JPH057582Y2 - - Google Patents
Info
- Publication number
- JPH057582Y2 JPH057582Y2 JP9116684U JP9116684U JPH057582Y2 JP H057582 Y2 JPH057582 Y2 JP H057582Y2 JP 9116684 U JP9116684 U JP 9116684U JP 9116684 U JP9116684 U JP 9116684U JP H057582 Y2 JPH057582 Y2 JP H057582Y2
- Authority
- JP
- Japan
- Prior art keywords
- switch
- current
- voltage
- input terminal
- turned
- 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
- 238000006243 chemical reaction Methods 0.000 claims description 18
- 238000005259 measurement Methods 0.000 claims description 9
- 239000003990 capacitor Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
Landscapes
- Testing Of Individual Semiconductor Devices (AREA)
- Measurement Of Current Or Voltage (AREA)
- Amplifiers (AREA)
Description
【考案の詳細な説明】
「産業上の利用分野」
この考案は例えば電流測定モードを持つデイジ
タル電圧計の入力回路に用いられる電流−電圧変
換回路に関する。[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a current-voltage conversion circuit used, for example, in an input circuit of a digital voltmeter having a current measurement mode.
「従来技術」
第４図に従来の電流−電圧変換回路の使用状態
を示す。図中１は電流−電圧変換回路を示す。電
流−電圧変換回路１の電流入力端子２には例えば
半導体素子のような被測定体３を接続し、被測定
体３に電圧源４から直流電圧Ｅを与える。電流−
電圧変換回路１の出力端子５には例えばAD変換
器６を接続し、AD変換器６によりデイジタル信
号に変換し、そのデイジタル信号を表示器７に与
え表示器７に入力端子２に入力された電流IXに相
当する値を表示する。８は電流−電圧変換回路１
に設けたスイツチS1，S2，S3を開閉制御すること
と、AD変換器６及び表示器７を所定の順序で動
作させる制御器を示す。また９は測定レンジ等を
設定する入力手段を示す。"Prior Art" FIG. 4 shows how a conventional current-voltage conversion circuit is used. In the figure, 1 indicates a current-voltage conversion circuit. A measured object 3 such as a semiconductor element is connected to a current input terminal 2 of the current-voltage conversion circuit 1, and a DC voltage E is applied to the measured object 3 from a voltage source 4. Current -
For example, an AD converter 6 is connected to the output terminal 5 of the voltage conversion circuit 1, and the signal is converted into a digital signal by the AD converter 6, and the digital signal is given to the display 7 and input to the input terminal 2 of the display 7. Displays the value corresponding to the current IX . 8 is a current-voltage conversion circuit 1
This figure shows a controller that controls the opening and closing of switches S 1 , S 2 , and S 3 provided in the controller, and operates the AD converter 6 and display 7 in a predetermined order. Further, numeral 9 indicates input means for setting measurement ranges and the like.
電流−電圧変換回路１は演算増幅器１Ａと、レ
ンジ切換回路１Ｂと、オフセツト電圧測定用スイ
ツチS3とによつて構成される。 The current-voltage conversion circuit 1 is composed of an operational amplifier 1A, a range switching circuit 1B, and an offset voltage measuring switch S3 .
つまり電流入力端子２は演算増幅器１Ａの反転
入力端子に接続し、演算増幅器１Ａの出力と反転
入力端子の間にレンジ切換回路１Ｂとオフセツト
電圧測定用スイツチS3を接続する。演算増幅器１
Ａの非反転入力端子は共通電位点１１に接続す
る。 That is, the current input terminal 2 is connected to the inverting input terminal of the operational amplifier 1A, and the range switching circuit 1B and the offset voltage measuring switch S3 are connected between the output of the operational amplifier 1A and the inverting input terminal. Operational amplifier 1
The non-inverting input terminal of A is connected to the common potential point 11.
この回路構造において電圧源４から被測定体３
に電圧を与えると共に被測定体３から出力される
電流IXを電流−電圧変換回路１に入力する。電流
IXは電流−電圧変換回路１で電圧に変換されAD
変換されて表示器７に与えられ、表示器７に電流
値として表示される。 In this circuit structure, from the voltage source 4 to the object to be measured 3
At the same time, the current IX output from the object to be measured 3 is input to the current-voltage conversion circuit 1. current
IX is converted to voltage by current-voltage conversion circuit 1 and AD
It is converted and given to the display 7, and displayed on the display 7 as a current value.
