JP5320929B2 - Current measuring device - Google Patents

Current measuring device Download PDF

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JP5320929B2
JP5320929B2 JP2008243253A JP2008243253A JP5320929B2 JP 5320929 B2 JP5320929 B2 JP 5320929B2 JP 2008243253 A JP2008243253 A JP 2008243253A JP 2008243253 A JP2008243253 A JP 2008243253A JP 5320929 B2 JP5320929 B2 JP 5320929B2
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JP2010071963A (en
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康雄 坂巻
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Yokogawa Electric Corp
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Description

本発明は、電流を電圧として測定する電流測定装置に関する。   The present invention relates to a current measuring device that measures current as voltage.

下記特許文献１，２には、電流−電圧変換回路が開示されている。このような電流−電圧変換回路は、演算増幅器、該演算増幅器の逆相入力端と出力端との間に接続された帰還抵抗とから構成されており、外部から逆相入力端に向けて入力される電流を演算増幅器の出力端の電圧に変換するものである。   Patent Documents 1 and 2 below disclose current-voltage conversion circuits. Such a current-voltage conversion circuit is composed of an operational amplifier and a feedback resistor connected between the negative phase input terminal and the output terminal of the operational amplifier, and is input from the outside toward the negative phase input terminal. The converted current is converted into the voltage at the output terminal of the operational amplifier.

このような電流−電圧変換回路は、例えば電圧源と組み合わせることにより、測定対象コンデンサの絶縁抵抗の測定に利用されている。すなわち、電流−電圧変換回路を用いた絶縁抵抗測定装置は、電圧源の正極端を測定対象コンデンサの一端に接続すると共に当該測定対象コンデンサの他端を上記演算増幅器の逆相入力端に接続、かつ電圧源の負極端及び演算増幅器の正相入力端とを接地することにより、測定対象コンデンサの絶縁抵抗値に基づいて当該測定対象コンデンサから帰還抵抗に流れる測定電流を演算増幅器の出力端の電圧として検出するものである。
なお、下記特許文献３、４には、上記電流−電圧変換回路を利用した２端子回路素子測定装置が開示されている。
特開２００３−３０９４３８号公報 特開２００２−０４３８５８号公報 特開２００４−０２０２４６号公報 特開２００４−２４５５８４号公報 Such a current-voltage conversion circuit is used for measuring the insulation resistance of a capacitor to be measured, for example, in combination with a voltage source. That is, the insulation resistance measuring device using the current-voltage conversion circuit connects the positive electrode end of the voltage source to one end of the measurement target capacitor and the other end of the measurement target capacitor to the reverse phase input end of the operational amplifier. In addition, by grounding the negative terminal of the voltage source and the positive phase input terminal of the operational amplifier, the measurement current flowing from the measurement target capacitor to the feedback resistor is converted to the voltage at the output terminal of the operational amplifier based on the insulation resistance value of the measurement target capacitor. Is detected.
The following Patent Documents 3 and 4 disclose a two-terminal circuit element measuring apparatus using the current-voltage conversion circuit.
JP 2003-309438 A JP 2002-043858 A JP 2004-020246 A Japanese Patent Laid-Open No. 2004-245584

ところで、上記従来の絶縁抵抗測定装置では、一対の測定端子と測定対象コンデンサの各端とを接触接続させることにより測定対象コンデンサを接続状態とするが、両者が正常に接触していない場合に、測定不能或いは測定対象コンデンサの絶縁抵抗値が極めて高い抵抗値として測定される。したがって、従来の絶縁抵抗測定装置では、正常な接触状態において高抵抗値が測定されたのか、或いは接続異常が原因で高抵抗値が測定されたのかを切り分けることができないという問題がある。   By the way, in the above conventional insulation resistance measuring device, the measurement target capacitor is brought into a connected state by contact-connecting the pair of measurement terminals and each end of the measurement target capacitor, but when both are not in normal contact, It is measured as a resistance value that is impossible to measure or an insulation resistance value of the capacitor to be measured is extremely high. Therefore, the conventional insulation resistance measuring apparatus has a problem that it cannot be determined whether the high resistance value is measured in a normal contact state or whether the high resistance value is measured due to the connection abnormality.

本発明は、上述した事情に鑑みてなされたものであり、測定対象コンデンサ等の外部装置と測定端子との接続異常を検知して信頼性の高い測定を実現することを目的とする。   The present invention has been made in view of the above-described circumstances, and an object thereof is to realize a highly reliable measurement by detecting a connection abnormality between an external device such as a capacitor to be measured and a measurement terminal.

上記目的を達成するために、本発明では、第１の解決手段として、外部装置から測定端子に入力された電流を電圧に変換して検出する電流測定装置において、所定のランプ信号が前記測定端子に印加された状態で前記測定端子に入力される電流を電圧に変換した信号が前記所定のランプ信号に重畳された信号と、前記所定のランプ信号とを比較することにより、前記測定端子と前記外部装置との接続異常を検知する接続異常検知手段を具備する、という手段を採用する。 In order to achieve the above object, according to the present invention, as a first solution, in a current measuring device that detects a current input from an external device by converting it into a voltage, a predetermined ramp signal is transmitted to the measuring terminal. By comparing the predetermined ramp signal with a signal obtained by superimposing a signal obtained by converting a current input to the measurement terminal into a voltage applied to the predetermined ramp signal with the predetermined ramp signal, A means is provided that includes a connection abnormality detection means for detecting a connection abnormality with an external device .

