JP4534421B2

JP4534421B2 - Flow measuring device

Info

Publication number: JP4534421B2
Application number: JP2003031194A
Authority: JP
Inventors: 修江口; 晃一竹村
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-02-07
Filing date: 2003-02-07
Publication date: 2010-09-01
Anticipated expiration: 2023-02-07
Also published as: JP2004125769A

Description

【０００１】
【発明の属する技術分野】
本発明は超音波を利用してガスなどの流量を計測する流量計測装置に関するものである。
【０００２】
【従来の技術】
従来のこの種の流量計測装置は、図１５に示すようなものが一般的であった。この装置は流体の流れる流路３１に設置した第１超音波振動子３２および第２超音波振動子３３と、第１超音波振動子３２、第２超音波振動子３３の送受信を切り換える切換手段３４と、第１超音波振動子３２及び第２超音波振動子３３を駆動する送信手段３５と、受信側の超音波振動子で受信し切り替え手段３４を通過した信号を所定の振幅まで増幅する増幅手段３６と、増幅手段３６で増幅された受信信号の電圧と基準電圧とを比較する基準比較手段３７と、図１６に示すように基準比較手段３７で基準電圧と比較し大小関係が反転した後の増幅信号の最初のゼロクロス点ａで繰り返し手段３９へ出力信号Ｄを出力する判定手段３８と、この判定手段３８からの信号をカウントし予め設定された回数だけカウントすると共に判定手段３８からの信号を制御手段４２へ出力する繰り返し手段３９と、繰り返し手段３９で予め設定された回数をカウントした時間を計時する計時手段４０と、計時手段４０の計時した時間に応じて流量を算出する流量算出手段４１と、流量算出手段４１から算出された流量出力、繰り返し手段３９からの信号を受け送信手段３５の動作を制御する制御手段４２と、判定手段３８、繰り返し手段３９、計時手段４０、流量算出手段４１、制御手段４２から構成されている。
【０００３】
この装置は制御手段４２により送信手段３５を動作させ超音波振動子３２で発信された超音波信号が、流れの中を伝搬し第２超音波振動子３３で受信され、増幅手段３６で増幅後、基準比較手段３７と判定手段３８で信号処理され、繰り返し手段３９を通り制御手段４２に入力される。この動作を予め設定されたｎ回数繰り返し行い、この間の時間を計時手段４０により測定する。そして、第１超音波振動子３２と第２超音波振動子３３とを切換手段３４により切り替えて、同様な動作を行い、被測定流体の上流から下流（この方向を正流とする）と下流から上流（この方向を逆流とする）のそれぞれの伝搬時間を測定し、（式１）より流量Ｑを求めていた（超音波振動子間の流れ方向の有効距離をＬ、上流から下流へのｎ回分の測定時間をｔ１、下流から上流へのｎ回分の測定時間をｔ２、被測定流体の流速をｖ、流路の断面積をＳ、センサ角度をφ、流量をＱとする）。
【０００４】
Ｑ＝Ｓ・ｖ＝Ｓ・Ｌ／２・ｃｏｓφ（（ｎ／ｔ１）−（ｎ／ｔ２））…（式１）
（実際には、式１に流量に応じた係数を乗じて流量を算出する）
また、増幅手段３６のゲインは受信側の超音波振動子で受信した信号を一定振幅となるようゲインを調整しており、受信信号のピーク電圧値が所定の電圧範囲に入るように調整される。これは繰り返し手段３９に設定された回数の計測を繰り返し中に、図１７の点線で示す受信信号ｂに示すように受信信号のピーク電圧値が所定の電圧範囲の下限より下回った回数と、同じく図１７の点線で示す受信信号ｃに示すように所定の電圧範囲の上限より上回った回数をカウントしておきその大小関係で次回の流量計測時のゲインを調整する（例えば下限より下回った回数が多ければゲインをアップして図１７の実線で示す受信信号ａのように電圧範囲の上限、下限の内に入るようにする）。
【０００５】
また、増幅手段３６により増幅された受信信号の電圧と比較する基準比較手段３７の基準電圧は判定手段３８により検知するゼロクロス点の位置を決めるもので図１６を例にすると受信信号の３波目のゼロクロス点ａを判定手段３８により検知するよう、受信信号の２波と３波のピーク電圧の中点の電圧に設定される。そうすることにより流量の変化及び流体の温度変化等で受信波形が変化し、受信信号の２波のピーク電圧が上昇、または３波のピーク電圧が減少しても双方に対してマージンをとれ、安定に判定手段３８により３波目のゼロクロス点ａが検知できるものである。
【０００６】
【発明が解決しようとする課題】
しかしながら上記従来の流量計測装置は、流量計測中において基準比較手段の基準電圧は固定電圧であり、また受信信号を増幅する増幅手段のゲインも固定であるので、流量計測中の繰り返し動作の中で超音波の受信信号の振幅レベルが変動した場合、基準電圧と受信信号との電圧レベルの相対関係が変化し、例えば受信信号の振幅レベルの変動が大きい場合には、基準電圧を超えていた受信波の３波のピーク電圧が基準電圧を超えなくなる。その結果、基準比較手段の出力が受信波の４波で出力され、判定手段は受信信号の４波目の負のゼロクロス点を検知するようになり、計時手段ではこの誤った時間を計時して、流量算出手段により誤った流量を算出するという課題を有していた。本発明は、前記従来の課題を解決するもので、判定手段により受信波の任意のポイント（受信波の３波目の負のゼロクロス点）を確実に検知出来るように、受信信号の振幅レベルの変動に対して大きなマージンを確保出来る位置に基準電圧を設定し、かつ流量計測中に受信信号の振幅レベルの変動に応じて基準電圧を調整することで、受信信号の振幅レベルの変動に強く、計測精度の高い流量計測装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
前記従来の課題を解決するために、本発明の流量計測装置は、流体管路に設けられ超音波信号を送受信する第１振動子及び第２振動子と、前記振動子を駆動する送信手段と、前記振動子の受信信号を増幅する増幅手段と、前記超音波信号の送受信の累積時間を計時する計時手段と、前記計時手段の計時した時間に基づいて流量を算出する流量算出手段と、前記第１振動子及び前記第２振動子のうち受信側の振動子の受信信号の電圧と基準電圧とを比較する基準比較手段と、前記基準比較手段と前記増幅手段の出力とから超音波信号の到達時期を判定する判定手段と、前記基準比較手段と前記判定手段の出力の時間差を計時する時間差計時手段と、前記基準比較手段の基準電圧を設定する基準設定手段を備えた流量計測装置において、基準電圧を設定可能範囲の最小から最大に変化させたときの前記時間差計時手段の計時する時間差（基準電圧と増幅手段の出力とを比較し、その大小関係が反転した時点を開始点とし、開始点以降で増幅手段の出力の符号が正から負に変わる最初の負のゼロクロス点を終了点とした場合の開始点から終了点に至る時間）が大きく変化する変曲点の測定結果に応じて基準電圧を設定する基準設定手段としたものである。
【０００８】
これによって基準設定手段が設定する基準電圧は判定手段により受信波の到達時期として検知させたい任意のポイント（例えばゼロクロス点）を含む波（例えば３波目）のピーク電圧と、１波前（２波目）のピーク電圧間で、１波前（２波目）のピーク電圧が流量計測中に変動する最大値を考慮した電圧より若干高い電圧に設定され、受信波の到達時期として検知させたい任意のポイントを含む波（３波目）のピーク電圧に対してマージンを大きく取れ、検知させたい任意のポイントを含む波（３波目）のピーク電圧が基準電圧を超えなくなるのを防ぐことが出来、受信信号の振幅レベルの変動に強く、超音波の受信信号の変動に対し一番安定な基準電圧に設定出来る流量計測装置とすることが出来る。
【０００９】
【発明の実施の形態】
本発明は、流体管路に設けられ超音波信号を送受信する第１振動子及び第２振動子と、前記振動子を駆動する送信手段と、前記振動子の受信信号を増幅する増幅手段と、前記超音波信号の送受信の累積時間を計時する計時手段と、前記計時手段の計時した時間に基づいて流量を算出する流量算出手段と、前記第１振動子及び前記第２振動子のうち受信側の振動子の受信信号の電圧と基準電圧とを比較する基準比較手段と、前記基準比較手段と前記増幅手段の出力とから超音波信号の到達時期を判定する判定手段と、前記基準比較手段と前記判定手段の出力の時間差を計時する時間差計時手段と、前記基準比較手段の基準電圧を設定する基準設定手段を備えた流量計測装置において、基準電圧を設定可能範囲の最小から最大に変化させたときの前記時間差計時手段の計時する時間差（基準電圧と増幅手段の出力とを比較し、その大小関係が反転した時点を開始点とし、開始点以降で増幅手段の出力の符号が正から負に変わる最初の負のゼロクロス点を終了点とした場合の開始点から終了点に至る時間）が大きく変化する変曲点の測定結果に応じて基準電圧を設定する基準設定手段とした流量計測装置とすることにより、超音波の受信信号の変動に対し一番安定な基準電圧に設定出来る流量計測装置とすることが出来る。
【００１０】
また、基準設定手段は基準電圧を設定可能範囲の最小から最大に変化させたときの前記時間差計時手段の計時する時間差が大きく変化する複数の変曲点の内、最大間隔の変曲点間の中点または任意の点に基準電圧を設定する基準設定手段とした流量計測装置とすることにより、基準電圧の設定を迅速かつ、精度良く行い、超音波の受信信号の変動に対し一番安定な基準電圧に設定出来る流量計測装置とすることが出来る。
【００１１】
また、基準設定手段は基準電圧を設定可能範囲の最小から最大まで変化させたときの前記時間差計時手段の計時した時間差の最大値、最小値より規定される所定の時間差の幅から、流量計測中に時間差計時手段が計時した時間差が外れた場合に基準電圧を変更する流量計測装置とすることにより、自動的に基準電圧の補正を行い、常に最適な基準電圧に保つことの出来る流量計測装置とすることが出来る。
【００１２】
また、流量計測中の時間差計時手段の計時した時間差が、基準電圧を設定可能範囲の最小から最大まで変化させたときの時間差の最大値、最小値の値両方を含んでいる場合に、基準電圧を再設定後に再度流量計測を行う流量計測装置とすることにより、流量計測中の超音波の受信信号の変動により基準電圧との大小関係が崩れたことを検知して基準電圧を再設定することで、最適な基準電圧に保つことの出来る流量計測装置とすることが出来る。