演算増幅器１Ａには一般にオフセツト電圧e0が
存在する。このオフセツト電圧e0は出力端子５か
らAD変換器６に与える測定電圧V0に加算されて
出力される。オフセツト電圧e0が大きい場合はそ
の誤差に占める割合が大きくなり無視できない値
となる。 An offset voltage e 0 generally exists in operational amplifier 1A. This offset voltage e 0 is added to the measurement voltage V 0 applied from the output terminal 5 to the AD converter 6 and output. When the offset voltage e 0 is large, its proportion to the error becomes large and becomes a value that cannot be ignored.
このため測定開始に先立つてオフセツト電圧e0
の値を予め測定しておき、電流測定値からオフセ
ツト電圧値を差し引いて真の電流値を求めるよう
にしている。 Therefore, before starting measurement, the offset voltage e 0
The value of is measured in advance, and the true current value is obtained by subtracting the offset voltage value from the measured current value.
「考案が解決しようとする問題点」
オフセツト電圧e0を測定する場合はオフセツト
電圧測定用スイツチS3をオンに操作し、演算増幅
器１Ａの反転入力端子と出力端子の間を短絡し、
反転入力端子の電圧つまりオフセツト電圧e0を出
力端子５に出力させる。この状態で表示器７はオ
フセツト電圧値を表示する。``Problem to be solved by the invention'' To measure the offset voltage e0 , turn on the offset voltage measurement switch S3 , short-circuit between the inverting input terminal and the output terminal of the operational amplifier 1A,
The voltage at the inverting input terminal, that is, the offset voltage e 0 is outputted to the output terminal 5. In this state, the display 7 displays the offset voltage value.
ここでオフセツト電圧測定用スイツチS3をオン
にしたとき電流入力端子２にスパイクノイズが発
生する。つまり演算増幅器１Ａの出力端子に例え
ば正極性の電圧が出力されている状態でスイツチ
S3をオンに操作したとするとスイツチS3をオンに
すると増幅器１Ａの応答遅れ時間分だけ入力側に
出力電圧V0が与えられ、この電圧V0が負帰還さ
れて出力電圧V0がゼロとなる。よつて増幅器１
Ａの応答遅れ分だけスパイクノイズとして表われ
る。 Here, when the offset voltage measurement switch S3 is turned on, spike noise is generated at the current input terminal 2. In other words, when the switch is activated while, for example, a positive polarity voltage is being output to the output terminal of the operational amplifier 1A,
Assuming that S 3 is turned on, when switch S 3 is turned on, output voltage V 0 is given to the input side for the response delay time of amplifier 1A, and this voltage V 0 is negatively fed back, causing the output voltage V 0 to be zero. becomes. Yotsute amplifier 1
The response delay of A appears as spike noise.
スパイクノイズが発生するとこのスパイクノイ
ズは被試験体３にも与えられる。被試験体が耐電
圧の低い半導体素子であつた場合はその素子を破
損させてしまう事故が起きる欠点がある。 When spike noise occurs, this spike noise is also applied to the test object 3. If the test object is a semiconductor element with a low withstand voltage, there is a drawback that the element may be damaged.
またレンジ切換時はレンジ切換回路１Ｂのスイ
ツチS1またはS2をオンからオフへ変化させ、レン
ジを切換えている。この結果わずかな時間ではあ
るが演算増幅器１Ａの負帰還ループが開放となり
このとき増幅器１Ａの出力は正または負方向に大
きく偏倚しようとする。この影響によりレンジ切
換時にもスパイクノイズが発生することがある。 Further, when changing the range, the switch S1 or S2 of the range changeover circuit 1B is changed from on to off to change the range. As a result, the negative feedback loop of the operational amplifier 1A is opened, albeit for a short time, and at this time the output of the amplifier 1A tends to deviate significantly in the positive or negative direction. Due to this effect, spike noise may also occur when switching ranges.
