JP3595999B2

JP3595999B2 - Liquid level measurement method

Info

Publication number: JP3595999B2
Application number: JP2000134497A
Authority: JP
Inventors: 憲幸牧; 浩一吉良; 克夫高橋; 秀昭岡; 滋中村
Original assignee: RKC INSTRUMENT Inc
Current assignee: RKC INSTRUMENT Inc
Priority date: 2000-05-08
Filing date: 2000-05-08
Publication date: 2004-12-02
Anticipated expiration: 2020-05-08
Also published as: JP2001317983A

Description

【０００１】
【発明の属する技術分野】
本発明は液面レベル計測方法に係り、各種の工業分野において貯溜された液体の液面レベル（液面までの高さ）を計測する背圧式の液面レベル計測方法の改良に関する。
【０００２】
【従来の技術】
従来、容器に貯溜された液体の液面レベルを計測するには、例えば気体の圧力を用いた手法がある。
【０００３】
すなわち、図６に示すように、容器１に被測定液３を溜め、不活性気体（ガス）を圧送する気体供給装置５に一端を連結した１本のパイプ７の他端（先端）側をその被測定液３中に挿入し、パイプ７の先端から被測定液３内に常に気泡９を発生させるとともに、パイプ７の途中において液面レベル計測装置１１を連結し、パイプ７内の気体圧力の測定を介して液面レベルを計測する計測方法である。
【０００４】
図６中の符号１３は液面レベル計測装置１１を連結するために、パイプ７の途中に挿入されたジョイントである。
【０００５】
一般に、容器１内に比重ρの被測定液３を溜め、この液面から任意の深さＨに仮想の基準面を考えると、この基準面における圧力Ｐは、重力加速度をｇとすれば、
Ｐ＝ρｇＨ
となり、深さＨは次のように表せる。
Ｈ＝Ｐ／ρｇ …… （１）
【０００６】
これによれば、被測定液３の比重ρが既知であれば、その圧力Ｐを測定することにより、液面レベルＨを知ることができる。
【０００７】
上述した背圧式の液面レベル計測方法では、パイプ７の先端の気体圧力（静圧）がパイプ７内の気体圧力に等しく、液面レベルが上がるほどパイプ７内の気体圧力が高くなるから、容器１内に被測定液３を満杯に溜めた状態でパイプ７の先端から気泡９を発生させるよう気体供給装置５からの気体圧送を調節しておけば、被測定液３の満杯状態から空の状態に至るまでの間、パイプ７内の気体圧力を液面レベル計測装置１１で測定するとともに、上述した式（１）に当てはめて液面レベルＨを求めることができる。
【０００８】
なお、液面レベル計測装置１１を形成しパイプ７途中の気体の圧力を測定する手段としては、背圧式圧力センサが用いられる。
【０００９】
【発明が解決しようとする課題】
しかしながら、上述した背圧式の液面レベル計測方法は、予め比重が分かっている被測定液３の液面レベル計測には向くが、同じ液位でも被測定液３の比重が異なると圧力も異なるから、比重が分かっていない被測定液３については液面レベルの計測が困難である。
【００１０】
また、被測定液３を溜める容器１についても、任意の形状を有する容器では、測定した液面レベルとは必ずしも所定の比例関係とならず、残容積の正確な計測が困難であった。
【００１１】
さらに、半導体製造工程等において、半導体ウエハを薬液中で処理する場合にあっては、半導体ウエハの処理回数に応じて薬液の比重が変化し易く、その比重変化に伴って液面レベルの正確な計測が困難となっていた。
【００１２】
本発明はそのような従来の課題を解決するためになされたもので、予め比重が分かっていない被測定液の液面レベル計測が可能な液面レベル計測方法の提供を目的とする。
【００１３】
また、本発明は、任意形状の容器に溜めた被測定液についても、正確な残容積の計測が可能な液面レベル計測方法の提供を目的とする。
【００１４】
さらに、本発明は、被処理物の処理毎に被測定液の比重が変化しても、正確な液面レベルの計測が可能な液面レベル計測方法の提供を目的とする。
【００１５】
【課題を解決するための手段】
そのような課題を解決するために本発明に係る第１の方法は、容器に入れた被測定液中に１本のパイプを挿入し、所定圧力の気体を供給してそのパイプの先端から被測定液中に気泡を発生させた状態で背圧を測定することにより、その被測定液の液面レベルを計測する液面レベル計測方法において、その容器に予め被測定液を入れて第１の設定点に達したときの第１の圧力と第１の設定点より高い第２の設定点に達したときの第２の圧力との圧力差と、比重が既知の基準液による圧力との比例関係からその被測定液の比重を算出する第１の工程と、この算出比重に基づき少なくともそれら第１および第２の設定点間における被測定液の圧力と液面レベルの比例関係を示す液面データテーブルを求める第２の工程と、本計測としてその容器に入れた被測定液の圧力値を液面データテーブルに対応させて当該液面レベルを計測する第３の工程とを具備している。
【００１６】
しかも、この第１の方法における上記第２の工程は、上記基準液に関する既知の下限圧力レベルおよび計測上限圧力レベルに相当する上記被測定液の計測下限レベルおよび計測上限レベルを、上記算出比重、基準液比重、第１、第２の設定点から算出し、この間の圧力と液面レベルとの比例関係を上記液面データテーブルとして求めるものである。
【００１７】
また、本発明に係る第２の方法は、被測定液の液面レベルを計測する液面レベル計測方法において、予め比重が既知の基準液を入れたときの容器の容積と液面レベルとの関係を容積データテーブルとして求める第４の工程と、その容器に予め被測定液を入れて第３の設定点に達したときの第３の圧力と第３の設定点より高い第４の設定点に達したときの第４の圧力との圧力差と、上記基準液による圧力との比例関係からその被測定液の比重を算出する第５の工程と、その算出比重に応じてその容積データテーブル中の液面レベルを補正する第６の工程と、本計測としてその容器に入れた被測定液の圧力値をその補正された容積データテーブルに対応させて上記被測定液の残容積を計測する第７の工程とを具備している。
【００１８】
さらに、本発明に係る第３の方法は、被測定液の液面レベルを計測する液面レベル計測方法において、上記容器に入れた被測定液中で被処理物を複数回処理する場合の処理前の初期比重と複数回目の処理後比重とを設定する第８の工程と、それら初期比重と処理後比重とから当該処理回数毎の変化比重を求め、変化比重と圧力の関係を記憶する第９の工程と、当該処理回数が入力されたとき毎の上記被測定液の圧力測定値を、当該圧力測定時の処理回数に応じた変化比重で補正して液面レベルを計測する第１０の工程とを具備している。
