JPH0355769B2 - - Google Patents
Info
- Publication number
- JPH0355769B2 JPH0355769B2 JP11293180A JP11293180A JPH0355769B2 JP H0355769 B2 JPH0355769 B2 JP H0355769B2 JP 11293180 A JP11293180 A JP 11293180A JP 11293180 A JP11293180 A JP 11293180A JP H0355769 B2 JPH0355769 B2 JP H0355769B2
- Authority
- JP
- Japan
- Prior art keywords
- liquid level
- pair
- electric wires
- rectangular wave
- wave voltage
- 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
Links
- 238000001514 detection method Methods 0.000 claims description 51
- 239000007788 liquid Substances 0.000 claims description 37
- 239000003990 capacitor Substances 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 20
- 230000001052 transient effect Effects 0.000 description 11
- 238000004804 winding Methods 0.000 description 6
- 238000005868 electrolysis reaction Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000012212 insulator Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
- G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
- G01F23/243—Schematic arrangements of probes combined with measuring circuits
Landscapes
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Description
【発明の詳細な説明】
〔技術分野〕
この発明は水位等を検出するための液位検出装
置に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid level detection device for detecting water level and the like.
従来の液位検出装置は、第１図に示すように、
液位検出装置本体Ａの交流電源１にトランス２の
１次巻線２ａを接続し、このトランス２の２次巻
線２ｂに電流検出部である抵抗３を直列接続し、
この２次巻線２ｂおよび抵抗３よりなる直列回路
の両端に一対の液位検出電極４Ａ，４Ｂを電線５
Ａ，５Ｂを介して接続し、その液位検出電極４
Ａ，４Ｂを絶縁体６で支持して水槽７内に配置し
ている。
The conventional liquid level detection device, as shown in Fig. 1,
The primary winding 2a of a transformer 2 is connected to the AC power supply 1 of the liquid level detection device main body A, and the resistor 3, which is a current detection part, is connected in series to the secondary winding 2b of this transformer 2.
A pair of liquid level detection electrodes 4A, 4B are connected to the electric wire 5 at both ends of the series circuit consisting of the secondary winding 2b and the resistor 3.
A, 5B, and the liquid level detection electrode 4
A and 4B are supported by an insulator 6 and placed in a water tank 7.
この液位検出装置は、水槽７内の水位がW1で
あるときには、電極４Ａ，４Ｂ間の抵抗値が無限
大であつて抵抗３の両端に電圧は現われない。水
位が上昇してW2を越えると、電極４Ａ，４Ｂ間
に水が介在することになつて電極４Ａ，４Ｂ間が
水の抵抗値をもち、したがつて、トランス２の２
次巻線２ｂ→電線５Ａ→液位検出電極４Ａ→水→
液位検出電極４Ｂ→電線５Ｂ→抵抗３→トランス
２の２次巻線２ｂの経路で電流が流れて抵抗３の
両端に電圧が現われることになり、この抵抗３の
両端電圧の有無により水槽７内の水位がW2に達
したがどうかを検出している。 In this liquid level detection device, when the water level in the water tank 7 is W1 , the resistance value between the electrodes 4A and 4B is infinite, and no voltage appears across the resistor 3. When the water level rises and exceeds W2 , water will be present between the electrodes 4A and 4B, and the resistance value of water will be present between the electrodes 4A and 4B.
Next winding 2b → Electric wire 5A → Liquid level detection electrode 4A → Water →
A current flows through the path of liquid level detection electrode 4B → electric wire 5B → resistor 3 → secondary winding 2b of transformer 2, and a voltage appears at both ends of resistor 3. Depending on the presence or absence of voltage across this resistor 3, water tank 7 It detects whether the water level inside has reached W2 .