「問題点を解決するための手段」
この考案ではオフセツト電圧測定用スイツチS3
を第１スイツチと称すると共に第１図に示すよう
に電流入力端子２と共通電位点１１の間に第２ス
イツチS4を接続する。これと共に電流入力端子２
と演算増幅器１Ａの反転入力端子の間に抵抗器
R3を接続し、電流入力端子２と演算増幅器１Ａ
の出力端子の間にレンジ切換回路１Ｂを接続す
る。更にこの考案では制御器８の制御シーケンス
としてオフセツト電圧測定時は第２スイツチS4を
オンにし、次に第１スイツチS3をオンにし、オフ
セツト電圧を測定する。その後に第１スイツチS3
をオフに戻し、次に第２スイツチS4をオフに戻す
ように制御する。またレンジ切換は第２スイツチ
S4をオンにし、次に第１スイツチS3をオフにした
後、レンジ切換回路１ＢのスイツチS1またはS2を
オンからオフに戻し、次に第２スイツチS4をオフ
に戻すように制御する。``Means for solving the problem'' In this invention, an offset voltage measurement switch S 3
is called a first switch, and a second switch S4 is connected between the current input terminal 2 and the common potential point 11 as shown in FIG. Along with this, current input terminal 2
and the inverting input terminal of the operational amplifier 1A.
Connect R 3 , current input terminal 2 and operational amplifier 1A
A range switching circuit 1B is connected between the output terminals of the . Furthermore, in this invention, as a control sequence of the controller 8, when measuring the offset voltage, the second switch S4 is turned on, and then the first switch S3 is turned on, and the offset voltage is measured. Then the first switch S 3
is turned off, and then the second switch S4 is controlled to be turned off again. Also, range switching is done using the second switch.
After turning on S 4 and then turning off the first switch S 3 , turn the switch S 1 or S 2 of the range switching circuit 1B from on to off, and then turn the second switch S 4 back to off. Control.
「作用」
このように構成することによりオフセツト電圧
測定時は第２スイツチS4をオンにした後に第１ス
イツチS3をオンに操作し、オフセツト電圧を測定
するから第２スイツチS4をオンにした時点で増幅
器１Ａの出力電圧V0はほぼ０となる。つまり増
幅器１Ａの出力が共通電位点１１の電圧であつた
とすると第１スイツチS3をオンに操作しても変化
がない。またレンジ切換時は第１スイツチS3をオ
ンにした後にレンジ切換回路１ＢのスイツチS1ま
たはS2をオンまたはオフに制御するから演算増幅
器１Ａの負帰還回路が開放状態になることはな
い。よつて電流入力端子２にスパイクノイズが発
生することはない。``Operation'' With this configuration, when measuring offset voltage, first switch S4 is turned on, then first switch S3 is turned on, and the offset voltage is measured, so second switch S4 is turned on. At this point, the output voltage V 0 of the amplifier 1A becomes approximately 0. In other words, if the output of the amplifier 1A is the voltage at the common potential point 11, there will be no change even if the first switch S3 is turned on. Furthermore, when switching the range, the switch S1 or S2 of the range switching circuit 1B is controlled to be turned on or off after the first switch S3 is turned on, so that the negative feedback circuit of the operational amplifier 1A is never opened. Therefore, no spike noise is generated at the current input terminal 2.
また逆にオフセツト電圧測定終了時は第１スイ
ツチS3をオフに戻し、その後に第２スイツチS4を
オフに戻すように動作させるものであるからスパ
イクノイズは発生しない。またレンジ切換時は第
１スイツチS3がオフに戻るときはレンジ切換用ス
イツチS1，S2の何れか一方がオンとなつており、
その状態で第２スイツチS4をオフに戻すから演算
増幅器１Ａの負帰還回路が開放されることはな
い。よつてこの点でもスパイクノイズの発生を抑
制することができる。 Conversely, when the offset voltage measurement is completed, the first switch S3 is turned off, and then the second switch S4 is turned off, so that no spike noise is generated. Also, when changing the range, when the first switch S 3 returns to OFF, one of the range selection switches S 1 and S 2 is turned on.