【００１９】
【発明の実施の形態】
以下本発明の実施の形態を図面を参照して説明する。
まず、便宜上、本発明の液面レベル計測方法を実施する液面レベル計測装置を説明する。
【００２０】
図１は本発明の液面レベル計測方法を実施する液面レベル計測装置を示すブロック図であり、例えば上述した図６における液面レベル計測装置１１に相当する。
【００２１】
図１において、符号１５は、図６中の液面レベル計測装置１１内に配置され、パイプ７中を圧送される気体圧力に応じたレベルのアナログ測定信号を出力する背圧式の圧力センサであり、入力部１７に接続されている。圧力センサとしては、例えば半導体式圧力センサ、その他従来公知のセンサ素子が用いられる。
【００２２】
入力部１７は、圧力センサ１５からの測定信号を所定のタイミングでＡ／Ｄ変換してデジタル信号に変換するものであり、演算部１９に接続されている。
【００２３】
演算部１９は、本発明の主要な演算、算出又は判断機能を実行するＣＰＵ１９ａと、このＣＰＵ１９ａの動作プログラムを格納したＲＯＭ１９ｂと、入出力インターフェイス１９ｃを有して形成されており、記憶部２１、表示部２３、設定部２５および警報部２７に接続されている。演算部１９の機能は後述する。
【００２４】
記憶部２１は、後述する液面データテーブルその他のデータテーブルや各種のデータを記憶する内蔵又は外部メモリであり、演算部１９の管理下でそれらの読み出し書き込みが制御されている。
【００２５】
表示部２３は、演算部１９で演算された液面レベルをｍｍや％で表示したり、他の項目を表示する液晶ディスプレイ等である。
【００２６】
設定部２５は、設定点に達した時に、当該液面の高さを入力するとともに、後述するように入力部１７からの圧力値を取込み記憶部２１へ格納するタイミングを指示したり、その他を外部から入力して記憶部２１へ格納するキーボードやオンライン接続部である。
【００２７】
なお、比重１の液体（純水）の高さ１０００ｍｍの圧力値９．８０７ｋＰａ（計測上限）、０ｋＰａ（計測下限）等は、予め設定部２５から又は製造時に固定的に入力設定される場合もある。
【００２８】
警報部２７は、演算部１９で演算された液面レベルその他が測定範囲外であった場合等に、外部へ警報を発する液晶ディスプレイ又はブザーであり、表示部２３の一部として構成される場合もある。
【００２９】
演算部１９には、上述した図６に示すように、実際に液面レベルを計測する被測定液３を予め容器１に流入させ、容器１の底から例えば２５０ｍｍ（第１の設定点Ｐ１）と４００ｍｍ（第２の設定点Ｐ２）に達した時の圧力を設定部２５からの指示によって取込み、記憶部２１に格納する機能を有している。第１および第２の設定点Ｐ１、Ｐ２は任意である。
【００３０】
図２は、被測定液３が２５０ｍｍ（第１の設定点Ｐ１）と４００ｍｍ（第２の設定点Ｐ２）に達した時の圧力が１．９６１ｋＰａと３．９２３ｋＰａであった場合、それら２点間における圧力と液面レベルの関係をリニアな関係で仮想的に示している。
【００３１】
演算部１９は、それら第１および第２の設定点Ｐ１、Ｐ２の圧力値および基準液の比重９．８０７ｋＰａから、次の算出式によって被測定液３の比重と、純水における０ｋＰａ（計測下限）の状態と９．８０７ｋＰａ（計測上限）の状態に相当する被測定液３の計測下限値および計測上限値を算出する機能を有している。
【００３２】

ここで、９．８０７ｋＰａは純水１０００ｍｍの深さの圧力相当値である。
【００３３】
すなわち、演算部１９は、被測定液３の第１および第２の設定点Ｐ１、Ｐ２における圧力値差（３．９２３ｋＰａ−１．９６１ｋＰａ）に対する基準液の比重９．８０７ｋＰａの比と、第１および第２の設定点Ｐ１、Ｐ２間の間隔（４００ｍｍ−２５０ｍｍ）との比から、純水の比重１に対する被測定液３の比重を算出する機能を有している。
【００３４】
また、演算部１９は、被測定液３について第１の設定点Ｐ１の圧力（１．９６１ｋＰａ）に対する基準液の圧力９．８０７ｋＰａの比と、被測定液３の算出比重（１．３３３）との比と、第１の設定点Ｐ１との関係から被測定液３の計測下限値を算出する一方、第１および第２の設定点Ｐ１、Ｐ２間の間隔（４００ｍｍ−２５０ｍｍ）と、第１および第２の設定点Ｐ１、Ｐ２の圧力値差（３．９２３ｋＰａ−１．９６１ｋＰａ）に対する基準液の圧力９．８０７ｋＰａの比との関係および第１の設定点Ｐ１の液面レベルとから被測定液３の計測上限値を算出する機能を有している。
【００３５】
さらに、演算部１９は、これら算出比重、計測下限値および計測上限値から、圧力値に対する液面レベルの関係をリニアな直線状にした液面データテーブル（図２参照）を作成し、記憶部２１に格納する機能を有している。
【００３６】
演算部１９は、本計測として容器１に入れられた被測定液３について入力部１７から入力された圧力値をその液面データテーブルと照合し、該当する圧力値と液面レベルを表示部２３に表示する機能の他、以下に示す各種の機能を有している。
【００３７】
次に、本発明の液面レベル計測方法に係る第１の方法を説明する。
図３は、上述した液面レベル計測装置の動作とともに本発明に係る第１の方法の要部を説明するためのフロチャートである。
【００３８】
上述した図６のように、気体供給装置５に一端を連結したパイプ７の他端（先端）側を容器１中の被測定液３中に液面から挿入し、気体供給装置５から不活性気体を圧送してパイプ７の先端から常に気泡９を発生させた状態を形成し、図１中の設定部２５から純水の液面レベル１０００ｍｍの圧力値である９．８０７ｋＰａと、純水が０ｋＰａ（計測下限）の状態と９．８０７ｋＰａ（計測上限）状態における各圧力値を、設定部２５から記憶部２１へ予め入力設定しておく。
【００３９】
ステップ３００でプログラムをスタートさせると、ステップ３０１では設定部２５からの指示に基づき第１の設定点Ｐ１を設定し、被測定液３が第１の設定点Ｐ１に達した時、ステップ３０２にて設定部２５から指示によって第１の圧力値を取込み、ステップ３０３は第１の圧力が液面レベル計測装置１１における測定可能範囲か否か演算部１９が判断する。
【００４０】
もし、第１の圧力が液面レベル計測装置１１において予め設定された測定可能範囲外であってＮの場合には、ステップ３１１で演算部１９が被測定液３による比重補正エラーである旨の処理を行い、例えば表示部２３にその旨を表示するとともに警報部２７へ警報を出力してステップ３１２のリターンへ移る。
【００４１】
測定可能範囲内であってＹの場合には、ステップ３０３からステップ３０４に移って設定部２５からの指示に基づき第２の設定点Ｐ２を入力設定し、被測定液３が第２の設定点Ｐ２に達した時、ステップ３０４にて設定部２５から指示によって第２の圧力を取込み、ステップ３０６では第２の圧力が液面レベル計測装置における測定可能範囲か否か演算部１９が判断する。
