48 is set to the potential on the high voltage side of the power supply 11, and the detection resistor 22
Since the voltage drop at is small, the shield 48
The charging and discharging of the capacitance between the lead wire 21 and the lead wire 21 is very small and can be almost ignored. Similarly, the shield 49 is grounded, and charging and discharging between it and the lead wire 23 is very small. In this case, each of the shields 48 and 49 is double shielded, and for example, on the shield 48 side, the inner shield is connected to the output side of the buffer circuit 31, and the outer shield is connected to the output side of the buffer amplifier 51. The influence of charging and discharging between the terminal and the lead wire is also eliminated.
なおバツフア回路３２は抵抗分割回路３５の基
準電位点を接続点２６に接続した場合に、接続点
２６に対して電流が入出力しないようにするため
のものである。同様に理由によりバツフア回路３
１が設けられている。 The buffer circuit 32 is provided to prevent current from inputting or outputting to the connection point 26 when the reference potential point of the resistance divider circuit 35 is connected to the connection point 26. For the same reason, buffer circuit 3
1 is provided.
なおアイソレーシヨン増幅器５２に利得を持た
せる場合は同様に差動増幅器５３に入力される増
幅器２８の出力を他の増幅器で増幅して利得を合
せる。この基準に対する電流或は抵抗の大小の測
定を行う部分、被測定抵抗１２を流れる電流値或
は抵抗値Rxを測定する部分の一方を省略しても
よい。 Note that when the isolation amplifier 52 has a gain, the output of the amplifier 28 that is input to the differential amplifier 53 is similarly amplified by another amplifier to match the gain. Either the part that measures the magnitude of the current or resistance with respect to this reference, or the part that measures the current value flowing through the resistance to be measured 12 or the resistance value R x may be omitted.
第１図はこの発明による電流測定回路の一例を
示す接続図、第２図はその動作の説明に供するた
めの一部の回路を示す図、第３図は従来の電流測
定回路を示す図である。
１２……被測定抵抗、２２，２４……検出抵抗
器、２７，２８……増幅器、３１，３２……バツ
フア回路、３５，３８……抵抗分割回路、４１，
４５……帰還増幅器、５３，５６……差動増幅
器、５２，５５……アイソレーシヨン増幅器、５
８……比較器。
FIG. 1 is a connection diagram showing an example of a current measuring circuit according to the present invention, FIG. 2 is a diagram showing a part of the circuit to explain its operation, and FIG. 3 is a diagram showing a conventional current measuring circuit. be. 12... Resistance to be measured, 22, 24... Detection resistor, 27, 28... Amplifier, 31, 32... Buffer circuit, 35, 38... Resistance divider circuit, 41,
45... Feedback amplifier, 53, 56... Differential amplifier, 52, 55... Isolation amplifier, 5
8... Comparator.
Claims (1)
れぞれ直列に挿入された第１、第２検出抵抗器
と、これら第１，第２検出抵抗器における各降下
電圧がそれぞれ供給され、互に逆極性の出力電圧
を出力する第１，第２増幅器と、上記第１、第２
検出抵抗器の上記被測定抵抗側にそれぞれ接続さ
れた第１、第２バツフア回路と、上記第１、第２
増幅器の出力側と上記第２、第１バツフア回路の
出力側との間にそれぞれ接続され、同一分割比の
第１、第２抵抗分割回路と、これら第１、第２抵
抗分割回路の各分割点と上記第１、第２検出抵抗
器の被測定抵抗側との間にそれぞれ接続された第
１、第２帰還増幅器とを具備する電流測定回路。1 The first and second detection resistors are inserted in series on the current inflow side and the current output side of the resistor to be measured, and the voltage drops in these first and second detection resistors are respectively supplied and mutually first and second amplifiers outputting output voltages of opposite polarity;
first and second buffer circuits respectively connected to the resistance to be measured side of the detection resistor;
first and second resistance divider circuits connected between the output side of the amplifier and the output sides of the second and first buffer circuits, respectively, and having the same division ratio; and respective divisions of the first and second resistance divider circuits. 1. A current measurement circuit comprising first and second feedback amplifiers connected between the point and the resistor to be measured side of the first and second detection resistors, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23576784A JPS61112969A (en) | 1984-11-07 | 1984-11-07 | Current measuring circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23576784A JPS61112969A (en) | 1984-11-07 | 1984-11-07 | Current measuring circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61112969A JPS61112969A (en) | 1986-05-30 |
| JPH056670B2 true JPH056670B2 (en) | 1993-01-27 |
Family
ID=16990931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23576784A Granted JPS61112969A (en) | 1984-11-07 | 1984-11-07 | Current measuring circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61112969A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104678159A (en) * | 2013-11-28 | 2015-06-03 | 哈尔滨市三和佳美科技发展有限公司 | Industrial three-phase isolation ampere meter |
| JP6487396B2 (en) * | 2016-09-06 | 2019-03-20 | ファナック株式会社 | Current detection circuit not affected by noise |
-
1984
- 1984-11-07 JP JP23576784A patent/JPS61112969A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61112969A (en) | 1986-05-30 |
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