第２の解決手段として、上記第１の解決手段において、接続異常検知手段は、逆相入力端が測定端子に接続された演算増幅器と逆相入力端と演算増幅器の出力端との間に接続された帰還抵抗とからなる電流電圧変換回路と、正傾斜及び逆傾斜のランプ信号を生成して演算増幅器の正相入力端に出力するランプ信号発生手段と、該ランプ信号発生手段から出力されるランプ信号と演算増幅器の出力端の電圧との差分を出力する差分手段と、該差分手段の出力が所定のしきい値を越えるか否かに基づいて測定端子と外部装置との接続異常を判定する判定手段とからなり、測定端子に入力する上記電流を前記演算増幅器の出力端の電圧として検出する、という手段を採用する。   As a second solution means, in the first solution means, the connection abnormality detection means is connected between the operational amplifier having the negative phase input terminal connected to the measurement terminal, the negative phase input terminal and the output terminal of the operational amplifier. A current-voltage conversion circuit comprising a feedback resistor, a ramp signal generating means for generating a ramp signal having a positive slope and a reverse slope and outputting the ramp signal to the positive phase input terminal of the operational amplifier, and output from the ramp signal generating means A differential means for outputting a difference between the ramp signal and the voltage at the output terminal of the operational amplifier, and determining whether the measurement terminal and the external device are abnormally connected based on whether the output of the differential means exceeds a predetermined threshold value And a means for detecting the current input to the measurement terminal as a voltage at the output terminal of the operational amplifier.

第３の解決手段として、上記第２の解決手段において、ランプ信号発生手段は、第２の演算増幅器を用いた逆相積分回路と、該逆相積分回路の入力端を正電圧あるいは負電圧に切り替える入力切替回路と、第２の演算増幅器の逆相入力端と出力端とを短絡させるスイッチとからなる、という手段を採用する。   As a third solving means, in the second solving means, the ramp signal generating means includes a negative phase integrating circuit using a second operational amplifier, and an input terminal of the negative phase integrating circuit is set to a positive voltage or a negative voltage. A means is adopted which comprises an input switching circuit for switching and a switch for short-circuiting the negative phase input terminal and the output terminal of the second operational amplifier.

第４の解決手段として、上記第２または第３の解決手段において、電圧源をさらに備え、当該電圧源の一方の出力端と測定端子との間に接続された測定対象コンデンサに流れる電流に基づいて測定対象コンデンサの絶縁抵抗値を演算増幅器の出力端の電圧として検出する、という手段を採用する。   As a fourth solution, based on the current flowing in the capacitor to be measured which is further provided with a voltage source in the second or third solution and is connected between one output terminal of the voltage source and the measurement terminal. Then, means for detecting the insulation resistance value of the capacitor to be measured as the voltage at the output terminal of the operational amplifier is adopted.

本発明によれば、測定端子と外部装置との接続異常を、測定端子に入力された電流を所定のランプ信号と比較することにより検知する接続異常検知手段を具備するので、測定端子と外部装置との接続異常による異常微小電流の測定と測定端子と外部装置との接続が正常な場合における正常微小電流の測定とを切り分けることが可能であり、よって従来よりも信頼性の高い電流測定を実現することができる。   According to the present invention, since the connection abnormality detecting means for detecting the connection abnormality between the measurement terminal and the external device by comparing the current input to the measurement terminal with a predetermined lamp signal is provided, the measurement terminal and the external device are provided. It is possible to separate the measurement of abnormal minute current due to abnormal connection with the measurement of normal minute current when the connection between the measurement terminal and the external device is normal, thus realizing more reliable current measurement than before can do.

以下、図面を参照して、本発明の一実施形態について説明する。
図１は、本実施形態に係る絶縁抵抗測定装置Ａ（電流測定装置）の構成を示す回路図である。この図において、符号Ｔ1，Ｔ2は一対の測定端子、１は電流電圧変換回路、２は電圧計、３はランプ信号発生回路、４は接触不良検知回路、５は電圧源、６は操作制御部、またＣｘは測定対象コンデンサである。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a configuration of an insulation resistance measuring apparatus A (current measuring apparatus) according to the present embodiment. In this figure, T1 and T2 are a pair of measurement terminals, 1 is a current-voltage conversion circuit, 2 is a voltmeter, 3 is a lamp signal generation circuit, 4 is a contact failure detection circuit, 5 is a voltage source, and 6 is an operation control unit. Cx is a capacitor to be measured.