【００１３】
また、基準設定手段は基準電圧を設定可能範囲の最小から最大まで変化させたときの前記時間差計時手段の計時した時間差の最大値、最小値より規定される所定の時間差の幅から、流量計測中に時間差計時手段が計時した時間差が外れた回数に応じて基準電圧を変更する流量計測装置とすることにより、流路を流れる流体の流量の影響により超音波信号の送受信の方向別に超音波の受信信号と基準電圧との大小関係が崩れたことを検知して超音波信号の送受信の方向別に増幅手段の増幅度を変更することで基準電圧を再設定することで、基準比較手段の基準電圧を最適に保つことの出来る流量計測装置とすることが出来る。
【００１４】
また、超音波信号の送受信の方向別の時間差計時手段が計時した時間差の超音波信号の送受信の方向別の差が、所定より大きくなった場合に超音波信号の送受信の方向別に基準電圧を設定する流量計測装置とすることにより、流路を流れる流体の流量の影響により超音波信号の送受信の方向で超音波の受信信号と基準電圧との大小関係が崩れた場合に超音波信号の送受信の方向毎に基準比較手段の基準電圧を設定することで、基準比較手段の基準電圧を最適に保つことの出来る流量計測装置とすることが出来る。
【００１５】
【実施例】
以下本発明の実施例について図面を参照しながら説明する。
【００１６】
（実施例１）
図１は本発明の請求項１の第１の実施例における流量計測装置のブロック図を示すものである。図２は同第１の実施例の流量計測装置の動作説明図であり、図３は同フローチャートである。図１において、流路１の途中に超音波を送信する第１超音波振動子２と受信する第２超音波振動子３が流れ方向に角度φで配置されている。５は第１超音波振動子２への送信手段であり、４は第１超音波振動子２、第２超音波振動子３の送受信を切り換える切換手段、６は受信側の超音波振動子で受信した信号を制御手段１２からの指示によるゲインで増幅する増幅手段、７は前記増幅手段６で増幅された信号と基準電圧とを比較する基準比較手段、８は基準比較手段７の出力と前記増幅手段６で増幅された信号とから超音波の到達時期を判定する判定手段、９は判定手段８の信号をカウントし予め設定された回数だけ制御手段１２へ繰り返し信号を出力する繰り返し手段である。
【００１７】
１０は繰り返し手段９で予め設定された回数をカウントした時間を計時する計時手段であり、１１は計時手段１０の計時した時間に応じて管路の大きさや流れの状態を考慮して流量を算出する流量算出手段である。また、１２は流量算出手段１１、繰り返し手段９からの信号を受け送信手段５、増幅手段６の動作を制御する制御手段である。１３はＤ／Ａコンバータや電子ボリューム等で構成される前記基準比較手段７の基準電圧を設定する基準設定手段である。
【００１８】
以上のように構成された流量計測装置について、以下その動作、作用を説明する。制御手段１２は電源投入後、まず初期設定動作としてゲイン調整と基準電圧設定を行う。尚、ゲイン調整動作は従来例と何ら変わりないので本実施例ではその詳細な説明は省略するが、ゲイン調整後は図２に示すように受信信号のピーク電圧（例えば受信信号の中で５波がピークとする。）が所定の電圧範囲内に入る様に増幅されるので、図２に示すように受信信号が電圧範囲下限を越えている期間にピーク検知信号ＰＤが増幅手段６より制御手段１２、基準設定手段１３に出力される。最初に受信側の超音波振動子で受信した信号を一定振幅となるようゲインを調整した後（図３のステップ１）、受信信号の到達時期を認識するために検知しようとする波（例えば３波目）の１波前（２波目）のピーク電圧が流量計測中に変動する幅を考慮し、増幅手段は更に所定の増幅度で増幅する（ステップ２）。同じく増幅後の受信信号の様子を図２に示す。
【００１９】
図２において点線がゲイン調整後の受信信号、実線がゲイン調整後に更に所定の増幅度で増幅した受信信号を示す。図２に示すようにゲイン調整後に更に所定の増幅度で増幅後の受信信号Ａに対して、基準設定手段は図２に示す基準電圧Ｒｅｆを最低の基準電圧から１制御単位（例えば５ｍＶ）分、増加させる（ステップ３）。（本実施例では最低の基準電圧Ｒｅｆは図２に示す受信信号Ａの１波のピーク電圧ｐ１よりも高く２波のピーク電圧ｐ２よりも低いとする。）制御手段１２は繰り返し手段９の繰り返し回数を１回に設定して、送信手段５を動作させ第１超音波振動子２より超音波信号を送信する（ステップ４）。第１超音波振動子２より送信された超音波信号は流路１の流れの中を伝搬し、第２超音波振動子３で受信され、増幅手段６で増幅されて、基準比較手段７、判定手段８へ出力される。つまり図２に示すように基準比較手段７は増幅手段６の出力（受信信号Ａ）と基準電圧Ｒｅｆとを比較し（ステップ５）、その大小関係が反転した時点で基準設定手段１３と判定手段８に出力信号Ｃ２、Ｃ３、Ｃ４、Ｃ５を出力する。基準設定手段１３は基準比較手段７からの出力数をカウントし（ステップ６）、増幅手段６からのピーク検知信号を入力するまで繰り返す（ステップ７）。増幅手段６からのピーク検知信号を入力すると、基準設定手段１３は基準比較手段７からの出力数が３であるかを判断し（ステップ８）、３でなければ１制御単位分、増加させ、（ステップ３）以下、ステップ４から８迄を繰り返す。基準比較手段７からの出力数が３になると、増幅手段６はゲイン調整後の増幅度に戻す（ステップ９）。
【００２０】
基準電圧Ｒｅｆが受信波の２波のピークｐ２以下である場合は、ピーク検知信号が増幅手段６より出力されるまで基準比較手段７の出力数はＣ２〜Ｃ５の４つであり、基準電圧Ｒｅｆが受信波の２波のピークｐ２を越えると基準比較手段７は信号Ｃ２を出力しなくなり、出力数はＣ３〜Ｃ５の３つになる。従って基準比較手段の出力数が４から３になった時点で基準電圧Ｒｅｆの増加を止め、増幅手段６はゲイン調整後の増幅度に戻すと基準設定手段１３の基準電圧は受信信号の２波のピーク電圧より僅かに高く、その差は２波のピーク電圧が流量計測中に変動する幅を考慮して設定されているので、流量計測中に振幅レベルの変動が生じても２波のピーク電圧が基準電圧Ｒｅｆを越えることはない。従ってこの基準電圧Ｒｅｆでは３波のピーク電圧とのマージンを大きく取れ、受信信号の振幅レベルの変動に対して最も安定に判定手段８が超音波の受信信号の到達時期を検知出来る。
【００２１】
以上のように本実施例においては基準比較手段７の出力に応じて基準電圧を基準設定手段１３が設定し、その基準電圧は受信信号の到達時期を認識するために検知しようとする波の１波長前の波が、流量計測中に変動する振幅レベルの最大値を考慮した電圧に設定されるので、受信信号の到達時期を認識するために検知しようとする波の１波長前の波が基準電圧を超えることが無く、受信信号の到達時期を認識するために検知しようとする波と基準電圧とのマージンを大きく取れ、計測中の受信信号の振幅レベルの変動に強く計測精度の高い流量計測装置とすることが出来る。尚、本実施例ではゲイン調整後に、更に所定の増幅度で増幅して基準電圧を設定するとしたが、受信信号の到達時期を認識するために検知しようとする波（例えば３波目）の１波前（２波目）のピーク電圧が流量計測中に変動する電圧幅を考慮し、最大変動時の２波目のピーク電圧より高い電圧に、基準電圧Ｒｅｆを最初に設定したり、さらには基準電圧を変更していった際の基準比較手段の出力数の変化する電圧が受信波の各波のピーク電圧を示すので、この基準比較手段の出力数の変化する電圧より受信信号と基準電圧との相対関係を認識し、受信信号の到達時期を認識するために検知しようとする波（例えば３波目）と１波前（２波目）のピーク電圧（図２におけるｐ２、ｐ３）の間で流量計測中に変動する振幅レベルを考慮して任意の電圧に設定する様にしても同じ効果を有するものである。
【００２２】
（実施例２）
図４は本発明の請求項２、３、４、５、６に係る第２の実施例における流量計測装置のブロック図を示すものである。図５及び図８は同第２の実施例の流量計測装置の動作説明図であり、図６、及び図７は同フローチャートである。
【００２３】
図４において、１５は前記基準比較手段７と前記判定手段８の出力の時間差を計時する時間差計時手段で、基準設定手段１４は前記時間差計時手段１５の出力より基準比較手段７の基準電圧を設定することが実施例１と異なるところである。他の構成要素は実施例１と同じであるので説明は省略する。
【００２４】
以上のように構成された流量計測装置について、以下その動作、作用を説明する。制御手段１２は電源投入後、まず初期設定動作としてゲイン調整と基準電圧設定を行う。尚、本実施例の説明ではゲイン調整の説明は省略する。最初に受信側の超音波振動子で受信した信号を一定振幅となるようゲインを調整した後（図６のステップ１０１）、基準設定手段１４は基準電圧を設定範囲の最低の電圧に設定する（ステップ１０２）。
【００２５】
最低の基準電圧に設定後、制御手段１２は繰り返し手段９の繰り返し回数を１回に設定して、送信手段５を動作させ第１超音波振動子２より超音波信号を送信する（ステップ１０３）。
【００２６】
第１超音波振動子２より送信された超音波信号は流路１の流れの中を伝搬し、第２超音波振動子３で受信され、増幅手段６で増幅されて、基準比較手段７、判定手段８へ出力される。ここで図２に増幅後の受信信号の様子を示す。つまり図２に示すように基準比較手段７は増幅手段６の出力（受信信号Ａ）と基準電圧とを比較し（図６のステップ１０４）、その大小関係が反転した時点（タイミングｃ）で時間差計時手段１５と判定手段８に出力信号Ｃを出力する。時間差計時手段１５は基準比較手段７からの出力信号Ｃを入力すると計時を開始し（ステップ１０５）、判定手段８ではタイミングｃ以降の増幅手段６出力の符号が正から負に変わる最初の負のゼロクロス点ａを超音波の到達ポイントと判定し（ステップ１０６）、出力信号Ｄを繰り返し手段９、時間差計時手段１５に出力する。時間差計時手段１５は、この判定手段８の出力信号Ｄを受けると計時を終了し（ステップ１０７）、計時した時間差Ｔｄを基準設定手段１４へ出力する。基準設定手段１４は基準電圧を基準電圧の可変範囲の１制御単位（例えば２ｍＶ）分増加させる（ステップ１０８）。制御手段１２は繰り返し手段９に設定された繰り返し回数が１回であるので、繰り返し動作が終了した旨の信号を繰り返し手段９より入力して再度、送信手段５を動作させ第１超音波振動子２より超音波信号を送信する。ここまでの動作を基準設定手段１４が基準電圧の設定範囲の最大電圧に設定するまで繰り返す。