Since the second switch S4 is turned off in this state, the negative feedback circuit of the operational amplifier 1A will not be opened. Therefore, in this respect as well, the generation of spike noise can be suppressed.
「実施例」
第２図にこの考案の一実施例を示す。この例で
は電流−電圧変換回路１の電流入力端子２に被試
験体３を接続すると共に出力端子５にAD変換器
６を接続し、電流−電圧変換回路１の出力電圧を
AD変換し、そのAD変換出力を表示器７に与え、
表示器７に入力電流IXの値を表示させるように構
成した場合を示す。``Example'' Figure 2 shows an example of this invention. In this example, a device under test 3 is connected to the current input terminal 2 of the current-voltage conversion circuit 1, and an AD converter 6 is connected to the output terminal 5, so that the output voltage of the current-voltage conversion circuit 1 is
perform AD conversion and give the AD conversion output to the display 7,
A case is shown in which the display 7 is configured to display the value of the input current IX .
この考案による電流−電圧変換回路１は第１図
で説明したように第１スイツチS3の外に第２スイ
ツチS4を電流入力端子２と共通電位点１１の間に
接続すると共に電流入力端子２と演算増幅器１Ａ
の反転入力端子の間に抵抗器R3を接続する。抵
抗器R3には演算増幅器１Ａが高入力インピーダ
ンスであれば抵抗器R3には電流が全く流れない
から抵抗器R3は演算増幅器１Ａの利得には何等
関与しない。よつてこの抵抗器R3の抵抗値は第
１スイツチS3の接触抵抗値より充分大きい値に選
定すればよい。 As explained in FIG. 1, the current-voltage conversion circuit 1 according to this invention has a second switch S4 connected between the current input terminal 2 and the common potential point 11 in addition to the first switch S3 , and the current input terminal 2 and operational amplifier 1A
Connect a resistor R 3 between the inverting input terminal of. If the operational amplifier 1A has a high input impedance, no current flows through the resistor R3 , so the resistor R3 has no effect on the gain of the operational amplifier 1A. Therefore, the resistance value of this resistor R3 may be selected to be sufficiently larger than the contact resistance value of the first switch S3 .
またこの考案では演算増幅器１Ａの出力と電流
入力端子２の間にレンジ切換回路１Ｂを接続した
構造とし、更に制御器８はオフセツト電圧測定時
に第２スイツチS4をオンにした後に第１スイツチ
をオンにしオフセツト電圧測定を行い、その後に
第１スイツチS3をオフに戻し、続いて第２スイツ
チS4をオフに戻すように制御を行う。 Furthermore, in this invention, a range switching circuit 1B is connected between the output of the operational amplifier 1A and the current input terminal 2, and the controller 8 turns on the second switch S4 and then turns on the first switch when measuring the offset voltage. The switch is turned on and the offset voltage is measured, after which the first switch S3 is turned off, and then the second switch S4 is turned off.
またレンジ切換時には制御器８は第２スイツチ
S4をオン、第１スイツチS3をオンにした状態でス
イツチS1，S2の状態を切換える。スイツチS1，S2
の状態を切換えた後に第１スイツチS3をオフ、第
２スイツチS4をオフに戻しレンジ切換を終了する
ようにスイツチS1〜S4を制御する。 Also, when changing the range, the controller 8 switches the second switch.
With S4 turned on and the first switch S3 turned on, the states of switches S1 and S2 are changed. Switch S 1 , S 2
After switching the state, the switches S1 to S4 are controlled so that the first switch S3 is turned off, the second switch S4 is turned off, and the range switching is completed.
「考案の効果」
上記したこの考案によればレンジ切換時はもと
より特にオフセツト電圧e0を測定するときに第２
スイツチS4をオンにした後に第１スイツチS3をオ
ンに制御するように構成したから第１スイツチS3
がオンになるときは演算増幅器１Ａの出力電圧
V0はほぼ共通電位点１１の電圧になつている。
よつてこの状態で第１スイツチS3がオンになつて
も第１スイツチS3を通じて演算増幅器１Ａの入力
側に大きい電圧が与えられることはない。よつて
スパイクノイズが発生することはない。``Effect of the invention'' According to the above-mentioned invention, the second
The first switch S3 is configured to turn on the first switch S3 after the switch S4 is turned on.