【００４２】
測定可能範囲外であってＮの場合にはステップ３１１で上述したエラー処理を行い、測定可能範囲内であってＹの場合にはステップ３０７にて演算部１９が上述した式（２）を用いて比重演算処理を行い、ステップ３０８はで演算部１９がその算出比重が測定可能範囲か否か判断する。
【００４３】
測定可能範囲外であってＮの場合にはステップ３１１で演算部１９が上述したエラー処理を行い、測定可能範囲内であってＹの場合にはステップ３０９で演算部１９が上述した（３）式を用いて計測下限値の演算処理を行い、ステップ３１０で（４）式を用いて計測上限値の演算処理を行って液面データテーブルを作成し、ステップ３１２のリターンへ移る。
【００４４】
そして、液面データテーブルを作成した後、被測定液３の液面レベル本計測に当っては、演算部１９が入力部１７から入力した圧力値を記憶部２１中の液面データテーブルと照合し、該当する液面レベルを表示部２３へ出力してそれを表示させる。
【００４５】
このように、本発明に係る第１の方法は、容器１に予め被測定液３を入れて容器１の底から第１の設定点Ｐ１に達したときの第１の圧力およびそれより高い第２の設定点Ｐ２に達したときの第２の圧力との圧力差と、純水による圧力値との比例関係から被測定液３の比重を算出し（第１の工程）、その基準液の計測下限レベルおよび計測上限レベルに相当する被測定液３の計測下限レベルおよび計測上限レベルを、それら算出比重、基準液の比重、第１、第２の設定点Ｐ１、Ｐ２から算出し、この間の圧力と液面レベルとの比例関係を液面データテーブルとして求め（第２の工程）、本計測として容器１に入れた被測定液３の圧力値をその液面データテーブルに対応させて実際の液面レベルを計測する（第３の工程）構成とした。
【００４６】
そのため、予め比重が分かっている基準液、例えば純水の比重を使用するだけで、比重の分からない被測定液３の液面レベルを計測することが可能となり、液面レベルの計測が簡素化される。
【００４７】
しかも、上述した第１の方法では、算出比重、基準液の比重、第１および第２の設定点Ｐ１、Ｐ２から計測下限値および計測上限値を算出してその液面データテーブルを作成するから、被測定液の圧力と高さが比例関係にあるので、第１および第２の設定点Ｐ１、Ｐ２を任意に選定しても、可能な限り広い計測範囲を自動的に確保できる利点がある。
【００４８】
もっとも、計測下限値に近い位置に第１の設定点Ｐ１を選定し、計測上限値に近い位置に第２の設定点Ｐ２を設定すれば、少なくともこれら第１および第２の設定点Ｐ１、Ｐ２間において、比重の分からない被測定液３の液面レベルを計測することが可能となる。
【００４９】
そのため、必ずしも、基準液の計測下限レベルおよび計測上限レベルに相当する被測定液３の計測下限レベルおよび計測上限レベルを演算する必要はない。
【００５０】
次に本発明に係る液面レベル計測方法の第２の方法を説明する。
この第２の方法を実施するために、図１に示す演算部１９および記憶部２１は上述した機能の他に以下の機能を有している。
【００５１】
演算部１９は、任意の容器２９において所定の液面レベルとこの液面レベル毎の残容積との関係を容積データテーブルとして作成し、記憶部２１へ格納する機能を有している。
【００５２】
すなわち、図４に示すように、球形の容器２９に純水１リットル、６リットル、１２リットル、１９リットル、２７リットル、３６リットル、４５リットル、５３リットル、６０リットル、６６リットル、７１リットルを入れたときの液面レベルを外部から作業者が読取り、それら１１点の液面レベルおよび容積を設定部２５から入力すると、演算部１９は容器２９の１１点毎の液面レベルと残容量との関係を容積データテーブルとして作成し、記憶部２１へ格納する。
【００５３】
さらに、演算部１９は、第１の方法と同様に（図２および図３参照）、実際に液面レベルを計測する被測定液３を容器２９に入れ、容器２９の底から例えば２２０ｍｍ（第３の設定点Ｐ３）と４２０ｍｍ（第４の設定点Ｐ４）に達した時の圧力（第３および第４の圧力）を、設定部２５からの指示によって取込んで記憶部２１に格納し、上述した（２）式によって被測定液３の比重を算出し、この算出比重によって容積データテーブル中の液面レベルを純水から被測定液３の比重に応じた液面レベルに補正し、記憶部２１を書換え格納する機能を有している。
【００５４】
そして、演算部１９は、容器２９中の被測定液３について、本計測中に入力部１７から入力された圧力値を補正容積データテーブルと照合し、測定圧力に対応する残容積を表示部２３に表示させるとともに、前回の測定圧力からの変化量を演算して表示させる機能を有している。
【００５５】
このように、本発明に係る第２の方法は、比重が既知の基準液を入れたときの容器２９の容積と液面レベルとの関係を容積データテーブルとして記憶し（第４の工程）、その容器２９に被測定液３を入れて容器２９の底から第３の設定点Ｐ３に達したときの第３の圧力および第３の設定点Ｐ３より高い第４の設定点Ｐ４に達したときの第４の圧力との圧力差と、比重が既知の基準液による圧力との関係からその被測定液３の比重を算出し（第５の工程）、その容積データテーブルの液面レベルを算出比重で補正して記憶し（第６の工程）、本計測として容器２９に入れた被測定液３の圧力値をその容積データテーブルに対応させて実際の残容積を計測する（第７の工程）から、被測定液３を溜める容器２９が単純な筒型形状でなくとも、被測定液３の圧力測定を介してその残容積や前回の測定圧力時からの変化量を計測可能となる。
【００５６】
しかも、予め比重が分かっていない被測定液３について、第３、第４の設定点Ｐ３、Ｐ４間の圧力と比重の既知の基準液の圧力とを用いて比重を算出し、この算出比重で容積データテーブルの液面レベルを補正するから、比重が未知の被測定液３と任意の容器２９に入れ残容積の計測が可能となる。
【００５７】
ところで、半導体ウエハを薬液中で処理すると、その処理回数に応じてその薬液の比重が変化するから、測定圧力から正確な液面レベルを計測するために、この第３の方法が有用である。
【００５８】
以下、本発明に係る液面レベル計測方法の第３の方法を説明する。
第３の方法を実施するために、図１に示す演算部１９および記憶部２１は以下の機能を有している。
【００５９】
演算部１９は、容器１に溜めた被測定液３について、初期比重、所定数処理の終了した状態での終了比重、およびその処理回数が設定部２５から入力されたとき、各処理毎にその処理回数と比重の変化を比重テーブルデータとして作成し、記憶部２１へ格納する機能を有している。
【００６０】