【００２７】
基準設定手段１４が基準電圧の最大電圧まで設定が終わると、基準設定手段１４は基準電圧を最小から最大に変化させたときの時間差計時手段１５の計時する時間差が大きく変化する（例えば前回の時間差と比較して１．３倍以上変化するか）複数の変曲点の内、最大間隔の変曲点間の中点に基準電圧を設定する（ステップ１１０）。この設定動作を図８を用いて説明する。図８は基準設定手段１４が基準電圧を最小から最大に変化させたときの時間差計時手段１５の計時した時間差を示した図である。時間差計時手段１５の計時した時間差は図５に示すように基準比較手段７と判定手段８の出力の時間差であるので受信信号の各波（１波、２波、３波．．．）のピーク電圧付近（図８において、それぞれｐ１、ｐ２、ｐ３．．．とする。）に基準電圧がある場合に時間差が最小（ｐ１、ｐ２、ｐ３．．．に対応してそれぞれＴｐ１、Ｔｐ２、Ｔｐ３．．．とする。）になり、その値は超音波の周期の約１／４（駆動周波数が５００ＫＨｚの場合、５００ｎｓ）になる。そこから基準電圧を増加させ、ピーク電圧を超えると時間差計時手段１５の計時した時間差は急に大きくなり図８に示すように時間差の変曲点（時間差の最小であるＴｐ１、Ｔｐ２、Ｔｐ３．．．）として現れる。（例えば基準電圧が２波のピークｐ２付近（但しｐ２を越えない）にあった場合から２波のピーク電圧ｐ２を超えた場合、変曲点はＴｐ２となる。）これは時間差の変曲点になる基準電圧が受信信号の各波のピーク電圧付近の電圧となることを意味している。そして変曲点間の幅（基準電圧幅）は受信信号各波のピーク電圧の電圧差である。
【００２８】
図８において変曲点Ｔｐ１、Ｔｐ２間の電圧差は受信信号の１波から２波のピーク電圧差で、変曲点Ｔｐ２、Ｔｐ３間の電圧差は受信信号の２波から３波のピーク電圧差を示している。このように基準電圧を最小から最大に変化させたときの時間差の変化には複数の変曲点が存在し、その変曲点間の幅が一番広い基準電圧範囲（図８において２波、３波のピーク電圧範囲）に基準電圧を設定すれば、受信信号の各波のピーク電圧差の一番大きい部分に設定することになり、例えば図８において２波、３波のピーク電圧の中点のＶｒｅに基準電圧を設定すれば２波、３波のピーク電圧と基準電圧との間にマージンを大きく取ることが出来、受信信号の電圧変動に対して最も安定に判定手段８が超音波の受信信号の到達時期を検知出来る。
【００２９】
基準設定手段１４が上記の様に基準電圧を設定すると制御手段１２は繰り返し手段９に正規の繰り返し回数（例えば２５６回）を設定して流量計測を開始する。流量計測を開始した後の基準設定手段１４の動作を図７を用いて説明する。流量計測を開始すると制御手段１２は送信手段５を動作させ第１超音波振動子２より超音波信号を送信し（図７のステップ１２）、増幅手段６で増幅された第２超音波振動子３で受信された超音波信号は基準比較手段７、判定手段８へ出力され、基準比較手段７で受信信号と基準電圧とを比較し（ステップ１３）、その大小関係が反転した時点から時間差計時手段１３で計時を開始し（ステップ１４）、判定手段８により増幅手段６出力の符号が正から負に変わる最初の負のゼロクロス点を検知するまで、時間差の計時を行う（ステップ１５、１６）。
【００３０】
判定手段８によりゼロクロス点（超音波の到達ポイント）の検知後、制御手段１２は送信手段５を再度動作させ超音波振動子２より超音波信号を送信する。この一連の動作を予め設定されたｎ回数繰り返し行い（ステップ１１）、所定の繰り返し回数終了後、基準設定手段１４は繰り返し回数分の時間差計時手段１５が計時した時間差の内、初期設定動作時に基準電圧を設定した際の変曲点（図８における変曲点Ｔｐ２、Ｔｐ３）における時間差の幅に所定の比率の範囲（例えば２０％〜８０％として変曲点ｂ、ｃの幅（８００ｎｓ−５００ｎｓ）×０．２＋５００＝５６０ｎｓから（８００ｎｓ−５００ｎｓ）×０．８＋５００＝７４０ｎｓ迄の範囲）外の時間差が存在したかどうかを判定して、時間差の分布の形態により基準電圧の再設定を決定する。つまり所定の比率の範囲よりも短い時間差（５６０ｎｓ未満）が存在したかを判定し（ステップ１７）、存在した場合は初期設定動作で行った基準電圧の設定動作を再度実行する（ステップ１９）。短かい時間差が存在しなかった場合は同様に（７４０ｎｓ超）が存在したかを判定し（ステップ１８）、存在した場合は初期設定動作で行った基準電圧の設定動作を再度実行（ステップ１９）し、所定の比率の範囲よりも短い時間差と長い時間差の両方が存在した場合は流量計測をやり直す。所定の比率の範囲外の時間差が存在しなかった場合は流量計測を終了し、流量計測開始から所定の繰り返し回数終了までの時間を計時手段１０により測定して、第１超音波振動子２と第２超音波振動子３とを切換手段４により切り替えて、同様な動作を行い、被測定流体の上流から下流と下流から上流のそれぞれの伝搬時間を測定し、これらの時間差より流量算出手段１１で流路の大きさや流れの状態を考慮して流量値を求める。また、図９を用いて基準設定手段１４の他の動作を説明する。
【００３１】
図９は基準設定手段１４の他の動作を説明するフローチャートである。
【００３２】
図９に於いて所定の繰り返し回数の動作を終えるまでのステップ１１〜１６迄の動作は図７の動作と同じなので、繰り返し動作終了後のステップ２１から説明を行う。繰り返し手段９に予め設定された回数の流量計測動作が終了すると基準設定手段１４は繰り返し回数分の時間差計時手段１５が計時した時間差の内、初期設定動作時に基準電圧を設定した際の変曲点における時間差の幅に所定の比率（上記と同様２０％）の範囲の上限下限両方の範囲外の時間差が存在したかどうかを判定して（ステップ２１）、存在していた場合は初期設定動作で行った基準電圧の設定動作を再度実行する（ステップ２２）。存在していなかった場合は範囲の上限（７４０ｎｓ）より長い時間差だけが存在したかを判断して（ステップ２３）、存在した場合はその回数が所定の回数（例えば１０回）以上有ったか判断する（ステップ２４）。所定の回数以上であれば基準電圧を１制御単位（２ｍＶ）分、基準電圧を２回増加させる（ステップ２５、２６）。所定の回数未満であれば基準電圧を１制御単位（２ｍＶ）分、基準電圧を増加させる（ステップ２６）。そして同様に、範囲の上限（７４０ｎｓ）より長い時間差ではなく範囲の下限（５６０ｎｓ）より短い時間差だけが存在したかを判定し（ステップ２７）、存在した場合はその回数が所定の回数（例えば１０回）以上有ったか判断する（ステップ２８）。所定の回数以上であれば基準電圧を１制御単位（２ｍＶ）分、基準電圧を２回減少させる（ステップ２９、３０）。所定の回数未満であれば基準電圧を１制御単位（２ｍＶ）分、基準電圧を減少させる（ステップ３０）。そして範囲の上限との比較（ステップ２３）、下限との比較（ステップ２７）の結果、全ての時間差が範囲内であったならば基準電圧は変更せずそのまま処理を終了する。このように流量計測時の時間差計時手段１５の計時する時間差が基準電圧を設定した際の時間差を基に決定される所定の時間差の幅から逸脱した回数に応じて基準電圧の再設定が行われる。また、本実施例では時間差計時手段１５の計時する時間差が大きく変化する複数の変曲点の内、最大間隔の変曲点間の中点に基準電圧を設定するとしたが、受信信号の電圧変動の方向（増加もしくは減少）に特徴があり、例えば受信信号の電圧変動が増加することは無く、減少することのみであれば基準電圧を時間差の変曲点間の中点ではなく、それよりも低い電圧に設定する方が受信信号の電圧変動（減少）に対して基準電圧とのマージンを大きく取れる。このような場合は、例えば時間差の最大間隔の変曲点間の１／３の点というように設定する基準電圧は受信信号の電圧変動に応じて任意の点に設定すればよい。以上のように本実施例においては初期設定時に基準電圧を最小から最大に変化させ、そのときの時間差計時手段１３の計時する時間差が大きく変化する複数の変曲点の内、最大間隔の変曲点間の中点または任意の点に基準電圧を設定する基準設定手段１４としたことにより基準電圧を超音波の受信波の中で受信信号の電圧変動に対して一番安定して超音波信号の到達時期を検知出来る電圧に設定出来、また、基準電圧の設定後、流量計測時の時間差計時手段１５の計時する時間差が基準電圧を設定した際の時間差を基に決定される所定の時間差の幅から逸脱した場合に基準電圧の再設定が行われる。これにより基準電圧の設定が人手を介することなく迅速に行われかつ、設定後、流量計測時に基準電圧を継続して最適な電圧に保つことの出来る流量計測装置とすることが出来る。
【００３３】
（実施例３）
図１０は本発明の請求項７に係る第３の実施例の流量計測装置のブロック図である。図１１は同フローチャートである。
【００３４】
図１０において基準設定手段１４が制御手段１２から第１振動子及び第２振動子から超音波を送信する方向の信号を受け設定する基準電圧を変更する様にしたのが実施例２と異なるところであり、他の構成要素は実施例２と同じであるので説明は省略する。
【００３５】
以上のように構成された流量計測装置について、以下実施例２と異なる基準設定手段１４の動作、作用を説明する。制御手段１２は電源投入後、まず初期設定動作としてゲイン調整と基準電圧設定を行う。実施例２と同様に基準電圧設定動作では基準設定手段１４が基準電圧を最小から最大に変化させたときの時間差計時手段１５の計時する時間差が大きく変化する複数の変曲点の内、最大間隔の変曲点間の中点に基準電圧を設定する。そして制御手段１２は実施例２と同様に繰り返し手段９に設定した回数、超音波の送受信を行い流量計測（図１１のステップ５１）を行う。そして流量計測後、時間差計時手段１５が計時した時間差の平均値を算出する（ステップ５２）。そして制御手段１２は、第１超音波振動子２と第２超音波振動子３とを切換手段４により切り替えて（ステップ５３）、同様な流量計測を行い（ステップ５４）、その後、時間差計時手段１５が計時した時間差の平均値を算出する（ステップ５５）。基準設定手段１４は第１超音波振動子２及び第２超音波振動子３の送信方向別の平均時間差を比較し（ステップ５６）、所定の差より大きい場合（例えば片方の時間差が６００ｎｓ、もう片方が６７０ｎｓと１０％以上の差がある場合）に送信方向別に基準電圧の設定動作を行い（ステップ５７）、以後方向に応じて別々の基準電圧を用いる。
【００３６】