しかし、このような従来の液位検出装置は、液
位検出装置本体Ａに対して水槽７をかなり遠方に
配置した場合に電線５Ａ，５Ｂが長くなり、その
長さが１Kmに達すると電線５Ａ，５Ｂに0.4μF〜
1μF程度の分布容量が発生し、この分布容量のた
めに水位がW1であつても電線５Ａ，５Ｂに電流
が流れ、この電流を電流検出部である抵抗３が検
出し、水位がW2を越えたかどうかを判断できな
くなるという問題があつた。例えば、電線５Ａ，
５Ｂの分布容量をCp、トランス２の２次巻線２ｂ
の誘起電圧をV2b、交流電源１の周波数をｆ、水
槽７内の水位をW1としたときに電流検出部であ
る抵抗３が検出する電流値Ifは
If＝ｊ・2πfCpV2b
となる。すなわち、抵抗３の両端電圧V3が
V3＝R3／R3＋Ｚ・V2b
となる。、ただし、R3は抵抗３の抵抗値、Ｚは電
線５Ａ，５Ｂの分布容量によるインピーダンス
で、
Ｚ＝ｊ・2πfCp
である。 However, in such a conventional liquid level detection device, when the water tank 7 is placed quite far away from the liquid level detection device main body A, the electric wires 5A and 5B become long, and when the length reaches 1 km, the electric wire 5A , 0.4 μF to 5B
A distributed capacitance of about 1 μF is generated, and due to this distributed capacitance, current flows through the wires 5A and 5B even when the water level is W 1. This current is detected by the resistor 3, which is a current detection section, and the water level becomes W 2. There was a problem that it was not possible to determine whether the limit had been exceeded. For example, electric wire 5A,
The distributed capacitance of 5B is C p , and the secondary winding 2b of transformer 2 is
When the induced voltage of is V 2b , the frequency of the AC power supply 1 is f, and the water level in the water tank 7 is W 1 , the current value I f detected by the resistor 3, which is the current detection section, is I f =j・2πfC p V It becomes 2b . That is, the voltage V 3 across the resistor 3 becomes V 3 =R 3 /R 3 +Z·V 2b . , where R 3 is the resistance value of the resistor 3, Z is the impedance due to the distributed capacitance of the electric wires 5A and 5B, and Z=j·2πfC p .
今、V2b＝20V、ｆ＝60Hz、Cp＝0.8μF、R3＝
1KΩとすると、液位検出電極４Ａ，４Ｂ間の抵
抗値が無限大であるにもかかわらず、電圧V3が
4.7Vにもなる。 Now, V 2b = 20V, f = 60Hz, C p = 0.8μF, R 3 =
If it is 1KΩ, the voltage V 3 will be
It also becomes 4.7V.
以上のように、従来の液位検出装置は、電線５
Ａ，５Ｂの分布容量の影響を著しく受け、遠距離
用および高感度のものを製造することが困難であ
つた。 As described above, the conventional liquid level detection device uses the electric wire 5
It was significantly affected by the distribution capacity of A and 5B, and it was difficult to manufacture long-distance and high-sensitivity products.
一方、直流電圧を液位検出電極間に印加するよ
うにすれば、一対の電線の分布容量の影響をなく
すことができるが、電気分解が生じるという問題
があつた。 On the other hand, if a DC voltage is applied between the liquid level detection electrodes, the influence of the distributed capacitance of the pair of electric wires can be eliminated, but there is a problem in that electrolysis occurs.
この発明の目的は、電気分解を生じさせること
なく、しかも電線の分布容量の影響を受けない液
位検出装置を提供することである。
An object of the present invention is to provide a liquid level detection device that does not cause electrolysis and is not affected by the distributed capacitance of electric wires.
この発明の液位検出装置は、矩形波電圧を出力
する矩形波電圧発生回路と、この矩形波電圧発生
回路の出力端に接続した一対の電線と、この一対
の電線の末端にそれぞれ接続した一対の液位検出
電極と、前記矩形波電圧発生回路と前記一対の電
線との間に介挿した電流検出検出用抵抗と、前記
一対の電線の分布容量より大きい容量を有し前記
電流検出用抵抗に並列接続しコンデンサとを備え
たものである。
The liquid level detection device of the present invention includes a rectangular wave voltage generation circuit that outputs a rectangular wave voltage, a pair of electric wires connected to the output end of the rectangular wave voltage generation circuit, and a pair of electric wires connected to the ends of the pair of electric wires, respectively. a liquid level detection electrode, a current detection resistance inserted between the rectangular wave voltage generation circuit and the pair of electric wires, and a current detection resistor having a capacitance larger than the distributed capacitance of the pair of electric wires. It is equipped with a capacitor and a capacitor connected in parallel.