すなわち、第３の方法では、図５Ａに示すように、初期状態における被測定液３の比重と、同図Ｂのように被処理物３１を１回処理して取り出した後の比重と、更に、同図Ｃのように被処理物３１の複数回処理が終了してそれを取り出した後の比重を入力設定するものである。
【００６１】
演算部１９は、被測定液３に被処理物３１が入れられて処理されて取り出され、設定部２５からその処理回数が入力されたとき、入力部１７から入力された圧力値を比重データテーブルと照合して対応する液面レベルを演算し、表示部２３に出力する機能を有している。
【００６２】
このように、本発明に係る第３の方法は、容器３に入れた被測定液３中で複数回の所定の処理を行う場合の処理前の初期比重と複数回目の処理後の比重とを測定し（第８の工程）、それら初期比重と処理後の比重とから当該処理回数毎の変化比重と圧力の関係を記憶し（第９の工程）、当該処理回数毎の被測定液の圧力測定値を当該圧力測定時の処理回数に応じた変化比重で補正して液面レベルを計測するから（第１０の工程）、被処理物３１の処理毎に処理用の被測定液３の比重が変化しても、各処理回数に従って比重が自動的に補正され、正確な液面レベルの計測が可能となる。
【００６３】
なお、本発明の液面レベル計測方法においては、パイプ７の先端を開放させたとき、すなわち容器１、２９内が空の状態における圧送気体の圧力を測定し、その圧力値が所定の初期値の範囲にあるか否かを判別し、もし初期値の範囲内にあれば測定を進め、初期値の範囲から外れる場合には警報信号を警報部２７にへ出力するよう構成することが好ましい。
【００６４】
【発明の効果】
以上、説明したように本発明の液面レベル計測方法に係る第１の方法によれば、予め比重が分かっていない被測定液の液面レベル計測が可能となる。
そして、第１の方法において、計測下限値および計測上限値を算出する方法を付加することにより、より広範囲の液面レベルの計測が可能となる利点がある。
また、本発明の第２の方法によれば、任意形状の容器に溜めた被測定液についても、残容積の計測が可能となる。
さらに、本発明の第３の方法によれば、被測定液の初期比重、最終比重、処理回数を予め入力設定すれば、被処理物の処理毎に被測定液の比重が変化しても、正確な液面レベルの計測が可能となる。
【図面の簡単な説明】
【図１】本発明の液面レベル計測方法を実施する液面レベル計測装置を示すブロック図である。
【図２】本発明の液面レベル計測方法に関し第１の方法を説明する特性図である。
【図３】本発明の液面レベル計測方法に関し第１の方法を説明するためのフローチャートである。
【図４】本発明の液面レベル計測方法に関し第２の方法を説明する図である。
【図５】本発明の液面レベル計測方法に関し第３の方法を説明する図である。
【図６】従来および本発明の液面レベル計測方法の参考となる図である。
【符号の説明】
１、２９容器
３被測定液
５気体供給装置
７パイプ
９気泡
１１液面レベル計測装置
１３ジョイント
１５センサ
１７入力部
１９演算部
２１記憶部
２３表示部
２５設定部
２７警報部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid level measurement method, and more particularly to an improvement of a back pressure type liquid level measurement method for measuring a liquid level (height to a liquid level) of liquid stored in various industrial fields.
[0002]
[Prior art]
Conventionally, for measuring the liquid level of the liquid stored in a container, for example, there is a method using the pressure of gas.
[0003]
That is, as shown in FIG. 6, the reservoir of test liquid 3 in the container 1, the other end (front end) side of the one pipe 7 which is connected at one end to a gas supply device 5 for pumping inert gas (gas) It is inserted into the liquid 3 to be measured, and bubbles 9 are always generated in the liquid 3 to be measured from the tip of the pipe 7, and a liquid level measuring device 11 is connected in the middle of the pipe 7, and the gas pressure in the pipe 7 is increased. This is a measurement method for measuring the liquid level through the measurement of (1).
[0004]
Reference numeral 13 in FIG. 6 denotes a joint inserted in the middle of the pipe 7 to connect the liquid level measuring device 11.
[0005]
In general, when a liquid 3 to be measured having a specific gravity ρ is stored in a container 1 and a virtual reference surface is considered at an arbitrary depth H from the liquid surface, the pressure P on the reference surface is given by the gravity acceleration g.
P = ρgH
And the depth H can be expressed as follows.
H = P / ρg (1)
[0006]
According to this, if the specific gravity ρ of the liquid 3 to be measured is known, the liquid level H can be known by measuring the pressure P.