また、上記電流電圧変換回路１は、演算増幅器Ｕ1と帰還抵抗器Ｒ1から構成され、上記ランプ信号発生回路３は、演算増幅器Ｕ2、積分コンデンサＣ1、積分抵抗器Ｒ2、３つのスイッチＳ1〜Ｓ3（開閉スイッチ）から構成され、また上記接触不良検知回路４は、差動増幅器７及び比較器８から構成されている。これら各構成要素のうち、測定対象コンデンサＣｘを除く一対の測定端子Ｔ1，Ｔ2、電流電圧変換回路１、電圧計２、ランプ信号発生回路３、接触不良検知回路４、電圧源５及び操作制御部６は一体として本絶縁抵抗測定装置Ａを構成する。なお、電圧源５については、本絶縁抵抗測定装置Ａ内に一体に設けられず、ユーザの使い勝手等を考慮して別体として設けられる場合がある。   The current-voltage conversion circuit 1 includes an operational amplifier U1 and a feedback resistor R1, and the ramp signal generation circuit 3 includes an operational amplifier U2, an integrating capacitor C1, an integrating resistor R2, and three switches S1 to S3 ( The contact failure detection circuit 4 includes a differential amplifier 7 and a comparator 8. Among these components, a pair of measurement terminals T1, T2, excluding the measurement target capacitor Cx, current-voltage conversion circuit 1, voltmeter 2, ramp signal generation circuit 3, contact failure detection circuit 4, voltage source 5 and operation control unit 6 constitutes the insulation resistance measuring apparatus A as a unit. Note that the voltage source 5 may not be provided integrally in the insulation resistance measuring apparatus A but may be provided as a separate body in consideration of user convenience.

また、本絶縁抵抗測定装置Ａを構成する各測定端子Ｔ1，Ｔ2、電流電圧変換回路１、電圧計２、ランプ信号発生回路３、接触不良検知回路４、電圧源５及び操作制御部６のうち、電圧計２を除く各測定端子Ｔ1，Ｔ2、電流電圧変換回路１、ランプ信号発生回路３、接触不良検知回路４、電圧源５及び操作制御部６は、本実施形態における接続異常検知手段を構成している。   Among the measurement terminals T1 and T2, the current-voltage conversion circuit 1, the voltmeter 2, the ramp signal generation circuit 3, the contact failure detection circuit 4, the voltage source 5 and the operation control unit 6 constituting the insulation resistance measuring apparatus A The measurement terminals T1 and T2, excluding the voltmeter 2, the current-voltage conversion circuit 1, the ramp signal generation circuit 3, the contact failure detection circuit 4, the voltage source 5 and the operation control unit 6 are connected abnormality detection means in this embodiment. It is composed.

上記一対の測定端子Ｔ1，Ｔ2のうち、一方の測定端子Ｔ1は、演算増幅器Ｕ1の逆相入力端に接続されると共に測定対象コンデンサＣｘの一端が接続される。他方の測定端子Ｔ2は、電圧源４を正極端に接続されると共に測定対象コンデンサＣｘの他端が接続される。   Of the pair of measurement terminals T1 and T2, one measurement terminal T1 is connected to the reverse phase input terminal of the operational amplifier U1 and one end of the measurement target capacitor Cx. The other measurement terminal T2 is connected to the voltage source 4 at the positive electrode end and to the other end of the measurement target capacitor Cx.

電流電圧変換回路１は、演算増幅器Ｕ1と当該演算増幅器Ｕ1の逆相入力端と出力端との間に設けられた帰還抵抗器Ｒ1からなる電流電圧変換回路である。このような電流電圧変換回路１は、上記一方の測定端子Ｔ1を介して入力される電流Ｉ1及びランプ信号発生回路３から入力される電圧Ｖ1とに基づいて電圧Ｖ2を生成するものであり、測定電圧として外部に出力すると共に評価信号として差動増幅器７の一方の入力端（例えば正相入力端）に出力する。   The current-voltage conversion circuit 1 is a current-voltage conversion circuit including an operational amplifier U1 and a feedback resistor R1 provided between the negative phase input terminal and the output terminal of the operational amplifier U1. Such a current-voltage conversion circuit 1 generates a voltage V2 based on the current I1 input through the one measurement terminal T1 and the voltage V1 input from the ramp signal generation circuit 3, A voltage is output to the outside and an evaluation signal is output to one input terminal (for example, a positive phase input terminal) of the differential amplifier 7.

電圧計２は、上記電流電圧変換回路１から出力される測定電圧を測定する積分型電圧計である。ランプ信号発生回路３は、演算増幅器Ｕ2と、当該演算増幅器Ｕ2の逆相入力端と出力端との間に設けられた積分コンデンサＣ1と、一端が上記演算増幅器Ｕ2の逆相入力端に接続された積分抵抗器Ｒ2とからなる逆相積分回路を備えると共に、積分抵抗器Ｒ2の他端と正極基準電圧＋Ｖrefとの間に設けられたスイッチＳ1、積分抵抗器Ｒ2の他端と負極基準電圧−Ｖrefとの間に設けられたスイッチＳ2及び上記積分コンデンサＣ1に並列接続されたスイッチＳ3を備える。   The voltmeter 2 is an integral voltmeter that measures the measurement voltage output from the current-voltage conversion circuit 1. The ramp signal generating circuit 3 has an operational amplifier U2, an integration capacitor C1 provided between the negative phase input terminal and the output terminal of the operational amplifier U2, and one end connected to the negative phase input terminal of the operational amplifier U2. And an integrating resistor R2, and a switch S1 provided between the other end of the integrating resistor R2 and the positive reference voltage + Vref, the other end of the integrating resistor R2 and the negative reference voltage − A switch S2 provided between Vref and a switch S3 connected in parallel to the integrating capacitor C1.