この発明の構成によれば、電流検出用抵抗およ
び一対の電線を介して一対の液位検出電極間に矩
形波電圧を印加しているため、電気分解を生じさ
せることなく液位を検出することができる。 According to the configuration of the present invention, since a rectangular wave voltage is applied between the pair of liquid level detection electrodes via the current detection resistor and the pair of electric wires, the liquid level can be detected without causing electrolysis. I can do it.
また、一対の電線の分布容量より大きい容量を
有するコンデンサを電流検出用抵抗に並列接続し
ているため、一対の電線の分布容量による矩形波
電圧の極性反転時の過渡現象をコンデンサで吸収
して電流検出用抵抗の両端の電圧には過渡現象に
よる電圧が現われないようにするとことができ、
一対の電線の分布容量による影響を受けることな
く正確に液位を検出することができる。このた
め、遠距離用および高感度のものの製造が容易に
なる。 In addition, since a capacitor with a capacitance larger than the distributed capacitance of the pair of wires is connected in parallel to the current detection resistor, the transient phenomenon when the polarity of the rectangular wave voltage is reversed due to the distributed capacitance of the pair of wires is absorbed by the capacitor. It is possible to prevent voltages caused by transient phenomena from appearing in the voltage across the current detection resistor.
The liquid level can be accurately detected without being affected by the distributed capacitance of the pair of electric wires. This facilitates the manufacture of long-distance and high-sensitivity devices.
実施例
この発明の一実施例を第２図に示す。すなわ
ち、この液位検出装置は、平均値が零である矩形
波電圧を発生する矩形波電圧発生回路８の出力端
に電流検出回路９を介して電線５Ａ，５Ｂを接続
し、この電線５Ａ，５Ｂの末端に絶縁体６で支持
した液位検出電極４Ａ，４Ｂを接続し、この液位
検出電極４Ａ，４Ｂを水槽７内に配置している。
この場合、電流検出回路９は抵抗９ａおよびコン
デンサ９ｂの並列回路で構成され、コンデンサ９
ｂの容量C9bを電線５Ａ，５Ｂの分布容量Cpに対
してC9b≫Cpとなるように設定している。また、
矩形波電圧発生回路８の周波数は液位検出電極４
Ａ，４Ｂに電蝕を発生しない程度に設定してい
る。Embodiment An embodiment of the present invention is shown in FIG. That is, in this liquid level detection device, electric wires 5A, 5B are connected via a current detection circuit 9 to the output end of a rectangular wave voltage generation circuit 8 that generates a rectangular wave voltage with an average value of zero. Liquid level detection electrodes 4A and 4B supported by an insulator 6 are connected to the ends of the liquid level detection electrodes 5B, and these liquid level detection electrodes 4A and 4B are arranged in a water tank 7.
In this case, the current detection circuit 9 is composed of a parallel circuit of a resistor 9a and a capacitor 9b, and the capacitor 9
The capacitance C 9b of the electric wires 5A and 5B is set so that C 9b ≫C p with respect to the distributed capacitance C p of the electric wires 5A and 5B. Also,
The frequency of the rectangular wave voltage generation circuit 8 is the same as that of the liquid level detection electrode 4.
A and 4B are set to such an extent that no electrolytic corrosion occurs.
つぎに、この液位検出装置の動作を第３図およ
び第４図により説明する。まず、水位がW2に達
していない場合において、矩形波電圧発生回路８
より第３図Ａの矩形波電圧が出力されると、この
矩形波電圧の極性反転時において、矩形波電圧発
生回路８から一対の電線５Ａ，５Ｂの分布容量Cp
を通して第３図Ｂに示すような過渡電流が流れ
る。この過渡電流は、コンデンサ９ｂの容量C9b
が分布容量Cpに比べてかなり大きいことから、大
部分コンデンサ９ｂを通して流れることになり、
コンデンサ９ｂの両端、すなわち検出用抵抗９ａ
の両端の電圧V9は過渡電流の影響をほとんど受
けず、第３図Ｃのようにほぼゼロの状態が保持さ
れる。 Next, the operation of this liquid level detection device will be explained with reference to FIGS. 3 and 4. First, when the water level has not reached W2 , the rectangular wave voltage generation circuit 8
Therefore, when the rectangular wave voltage shown in FIG. 3A is output, when the polarity of this rectangular wave voltage is reversed, the distributed capacitance C p of the pair of electric wires 5A and 5B from the rectangular wave voltage generation circuit 8 is increased.