以上のように本実施例においては流路を流れる流体の流量によって被測手流体の上流から下流と、下流から上流へと超音波信号を送信する方向で受信信号の感度の差が発生し、受信波の電圧と基準電圧との関係が変化し、その結果、時間差計時手段が計時する時間差が超音波信号を送信する方向で異なった場合にそれぞれの方向で最適な基準電圧の設定ができる。このように超音波信号の送信方向で受信信号の電圧に差が発生しても基準電圧を最適な電圧に保つ流量計測装置とすることが出来る。
【００３７】
（実施例４）
図１２は本発明の請求項８の実施例４の流量計測装置のブロック図である。図１３、図１４は本発明の実施例４の流量計測装置の動作説明図であり、基準電圧の決定動作を説明したものである。図１２において７ａは予め設定されるか、基準電圧の設定を変更する電子ボリューム等の基準設定部で、７ｂは基準設定部７ａの基準電圧と受信側の振動子の受信信号の電圧とを比較する比較部であり、７ｃは比較部７ｂの出力と判定手段８からの出力の時間差を計時する時間差計時部である。基準設定部７ａと比較部７ｂと時間差計時部７ｃとで基準比較手段７を構成していることが第１の実施例と異なっている。１６は基準比較手段７の出力後、前記増幅手段６の出力の任意のポイント間の時間を算出する信号幅検出手段である。他の構成要素は実施例１と同じであるので説明は省略する。
【００３８】
以上のように構成された流量計測装置について、以下、その動作について説明する。基準比較手段７は自らの基準電圧の設定値を以下のように決定する。制御手段１２は電源投入時の初期設定動作や、流量算出手段１１が異常値を算出した場合や判定手段８が超音波信号の到達時期を判定出来なかった場合に基準比較手段７に基準電圧の決定動作の実行を指示する。制御手段１２からの指示により基準比較手段７は自らの基準電圧の決定動作モードとなると、基準設定部７ａは基準電圧を増幅手段６により増幅された超音波の受信信号のピーク電圧付近に設定する。（図１３に示すように第４波が受信波のピーク電圧である場合、基準電圧をそのピーク電圧に設定する。この時の電圧をＲｅｆｓ）そして、その電圧Ｒｅｆｓから徐々に電圧（設定値）を下げていきながら比較部７ｂの出力信号と判定手段８の出力信号の時間差を時間差計時部７ｃで計時する。
【００３９】
これは例えば基準電圧が図１３の点線で示すＲｅｆｐであった場合、比較部７ｂの出力信号Ｃと判定手段８の出力信号Ｅとの時間差ｔｄを時間差計時部７ｃで計時するわけである。そしてこのように基準電圧を下げていった場合の時間差計時部７ｃで計時する時間差は図１４のようになり、超音波の受信信号の各波（第２波、第３波・・・）のピーク電圧で超音波の周波数の１／４波長の時間となり、他の部分では基準電圧を下げるに従って時間差が長くなる。
【００４０】
このように基準電圧と時間差とは相関があり、超音波の周波数の１／４波長となる基準電圧値が超音波の受信信号の各波のピーク電圧であるので第３波ピーク電圧値と第２波ピーク電圧の中間電圧を基準電圧ｒ２、第２波ピーク電圧値と第１波ピーク電圧の中間電圧を基準電圧ｒ１として基準設定部７ａに記憶して、基準比較手段７は自らの基準電圧の決定動作モードを終了する。
【００４１】
そして受信信号の到達時期を認識するために検知しようとする波を例えば３波目とした場合、その１波前の２波目のピーク電圧との中間電圧の基準電圧ｒ２に基準電圧を設定して流量計測を開始する。尚、本実施例ではゲイン調整後に、基準電圧の決定動作モードで、最初に基準電圧を受信信号のピーク電圧から徐々に電圧を下げていくとしたが、反対に受信信号の最も振幅の小さい波（１波目）付近から徐々に上げていき時間差計時部７ｃの計時する時間差により特定の波間（例えば２波、３波間の中間電圧に基準電圧を設定する様にしても同じ効果を有するものである。さらに本実施例では受信信号のピーク電圧の中間電圧としたが実施例２で述べたように、受信信号の電圧（振幅）変動の方向（増加もしくは減少）に特徴がある場合、受信信号の電圧変動に対して特定のピーク電圧間の中で、基準電圧とのマージンを大きく取れる任意の電圧に設定すればよい（例えば実施例２で述べたように特定ピーク電圧間の１／３の点）。
【００４２】
以上のように本実施例においては電源投入時の初期設定動作時や、その後の基準電圧設定動作時に、時間差計時部７ｃが計時する比較部７ｂと判定手段８の出力の時間差より基準設定部７ａの基準電圧設定値を決定する設定値決定及び記憶動作が行われ、この基準電圧は実際の超音波信号の受信波を基に決定されるので、基準電圧を最適な電圧とする流量計測装置とすることが出来る。
【００４３】
【発明の効果】
以上説明したように本発明の流量計測装置は、超音波の受信信号の変動に対し一番安定な基準電圧に設定出来る流量計測装置とすることが出来る効果がある。
【図面の簡単な説明】
【図１】本発明の実施例１における流量計測装置のブロック図
【図２】同装置の動作を説明する図
【図３】同装置のフローチャート
【図４】第２の実施例における流量計測装置のブロック図動作を説明する図
【図５】同装置の動作を説明する図
【図６】同装置のフローチャート
【図７】同装置のフローチャート
【図８】同装置の動作を説明する図
【図９】同装置の基準設定手段の他の動作を説明するフローチャート
【図１０】本発明の実施例３における流量計測装置のブロック図
【図１１】同装置のフローチャート
【図１２】本発明の実施例４における流量計測装置のブロック図
【図１３】同装置の動作を説明する図
【図１４】同装置の動作を説明する図
【図１５】従来の流量計測装置のブロック図
【図１６】従来の流量計測装置の動作説明図
【図１７】従来の流量計測装置の増幅手段の動作説明図
【符号の説明】
１流路
２第１超音波振動子（第１振動子）
３第２超音波振動子（第２振動子）
４切換手段
５送信手段
６増幅手段
７基準比較手段
８判定手段
９繰り返し手段
１０計時手段
１１流量算出手段
１２制御手段
１３基準設定手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device that measures a flow rate of gas or the like using ultrasonic waves.
[0002]
[Prior art]
A conventional flow measuring device of this type is generally as shown in FIG. This apparatus includes a first ultrasonic transducer 32 and a second ultrasonic transducer 33 installed in a flow path 31 through which fluid flows, and switching means for switching between transmission and reception of the first ultrasonic transducer 32 and the second ultrasonic transducer 33. 34, transmission means 35 for driving the first ultrasonic transducer 32 and the second ultrasonic transducer 33, and a signal received by the ultrasonic transducer on the receiving side and passed through the switching means 34 are amplified to a predetermined amplitude. The amplifying means 36, the reference comparing means 37 for comparing the voltage of the received signal amplified by the amplifying means 36 with the reference voltage, and the reference comparing means 37 as shown in FIG. A determination unit 38 that outputs the output signal D to the repetition unit 39 at the first zero cross point a of the subsequent amplified signal, a signal from the determination unit 38 is counted, and the determination unit 38 counts a preset number of times. The flow rate is calculated according to the repeating means 39 for outputting these signals to the control means 42, the time measuring means 40 for measuring the time counted by the number of times preset by the repeating means 39, and the time measured by the time measuring means 40. A flow rate calculation means 41; a flow rate output calculated from the flow rate calculation means 41; a control means 42 for receiving the signal from the repetition means 39 and controlling the operation of the transmission means 35; a determination means 38; a repetition means 39; a time measurement means 40; The flow rate calculation means 41 and the control means 42 are comprised.
