JPH01191035A - Method for measuring concentration of dissolved oxygen in liquid - Google Patents
Method for measuring concentration of dissolved oxygen in liquidInfo
- Publication number
- JPH01191035A JPH01191035A JP63016303A JP1630388A JPH01191035A JP H01191035 A JPH01191035 A JP H01191035A JP 63016303 A JP63016303 A JP 63016303A JP 1630388 A JP1630388 A JP 1630388A JP H01191035 A JPH01191035 A JP H01191035A
- Authority
- JP
- Japan
- Prior art keywords
- oxygen
- sample liquid
- carrier gas
- gas
- concn
- 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.)
- Pending
Links
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 239000001301 oxygen Substances 0.000 title claims abstract description 98
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 98
- 239000007788 liquid Substances 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title description 10
- 239000012159 carrier gas Substances 0.000 claims abstract description 34
- 230000005587 bubbling Effects 0.000 claims abstract description 12
- 238000005259 measurement Methods 0.000 claims description 28
- 239000007789 gas Substances 0.000 abstract description 17
- 238000011088 calibration curve Methods 0.000 abstract description 12
- 239000008246 gaseous mixture Substances 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 30
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 10
- 239000000203 mixture Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 239000012488 sample solution Substances 0.000 description 3
- 239000007784 solid electrolyte Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910002076 stabilized zirconia Inorganic materials 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
この発明は、液中溶存酸素濃度の測定方法に関し、特に
従来の気中酸素濃度測定センサを使用できるようにした
ものである。DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for measuring dissolved oxygen concentration in a liquid, and in particular, allows use of a conventional atmospheric oxygen concentration measurement sensor.
［従来技術およびその課題］
従来、酸素濃度測定センサとして多種多様な材料と原理
が利用されたものが用いられており、中でも固体電解質
のイオン導電性を利用した固体電解質ガスセンサの一つ
であるジルコニア酸素センサは、その測定精度が高いこ
とから、気中酸素濃度の測定に広く使用されている。[Prior art and its issues] Conventionally, oxygen concentration measurement sensors have been used that utilize a wide variety of materials and principles. Among them, zirconia, which is a solid electrolyte gas sensor that utilizes the ionic conductivity of a solid electrolyte, has been used. Oxygen sensors are widely used to measure atmospheric oxygen concentration because of their high measurement accuracy.
このジルコニア酸素センサは、酸化ジルコニウムに酸化
カルシウムまたは酸化イツトリウムを１０モル％程度固
溶させた安定化ノルコニアを、２枚の多孔質白金電極間
に挟着してなるらのであり、」二足電極間の電位差を検
出し、この電位差から各電極両側の酸素分圧を測定する
ものである。This zirconia oxygen sensor is made by sandwiching stabilized norconia, which is a solid solution of about 10 mol% of calcium oxide or yttrium oxide in zirconium oxide, between two porous platinum electrodes. The potential difference between the electrodes is detected, and the oxygen partial pressure on both sides of each electrode is measured from this potential difference.
しかしながら、電極両側の酸素分圧と両電極間の電位差
との間に相関関係が成仏するのは、電極間の安定化ジル
コニアが５００〜８００℃の温度範囲に限られるので液
中溶存酸素濃度の測定には不適である。However, the correlation between the oxygen partial pressure on both sides of the electrodes and the potential difference between the two electrodes is limited to the temperature range of 500 to 800°C for the stabilized zirconia between the electrodes. Not suitable for measurement.
これに対し、液中溶存酸素濃度を測定するしのとしては
、クラーク型酸素電極を用いた模式酸素センサが一般に
使用されている。このセンサは、カソード、アノードお
よび電解液とから成り、酸素透過性プラスチック膜をカ
ソードに取り付けたものであり、この膜を透過する酸素
をカソード表面で電気化学的に還元する際に必要とする
電流値を求め、この値から酸素の分圧を測定するもので
あり、酸素の電気化学還元の方法により、定電位電解式
酸素センサ、ガルバニ電池式酸素センサとに区分される
。On the other hand, a model oxygen sensor using a Clark type oxygen electrode is generally used to measure the dissolved oxygen concentration in a liquid. This sensor consists of a cathode, an anode, and an electrolyte, with an oxygen-permeable plastic membrane attached to the cathode, and the current required to electrochemically reduce oxygen passing through the membrane at the cathode surface. This sensor calculates a value and measures the partial pressure of oxygen from this value. Depending on the method of electrochemical reduction of oxygen, it is classified into a constant potential electrolysis type oxygen sensor and a galvanic cell type oxygen sensor.