[0007]
In the above-described back pressure type liquid level measurement method, the gas pressure (static pressure) at the tip of the pipe 7 is equal to the gas pressure in the pipe 7, and the gas pressure in the pipe 7 increases as the liquid level increases. If the pressure of gas supplied from the gas supply device 5 is adjusted so that bubbles 9 are generated from the tip of the pipe 7 in a state where the liquid 3 to be measured is fully stored in the container 1, the liquid 3 becomes empty from the full state. Until the state, the gas pressure in the pipe 7 is measured by the liquid level measuring device 11 and the liquid level H can be obtained by applying the above equation (1).
[0008]
As a means for forming the liquid level measuring device 11 and measuring the pressure of the gas in the middle of the pipe 7, a back pressure type pressure sensor is used.
[0009]
[Problems to be solved by the invention]
However, the above-described back-pressure type liquid level measurement method is suitable for measuring the liquid level of the liquid 3 to be measured whose specific gravity is known in advance, but the pressure is also different if the specific gravity of the liquid 3 is different even at the same liquid level. Therefore, it is difficult to measure the liquid level of the measured liquid 3 whose specific gravity is unknown.
[0010]
Also, with respect to the container 1 for storing the liquid 3 to be measured, in a container having an arbitrary shape, the measured liquid level does not always have a predetermined proportional relationship, and it is difficult to accurately measure the remaining volume.
[0011]
Further, in the case of processing a semiconductor wafer in a chemical solution in a semiconductor manufacturing process or the like, the specific gravity of the chemical solution is likely to change in accordance with the number of times the semiconductor wafer is processed. Measurement became difficult.
[0012]
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a liquid level measuring method capable of measuring the liquid level of a liquid to be measured whose specific gravity is not known in advance.
[0013]
Another object of the present invention is to provide a liquid level measurement method capable of accurately measuring the remaining volume of a liquid to be measured stored in a container having an arbitrary shape.
[0014]
Still another object of the present invention is to provide a liquid level measurement method capable of accurately measuring the liquid level even when the specific gravity of the liquid to be measured changes each time the object is processed.
[0015]
[Means for Solving the Problems]
In order to solve such a problem, a first method according to the present invention is to insert a single pipe into a liquid to be measured placed in a container, supply gas at a predetermined pressure, and cover the pipe from the end of the pipe. In the liquid level measurement method of measuring the liquid level of the liquid to be measured by measuring the back pressure in a state in which bubbles are generated in the liquid to be measured, the liquid to be measured is put in the container in advance and the first Proportion of the pressure difference between the first pressure when the set point is reached and the second pressure when the second set point is higher than the first set point, and the pressure by the reference liquid whose specific gravity is known A first step of calculating the specific gravity of the liquid to be measured from the relationship, and a liquid level indicating a proportional relationship between the pressure of the liquid to be measured and the liquid level at least between the first and second set points based on the calculated specific gravity. The second step of obtaining the data table and the actual measurement And by the pressure value of the test liquid in correspondence to the liquid level data tables are being and a third step of measuring the fluid level.
[0016]
In addition, the second step in the first method includes the steps of: calculating the measurement lower limit level and the measurement upper limit level of the liquid to be measured corresponding to the known lower pressure level and the measurement upper limit pressure level of the reference liquid; The reference liquid specific gravity is calculated from the first and second set points, and the proportional relationship between the pressure and the liquid level during this is obtained as the liquid level data table .
[0017]
Further, a second method according to the present invention is the liquid level measurement method for measuring the liquid level of the liquid to be measured, wherein a liquid having a specific gravity known in advance is filled with a reference volume and a volume of the container. A fourth step of obtaining the relationship as a volume data table, a third pressure when the liquid to be measured is previously placed in the container and a third set point, and a fourth set point higher than the third set point A fifth step of calculating the specific gravity of the liquid to be measured from a proportional relationship between the pressure difference from the fourth pressure when the pressure reaches the pressure and the pressure of the reference liquid, and a volume data table corresponding to the calculated specific gravity. A sixth step of correcting the liquid level in the container, and measuring the remaining volume of the liquid to be measured by associating the pressure value of the liquid to be measured put in the container with the corrected volume data table as the main measurement. And a seventh step.
[0018]
Further, a third method according to the present invention is a liquid level measurement method for measuring a liquid level of a liquid to be measured, the method comprising: an eighth step of setting the immediate early gravity and multiple-time processing after specific gravity, from those original gravity and processing specific gravity after seeking change specific gravity of each said processing number, you store the relationship between changes in specific gravity and pressure A ninth step and a tenth step of correcting the pressure measurement value of the liquid to be measured every time the number of times of the processing is input with a change specific gravity corresponding to the number of times of the processing at the time of the pressure measurement to measure the liquid level. And the steps of
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, for convenience, a liquid level measurement device that implements the liquid level measurement method of the present invention will be described.
[0020]
FIG. 1 is a block diagram showing a liquid level measuring device for implementing the liquid level measuring method of the present invention, and corresponds to, for example, the liquid level measuring device 11 in FIG. 6 described above.
[0021]
In FIG. 1, reference numeral 15 denotes a back pressure type pressure sensor which is disposed in the liquid level measuring device 11 in FIG. 6 and outputs an analog measurement signal at a level corresponding to the gas pressure fed through the pipe 7. , And an input unit 17. As the pressure sensor, for example, a semiconductor type pressure sensor and other conventionally known sensor elements are used.
[0022]
The input unit 17 converts the measurement signal from the pressure sensor 15 into a digital signal by A / D conversion at a predetermined timing, and is connected to the calculation unit 19.
[0023]
The arithmetic unit 19 includes a CPU 19a that executes a main arithmetic, calculating or determining function of the present invention, a ROM 19b storing an operation program of the CPU 19a, and an input / output interface 19c. The display unit 23, the setting unit 25, and the alarm unit 27 are connected. The function of the calculation unit 19 will be described later.
[0024]
The storage unit 21 is a built-in or external memory that stores a liquid level data table and other data tables, which will be described later, and various data, and the reading and writing of these are controlled under the control of the arithmetic unit 19.
[0025]
The display unit 23 is a liquid crystal display or the like that displays the liquid level calculated by the calculation unit 19 in mm or%, or displays other items.