[0003]
In this apparatus, the transmission means 35 is operated by the control means 42 and the ultrasonic signal transmitted from the ultrasonic vibrator 32 propagates in the flow and is received by the second ultrasonic vibrator 33, and is amplified by the amplification means 36. The signal is processed by the reference comparison unit 37 and the determination unit 38, and is input to the control unit 42 through the repetition unit 39. This operation is repeated n times set in advance, and the time between them is measured by the time measuring means 40. Then, the first ultrasonic transducer 32 and the second ultrasonic transducer 33 are switched by the switching means 34, and the same operation is performed. From the upstream to the downstream of the fluid to be measured (this direction is a positive flow) and the downstream , The propagation time of each upstream (this direction is the reverse flow) was measured, and the flow rate Q was obtained from (Equation 1) (the effective distance in the flow direction between the ultrasonic transducers was L, the upstream to downstream The measurement time for n times is t1, the measurement time for n times from downstream to upstream is t2, the flow velocity of the fluid to be measured is v, the cross-sectional area of the flow path is S, the sensor angle is φ, and the flow rate is Q).
[0004]
Q = S · v = S · L / 2 · cos φ ((n / t1) − (n / t2)) (Formula 1)
(In practice, the flow rate is calculated by multiplying Equation 1 by a coefficient corresponding to the flow rate.)
The gain of the amplifying means 36 is adjusted so that the signal received by the ultrasonic transducer on the receiving side has a constant amplitude so that the peak voltage value of the received signal falls within a predetermined voltage range. . This is the same as the number of times when the peak voltage value of the received signal falls below the lower limit of the predetermined voltage range as shown by the received signal b shown by the dotted line in FIG. As shown in the received signal c shown by the dotted line in FIG. 17, the number of times that the upper limit of the predetermined voltage range is exceeded is counted, and the gain at the next flow rate measurement is adjusted according to the magnitude (for example, the number of times that the lower limit is exceeded). If there are more, the gain is increased so that it falls within the upper and lower limits of the voltage range as in the received signal a shown by the solid line in FIG.
[0005]
Further, the reference voltage of the reference comparison means 37 for comparing with the voltage of the reception signal amplified by the amplification means 36 determines the position of the zero cross point detected by the determination means 38. Taking FIG. 16 as an example, the third wave of the reception signal is determined. The zero-cross point a of the received signal is set to the midpoint voltage of the peak voltage of the two waves and three waves of the received signal so that the determination means 38 detects the zero cross point a. By doing so, the received waveform changes due to changes in flow rate and fluid temperature, etc., and even if the peak voltage of the two waves of the received signal rises or the peak voltage of the three waves decreases, a margin is taken for both, The zero cross point a of the third wave can be detected stably by the determination means 38.
[0006]
[Problems to be solved by the invention]
However, in the above conventional flow rate measuring device, the reference voltage of the reference comparison unit is a fixed voltage during the flow rate measurement, and the gain of the amplification unit for amplifying the received signal is also fixed. When the amplitude level of the ultrasonic reception signal fluctuates, the relative relationship between the voltage level of the reference voltage and the reception signal changes. For example, when the fluctuation of the amplitude level of the reception signal is large, the reception that has exceeded the reference voltage The peak voltage of the three waves does not exceed the reference voltage. As a result, the output of the reference comparison unit is output as four received waves, and the determination unit detects the negative zero-cross point of the fourth wave of the received signal. The timing unit counts this incorrect time. Therefore, there is a problem of calculating an incorrect flow rate by the flow rate calculation means. The present invention solves the above-described conventional problem, and the amplitude level of the received signal is determined so that an arbitrary point of the received wave (the negative zero-cross point of the third wave of the received wave) can be reliably detected by the judging means. By setting the reference voltage at a position where a large margin can be secured against fluctuations and adjusting the reference voltage according to fluctuations in the amplitude level of the received signal during flow measurement, it is resistant to fluctuations in the amplitude level of the received signal. It aims at providing a flow measuring device with high measurement accuracy.
[0007]
[Means for Solving the Problems]
In order to solve the conventional problem, the flow rate measuring device of the present invention is A first vibrator and a second vibrator that are provided in a fluid conduit and transmit / receive an ultrasonic signal, a transmission unit that drives the transducer, an amplification unit that amplifies a reception signal of the transducer, and the ultrasonic wave Time measuring means for measuring the accumulated time of signal transmission / reception, flow rate calculating means for calculating a flow rate based on the time measured by the time measuring means, and a receiving-side vibrator among the first vibrator and the second vibrator Reference comparison means for comparing the voltage of the received signal with the reference voltage, determination means for determining the arrival time of the ultrasonic signal from the outputs of the reference comparison means and the amplification means, the reference comparison means, and the determination means In the flow rate measuring device provided with the time difference measuring means for measuring the time difference between the outputs of the output and the reference setting means for setting the reference voltage of the reference comparison means, the reference voltage is changed from the minimum of the settable range to the maximum. time The time difference measured by the time measuring means (comparing the reference voltage and the output of the amplifying means, starting from the time when the magnitude relationship has been reversed, and the first negative that changes the sign of the output of the amplifying means from positive to negative after the start point. The reference setting means is used to set the reference voltage according to the measurement result of the inflection point where the time from the start point to the end point (when the zero crossing point is the end point) Is.
[0008]
As a result, the reference voltage set by the reference setting means is a peak voltage of a wave (for example, the third wave) including an arbitrary point (for example, the zero cross point) to be detected as the arrival time of the received wave by the determination means, and one wave before (2 The peak voltage of the first wave (second wave) between the peak voltages of the first wave is set to a voltage that is slightly higher than the voltage that takes into account the maximum value that fluctuates during flow measurement, and you want to detect the arrival time of the received wave The margin for the peak voltage of the wave including the arbitrary point (third wave) can be increased to prevent the peak voltage of the wave including the arbitrary point to be detected (third wave) from exceeding the reference voltage. Can withstand fluctuations in the amplitude level of the received signal Can be set to the most stable reference voltage against fluctuations in ultrasonic reception signals It can be set as a flow measuring device.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention A first vibrator and a second vibrator provided in a fluid conduit for transmitting and receiving an ultrasonic signal; a transmitting means for driving the vibrator; an amplifying means for amplifying a received signal of the vibrator; and the ultrasonic signal. Measuring means for measuring the accumulated transmission / reception time, flow rate calculating means for calculating a flow rate based on the time measured by the time measuring means, and a receiving-side vibrator of the first vibrator and the second vibrator. A reference comparison means for comparing the voltage of the received signal with a reference voltage, a determination means for determining the arrival time of the ultrasonic signal from the outputs of the reference comparison means and the amplification means, and the reference comparison means and the determination means In the flow rate measuring device having a time difference measuring means for measuring a time difference of output and a reference setting means for setting a reference voltage of the reference comparison means, the time difference when the reference voltage is changed from the minimum of the settable range to the maximum. The time difference for measuring of time means (Comparing the reference voltage and the output of the amplification means, the starting point is the time when the magnitude relationship is reversed, and the first negative zero cross point where the sign of the amplification means output changes from positive to negative after the start point is the end point. Time from start point to end point) The flow rate can be set to the most stable reference voltage against fluctuations in the received ultrasonic signal by using the flow rate measurement device as the reference setting means to set the reference voltage according to the measurement result of the inflection point where the value changes greatly It can be set as a measuring device.
[0010]
In addition, the reference setting means has a maximum interval between inflection points among a plurality of inflection points where the time difference measured by the time difference measuring means changes greatly when the reference voltage is changed from the minimum of the settable range to the maximum. Reference setting means for setting the reference voltage at the midpoint or any point Flow measurement device By doing so, it is possible to provide a flow rate measuring apparatus that can set the reference voltage quickly and accurately, and can set the reference voltage that is most stable with respect to fluctuations in the received ultrasonic signal.
[0011]
In addition, the reference setting means is measuring the flow rate from the range of the predetermined time difference defined by the maximum value and the minimum value of the time difference measured by the time difference measuring means when the reference voltage is changed from the minimum to the maximum of the settable range. The reference voltage is changed when the time difference measured by the time difference measuring means is off. Flow measurement device By doing so, it is possible to provide a flow rate measuring apparatus that automatically corrects the reference voltage and can always maintain the optimum reference voltage.
[0012]
In addition, the time difference measured by the time difference measuring means during flow rate measurement is the maximum value of the time difference when the reference voltage is changed from the minimum of the settable range to the maximum. Minimum value If both values are included, measure the flow rate again after resetting the reference voltage. Flow rate measuring device to perform By detecting that the magnitude relationship with the reference voltage has collapsed due to fluctuations in the ultrasonic reception signal during flow measurement, the flow rate can be maintained at the optimum reference voltage by resetting the reference voltage. It can be set as a measuring device.
[0013]
In addition, the reference setting means is measuring the flow rate from the range of the predetermined time difference defined by the maximum value and the minimum value of the time difference measured by the time difference measuring means when the reference voltage is changed from the minimum to the maximum of the settable range. The reference voltage is changed according to the number of times the time difference measured by the time difference measuring means is off. Flow measurement device By detecting that the magnitude relationship between the ultrasonic reception signal and the reference voltage is broken depending on the transmission / reception direction of the ultrasonic signal due to the flow rate of the fluid flowing in the flow path, the transmission / reception direction of the ultrasonic signal is detected. By separately resetting the reference voltage by changing the amplification degree of the amplification means, a flow rate measuring device capable of maintaining the reference voltage of the reference comparison means optimally can be obtained.