このようなランプ信号発生回路３は、３つのスイッチＳ1〜Ｓ3の開閉状態に応じて正傾斜のランプ信号、逆傾斜のランプ信号あるいは一定電圧信号からなる電圧Ｖ1を生成して演算増幅器Ｕ1の正相入力端及び差動増幅器７の他方の入力端（例えば逆相入力端）に出力する。このランプ信号発生回路３は、本実施形態におけるランプ信号発生手段である。なお、上記３つのスイッチＳ1〜Ｓ3のうち、２つのスイッチＳ1，Ｓ2は、本実施形態における入力切替回路である。   Such a ramp signal generating circuit 3 generates a voltage V1 composed of a ramp signal having a positive slope, a ramp signal having a reverse slope, or a constant voltage signal in accordance with the open / closed state of the three switches S1 to S3. It outputs to the phase input terminal and the other input terminal (for example, reverse phase input terminal) of the differential amplifier 7. This ramp signal generating circuit 3 is a ramp signal generating means in this embodiment. Of the three switches S1 to S3, two switches S1 and S2 are input switching circuits in the present embodiment.

接触不良検知回路４は、電圧Ｖ1と電圧Ｖ2との差分を増幅して電圧Ｖ3を出力する差動増幅器７と、操作制御部６から入力される判定パルスのタイミングにおいて上記電圧Ｖ3を所定のしきい値と比較する比較器８とから構成されており、比較器７の出力を接触不良検知信号として外部に出力する。このような接触不良検知信号は、上記一対の測定端子Ｔ1，Ｔ2における測定対象コンデンサＣｘの接続状態が正常な接触による正常接続かあるいは接触不良による異常接続かを示す信号である。なお、上記差動増幅器７は本実施形態における差分手段、また比較器８は本実施形態における判定手段である。 Contact failure detection circuit 4 includes a differential amplifier 7 which outputs a voltage V3 by amplifying a difference between the voltages V1 and V2, the voltage V3 predetermined teeth at the timing of determination pulse input from the operation control section 6 Comparing with a threshold value comparator 8, the output of the comparator 7 is output to the outside as a contact failure detection signal. Such a contact failure detection signal is a signal indicating whether the connection state of the capacitor Cx to be measured at the pair of measurement terminals T1 and T2 is normal connection due to normal contact or abnormal connection due to contact failure. The differential amplifier 7 is a difference means in this embodiment, and the comparator 8 is a determination means in this embodiment.

電圧源５は、一定電圧Ｖｄを出力する定電圧源である。操作制御部６は、ユーザーの操作指示を受け付けると共に当該操作指示と予め記憶された制御プログラムに基づいて上記各スイッチＳ1〜Ｓ3及び比較器６を操作することにより、本絶縁抵抗測定装置Ａの全体動作を制御するものである。
また、上記測定対象コンデンサＣｘは、電子素子として周知なコンデンサであって、特にその種類に特徴はない。すなわち、測定対象コンデンサＣｘは、各種の電解コンデンサ、各種のフィルムコンデンサ等、どのようなものでも良い。なお、この測定対象コンデンサＣｘは本実施形態における外部装置である。 The voltage source 5 is a constant voltage source that outputs a constant voltage Vd. The operation control unit 6 receives the user's operation instruction and operates the switches S1 to S3 and the comparator 6 based on the operation instruction and a control program stored in advance, so that the entire insulation resistance measuring apparatus A is entirely operated. It controls the operation.
The capacitor Cx to be measured is a capacitor well-known as an electronic element, and there is no particular feature in its type. That is, the measurement target capacitor Cx may be any type of electrolytic capacitor, various film capacitor, and the like. This measurement target capacitor Cx is an external device in the present embodiment.

次に、このように構成された本絶縁抵抗測定装置Ａの特徴的動作について、図２をも参照して詳しく説明する。   Next, the characteristic operation of the insulation resistance measuring apparatus A configured as described above will be described in detail with reference to FIG.

本絶縁抵抗測定装置Ａを用いた絶縁抵抗測定は、図２に示すように３つの工程を経て完了する。第1の工程が接続チェック工程であり、第２の工程が放電工程であり、また第３の工程が絶縁抵抗測定工程である。   The insulation resistance measurement using this insulation resistance measuring apparatus A is completed through three steps as shown in FIG. The first process is a connection check process, the second process is a discharge process, and the third process is an insulation resistance measurement process.