しかしながら、これらクラーク型酸素電極を用いた模式
酸素センサはいずれも酸素の還元反応を利用したもので
あるので、その測定精度がセンサの測定範囲の±２％程
度であり、−回の測定に数十秒を要し、電極寿命も短い
等の課題があった。However, since all of these model oxygen sensors using Clark-type oxygen electrodes utilize the reduction reaction of oxygen, their measurement accuracy is about ±2% of the sensor's measurement range, and it takes several measurements per measurement. There were problems such as it took 10 seconds and the electrode life was short.
この発明は上記課題を解決するためになされたものであ
り、測定精度の良好な従来の気中酸素濃度測定センサを
使用して容易に液中溶存酸素濃度を高精度で測定するこ
とのできるような方法を提供することを目的としている
。This invention was made to solve the above problems, and it is possible to easily measure dissolved oxygen concentration in liquid with high accuracy using a conventional atmospheric oxygen concentration measurement sensor with good measurement accuracy. The purpose is to provide a method.
［課題を解決するための手段］
この発明は、キャリアガスを試料液中でバブリングする
ことにより試料液中の溶存酸素をキャリアガスに捕集し
、気中酸素濃度測定センサを用いてキャリアガス中の酸
素濃度を検出することを解決手段とした。[Means for Solving the Problems] The present invention collects dissolved oxygen in the sample liquid by bubbling the carrier gas in the sample liquid, and captures dissolved oxygen in the carrier gas using an atmospheric oxygen concentration measurement sensor. The solution was to detect the oxygen concentration.
［作用 ］
試料液中でキャリアガスをバブリングすることにより、
試料液中に溶存している酸素の一部または全部を脱気す
ることができる。脱気される酸素量は液中溶存酸素濃度
およびキャリアガスのバブリングの条件、試料液の液温
等に依存するので、一定条件下でのキャリアガスのバブ
リングに上り脱気された酸素量は試料液中の溶存酸素濃
度と相関関係を有する。したがって、脱気された酸素を
キャリアガスと共に捕集した後、キャリアガス中の酸素
濃度を測定し、予め作成しておいた検量線を用いてキャ
リアガス中の酸素濃度から試料液中の溶存酸素濃度を求
めることができる。[Effect] By bubbling carrier gas in the sample liquid,
Part or all of the oxygen dissolved in the sample solution can be degassed. The amount of oxygen degassed depends on the concentration of dissolved oxygen in the liquid, the bubbling conditions of the carrier gas, the temperature of the sample liquid, etc. Therefore, the amount of oxygen degassed due to bubbling of the carrier gas under certain conditions is It has a correlation with the dissolved oxygen concentration in the liquid. Therefore, after collecting the degassed oxygen together with the carrier gas, the oxygen concentration in the carrier gas is measured, and the dissolved oxygen in the sample solution is calculated from the oxygen concentration in the carrier gas using a calibration curve prepared in advance. Concentration can be determined.
［実施例］ 以下、本発明の詳細な説明する。[Example] The present invention will be explained in detail below.
第１図は本発明の液中溶存酸素濃度の測定方法を実施す
る際に使用される装置の一実施例を示したものである。FIG. 1 shows an embodiment of an apparatus used to carry out the method of measuring dissolved oxygen concentration in liquid according to the present invention.
第１図中、符号ｌは貯槽である。In FIG. 1, the symbol l is a storage tank.
この貯槽ｌ内には試料液りが満たされている。貯槽ｌは
上部が開口した有底筒状の恒温槽であり、その底部には
試料液り内の溶存酸素を脱気するためのキャリアガスＧ
を導く導気管２が取り付けられている。この導気管２は
キャリアガスＧと試料液りとの接触が最大になるように
、一端は貯槽ｌの底面の中心に達した部分で上方へ湾曲
されている。さらに、貯槽ｌの上部開口部に向って所望
量のキャリアガスＧのバブリング赤容易なように、この
一端は縮径されてノズルとなっている。この導気管２の
他端は貯槽！外部へ導かれ、図示しないキャリアガスＧ
の発生装置あるいはガスボンベ等に接続され、試料液り
中にバブリングするキャリアガスの供給量を調節できる
ようになっている。This storage tank 1 is filled with a sample liquid. The storage tank L is a bottomed cylindrical constant temperature bath with an open top, and a carrier gas G is placed at the bottom to degas the dissolved oxygen in the sample liquid.