When turns on, the output voltage of the operational amplifier 1A
V 0 is approximately the voltage at the common potential point 11 .
Therefore, even if the first switch S3 is turned on in this state, a large voltage will not be applied to the input side of the operational amplifier 1A through the first switch S3. Therefore, no spike noise is generated.
またレンジ切換時も第２スイツチS4をオンに
し、次に第１スイツチS3をオンにし、その状態で
レンジ切換回路１ＢのスイツチS1，S2を切換るよ
うに制御するから、レンジ切換時に演算増幅器１
Ａの負帰還回路が開放状態になることはなく、こ
の点でもレンジ切換終了時に入力側に大きいスパ
イクノイズが発生することはない。 Also, when changing the range, the second switch S 4 is turned on, then the first switch S 3 is turned on, and in that state, the switches S 1 and S 2 of the range switching circuit 1B are controlled. Sometimes operational amplifier 1
The negative feedback circuit of A is never open, and in this respect, no large spike noise is generated on the input side at the end of range switching.
「変形実施例」
第３図にこの考案の変形実施例を示す。この例
では演算増幅器１Ａの反転入力端子と抵抗器R3
の間にコンデンサＣを直列に接続し、このコンデ
ンサＣにオフセツト電圧e0を充電して記憶させコ
ンデンサc0に充電したオフセツト電圧e0を出力電
圧V0から減算して出力するように構成した場合
を示す。"Modified Embodiment" FIG. 3 shows a modified embodiment of this invention. In this example, the inverting input terminal of operational amplifier 1A and resistor R 3
A capacitor C is connected in series between the capacitors and the capacitor C to charge and store an offset voltage e0 , and the offset voltage e0 charged in the capacitor c0 is subtracted from the output voltage V0 and output. Indicate the case.
つまりこの構成において、第２スイツチS4と第
１スイツチS3をオンにするとコンデンサＣにオフ
セツト電圧e0が充電される。コンデンサＣに充電
されたオフセツト電圧はスイツチS3とS4をオフに
戻したとき本来のオフセツト電圧e0に対して逆極
性で演算増幅器１Ａに与えられる。この結果オフ
セツト電圧e0は相互に打消されるため電流−電圧
変換値からオフセツト電圧e0を減算する必要がな
い。 That is, in this configuration, when the second switch S4 and the first switch S3 are turned on, the capacitor C is charged with the offset voltage e0 . The offset voltage charged in the capacitor C is applied to the operational amplifier 1A with a polarity opposite to the original offset voltage e0 when the switches S3 and S4 are turned off. As a result, the offset voltages e0 cancel each other out, so there is no need to subtract the offset voltage e0 from the current-voltage conversion value.
第１図はこの考案の構成を説明するための接続
図、第２図はこの考案の一実施例を示す接続図、
第３図はこの考案の他の実施例を説明するための
接続図、第４図は従来の電流−電圧変換回路を説
明するための接続図である。
１……電流−電圧変換回路、１Ａ……演算増幅
器、１Ｂ……レンジ切換回路、２……電流入力端
子、３……被試験体、４……電圧源、５……出力
端子、６……AD変換器、７……表示器、８……
制御器、９……入力手段。
Fig. 1 is a connection diagram for explaining the configuration of this invention, Fig. 2 is a connection diagram showing an embodiment of this invention,
FIG. 3 is a connection diagram for explaining another embodiment of this invention, and FIG. 4 is a connection diagram for explaining a conventional current-voltage conversion circuit. DESCRIPTION OF SYMBOLS 1... Current-voltage conversion circuit, 1A... Operational amplifier, 1B... Range switching circuit, 2... Current input terminal, 3... Test object, 4... Voltage source, 5... Output terminal, 6... ...AD converter, 7...Display device, 8...
Controller, 9...Input means.