ユーザが測定対象コンデンサＣｘを測定端子Ｔ1，Ｔ2に接続すると、電圧源５により充電が開始される（図示略）。満充電になった後操作制御装置６に測定開始を指示すると、操作制御装置６は、最初の接続チェック工程において、スイッチＳ1をＯＦＦ状態に、スイッチＳ2を時刻ｔ1〜ｔ2の期間Ｔａ（積分時間）だけＯＮ状態に、またスイッチＳ3を上記スイッチＳ2に同期させて時刻ｔ1からＯＦＦ状態にそれぞれ設定する。このようなスイッチＳ1〜Ｓ3の設定状態では、ランプ信号発生回路３の逆相積分回路には負極基準電圧−Ｖrefが期間Ｔａに亘って供給されるので、その出力である電圧Ｖ1は、図２に示すように、時間経過と共に順次値が一定傾斜で増加する正傾斜のランプ信号となる。 When the user connects the capacitor Cx to be measured to the measurement terminals T1 and T2, charging is started by the voltage source 5 (not shown). When the operation control device 6 is instructed to start measurement after full charge, the operation control device 6 turns off the switch S1 and sets the switch S2 to the period Ta (integration time) from time t1 to t2 in the first connection check process. ) Only in the ON state, and the switch S3 is set in the OFF state from time t1 in synchronization with the switch S2. In such a set state of the switches S1 to S3, the negative reference voltage -Vref is supplied to the negative phase integrating circuit of the ramp signal generating circuit 3 over the period Ta, so that the output voltage V1 is shown in FIG. As shown in FIG. 4, the ramp signal has a positive slope whose value increases with a constant slope sequentially with time.

また、このような電圧Ｖ1は、負極基準電圧−Ｖref、積分抵抗器Ｒ2、積分コンデンサＣ1及び時間変数ｔとからなる下式（１）によって表される。そして、このような正傾斜のランプ信号は、演算増幅器Ｕ1の正相入力端に入力される。   Such a voltage V1 is represented by the following equation (1) including a negative reference voltage -Vref, an integrating resistor R2, an integrating capacitor C1, and a time variable t. Such a ramp signal having a positive slope is input to the positive phase input terminal of the operational amplifier U1.

Figure 0005320929
Figure 0005320929

演算増幅器Ｕ1の逆相入力端には、負帰還制御により正相入力端と同じになる様に制御されるため、電圧Ｖ1と同じ信号が発生する。これにより、測定端子Ｔ1には、下式（２）に示すように測定対象コンデンサＣｘ（静電容量）に応じた電流Ｉ1が入力される。すなわち、この電流Ｉ1は、時刻ｔ2における電圧Ｖ1の値をＶｐとし、また測定対象コンデンサＣｘの絶縁抵抗値が十分に大きいとすると、測定対象コンデンサＣｘ（静電容量）、電圧Ｖｐ及び期間Ｔａとからなる下式（２）によって表される。   Since the negative phase input terminal of the operational amplifier U1 is controlled to be the same as the positive phase input terminal by negative feedback control, the same signal as the voltage V1 is generated. As a result, the current I1 corresponding to the measurement target capacitor Cx (capacitance) is input to the measurement terminal T1 as shown in the following equation (2). That is, the current I1 is obtained by assuming that the value of the voltage V1 at time t2 is Vp, and that the insulation resistance value of the measurement target capacitor Cx is sufficiently large, the measurement target capacitor Cx (capacitance), the voltage Vp, It is represented by the following formula (2) consisting of

Figure 0005320929
Figure 0005320929

このような電流Ｉ1と上記正傾斜のランプ信号とが電流電圧変換回路１に入力されることにより、電流電圧変換回路１（演算増幅器Ｕ1）の出力端における電圧Ｖ2は、図２に示すように、電流Ｉ1と帰還抵抗器Ｒ1とによって発生する電圧ΔＶｃが正傾斜のランプ信号に重畳したものとなる。この電圧ΔＶｃは、演算増幅器Ｕ1の入力インピーダンスが十分い大きいとすると、電流Ｉ1と帰還抵抗器Ｒ1とに依存するので、測定対象コンデンサＣｘの静電容量を反映した値となる。   When such a current I1 and the ramp signal having the positive slope are input to the current-voltage conversion circuit 1, the voltage V2 at the output terminal of the current-voltage conversion circuit 1 (operational amplifier U1) is as shown in FIG. The voltage ΔVc generated by the current I1 and the feedback resistor R1 is superimposed on the positive ramp signal. If the input impedance of the operational amplifier U1 is sufficiently large, the voltage ΔVc depends on the current I1 and the feedback resistor R1, and thus has a value reflecting the capacitance of the measurement target capacitor Cx.

ここで、上記電圧ΔＶｃは、測定対象コンデンサＣｘが各測定端子Ｔ1，Ｔ2に正常に接触接続されている場合は測定対象コンデンサＣｘの静電容量を示す値となるが、測定対象コンデンサＣｘが各測定端子Ｔ1，Ｔ2に正常に接触接続されていない場合には、各測定端子Ｔ1，Ｔ2間の静電容量は測定対象コンデンサＣｘよりも大幅に小さな値となるので、測定対象コンデンサＣｘの静電容量を示す値にならない。 Here, the voltage ΔVc is a value indicating the capacitance of the measurement target capacitor Cx when the measurement target capacitor Cx is normally contact-connected to the measurement terminals T1 and T2. When the measurement terminals T1 and T2 are not normally contact-connected, the capacitance between the measurement terminals T1 and T2 is much smaller than the measurement target capacitor Cx. The value does not indicate capacity.