[0014]
In addition, when the difference in the time difference of the ultrasonic signal transmission / reception direction of the ultrasonic signal transmission / reception direction becomes larger than a predetermined time difference, the reference voltage is set for each direction of transmission / reception of the ultrasonic signal. Flow measurement device Therefore, when the magnitude relationship between the ultrasonic reception signal and the reference voltage is disrupted in the direction of ultrasonic signal transmission / reception due to the influence of the flow rate of the fluid flowing through the flow path, the reference is made for each direction of ultrasonic signal transmission / reception. By setting the reference voltage of the comparison means, a flow rate measuring device that can keep the reference voltage of the reference comparison means optimal can be obtained.
[0015]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
Example 1
FIG. 1 shows a block diagram of a flow rate measuring apparatus according to a first embodiment of claim 1 of the present invention. FIG. 2 is an operation explanatory view of the flow rate measuring apparatus according to the first embodiment, and FIG. 3 is a flowchart of the same. In FIG. 1, a first ultrasonic transducer 2 that transmits ultrasonic waves and a second ultrasonic transducer 3 that receives ultrasonic waves are disposed in the flow direction 1 at an angle φ in the flow direction. 5 is a transmission means to the first ultrasonic transducer 2, 4 is a switching means for switching between transmission and reception of the first ultrasonic transducer 2 and the second ultrasonic transducer 3, and 6 is an ultrasonic transducer on the receiving side. Amplifying means for amplifying the received signal with a gain according to an instruction from the control means 12, 7 is a reference comparing means for comparing the signal amplified by the amplifying means 6 with a reference voltage, and 8 is an output of the reference comparing means 7 and the above-mentioned Determining means for determining the arrival time of the ultrasonic wave from the signal amplified by the amplifying means 6, and 9 a repeating means for counting the signal of the determining means 8 and outputting a repetitive signal to the control means 12 for a preset number of times. .
[0017]
Reference numeral 10 denotes a time measuring means for counting the time counted in advance by the repetition means 9, and 11 denotes a flow rate in consideration of the size of the pipeline and the flow state according to the time measured by the time measuring means 10. The flow rate calculation means. A control unit 12 receives signals from the flow rate calculation unit 11 and the repetition unit 9 and controls operations of the transmission unit 5 and the amplification unit 6. Reference numeral 13 denotes a reference setting means for setting a reference voltage of the reference comparison means 7 constituted by a D / A converter, an electronic volume, or the like.
[0018]
The operation and action of the flow rate measuring apparatus configured as described above will be described below. After the power is turned on, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. Since the gain adjustment operation is not different from the conventional example, a detailed description thereof will be omitted in this embodiment. However, after gain adjustment, the peak voltage of the received signal (for example, 5 waves in the received signal) as shown in FIG. 2), the peak detection signal PD is controlled by the control means from the amplification means 6 during the period when the received signal exceeds the lower limit of the voltage range as shown in FIG. 12 and output to the reference setting means 13. First, after adjusting the gain so that the signal received by the ultrasonic transducer on the receiving side has a constant amplitude (step 1 in FIG. 3), the wave to be detected in order to recognize the arrival time of the received signal (for example, 3 In consideration of the range in which the peak voltage before the second wave (the second wave) fluctuates during flow rate measurement, the amplifying means further amplifies at a predetermined amplification degree (step 2). Similarly, FIG. 2 shows the state of the received signal after amplification.
[0019]
In FIG. 2, the dotted line indicates a received signal after gain adjustment, and the solid line indicates a received signal further amplified with a predetermined amplification degree after gain adjustment. As shown in FIG. 2, for the received signal A that has been further amplified with a predetermined amplification degree after gain adjustment, the reference setting means converts the reference voltage Ref shown in FIG. 2 by one control unit (for example, 5 mV) from the lowest reference voltage. (Step 3). (In this embodiment, it is assumed that the lowest reference voltage Ref is higher than the peak voltage p1 of one wave of the reception signal A shown in FIG. 2 and lower than the peak voltage p2 of two waves). The number of times is set to 1, and the transmitting means 5 is operated to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 4). The ultrasonic signal transmitted from the first ultrasonic transducer 2 propagates through the flow path 1, is received by the second ultrasonic transducer 3, is amplified by the amplification means 6, It is output to the determination means 8. That is, as shown in FIG. 2, the reference comparison means 7 compares the output (reception signal A) of the amplification means 6 with the reference voltage Ref (step 5), and the reference setting means 13 and the determination means when the magnitude relationship is reversed. 8 output signals C2, C3, C4 and C5. The reference setting means 13 counts the number of outputs from the reference comparison means 7 (step 6) and repeats until the peak detection signal from the amplification means 6 is input (step 7). When the peak detection signal from the amplifying unit 6 is input, the reference setting unit 13 determines whether the number of outputs from the reference comparison unit 7 is 3 (step 8). (Step 3) Hereinafter, steps 4 to 8 are repeated. When the number of outputs from the reference comparison means 7 becomes 3, the amplification means 6 returns to the amplification degree after gain adjustment (step 9).
[0020]
When the reference voltage Ref is equal to or lower than the peak p2 of the two received waves, the number of outputs of the reference comparison means 7 is four from C2 to C5 until the peak detection signal is outputted from the amplification means 6, and the reference voltage Ref Exceeds the peak p2 of the two received waves, the reference comparison means 7 does not output the signal C2, and the number of outputs becomes three of C3 to C5. Therefore, when the number of outputs of the reference comparison means is changed from 4 to 3, the increase of the reference voltage Ref is stopped, and when the amplification means 6 returns to the amplification degree after gain adjustment, the reference voltage of the reference setting means 13 becomes two waves of the received signal. The peak voltage is slightly higher than the peak voltage, and the difference is set in consideration of the fluctuation width of the peak voltage of the two waves during the flow measurement, so even if the amplitude level fluctuates during the flow measurement, the peak of the two waves The voltage does not exceed the reference voltage Ref. Therefore, the reference voltage Ref can have a large margin with respect to the peak voltage of the three waves, and the determination means 8 can detect the arrival time of the ultrasonic reception signal most stably with respect to fluctuations in the amplitude level of the reception signal.
[0021]
As described above, in this embodiment, the reference setting unit 13 sets the reference voltage in accordance with the output of the reference comparison unit 7, and the reference voltage is 1 of the wave to be detected to recognize the arrival time of the received signal. Since the wave before the wavelength is set to a voltage that takes into account the maximum value of the amplitude level that fluctuates during flow measurement, the wave one wavelength before the wave to be detected to recognize the arrival time of the received signal is the reference. Flow rate measurement with high measurement accuracy that can withstand large fluctuations in the amplitude level of the received signal during measurement without exceeding the voltage, allowing a large margin between the wave to be detected and the reference voltage to recognize the arrival time of the received signal It can be a device. In this embodiment, after the gain adjustment, the reference voltage is set by further amplifying with a predetermined amplification degree. However, in order to recognize the arrival time of the received signal, one of the waves to be detected (for example, the third wave) is set. In consideration of the voltage range in which the peak voltage before the wave (second wave) fluctuates during flow measurement, the reference voltage Ref is first set to a voltage higher than the peak voltage of the second wave at the maximum fluctuation, Since the voltage at which the output number of the reference comparison means changes when the reference voltage is changed indicates the peak voltage of each wave of the received wave, the received signal and the reference voltage are determined from the voltage at which the output number of the reference comparison means changes. And the peak voltage (p2, p3 in FIG. 2) of the wave to be detected (for example, the third wave) and the previous wave (the second wave) to recognize the arrival time of the received signal. Arbitrary considering the amplitude level that fluctuates during flow rate measurement Even in the manner set to a voltage are those having the same effect.
[0022]
(Example 2)
FIG. 4 shows a block diagram of a flow rate measuring apparatus in the second embodiment according to claims 2, 3, 4, 5, and 6 of the present invention. 5 and 8 are explanatory diagrams of the operation of the flow rate measuring apparatus according to the second embodiment, and FIGS. 6 and 7 are flowcharts thereof.
[0023]
In FIG. 4, reference numeral 15 denotes a time difference timing means for measuring the time difference between the outputs of the reference comparison means 7 and the determination means 8, and the reference setting means 14 sets the reference voltage of the reference comparison means 7 from the output of the time difference measurement means 15. This is different from the first embodiment. Since other components are the same as those in the first embodiment, description thereof is omitted.
[0024]
The operation and action of the flow rate measuring apparatus configured as described above will be described below. After the power is turned on, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. In the description of this embodiment, description of gain adjustment is omitted. After adjusting the gain so that the signal first received by the ultrasonic transducer on the receiving side has a constant amplitude (step 101 in FIG. 6), the reference setting means 14 sets the reference voltage to the lowest voltage in the setting range ( Step 102).
[0025]
After setting to the lowest reference voltage, the control means 12 sets the number of repetitions of the repetition means 9 to 1, operates the transmission means 5 and transmits an ultrasonic signal from the first ultrasonic transducer 2 (step 103). .
[0026]
The ultrasonic signal transmitted from the first ultrasonic transducer 2 propagates through the flow path 1, is received by the second ultrasonic transducer 3, is amplified by the amplification means 6, It is output to the determination means 8. FIG. 2 shows the state of the received signal after amplification. That is, as shown in FIG. 2, the reference comparison means 7 compares the output (reception signal A) of the amplification means 6 with the reference voltage (step 104 in FIG. 6), and the time difference is obtained when the magnitude relationship is inverted (timing c). An output signal C is output to the time measuring means 15 and the judging means 8. The time difference timing means 15 starts timing when the output signal C from the reference comparison means 7 is input (step 105), and the determination means 8 first determines the sign of the output of the amplification means 6 after the timing c from the positive to the negative. The zero cross point a is determined as the arrival point of the ultrasonic wave (step 106), and the output signal D is output to the repeater 9 and the time difference timer 15. When receiving the output signal D of the determination means 8, the time difference timing means 15 ends the time measurement (step 107) and outputs the time difference Td measured to the reference setting means 14. The reference setting means 14 increases the reference voltage by one control unit (for example, 2 mV) in the variable range of the reference voltage (step 108). Since the control means 12 has set the number of repetitions of 1 in the repetition means 9, a signal indicating that the repetition operation has been completed is input from the repetition means 9 to operate the transmission means 5 again to operate the first ultrasonic transducer. 2 transmits an ultrasonic signal. The operation so far is repeated until the reference setting means 14 sets the maximum voltage within the reference voltage setting range.