Claims (1)
イツチを接続し、反転入力端子と電流入力端子の
間に抵抗器を接続し、電流入力端子と上記演算増
幅器の出力端子の間にレンジ切換回路を接続する
と共に上記電流入力端子と共通電位点の間に第２
スイツチを接続し、オフセツト電圧測定時は上記
第２スイツチ、第１スイツチの順にオンに操作
し、オフセツト電圧測定終了時は第１スイツチ、
第２スイツチの順にオフに操作する制御器を設け
て成る電流−電圧変換回路。 A first switch is connected between the output of the operational amplifier and the inverting input terminal, a resistor is connected between the inverting input terminal and the current input terminal, and a range switching circuit is connected between the current input terminal and the output terminal of the operational amplifier. and a second terminal between the current input terminal and the common potential point.
When measuring the offset voltage, turn on the second switch and then the first switch, and when the offset voltage measurement is finished, turn on the first switch,
A current-voltage conversion circuit comprising a controller that turns off a second switch in order.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9116684U JPS616775U (en) | 1984-06-18 | 1984-06-18 | Current-voltage conversion circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9116684U JPS616775U (en) | 1984-06-18 | 1984-06-18 | Current-voltage conversion circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS616775U JPS616775U (en) | 1986-01-16 |
| JPH057582Y2 true JPH057582Y2 (en) | 1993-02-25 |
Family
ID=30646823
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9116684U Granted JPS616775U (en) | 1984-06-18 | 1984-06-18 | Current-voltage conversion circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS616775U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08334482A (en) * | 1995-06-09 | 1996-12-17 | Ishikawajima Harima Heavy Ind Co Ltd | Temperature limiting circuit |
| JP2006319427A (en) * | 2005-05-10 | 2006-11-24 | Sumitomo Electric Ind Ltd | Optical receiver |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5290617B2 (en) * | 2008-05-08 | 2013-09-18 | 日置電機株式会社 | Impedance measuring apparatus and impedance measuring method |
| JP5305519B2 (en) * | 2009-04-21 | 2013-10-02 | ルネサスエレクトロニクス株式会社 | Voltage regulator circuit |
| JP6241989B2 (en) * | 2013-05-30 | 2017-12-06 | セイコーＮｐｃ株式会社 | Offset cancel circuit and signal detection circuit using this circuit |
| JP6380882B2 (en) * | 2013-06-17 | 2018-08-29 | セイコーＮｐｃ株式会社 | Signal detection circuit |
| JP6345094B2 (en) * | 2014-11-28 | 2018-06-20 | 株式会社アドバンテスト | measuring device |
-
1984
- 1984-06-18 JP JP9116684U patent/JPS616775U/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08334482A (en) * | 1995-06-09 | 1996-12-17 | Ishikawajima Harima Heavy Ind Co Ltd | Temperature limiting circuit |
| JP2006319427A (en) * | 2005-05-10 | 2006-11-24 | Sumitomo Electric Ind Ltd | Optical receiver |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS616775U (en) | 1986-01-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPH04351969A (en) | Electric current measuring circuit | |
| US4604584A (en) | Switched capacitor precision difference amplifier | |
| JPH057582Y2 (en) | ||
| JPH06232706A (en) | Comparator | |
| JP2710507B2 (en) | Amplifier circuit | |
| JPH0749423Y2 (en) | Conductivity measurement detection circuit | |
| JP3129874B2 (en) | Magnetic sensor device | |
| JP2629603B2 (en) | Resistance measuring device | |
| JPS63133069A (en) | Apparatus for measuring dc difference voltage | |
| JPS5824791Y2 (en) | Switching circuit for indicator with enlarged scale | |
| JPS63209436A (en) | Charger | |
| JPS633222Y2 (en) | ||
| JPH07946Y2 (en) | AC voltmeter | |
| US3523237A (en) | Device converting electric current ratio into time ratio | |
| JPH0731218B2 (en) | Resistance measuring device | |
| JPH0546090Y2 (en) | ||
| RU2099722C1 (en) | Low-resistance meter | |
| JPS6023993Y2 (en) | Hall element residual voltage adjustment circuit | |
| JP2897941B2 (en) | Constant current circuit for resistance measurement | |
| JPH0641179Y2 (en) | Current switching circuit | |
| SU1688288A1 (en) | Selection/ storage device | |
| JPH0349469Y2 (en) | ||
| JPH0527830B2 (en) | ||
| JPH0353181Y2 (en) | ||
| JPS60251600A (en) | Sample and hold circuit |