このような電圧Ｖ2と上記正傾斜のランプ信号とは差動増幅器７によって差分増幅され、差動増幅器７の出力である電圧Ｖ3は、図２に示すように電流Ｉ1の大きさによって規定される上記信号となる。そして、比較器８は、このような電圧ΔＶｃを示す電圧Ｖ3を操作制御部６から入力される判定パルスのタイミングで所定のしきい値と比較することによって接触不良検知信号を出力する。   Such a voltage V2 and the positive slope ramp signal are differentially amplified by the differential amplifier 7, and the voltage V3 which is the output of the differential amplifier 7 is defined by the magnitude of the current I1 as shown in FIG. The above signal. Then, the comparator 8 outputs a contact failure detection signal by comparing the voltage V3 indicating the voltage ΔVc with a predetermined threshold at the timing of the determination pulse input from the operation control unit 6.

このしきい値は、測定対象コンデンサＣｘの正常接続の場合と異常接続（接続不良）の場合とによる各測定端子Ｔ1，Ｔ2間の静電容量の違いを考慮することにより測定対象コンデンサＣｘと各測定端子Ｔ1，Ｔ2との接続状態の正常／異常を識別可能な値として設定されたものであり、接触不良検知信号は、測定対象コンデンサＣｘと各測定端子Ｔ1，Ｔ2との接続状態の正常／異常に応じて異なる論理レベルの信号、つまり上記接続状態の正常／異常を論理レベルの相違で示す信号となる。   This threshold is determined by taking into account the difference in capacitance between the measurement terminals T1, T2 depending on whether the measurement target capacitor Cx is normally connected or abnormally connected (connection failure). The connection failure detection signal is set as a value that can identify whether the connection state between the measurement terminals T1 and T2 is normal or abnormal, and the contact failure detection signal indicates whether the connection state between the measurement target capacitor Cx and each measurement terminal T1 or T2 is normal / normal. It becomes a signal having a different logic level depending on the abnormality, that is, a signal indicating whether the connection state is normal or abnormal by a difference in logic level.

このように、測定開始直後の接続チェック工程では、スイッチＳ1をＯＮ状態、かつスイッチＳ2，Ｓ3をＯＦＦ状態に設定した状態で電圧ΔＶｃの大小（つまり各測定端子Ｔ1，Ｔ2間の静電容量）を評価することにより測定対象コンデンサＣｘと各測定端子Ｔ1，Ｔ2との接続状態の正常／異常を検知し、この検知結果を示す接触不良検知信号を外部に出力する。   As described above, in the connection check process immediately after the start of measurement, the voltage ΔVc is large (that is, the capacitance between the measurement terminals T1 and T2) with the switch S1 in the ON state and the switches S2 and S3 in the OFF state. Is detected to detect normality / abnormality of the connection state between the measurement target capacitor Cx and each of the measurement terminals T1, T2, and a contact failure detection signal indicating the detection result is output to the outside.

続いて、放電工程は、上記接続チェック工程の後に行われるものであり、図２に示すように、スイッチＳ1を時刻ｔ3〜ｔ4の期間Ｔｂ（積分時間）だけＯＮ状態、かつスイッチＳ2，Ｓ3をＯＦＦ状態に設定することにより電圧Ｖ2を負傾斜のランプ信号とする。この際の電圧Ｖ2は、ランプ信号発生回路３の逆相積分回路には正極基準電圧＋Ｖrefが供給されるので、下式（３）によって表される。   Subsequently, the discharge process is performed after the connection check process. As shown in FIG. 2, the switch S1 is turned on for the period Tb (integration time) from time t3 to t4, and the switches S2 and S3 are turned on. By setting the switch to the OFF state, the voltage V2 is changed to a ramp signal having a negative slope. The voltage V2 at this time is expressed by the following expression (3) because the positive phase reference voltage + Vref is supplied to the negative phase integrating circuit of the ramp signal generating circuit 3.

Figure 0005320929
Figure 0005320929

このような放電工程では、電圧Ｖ2を負傾斜のランプ信号とすることにより、先の接続チェック工程で測定対象コンデンサＣｘに蓄積された電荷を完全に放電させる。これによって、後ろの絶縁抵抗測定工程において測定対象コンデンサＣｘに過大な放電電流が流れて当該測定対象コンデンサＣｘにダメージを与えること、また演算増幅器Ｕ1の動作不安定を回避する。   In such a discharge process, the voltage V2 is used as a ramp signal having a negative slope, so that the charge accumulated in the measurement target capacitor Cx in the previous connection check process is completely discharged. As a result, in the subsequent insulation resistance measurement step, an excessive discharge current flows through the measurement target capacitor Cx to damage the measurement target capacitor Cx, and the operational instability of the operational amplifier U1 is avoided.