[0026]
When the set point is reached, the setting section 25 inputs the height of the liquid level, instructs the timing of taking the pressure value from the input section 17 and storing it in the storage section 21 as described later, A keyboard or an online connection unit that is input from the outside and stored in the storage unit 21.
[0027]
Note that the pressure value of 9.807 kPa (measurement upper limit), 0 kPa (measurement lower limit), etc. of a liquid (pure water) having a specific gravity of 1 at a height of 1000 mm may be fixedly set in advance from the setting unit 25 or at the time of manufacture. is there.
[0028]
The alarm unit 27 is a liquid crystal display or a buzzer that issues an alarm to the outside when the liquid level or the like calculated by the calculation unit 19 is out of the measurement range, and is configured as a part of the display unit 23. There is also.
[0029]
As shown in FIG. 6 described above, the liquid to be measured 3 for which the liquid level is to be actually measured is flowed into the container 1 in advance and, for example, 250 mm from the bottom of the container 1 (first set point P1), as shown in FIG. And a pressure when the pressure reaches 400 mm (second set point P2) according to an instruction from the setting unit 25, and stores it in the storage unit 21. The first and second set points P1 and P2 are arbitrary.
[0030]
FIG. 2 shows two points when the pressures when the liquid 3 reaches 250 mm (first set point P1) and 400 mm (second set point P2) are 1.961 kPa and 3.923 kPa, respectively. The relationship between the pressure and the liquid level between them is virtually shown as a linear relationship.
[0031]
From the pressure values of the first and second set points P1 and P2 and the specific gravity of the reference liquid of 9.807 kPa, the calculation unit 19 calculates the specific gravity of the measured liquid 3 and the specific gravity of 0 kPa in the pure water by the following formula. ) And a function of calculating the measurement lower limit value and the measurement upper limit value of the liquid 3 to be measured corresponding to the state of 9.807 kPa (measurement upper limit).
[0032]

Here, 9.807 kPa is a pressure equivalent value at a depth of 1000 mm of pure water.
[0033]
That is, the calculation unit 19 calculates the ratio of the specific gravity of the reference liquid to 9.807 kPa to the pressure value difference (3.923 kPa to 1.961 kPa) at the first and second set points P1 and P2 of the liquid 3 to be measured, and And a function of calculating the specific gravity of the liquid 3 to be measured with respect to the specific gravity 1 of pure water from the ratio of the distance between the second set points P1 and P2 (400 mm-250 mm).
[0034]
The calculating unit 19 also calculates the ratio of the pressure of the reference liquid 9.807 kPa to the pressure (1.961 kPa) of the first set point P1 for the liquid 3 to be measured, the calculated specific gravity of the liquid 3 to be measured (1.333), and Is calculated from the relationship between the first set point P1 and the first set point P1, while the distance between the first and second set points P1 and P2 (400 mm-250 mm) and the first set point P2 are calculated. And the relationship between the pressure value difference between the second set points P1 and P2 (3.923 kPa-1.961 kPa) and the ratio of the reference liquid pressure 9.807 kPa, and the liquid level at the first set point P1. It has a function of calculating the measurement upper limit value of the liquid 3.
[0035]
Further, the computing unit 19 creates a liquid level data table (see FIG. 2) in which the relationship between the pressure level and the liquid level is linearized linearly from the calculated specific gravity, the lower limit of measurement, and the upper limit of measurement. 21 is provided.
[0036]
The arithmetic unit 19 compares the pressure value input from the input unit 17 with the liquid level data table for the liquid 3 to be measured placed in the container 1 as the main measurement, and displays the corresponding pressure value and liquid level on the display unit 23. In addition to the functions shown in FIG.
[0037]
Next, a first method according to the liquid level measurement method of the present invention will be described.
FIG. 3 is a flowchart for explaining the operation of the above-described liquid level measuring device and the main part of the first method according to the present invention.
[0038]
As shown in FIG. 6 described above, the other end (end) of the pipe 7 having one end connected to the gas supply device 5 is inserted into the liquid 3 to be measured in the container 1 from the liquid level, and the gas supply device 5 makes the gas supply device 5 inactive. A state where bubbles 9 are constantly generated from the end of the pipe 7 by feeding the gas under pressure is formed, and 9.807 kPa, which is the pressure value of the pure water liquid level of 1000 mm, from the setting unit 25 in FIG. The pressure values in the 0 kPa (measurement lower limit) state and the 9.807 kPa (measurement upper limit) state are input and set from the setting unit 25 to the storage unit 21 in advance.
[0039]
When the program is started in step 300, a first set point P1 is set in step 301 based on an instruction from the setting unit 25. When the measured liquid 3 reaches the first set point P1, in step 302, The first pressure value is fetched according to an instruction from the setting unit 25, and in step 303, the calculation unit 19 determines whether the first pressure is within the measurable range of the liquid level measurement device 11.
[0040]
If the first pressure is out of the measurable range preset in the liquid level measuring device 11 and is N, the arithmetic unit 19 determines in step 311 that the error is a specific gravity correction error due to the liquid 3 to be measured. The processing is performed, for example, the fact is displayed on the display unit 23, an alarm is output to the alarm unit 27, and the process proceeds to the return of step 312.
[0041]
In the case of Y within the measurable range, the process proceeds from step 303 to step 304 to input and set the second set point P2 based on the instruction from the setting unit 25, and the measured liquid 3 is set to the second set point. When the pressure reaches P2, the second pressure is taken in accordance with an instruction from the setting unit 25 in step 304, and in step 306, the calculation unit 19 determines whether or not the second pressure is within the measurable range of the liquid level measuring device.
[0042]
If it is out of the measurable range and is N, the above-described error processing is performed in step 311. If it is in the measurable range and it is Y, the arithmetic unit 19 uses the above-described equation (2) in step 307. In step 308, the calculating unit 19 determines whether the calculated specific gravity is within the measurable range.
[0043]
If it is out of the measurable range and is N, the calculating unit 19 performs the above-described error processing in Step 311. If it is in the measurable range and is Y, the calculating unit 19 is described in Step 309 (3). The calculation processing of the measurement lower limit value is performed by using the equation, and the calculation processing of the measurement upper limit value is performed by using the equation (4) in step 310 to create a liquid level data table, and the flow proceeds to the return of step 312.