A transient current as shown in FIG. 3B flows through the capacitor. This transient current is caused by the capacitance C 9b of capacitor 9b.
Since is considerably larger than the distributed capacitance Cp , most of the current flows through the capacitor 9b,
Both ends of the capacitor 9b, that is, the detection resistor 9a
The voltage V 9 across is hardly affected by the transient current, and remains almost zero as shown in FIG. 3C.
一方、水位がW2に達した場合において、矩形
波電圧発生回路８より第４図Ａの矩形波電圧が出
力されると、矩形波電圧発生回路８から、水の抵
抗を通して流れる矩形波電流に分布容量Cpを通し
て流れる過渡電流を重畳した第４図Ｂのような電
流が流れる。この第４図Ｂの電流のうち矩形波電
圧の極性反転時に流れる過渡電流は第３図の場合
と同様に大部分コンデンサ９ｂを通して流れ、矩
形波電流は大部分抵抗９ａを通して流れることに
なり、過渡電流による電圧V9の変化は、第３図
と同様にほとんどなく、矩形波電流によつて電圧
V9が第４図Ｃのようにほぼ矩形波状に変化する
のみとなる。 On the other hand, when the water level reaches W2 , when the rectangular wave voltage generation circuit 8 outputs the rectangular wave voltage shown in FIG. A current flows as shown in FIG. 4B, which is a superimposed transient current flowing through the distributed capacitance Cp . Among the currents shown in FIG. 4B, most of the transient current that flows when the polarity of the rectangular wave voltage is reversed flows through the capacitor 9b as in the case of FIG. There is almost no change in the voltage V9 due to the current, as shown in Figure 3, and the voltage V9 changes due to the square wave current.
V9 only changes in a substantially rectangular waveform as shown in FIG. 4C.
したがつて、電圧V9の有無をレベル弁別器等
で判断することにより水位がW2に達したかどう
かを判定できる。 Therefore, it is possible to determine whether the water level has reached W 2 by determining the presence or absence of voltage V 9 using a level discriminator or the like.
この実施例の液位検出装置によれば、電流検出
用抵抗９ａおよび一対の電線５Ａ，５Ｂを介して
一対の液位検出電極４Ａ，４Ｂ間に矩形波電圧を
印加しているため、電気分解を生じさせることな
く液位を検出することができる。 According to the liquid level detection device of this embodiment, since a rectangular wave voltage is applied between the pair of liquid level detection electrodes 4A and 4B via the current detection resistor 9a and the pair of electric wires 5A and 5B, electrolysis The liquid level can be detected without causing any
また、一対の電線５Ａ，５Ｂの分布容量Cpより
かなり大きい容量C9bを有するコンデンサ９ｂを
電流検出用抵抗９ａに並列接続しているため、一
対の電線５ａ，５ｂの分布容量Cpによる矩形波電
圧の極性反転時の過渡現象をコンデンサ９ｂで吸
収して電流検出用抵抗９ａの両端の電圧には過渡
現象による電圧が現われないようにすることがで
き、一対の電線５Ａ，５Ｂの分布容量Cpによる影
響を受けることなく正確に液位を検出することが
できる。このため、遠距離用および高感度のもの
の製造が容易になる。 In addition, since a capacitor 9b having a capacitance C9b considerably larger than the distributed capacitance Cp of the pair of electric wires 5A and 5B is connected in parallel to the current detection resistor 9a, a rectangular shape due to the distributed capacitance Cp of the pair of electric wires 5a and 5b is The capacitor 9b absorbs the transient phenomenon at the time of polarity reversal of the wave voltage, so that no voltage due to the transient phenomenon appears in the voltage across the current detection resistor 9a, and the distributed capacitance of the pair of electric wires 5A and 5B is The liquid level can be detected accurately without being affected by C p . This facilitates the manufacture of long-distance and high-sensitivity devices.