最後の絶縁抵抗測定工程では、図２に示すように、スイッチＳ1，Ｓ2をＯＦＦ状態、かつスイッチＳ3をＯＮ状態に設定することにより、電圧Ｖ2を接地電位（演算増幅器Ｕ2の正相入力端の電位）とする。したがって、電流電圧変換回路１における演算増幅器Ｕ1の正相入力端の電位も接地電位となる。   In the final insulation resistance measurement step, as shown in FIG. 2, by setting the switches S1 and S2 to the OFF state and the switch S3 to the ON state, the voltage V2 is set to the ground potential (the positive phase input terminal of the operational amplifier U2). Potential). Therefore, the potential of the positive phase input terminal of the operational amplifier U1 in the current-voltage conversion circuit 1 is also the ground potential.

この絶縁抵抗測定工程では、図示するように、測定対象コンデンサＣｘは満充電状態なので、電流Ｉ1は測定対象コンデンサＣｘの絶縁抵抗値を示す電圧ΔＶiとなる。このような電圧Ｖ2（＝ΔＶi）を電圧計２で計測し、電圧Ｖ2、帰還抵抗器Ｒ1及び電圧源５の出力電圧Ｖｄからなる下式（４）に代入することにより絶縁抵抗値Ｒｘが得られる。   In this insulation resistance measurement step, as shown in the figure, the measurement target capacitor Cx is in a fully charged state, so the current I1 becomes a voltage ΔVi indicating the insulation resistance value of the measurement target capacitor Cx. Such a voltage V2 (= ΔVi) is measured by the voltmeter 2 and substituted into the following equation (4) consisting of the voltage V2, the feedback resistor R1 and the output voltage Vd of the voltage source 5 to obtain the insulation resistance value Rx. It is done.

Figure 0005320929
Figure 0005320929

本実施形態によれば、絶縁抵抗測定工程の前工程として行われる接続チェック工程において、各測定端子Ｔ1，Ｔ2間の静電容量を評価することにより測定対象コンデンサＣｘと各測定端子Ｔ1，Ｔ2との接続状態の正常／異常を検知するので、測定対象コンデンサＣｘについて信頼性の高い絶縁抵抗測定を実現することができる。
また、放電工程を行うので、後工程において測定対象コンデンサＣｘに短絡などによる過大な放電電流が流れて当該測定対象コンデンサＣｘにダメージを与えることを防止することができる。 According to the present embodiment, in the connection check process performed as a pre-process of the insulation resistance measurement process, the measurement target capacitor Cx and the measurement terminals T1, T2 are evaluated by evaluating the capacitance between the measurement terminals T1, T2. Therefore, it is possible to realize highly reliable insulation resistance measurement for the measurement target capacitor Cx.
Further, since the discharging process is performed, it is possible to prevent an excessive discharge current caused by a short circuit or the like from flowing in the measurement target capacitor Cx in a subsequent process and damaging the measurement target capacitor Cx.

なお、本発明は、上記実施形態に限定されるものではなく、例えば以下のような変形例が考えられる。
（１）上記実施形態は、本発明を測定対象コンデンサＣｘの絶縁抵抗の測定に適用したものであるが、本発明は、このような絶縁抵抗の測定に限定されることなく種々の電子部品の絶縁抵抗の測定や各種の電流測定に適用することができる。 In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the present invention is applied to the measurement of the insulation resistance of the capacitor Cx to be measured. However, the present invention is not limited to such measurement of the insulation resistance, and various electronic components can be used. It can be applied to measurement of insulation resistance and various current measurements.

（２）上記実施形態では、接続チェック工程の後で放電工程を行うようにしたが、必要に応じて放電工程を削除しても良い。また、上記実施形態では、接続チェック工程を絶縁抵抗測定工程の前工程としたが、絶縁抵抗測定工程の後工程としても良い。 (2) In the above embodiment, the discharge process is performed after the connection check process. However, the discharge process may be deleted as necessary. Moreover, in the said embodiment, although the connection check process was made into the front process of the insulation resistance measurement process, it is good also as a post process of an insulation resistance measurement process.

（３）上記実施形態では、本発明のランプ信号発生手段をランプ信号発生回路３として構成したが、ランプ信号発生手段の構成はランプ信号発生回路３に限定されない。例えば、波形生成プログラムによってランプ信号発生回路３の出力信号と同等な信号を発生させるようにランプ信号発生手段を構成しても良い。 (3) In the above embodiment, the ramp signal generating means of the present invention is configured as the ramp signal generating circuit 3, but the configuration of the ramp signal generating means is not limited to the ramp signal generating circuit 3. For example, the ramp signal generation means may be configured to generate a signal equivalent to the output signal of the ramp signal generation circuit 3 by a waveform generation program.

（４）上記実施形態では、本発明の差分手段を差動増幅器７として構成し、また本発明の判定手段を比較器として構成したが、本発明はこれに限定されない。例えばソフトウエアに基づくデジタル信号処理によって差動増幅器７及び比較器８の機能を実現しても良い。 (4) In the above embodiment, the difference means of the present invention is configured as the differential amplifier 7 and the determination means of the present invention is configured as a comparator, but the present invention is not limited to this. For example, the functions of the differential amplifier 7 and the comparator 8 may be realized by digital signal processing based on software.