An air guide pipe 2 is attached to guide the air. One end of this air guide tube 2 is curved upward at a portion reaching the center of the bottom surface of the storage tank 1 so as to maximize contact between the carrier gas G and the sample liquid. Furthermore, one end is reduced in diameter to form a nozzle to facilitate bubbling of a desired amount of carrier gas G toward the upper opening of the storage tank I. The other end of this air guide pipe 2 is a storage tank! A carrier gas G (not shown) is guided to the outside.
It is connected to a gas generator or gas cylinder, etc., so that the supply amount of carrier gas bubbling into the sample liquid can be adjusted.
キャリアガスＧには、試料液りおよび酸素と不活性なヘ
リウムガス、窒素ガス等の気体を使用するのが望ましい
。As the carrier gas G, it is desirable to use a sample liquid, oxygen, and an inert gas such as helium gas or nitrogen gas.
また、貯槽１の上部には逆ロート型の捕集フード３が支
持されている。この捕集フード３は、試料液り内でバブ
リングされたキャリアガスＧと試料液りから脱気された
酸素の混合気体を捕集するためのもので、捕集フード３
の中心線上およびその延長線上でキャリアガスＧかバブ
リングされるように設置され、かつ捕集フード３の拡径
された下部開口部は試料液り中に浸漬されており、上部
開口部は気中酸素濃度測定センサ４に接続されている。Further, an inverted funnel type collection hood 3 is supported at the upper part of the storage tank 1. This collection hood 3 is for collecting a mixed gas of carrier gas G bubbled in the sample liquid and oxygen degassed from the sample liquid.
The collection hood 3 is installed so that the carrier gas G is bubbled on the center line and its extension, and the enlarged lower opening of the collection hood 3 is immersed in the sample liquid, and the upper opening is immersed in the sample liquid. It is connected to the oxygen concentration measurement sensor 4.
この気中酸素濃度測定センサ４は上記捕集フード３によ
って捕集されたキャリアガスＧと試料液りから脱気され
た酸素との混合気体中の酸素の濃度を測定するためのら
のであり、測定速度および測定精度が高くかつ故障の少
ないジルコニア酸素センサからなっている。なお、気中
酸素濃度測定センサ４には、本実施例で用いたジルコニ
ア酸１センザのほか、気中酸素濃度測定センサのうち、
測定速度よび測定精度の良好ならのを使用することが可
能である。This atmospheric oxygen concentration measurement sensor 4 is for measuring the concentration of oxygen in the mixed gas of the carrier gas G collected by the collection hood 3 and the oxygen degassed from the sample liquid. It consists of a zirconia oxygen sensor that has high measurement speed and accuracy, and has few failures. In addition to the zirconia acid 1 sensor used in this example, the atmospheric oxygen concentration measurement sensor 4 includes:
It is possible to use a method with good measurement speed and measurement accuracy.
さらに、この気中酸素濃度測定センサ４は検出器５と接
続されている。この検出器５では上記気中酸素濃度測定
センサ４で測定された混合気体中の酸素濃度の測定値の
出力を規格化した値と、試料液■７中の溶存酸素濃度と
の相関関係を用いた検量線を使用して、試料液り中の溶
存酸素濃度を演算し検出するようになっている。キャリ
アガスＧ゛と脱気された酸素との混合気体中の酸素濃度
の測定値の出力を規格化した値と、試料液り中の溶存酸
素濃度との間の検量線は、試料液りの液温、大気用、キ
ャリアガスＧの種類およびそのの供給量等の各々の条件
により、種々用意する必要がある。Furthermore, this atmospheric oxygen concentration measuring sensor 4 is connected to a detector 5. This detector 5 uses the correlation between the normalized output of the oxygen concentration in the mixed gas measured by the atmospheric oxygen concentration measurement sensor 4 and the dissolved oxygen concentration in the sample liquid 7. Using the calculated calibration curve, the dissolved oxygen concentration in the sample liquid is calculated and detected. The calibration curve between the normalized output of the measured value of oxygen concentration in a mixed gas of carrier gas G and degassed oxygen and the dissolved oxygen concentration in the sample liquid is It is necessary to prepare various types depending on each condition such as liquid temperature, atmosphere, type of carrier gas G, and its supply amount.