[0027]
When the reference setting unit 14 finishes setting up to the maximum reference voltage, the reference setting unit 14 greatly changes the time difference counted by the time difference counting unit 15 when the reference voltage is changed from the minimum to the maximum (for example, the previous time difference). The reference voltage is set at the midpoint between the inflection points having the maximum interval among the plurality of inflection points (step 110). This setting operation will be described with reference to FIG. FIG. 8 is a diagram showing the time difference measured by the time difference measuring means 15 when the reference setting means 14 changes the reference voltage from the minimum to the maximum. As shown in FIG. 5, the time difference measured by the time difference measuring means 15 is the time difference between the outputs of the reference comparison means 7 and the determination means 8, so that the peak of each wave (1 wave, 2 waves, 3 waves ...) of the received signal is obtained. When there is a reference voltage in the vicinity of the voltage (in FIG. 8, p1, p2, p3,...), The time difference is minimum (p1, p2, p3,... Corresponding to p1, p2, p3,. The value is about 1/4 of the period of the ultrasonic wave (500 ns when the drive frequency is 500 KHz). When the reference voltage is increased from the peak voltage and the peak voltage is exceeded, the time difference measured by the time difference measuring means 15 suddenly increases and the time difference inflection points (Tp1, Tp2, Tp3,. .). (For example, if the reference voltage is in the vicinity of the peak p2 of two waves (but does not exceed p2) but exceeds the peak voltage p2 of two waves, the inflection point is Tp2.) This is the inflection point of the time difference. This means that the reference voltage becomes a voltage near the peak voltage of each wave of the received signal. The width between the inflection points (reference voltage width) is the voltage difference between the peak voltages of the received signal waves.
[0028]
In FIG. 8, the voltage difference between the inflection points Tp1 and Tp2 is a peak voltage difference between one wave and two waves of the received signal, and the voltage difference between the inflection points Tp2 and Tp3 is a peak voltage between two waves and three waves of the received signal. Showing the difference. Thus, there are a plurality of inflection points in the change of the time difference when the reference voltage is changed from the minimum to the maximum, and the reference voltage range having the widest width between the inflection points (two waves in FIG. 8, If the reference voltage is set to (the peak voltage range of 3 waves), it is set to the portion where the peak voltage difference of each wave of the received signal is the largest. For example, in FIG. If the reference voltage is set to the point Vre, a large margin can be secured between the peak voltage of the second wave and the third wave and the reference voltage, and the determination means 8 is most stable against the voltage fluctuation of the received signal. The arrival time of the received signal can be detected.
[0029]
When the reference setting unit 14 sets the reference voltage as described above, the control unit 12 sets a regular number of repetitions (for example, 256 times) in the repetition unit 9 and starts flow measurement. The operation of the reference setting unit 14 after starting the flow measurement will be described with reference to FIG. When the flow rate measurement is started, the control unit 12 operates the transmission unit 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 12 in FIG. 7), and the second ultrasonic transducer amplified by the amplification unit 6. 3 is output to the reference comparison means 7 and the determination means 8, the reference comparison means 7 compares the received signal with the reference voltage (step 13), and the time difference is measured from the time when the magnitude relationship is inverted. Time measurement is started by means 13 (step 14), and time difference is measured until the first negative zero cross point at which the sign of the output of amplification means 6 changes from positive to negative is detected by determination means 8 (steps 15 and 16). .
[0030]
After the zero crossing point (ultrasonic arrival point) is detected by the determination unit 8, the control unit 12 operates the transmission unit 5 again to transmit an ultrasonic signal from the ultrasonic transducer 2. This series of operations is repeated n times set in advance (step 11), and after the predetermined number of repetitions, the reference setting means 14 uses the time difference counted by the time difference counting means 15 for the number of repetitions as a reference during the initial setting operation. The range of a predetermined ratio to the width of the time difference at the inflection points (inflection points Tp2, Tp3 in FIG. 8) when the voltage is set (for example, 20 to 80%, the width of the inflection points b and c (800 ns to 500 ns). ) × 0.2 + 500 = 560 ns to (800 ns−500 ns) × 0.8 + 500 = 740 ns) It is determined whether there is a time difference outside, and the resetting of the reference voltage is determined according to the form of the time difference distribution. . That is, it is determined whether there is a time difference (less than 560 ns) shorter than the predetermined ratio range (step 17), and if it exists, the reference voltage setting operation performed in the initial setting operation is executed again (step 19). If there is no short time difference, it is similarly determined whether (exceeding 740 ns) is present (step 18), and if it is present, the reference voltage setting operation performed in the initial setting operation is executed again (step 19). If both a time difference shorter than a predetermined ratio range and a time difference longer than the predetermined ratio range are present, the flow rate measurement is repeated. If there is no time difference outside the range of the predetermined ratio, the flow rate measurement is terminated, the time from the start of the flow rate measurement to the end of the predetermined number of repetitions is measured by the time measuring means 10, and the first ultrasonic transducer 2 and The second ultrasonic transducer 3 is switched by the switching means 4 and the same operation is performed to measure the propagation times of the fluid under measurement from upstream to downstream and from downstream to upstream, and the flow rate calculation means 11 is calculated from these time differences. Thus, the flow rate value is obtained in consideration of the size of the flow path and the flow state. Further, another operation of the reference setting unit 14 will be described with reference to FIG.
[0031]
FIG. 9 is a flowchart for explaining another operation of the reference setting means 14.
[0032]
In FIG. 9, the operations from step 11 to step 16 until the operation of the predetermined number of repetitions is completed are the same as the operation of FIG. 7, so the description will be made from step 21 after the end of the repetition operation. When the flow measurement operation of the preset number of times in the repetition means 9 is completed, the reference setting means 14 is the inflection point when the reference voltage is set during the initial setting operation among the time differences counted by the time difference timing means 15 for the number of repetitions. It is determined whether there is a time difference outside the upper and lower limits of the predetermined ratio (20% as above) in the time difference width at step 21 (step 21). The set reference voltage setting operation is executed again (step 22). If it does not exist, it is determined whether there is only a time difference longer than the upper limit (740 ns) of the range (step 23). If it exists, it is determined whether the number of times is a predetermined number (for example, 10 times) or more. (Step 24). If the predetermined number of times is exceeded, the reference voltage is increased twice by one control unit (2 mV) (steps 25 and 26). If it is less than the predetermined number of times, the reference voltage is increased by one control unit (2 mV) (step 26). Similarly, it is determined whether there is only a time difference shorter than the lower limit (560 ns) of the range rather than a time difference longer than the upper limit (740 ns) of the range (step 27). Times) or more (step 28). If the number of times is equal to or greater than the predetermined number, the reference voltage is decreased by one control unit (2 mV) and the reference voltage is decreased twice (steps 29 and 30). If it is less than the predetermined number of times, the reference voltage is decreased by one control unit (2 mV) (step 30). As a result of comparison with the upper limit of the range (step 23) and comparison with the lower limit (step 27), if all the time differences are within the range, the reference voltage is not changed and the process is terminated. Thus, the reference voltage is reset according to the number of times that the time difference measured by the time difference measuring means 15 at the time of flow rate deviates from the predetermined time difference determined based on the time difference when the reference voltage is set. . In this embodiment, the reference voltage is set at the midpoint between the inflection points of the maximum interval among the plurality of inflection points where the time difference measured by the time difference measuring means 15 changes greatly. For example, the voltage fluctuation of the received signal does not increase, and if it only decreases, the reference voltage is not the midpoint between the inflection points of the time difference, but more than that. Setting a lower voltage allows a larger margin with respect to the reference voltage with respect to voltage fluctuation (decrease) in the received signal. In such a case, for example, the reference voltage that is set to be 1/3 between the inflection points of the maximum interval of time difference may be set to an arbitrary point according to the voltage fluctuation of the received signal. As described above, in this embodiment, the reference voltage is changed from the minimum to the maximum at the time of initial setting, and among the inflection points at which the time difference measured by the time difference measuring means 13 changes greatly, the inflection at the maximum interval. By using the reference setting means 14 for setting the reference voltage at a midpoint between points or at an arbitrary point, the reference voltage is the most stable ultrasonic signal with respect to voltage fluctuations of the received signal in the ultrasonic wave. The time difference measured by the time difference measuring means 15 at the time of flow rate measurement is determined based on the time difference when the reference voltage is set after setting the reference voltage. The reference voltage is reset when it deviates from the width. As a result, the reference voltage can be set quickly without human intervention, and after setting, the flow rate measuring device can keep the reference voltage at the optimum voltage during flow rate measurement.
[0033]
(Example 3)
FIG. 10 is a block diagram of a flow rate measuring apparatus according to a third embodiment of the present invention. FIG. 11 is a flowchart of the same.
[0034]
In FIG. 10, the reference setting unit 14 receives a signal in the direction in which ultrasonic waves are transmitted from the first transducer and the second transducer from the control unit 12 and changes the reference voltage to be set. The other components are the same as those in the second embodiment, and the description thereof is omitted.