本発明の一実施形態に係わる絶縁抵抗測定装置Ａの構成を示す回路図である。It is a circuit diagram which shows the structure of the insulation resistance measuring apparatus A concerning one Embodiment of this invention. 本発明の一実施形態に係わる絶縁抵抗測定装置Ａの動作を示す波形図である。It is a wave form diagram which shows operation | movement of the insulation resistance measuring apparatus A concerning one Embodiment of this invention.

符号の説明Explanation of symbols

Ａ…絶縁抵抗測定装置、Ｔ1，Ｔ2…測定端子、１…電流電圧変換回路、２…電圧計、３…ランプ信号発生回路、４…接触不良検知回路、５…電圧源、６…操作制御部、Ｃｘ…測定対象コンデンサ、Ｕ1，Ｕ2…演算増幅器、Ｒ1…帰還抵抗器、Ｃ1…積分コンデンサ、Ｒ2…積分抵抗器、Ｓ1〜Ｓ3…スイッチ、７…差動増幅器、８…比較器   A ... insulation resistance measuring device, T1, T2 ... measurement terminal, 1 ... current-voltage conversion circuit, 2 ... voltmeter, 3 ... lamp signal generation circuit, 4 ... contact failure detection circuit, 5 ... voltage source, 6 ... operation control unit , Cx: capacitor to be measured, U1, U2: operational amplifier, R1: feedback resistor, C1: integration capacitor, R2: integration resistor, S1 to S3: switch, 7: differential amplifier, 8: comparator

Claims (4)

外部装置から測定端子に入力された電流を電圧に変換して検出する電流測定装置において、
所定のランプ信号が前記測定端子に印加された状態で前記測定端子に入力される電流を電圧に変換した信号が前記所定のランプ信号に重畳された信号と、前記所定のランプ信号とを比較することにより、前記測定端子と前記外部装置との接続異常を検知する接続異常検知手段を具備することを特徴とする電流測定装置。 In the current measurement device that detects by converting the current input from the external device to the measurement terminal into a voltage,
A signal obtained by converting a current input to the measurement terminal into a voltage in a state where the predetermined ramp signal is applied to the measurement terminal is superimposed on the predetermined ramp signal is compared with the predetermined ramp signal. Thus , a current measurement device comprising a connection abnormality detection means for detecting a connection abnormality between the measurement terminal and the external device. 接続異常検知手段は、
逆相入力端が前記測定端子に接続された演算増幅器と前記逆相入力端と前記演算増幅器の出力端との間に接続された帰還抵抗とからなる電流電圧変換回路と、
正傾斜及び逆傾斜のランプ信号を生成して前記演算増幅器の正相入力端に出力するランプ信号発生手段と、
該ランプ信号発生手段から出力される前記ランプ信号と前記演算増幅器の出力端の電圧との差分を出力する差分手段と、
該差分手段の出力が所定のしきい値を越えるか否かに基づいて前記測定端子と前記外部装置との接続異常を判定する判定手段とからなり、
前記測定端子に入力する前記電流を前記演算増幅器の出力端の電圧として検出することを特徴とする請求項１記載の電流測定装置。 Connection abnormality detection means
A current-voltage conversion circuit comprising an operational amplifier having a negative phase input terminal connected to the measurement terminal, and a feedback resistor connected between the negative phase input terminal and the output terminal of the operational amplifier;
A ramp signal generating means for generating a ramp signal having a forward slope and a reverse slope and outputting the ramp signal to the positive phase input terminal of the operational amplifier;
Differential means for outputting a difference between the ramp signal output from the ramp signal generating means and the voltage at the output terminal of the operational amplifier;
A determination means for determining a connection abnormality between the measurement terminal and the external device based on whether the output of the difference means exceeds a predetermined threshold;
The current measuring apparatus according to claim 1, wherein the current input to the measuring terminal is detected as a voltage at an output terminal of the operational amplifier. 前記ランプ信号発生手段は、
第２の演算増幅器を用いた逆相積分回路と、
該逆相積分回路の入力端を正電圧あるいは負電圧に切り替える入力切替回路と、
前記第２の演算増幅器の逆相入力端と出力端とを短絡させるスイッチと
からなることを特徴とする請求項２記載の電流測定装置。 The ramp signal generating means includes:
A negative phase integrating circuit using a second operational amplifier;
An input switching circuit for switching the input terminal of the negative-phase integrating circuit to a positive voltage or a negative voltage;
The current measuring device according to claim 2, further comprising: a switch that short-circuits the negative-phase input terminal and the output terminal of the second operational amplifier. 電圧源をさらに備え、当該電圧源の一方の出力端と前記測定端子との間に接続された測定対象コンデンサに流れる電流に基づいて前記測定対象コンデンサの絶縁抵抗値を前記演算増幅器の出力端の電圧として検出することを特徴とする請求項２または３に記載の電流測定装置。   A voltage source; and an insulation resistance value of the measurement target capacitor based on a current flowing in the measurement target capacitor connected between one output terminal of the voltage source and the measurement terminal. The current measuring device according to claim 2, wherein the current measuring device is detected as a voltage.
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