第２図に試料液温２０℃、大気圧７６０ｍｍＨｇ、キャ
リアガスの供給ｆ１１．８Ｉ２／分とした場合の検量線
の一例を示す。この検量線を作成するには試料液りとし
て純水を用い、キャリアガスＧとして窒素と酸素との混
合気体を用い、この混合気体の酸素の混合比を０〜１０
０％まで変化させて、この酸素の組成比を変化させたキ
ャリアガスＧをそれぞれ試料液り中でバブリングした後
、捕集フード３で捕集された気体中の酸素濃度を気中酸
素濃度測定センサ４で測定することにより行った。FIG. 2 shows an example of a calibration curve when the sample liquid temperature is 20° C., the atmospheric pressure is 760 mmHg, and the carrier gas is supplied f11.8 I2/min. To create this calibration curve, use pure water as the sample liquid, use a gas mixture of nitrogen and oxygen as the carrier gas G, and adjust the oxygen mixing ratio of this gas mixture from 0 to 10.
After bubbling the carrier gas G with the oxygen composition ratio changed up to 0% in each sample liquid, the oxygen concentration in the gas collected by the collection hood 3 is measured as the atmospheric oxygen concentration. This was done by measuring with sensor 4.
このような装置を用いて、試料液りの溶存酸素濃度を測
定するには、まず試料液り内の溶存酸素濃度と上述の測
定装置の出力を規格化した値との間に相関関係が成り立
つことを確認し、試料液温、気圧等を一定条件下で検量
線を作成する。この検量線と同一条件下で、貯槽ｌ内に
満たされた試料液■７中に導気管２よりキャリアガスＧ
を供給しバブリングにより試料液り中の酸素を脱気する
。このキャリアガスＧと脱気された酸素との混合気体は
試料液■７中を上昇し、捕集フード３で捕集された後、
気中酸素濃度測定センサ４で酸素濃度が測定され、この
測定値の出力を規格化した値より、先に作成した検量線
を用いて検出器５で、試料液り中の溶存酸素濃度を演算
、検出する。To measure the dissolved oxygen concentration in a sample liquid using such a device, first a correlation is established between the dissolved oxygen concentration in the sample liquid and the normalized output of the above-mentioned measuring device. Confirm that this is the case, and create a calibration curve under constant conditions such as sample liquid temperature and atmospheric pressure. Under the same conditions as this calibration curve, the carrier gas G is introduced into the sample liquid 7 filled in the storage tank 1 from the air guide tube 2.
The oxygen in the sample liquid is degassed by bubbling. This gas mixture of carrier gas G and degassed oxygen rises in the sample liquid 7, and after being collected by the collection hood 3,
The oxygen concentration is measured by the atmospheric oxygen concentration measurement sensor 4, and the dissolved oxygen concentration in the sample liquid is calculated by the detector 5 using the previously created calibration curve from the normalized output of this measurement value. ,To detect.
また、本発明の測定方法を用いて純水中の溶存酸素濃度
を測定した場合、気中酸素濃度測定センサ４および検出
器５の出力が安定し正確な測定が可能となるまでに要し
た時間は、約１０秒であり、これは、従来の液中酸素濃
度測定用のクラーク型酸素電極を備えた模式酸素センサ
等を用いた場合の２０〜３０秒に対し高速であり、同一
条件で同一酸素濃度の試料液を複数回測定した測定値の
バラツキら従来型の酸素センサを用いた場合の±５％に
比較して、本発明の方法による測定値のバラツキは、約
±１％で非常に良好であった。In addition, when measuring the dissolved oxygen concentration in pure water using the measurement method of the present invention, the time required until the output of the atmospheric oxygen concentration measurement sensor 4 and the detector 5 becomes stable and accurate measurement becomes possible. is about 10 seconds, which is faster than 20 to 30 seconds when using a conventional oxygen sensor equipped with a Clark-type oxygen electrode for measuring oxygen concentration in liquid. The variation in the measured values obtained by measuring the oxygen concentration of the sample solution multiple times is about ±5% when using a conventional oxygen sensor, whereas the variation in the measured values by the method of the present invention is approximately ±1%, which is very small. It was in good condition.