[0035]
With respect to the flow rate measuring apparatus configured as described above, the operation and action of the reference setting means 14 different from the second embodiment will be described below. After the power is turned on, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. As in the second embodiment, in the reference voltage setting operation, the maximum interval among a plurality of inflection points at which the time difference measured by the time difference measuring means 15 changes greatly when the reference setting means 14 changes the reference voltage from the minimum to the maximum. Set a reference voltage at the midpoint between the inflection points. Then, similarly to the second embodiment, the control unit 12 transmits and receives ultrasonic waves for the number of times set in the repetition unit 9 and performs flow rate measurement (step 51 in FIG. 11). Then, after measuring the flow rate, the average value of the time differences measured by the time difference measuring means 15 is calculated (step 52). Then, the control means 12 switches between the first ultrasonic transducer 2 and the second ultrasonic transducer 3 by the switching means 4 (step 53), performs the same flow rate measurement (step 54), and then the time difference timing means. The average value of the time difference measured by 15 is calculated (step 55). The reference setting means 14 compares the average time difference of the first ultrasonic transducer 2 and the second ultrasonic transducer 3 for each transmission direction (step 56), and if it is larger than the predetermined difference (for example, the time difference of one is 600 ns, the other When one side is 670 ns and there is a difference of 10% or more), a reference voltage setting operation is performed for each transmission direction (step 57), and thereafter different reference voltages are used depending on the direction.
[0036]
As described above, in this embodiment, the difference in sensitivity of the received signal occurs in the direction in which the ultrasonic signal is transmitted from the upstream to the downstream of the fluid to be measured, and from the downstream to the upstream, depending on the flow rate of the fluid flowing through the flow path. When the relationship between the voltage of the received wave and the reference voltage changes and, as a result, the time difference measured by the time difference measuring means differs in the direction in which the ultrasonic signal is transmitted, the optimum reference voltage can be set in each direction. Thus, even if a difference occurs in the voltage of the reception signal in the transmission direction of the ultrasonic signal, a flow rate measuring device that maintains the reference voltage at an optimum voltage can be obtained.
[0037]
Example 4
FIG. 12 is a block diagram of a flow rate measuring apparatus according to the fourth embodiment of the present invention. FIG. 13 and FIG. 14 are diagrams for explaining the operation of the flow rate measuring apparatus according to the fourth embodiment of the present invention and explain the determination operation of the reference voltage. In FIG. 12, 7a is a reference setting unit such as an electronic volume that is set in advance or changes the setting of the reference voltage, and 7b compares the reference voltage of the reference setting unit 7a with the voltage of the reception signal of the transducer on the receiving side. 7c is a time difference timing unit that measures the time difference between the output of the comparison unit 7b and the output from the determination means 8. Unlike the first embodiment, the reference setting unit 7a, the comparison unit 7b, and the time difference measuring unit 7c constitute the reference comparison means 7. Reference numeral 16 denotes signal width detection means for calculating the time between arbitrary points of the output of the amplification means 6 after the output of the reference comparison means 7. Since other components are the same as those in the first embodiment, description thereof is omitted.
[0038]
The operation of the flow rate measuring apparatus configured as described above will be described below. The reference comparison means 7 determines the set value of its own reference voltage as follows. The control unit 12 sets the reference voltage to the reference comparison unit 7 when the power is turned on, when the flow rate calculation unit 11 calculates an abnormal value, or when the determination unit 8 cannot determine the arrival time of the ultrasonic signal. Instructs execution of decision operation. When the reference comparison unit 7 enters the operation mode for determining its own reference voltage according to an instruction from the control unit 12, the reference setting unit 7 a sets the reference voltage near the peak voltage of the ultrasonic reception signal amplified by the amplification unit 6. . (When the fourth wave is the peak voltage of the received wave as shown in FIG. 13, the reference voltage is set to the peak voltage. The voltage at this time is Refs), and the voltage (set value) is gradually increased from the voltage Refs. The time difference between the output signal of the comparison unit 7b and the output signal of the determination means 8 is measured by the time difference counting unit 7c.
[0039]
For example, when the reference voltage is Refp shown by a dotted line in FIG. 13, the time difference td between the output signal C of the comparison unit 7b and the output signal E of the determination means 8 is measured by the time difference timing unit 7c. The time difference measured by the time difference measuring unit 7c when the reference voltage is lowered in this way is as shown in FIG. 14, and each wave (second wave, third wave,...) Of the ultrasonic reception signal is obtained. At the peak voltage, the time is ¼ wavelength of the ultrasonic frequency, and in other parts, the time difference becomes longer as the reference voltage is lowered.
[0040]
Thus, there is a correlation between the reference voltage and the time difference. Since the reference voltage value that is a quarter wavelength of the ultrasonic frequency is the peak voltage of each wave of the ultrasonic reception signal, the third wave peak voltage value and the The reference voltage r2 is stored in the reference setting unit 7a as the reference voltage r2 and the intermediate voltage between the second wave peak voltage value and the first wave peak voltage is stored in the reference setting unit 7a. The determination operation mode is terminated.
[0041]
If the wave to be detected for recognizing the arrival time of the received signal is the third wave, for example, the reference voltage is set to the reference voltage r2 that is an intermediate voltage between the peak voltage of the second wave and the second wave. Start flow measurement. In this embodiment, after the gain adjustment, the reference voltage is first gradually lowered from the peak voltage of the received signal in the reference voltage determining operation mode. On the contrary, the wave having the smallest amplitude of the received signal is used. Even if the reference voltage is set to a specific wave interval (for example, an intermediate voltage between 2 waves and 3 waves) due to the time difference measured by the time difference measuring unit 7c, gradually increasing from the vicinity of the (first wave), the same effect is obtained. Furthermore, in the present embodiment, the intermediate voltage of the peak voltage of the received signal is used, but as described in the second embodiment, when there is a characteristic in the direction (increase or decrease) of the voltage (amplitude) fluctuation of the received signal, the received signal The voltage may be set to an arbitrary voltage with a large margin with respect to the reference voltage among the specific peak voltages with respect to voltage fluctuations (for example, as described in the second embodiment, １／ of the specific peak voltage point).
[0042]
As described above, in this embodiment, the reference setting unit 7a is determined based on the time difference between the output of the comparison unit 7b and the determination means 8 measured by the time difference measuring unit 7c during the initial setting operation when the power is turned on or during the subsequent reference voltage setting operation. The reference voltage setting value is determined and stored, and the reference voltage is determined based on the received wave of the actual ultrasonic signal. I can do it.
[0043]
【The invention's effect】
As described above, the flow rate measuring device of the present invention is Can be set to the most stable reference voltage against fluctuations in the received ultrasonic signal There exists an effect which can be set as a flow measuring device.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining the operation of the apparatus
FIG. 3 is a flowchart of the apparatus.
FIG. 4 is a block diagram for explaining the operation of the flow rate measuring apparatus according to the second embodiment.
FIG. 5 is a diagram for explaining the operation of the apparatus;
FIG. 6 is a flowchart of the apparatus.
FIG. 7 is a flowchart of the apparatus.
FIG. 8 is a diagram for explaining the operation of the apparatus;
FIG. 9 is a flowchart for explaining another operation of the reference setting unit of the apparatus.
FIG. 10 is a block diagram of a flow rate measuring device according to Embodiment 3 of the present invention.
FIG. 11 is a flowchart of the apparatus.
FIG. 12 is a block diagram of a flow rate measuring device according to Embodiment 4 of the present invention.
FIG. 13 is a diagram for explaining the operation of the apparatus;
FIG. 14 is a diagram for explaining the operation of the apparatus;
FIG. 15 is a block diagram of a conventional flow rate measuring device.
FIG. 16 is a diagram illustrating the operation of a conventional flow rate measuring device.
FIG. 17 is an operation explanatory diagram of the amplifying means of the conventional flow rate measuring device.
[Explanation of symbols]
1 channel
2 First ultrasonic transducer (first transducer)
3 Second ultrasonic transducer (second transducer)
4 Switching means
5 Transmission means
6 Amplification means
7 Standard comparison means
8 judgment means
9 Repeat means
10 Timekeeping means
11 Flow rate calculation means
12 Control means
13 Standard setting means

Claims

A first vibrator and a second vibrator provided in a fluid conduit for transmitting and receiving an ultrasonic signal; a transmitting means for driving the vibrator; an amplifying means for amplifying a received signal of the vibrator; and the ultrasonic signal. Measuring means for measuring the accumulated transmission / reception time, flow rate calculating means for calculating a flow rate based on the time measured by the time measuring means, and a receiving-side vibrator of the first vibrator and the second vibrator. A reference comparison means for comparing the voltage of the received signal with a reference voltage, a determination means for determining the arrival time of the ultrasonic signal from the outputs of the reference comparison means and the amplification means, and the reference comparison means and the determination means In the flow rate measuring device having a time difference measuring means for measuring a time difference of output and a reference setting means for setting a reference voltage of the reference comparison means, the time difference when the reference voltage is changed from the minimum of the settable range to the maximum. Reference setting means for setting a reference voltage according to the measurement result of the inflection point at which the time difference measured by the time means changes greatly, and the time difference is a comparison between the reference voltage and the output of the amplification means. The flow rate that is the time from the start point to the end point when the first negative zero-cross point where the sign of the output of the amplification means changes from positive to negative after the start point is the end point. Measuring device.

The reference setting means is a midpoint between the inflection points of the maximum interval among a plurality of inflection points where the time difference measured by the time difference measuring means changes greatly when the reference voltage is changed from the minimum of the settable range to the maximum. The flow rate measuring device according to claim 1, wherein a reference voltage is set at an arbitrary point.

The reference setting means determines the time difference during flow measurement from the range of the predetermined time difference defined by the maximum and minimum values of the time difference measured by the time difference measuring means when the reference voltage is changed from the minimum to the maximum of the settable range. The flow rate measuring device according to claim 1 or 2, wherein the reference voltage is changed when the time difference measured by the time measuring means deviates.

The reference setting means determines the time difference during flow rate measurement from the predetermined time difference width defined by the maximum and minimum time differences measured by the time difference measuring means when the reference voltage is changed from the minimum to the maximum of the settable range. The flow rate measuring device according to claim 1 or 2, wherein the reference voltage is changed in accordance with the number of times that the time difference counted by the time measuring means deviates.

Request for setting a reference voltage for each direction of transmission / reception of ultrasonic signals when the difference for each direction of transmission / reception of ultrasonic signals of the time difference measured by the time difference measuring means for each direction of transmission / reception of ultrasonic signals is larger than a predetermined value. Item 5. The flow rate measuring device according to any one of Items 1 to 4 .