この発明の液位検出装置によれば、電流検出用
抵抗および一対の電線を介して一対の液位検出電
極間に矩形波電圧を印加しているため、電気分解
を生じさせることなく液位を検出することができ
る。
According to the liquid level detection device of the present invention, since a rectangular wave voltage is applied between the pair of liquid level detection electrodes via the current detection resistor and the pair of electric wires, the liquid level can be measured without causing electrolysis. can be detected.
また、一対の電線の分布容量より大きい容量を
有するコンデンサを電流検出用抵抗に並列接続し
ているため、一対の電線の分布容量による矩形波
電圧の極性反転時の過渡現象をコンデンサで吸収
して電流検出用抵抗の両端の電圧には過渡現象に
よる電圧が現われないようにすることができ、一
対の電線の分布容量による影響を受けることなく
正確に液位を検出することができる。このため、
遠距離用および高感度のものの製造が容易にな
る。 In addition, since a capacitor with a capacitance larger than the distributed capacitance of the pair of wires is connected in parallel to the current detection resistor, the transient phenomenon when the polarity of the rectangular wave voltage is reversed due to the distributed capacitance of the pair of wires is absorbed by the capacitor. It is possible to prevent a voltage caused by a transient phenomenon from appearing in the voltage across the current detection resistor, and it is possible to accurately detect the liquid level without being affected by the distributed capacitance of the pair of electric wires. For this reason,
It becomes easier to manufacture long-distance and high-sensitivity products.
第１図は従来の液位検出装置の回路図、第２図
はこの発明の一実施例の液位検出装置の回路図、
第３図および第４図はその各部の波形図である。
４Ａ，４Ｂ……液位検出電極、５Ａ，５Ｂ……
電線、７……水槽、８……矩形波電圧発生回路、
９ａ……電流検出用抵抗、９ｂ……コンデンサ。
FIG. 1 is a circuit diagram of a conventional liquid level detection device, and FIG. 2 is a circuit diagram of a liquid level detection device according to an embodiment of the present invention.
FIGS. 3 and 4 are waveform diagrams of each part. 4A, 4B...Liquid level detection electrode, 5A, 5B...
Electric wire, 7...water tank, 8...square wave voltage generation circuit,
9a...Resistor for current detection, 9b...Capacitor.
Claims (1)
と、この矩形波電圧発生回路の出力端に接続した
一対の電線と、この一対の電線の末端にそれぞれ
接続した一対の液位検出電極と、前記矩形波電圧
発生回路と前記一対の電線との間に介挿した電流
検出用抵抗と、前記一対の電線の分布容量より大
きい容量を有し前記電流検出用抵抗に並列接続し
たコンデンサとを備えた液位検出装置。1. A rectangular wave voltage generation circuit that outputs a rectangular wave voltage, a pair of electric wires connected to the output end of the rectangular wave voltage generation circuit, a pair of liquid level detection electrodes connected to the ends of the pair of electric wires, and the A current detection resistor inserted between a rectangular wave voltage generation circuit and the pair of electric wires, and a capacitor having a capacitance larger than the distributed capacitance of the pair of electric wires and connected in parallel to the current detection resistor. Liquid level detection device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11293180A JPS5735723A (en) | 1980-08-13 | 1980-08-13 | Detector of liquid level |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11293180A JPS5735723A (en) | 1980-08-13 | 1980-08-13 | Detector of liquid level |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5735723A JPS5735723A (en) | 1982-02-26 |
| JPH0355769B2 true JPH0355769B2 (en) | 1991-08-26 |
Family
ID=14599063
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11293180A Granted JPS5735723A (en) | 1980-08-13 | 1980-08-13 | Detector of liquid level |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5735723A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4936133B2 (en) * | 2007-03-19 | 2012-05-23 | 横河電機株式会社 | amplifier |
| DE102014107927A1 (en) * | 2014-06-05 | 2015-12-17 | Endress + Hauser Gmbh + Co. Kg | Method and device for monitoring the level of a medium in a container |
-
1980
- 1980-08-13 JP JP11293180A patent/JPS5735723A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5735723A (en) | 1982-02-26 |
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