［発明の効果］
以上説明したように、本発明の液中溶存酸素濃度の測定
方法は、キャリアガスを試料液中でバブリングすること
により試料液中の溶存酸素をキャリアガスに捕集し、気
中酸素濃度測定センサを用いてキャリアガス中の酸素濃
度を検出するするものであるので、ジルコニア酸素セン
サ等の固体電解質ガスセンサを使用することが可能とな
り、従来液中の溶存酸素濃度測定に用いられているクラ
ーク型酸素電極等に比較して、測定精度、耐久性、測定
速度等が向上し、液中溶存酸素濃度を迅速かつ正確に測
定することが可能となった。また、液中溶存酸素の脱気
および捕集方法も簡便であり、必要時に容易に測定を行
うことが可能である。[Effects of the Invention] As explained above, the method for measuring dissolved oxygen concentration in a liquid according to the present invention collects dissolved oxygen in the sample liquid by bubbling the carrier gas in the sample liquid, and Since the oxygen concentration in the carrier gas is detected using a medium oxygen concentration measurement sensor, it is possible to use a solid electrolyte gas sensor such as a zirconia oxygen sensor, which is conventionally used to measure dissolved oxygen concentration in liquids. Compared to Clark-type oxygen electrodes, etc., the measurement accuracy, durability, and measurement speed are improved, making it possible to quickly and accurately measure dissolved oxygen concentration in liquid. Furthermore, the method for degassing and collecting oxygen dissolved in the liquid is simple, and measurement can be easily performed when necessary.
第１図は本発明の液中溶存酸素濃度の測定方法に使用さ
れる装置の一実施例の概略構成図、第２図は第１図に示
された装置を用いて本発明の液中溶存酸素濃度の測定を
行う際に使用する検量線の一例を示したグラフである。
Ｇ・・・キャリアガス、
■、・・試料液、
４・・・気中酸素濃度測定センサ。FIG. 1 is a schematic diagram of an embodiment of a device used in the method of measuring dissolved oxygen concentration in a liquid according to the present invention, and FIG. It is a graph showing an example of a calibration curve used when measuring oxygen concentration. G...Carrier gas, ■...Sample liquid, 4...Air oxygen concentration measurement sensor.
Claims (1)
料液中の溶存酸素をキャリアガスに捕集し、気中酸素濃
度測定センサを用いてキャリアガス中の酸素濃度を検出
することを特徴とする液中溶存酸素濃度の測定方法。In a liquid, the dissolved oxygen in the sample liquid is collected by the carrier gas by bubbling the carrier gas in the sample liquid, and the oxygen concentration in the carrier gas is detected using an air oxygen concentration measurement sensor. How to measure dissolved oxygen concentration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63016303A JPH01191035A (en) | 1988-01-27 | 1988-01-27 | Method for measuring concentration of dissolved oxygen in liquid |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63016303A JPH01191035A (en) | 1988-01-27 | 1988-01-27 | Method for measuring concentration of dissolved oxygen in liquid |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01191035A true JPH01191035A (en) | 1989-08-01 |
Family
ID=11912773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63016303A Pending JPH01191035A (en) | 1988-01-27 | 1988-01-27 | Method for measuring concentration of dissolved oxygen in liquid |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01191035A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0576888A (en) * | 1991-09-24 | 1993-03-30 | Ngk Insulators Ltd | Gas collecting device of aeration tank |
| CN113777262A (en) * | 2021-09-24 | 2021-12-10 | 同济大学 | Seawater methane sensor calibration device and method based on constant temperature control |
-
1988
- 1988-01-27 JP JP63016303A patent/JPH01191035A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0576888A (en) * | 1991-09-24 | 1993-03-30 | Ngk Insulators Ltd | Gas collecting device of aeration tank |
| CN113777262A (en) * | 2021-09-24 | 2021-12-10 | 同济大学 | Seawater methane sensor calibration device and method based on constant temperature control |
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