[0044]
After the liquid level data table is created, in the actual measurement of the liquid level of the liquid 3 to be measured, the operation unit 19 compares the pressure value input from the input unit 17 with the liquid level data table in the storage unit 21. Then, the corresponding liquid level is output to the display unit 23 to be displayed.
[0045]
As described above, in the first method according to the present invention, the first pressure when the liquid 3 to be measured is previously placed in the container 1 and the first set point P1 is reached from the bottom of the container 1 and the first pressure higher than the first pressure P1 are set. The specific gravity of the liquid 3 to be measured is calculated from the proportional relationship between the pressure difference from the second pressure when reaching the set point P2 of 2 and the pressure value due to pure water (first step), The measurement lower limit level and the measurement upper limit level of the liquid 3 to be measured corresponding to the measurement lower limit level and the measurement upper limit level are calculated from the calculated specific gravity, the specific gravity of the reference liquid, and the first and second set points P1 and P2. The proportional relationship between the pressure and the liquid level is obtained as a liquid level data table (second step), and the actual measurement is performed by associating the pressure value of the measured liquid 3 put in the container 1 with the liquid level data table. The liquid level was measured (third step).
[0046]
Therefore, it is possible to measure the liquid level of the liquid 3 to be measured whose specific gravity is not known simply by using the reference liquid whose specific gravity is known in advance, for example, the specific gravity of pure water, thereby simplifying the measurement of the liquid level. Is done.
[0047]
Moreover, in the above-described first method, the measurement lower limit value and the measurement upper limit value are calculated from the calculated specific gravity, the specific gravity of the reference liquid, and the first and second set points P1 and P2, and the liquid level data table is created. Since the pressure and the height of the liquid to be measured are in a proportional relationship, even if the first and second set points P1 and P2 are arbitrarily selected, there is an advantage that the widest possible measurement range can be automatically secured. .
[0048]
However, if the first set point P1 is selected at a position close to the measurement lower limit and the second set point P2 is set at a position close to the measurement upper limit, at least the first and second set points P1, P2 are set. In the meantime, it is possible to measure the liquid level of the measured liquid 3 whose specific gravity is unknown.
[0049]
Therefore, it is not always necessary to calculate the measurement lower limit level and the measurement upper limit level of the measured liquid 3 corresponding to the measurement lower limit level and the measurement upper limit level of the reference liquid.
[0050]
Next, a second method of the liquid level measurement method according to the present invention will be described.
In order to carry out the second method, the calculation unit 19 and the storage unit 21 shown in FIG. 1 have the following functions in addition to the functions described above.
[0051]
The calculation unit 19 has a function of creating a relationship between a predetermined liquid level in an arbitrary container 29 and the remaining volume for each liquid level as a volume data table, and storing it in the storage unit 21.
[0052]
That is, as shown in FIG. 4, 1 liter, 6 liters, 12 liters, 19 liters, 27 liters, 36 liters, 45 liters, 53 liters, 60 liters, 66 liters, and 71 liters of pure water are placed in a spherical container 29. When the operator reads the liquid level at the time of reading from the outside and inputs the liquid level and volume of these 11 points from the setting unit 25, the calculating unit 19 calculates the liquid level and the remaining capacity of each of the 11 points of the container 29. The relationship is created as a volume data table and stored in the storage unit 21.
[0053]
Further, similarly to the first method (see FIGS. 2 and 3), the calculation unit 19 puts the liquid 3 to be actually measured in the liquid level into the container 29 and, for example, 220 mm from the bottom of the container 29 (second position). The pressure (third and fourth pressures) when the set point P3 reaches 420 mm (the fourth set point P4) and 420 mm (the fourth set point P4) are obtained by an instruction from the setting unit 25 and stored in the storage unit 21, The specific gravity of the liquid 3 to be measured is calculated by the above equation (2), and the liquid level in the volume data table is corrected from pure water to a liquid level corresponding to the specific gravity of the liquid 3 to be measured by the calculated specific gravity, and stored. The unit 21 has a function of rewriting and storing.
[0054]
Then, for the liquid 3 to be measured in the container 29, the calculation unit 19 checks the pressure value input from the input unit 17 during the main measurement with the corrected volume data table, and displays the remaining volume corresponding to the measured pressure on the display unit 23. And a function of calculating and displaying the amount of change from the previous measured pressure.
[0055]
As described above, in the second method according to the present invention, the relationship between the volume of the container 29 and the liquid level when a reference liquid having a known specific gravity is charged is stored as a volume data table (fourth step). When the liquid 3 to be measured is put into the container 29 and the third set point P3 is reached from the bottom of the container 29 and the fourth set point P4 higher than the third set point P3 is reached. The specific gravity of the measured liquid 3 is calculated from the relationship between the pressure difference from the fourth pressure and the pressure of the reference liquid whose specific gravity is known (fifth step), and the liquid level of the volume data table is calculated. Corrected by the specific gravity and stored (sixth step), the actual remaining volume is measured by associating the pressure value of the liquid 3 to be measured in the container 29 with the volume data table as the main measurement (seventh step). ), Even if the container 29 for storing the liquid 3 to be measured is not a simple cylindrical shape, The variation from the measurement pressure of the residual volume and the last becomes possible to measure through the pressure measurement of the liquid 3.
[0056]
In addition, for the liquid 3 to be measured whose specific gravity is not known in advance, the specific gravity is calculated using the pressure between the third and fourth set points P3 and P4 and the pressure of the reference liquid whose specific gravity is known. Since the liquid level in the volume data table is corrected, the remaining volume can be measured by placing the liquid 3 to be measured having an unknown specific gravity and an arbitrary container 29.
[0057]
By the way, when a semiconductor wafer is processed in a chemical solution, the specific gravity of the chemical solution changes according to the number of times of the processing. Therefore, the third method is useful for accurately measuring the liquid level from the measured pressure.
[0058]
Hereinafter, a third method of the liquid level measurement method according to the present invention will be described.
In order to carry out the third method, the arithmetic unit 19 and the storage unit 21 shown in FIG. 1 have the following functions.
[0059]
When the initial specific gravity, the end specific gravity in a state where a predetermined number of processes have been completed, and the number of times of processing are input from the setting unit 25 for the liquid 3 stored in the container 1, the calculating unit 19 It has a function of creating a change in the number of times of processing and specific gravity as specific gravity table data and storing it in the storage unit 21.
[0060]
That is, in the third method, as shown in FIG. 5A, the specific gravity of the liquid 3 to be measured in the initial state, the specific gravity after the processing object 31 is processed once and taken out as shown in FIG. As shown in Fig. C, the specific gravity after the processing of the processing object 31 is completed a plurality of times and the processing object 31 is taken out is input and set.
[0061]
When the processing object 31 is put into the liquid 3 to be measured and processed and taken out, and when the number of times of processing is input from the setting unit 25, the calculating unit 19 calculates the pressure value input from the input unit 17 into a specific gravity data table. And a function of calculating a corresponding liquid level by comparing with the display unit 23 and outputting the same to the display unit 23.
[0062]
As described above, in the third method according to the present invention, the initial specific gravity before processing and the specific gravity after multiple processing are performed when the predetermined processing is performed a plurality of times in the liquid 3 to be measured contained in the container 3. Measurement (eighth step), the relationship between the change specific gravity and the pressure for each number of processings is stored from the initial specific gravity and the specific gravity after the processing (ninth step), and the pressure of the liquid to be measured for each number of processings is stored. Since the measured value is corrected by the change specific gravity corresponding to the number of times of processing at the time of the pressure measurement and the liquid level is measured (tenth step), the specific gravity of the liquid to be measured 3 for processing is processed for each processing of the processing target 31. Is changed, the specific gravity is automatically corrected according to the number of times of processing, and accurate measurement of the liquid level can be performed.
[0063]
In the liquid level measurement method of the present invention, when the end of the pipe 7 is opened, that is, when the pressure of the pumping gas in the empty state of the containers 1 and 29 is measured, the pressure value is set to a predetermined initial value. It is preferable to determine whether or not it is within the range of the initial value. If it is within the range of the initial value, the measurement is advanced, and if it is out of the range of the initial value, it is preferable to output a warning signal to the warning unit 27.
[0064]
【The invention's effect】
As described above, according to the first method of the liquid level measurement method of the present invention, it is possible to measure the liquid level of the liquid to be measured whose specific gravity is not known in advance.
In the first method, by adding a method of calculating the measurement lower limit value and the measurement upper limit value, there is an advantage that a wider range of liquid level measurement can be performed.
Further, according to the second method of the present invention, it is possible to measure the remaining volume of the liquid to be measured stored in a container having an arbitrary shape.
Furthermore, according to the third method of the present invention, if the initial specific gravity, the final specific gravity, and the number of times of processing of the liquid to be measured are set in advance, even if the specific gravity of the liquid to be measured changes for each processing of the processing object, Accurate liquid level measurement is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a liquid level measuring device for implementing a liquid level measuring method of the present invention.
FIG. 2 is a characteristic diagram illustrating a first method for the liquid level measurement method according to the present invention.
FIG. 3 is a flowchart for explaining a first method relating to the liquid level measurement method of the present invention.
FIG. 4 is a diagram illustrating a second method relating to the liquid level measurement method of the present invention.
FIG. 5 is a diagram illustrating a third method relating to the liquid level measurement method of the present invention.
FIG. 6 is a reference drawing of the liquid level measurement method of the related art and the present invention.
[Explanation of symbols]
1, 29 container 3 liquid to be measured 5 gas supply device 7 pipe 9 air bubble 11 liquid level measurement device 13 joint 15 sensor 17 input unit 19 calculation unit 21 storage unit 23 display unit 25 setting unit 27 alarm unit

Claims

By inserting one pipe into the liquid to be measured placed in the container, supplying gas at a predetermined pressure, and measuring the back pressure in a state where bubbles are generated in the liquid to be measured from the end of the pipe, In the liquid level measurement method for measuring the liquid level of the liquid to be measured,
The liquid to be measured is previously placed in the container, and the first pressure when the first set point is reached and the second pressure when the second set point higher than the first set point is reached A first step of calculating the specific gravity of the liquid to be measured from a pressure difference and a proportional relationship between the specific gravity and the pressure of the known reference liquid;
A second step of obtaining a liquid level data table indicating a proportional relationship between a pressure of the liquid to be measured and a liquid level at least between the first and second set points based on the calculated specific gravity; The measurement upper limit level and the measurement lower limit level of the liquid to be measured corresponding to the known lower limit pressure and upper limit pressure are calculated from the calculated specific gravity, the reference liquid specific gravity, and the first and second set points. A second step of obtaining a proportional relationship with a surface level as the liquid level data table;
A third step of measuring the liquid level in association with the pressure value of the liquid to be measured put in the container as the main measurement in the liquid level data table;
A liquid level measurement method comprising:

By inserting one pipe into the liquid to be measured placed in the container, supplying gas at a predetermined pressure, and measuring the back pressure in a state where bubbles are generated in the liquid to be measured from the end of the pipe, In the liquid level measurement method for measuring the liquid level of the liquid to be measured,
A fourth step of obtaining a relationship between the volume of the container and the liquid level when a reference liquid having a known specific gravity is previously put into the container as a volume data table,
The liquid to be measured is put in the container in advance, and the third pressure when reaching the third set point and the fourth pressure when reaching the fourth set point higher than the third set point are calculated. A fifth step of calculating a specific gravity of the liquid to be measured from a pressure difference and a proportional relationship between the pressure of the reference liquid and
A sixth step of correcting a liquid level in the volume data table according to the calculated specific gravity;
As the main measurement, a seventh step of measuring the remaining volume of the liquid to be measured corresponding to the corrected volume data table with the pressure value of the liquid to be measured put in the container,
A liquid level measurement method comprising:

By inserting one pipe into the liquid to be measured placed in the container, supplying gas at a predetermined pressure, and measuring the back pressure in a state where bubbles are generated in the liquid to be measured from the end of the pipe, In the liquid level measurement method for measuring the liquid level of the liquid to be measured,
Eighth step of measuring the initial specific gravity before processing and the specific gravity after processing a plurality of times in the case where the object to be processed is processed a plurality of times in the liquid to be measured placed in the container,
A ninth step of obtaining a change specific gravity for each of the processing times from the initial specific gravity and the post-process specific gravity, and storing a relationship between the change specific gravity and the pressure;
The pressure value of the test liquid for each time the person the process number has been entered, a tenth step of measuring the liquid level by correcting a change gravity in accordance with the number of processing times during the pressure measurement,
A liquid level measurement method comprising: