JP2004069525A

JP2004069525A - Flow rate measuring apparatus

Info

Publication number: JP2004069525A
Application number: JP2002229734A
Authority: JP
Inventors: Koichi Takemura; 竹村　晃一; Osamu Eguchi; 江口　修
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-08-07
Filing date: 2002-08-07
Publication date: 2004-03-04
Anticipated expiration: 2022-08-07
Also published as: JP4013697B2

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly and accurately set a reference voltage so that the arrival time of a reception signal in ultrasonic waves can be detected most stably. <P>SOLUTION: A reference setting means 14 changes a reference voltage to be applied to a reference comparison means 7 from the minimum to the maximum, and sets the supply voltage according to the distribution condition of the inflection point of an output width clocked by an output width clocking means 13 obtained at that time. As a result, even if a voltage change in the reception signal of ultrasonic waves occurs, the reference voltage can be rapidly and accurately set to a position where the arrival timing of the reception signal of the ultrasonic waves can be detected most stably. <P>COPYRIGHT: (C)2004,JPO

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１６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１に設置した第１超音波振動子２および第２超音波振動子３と、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４と、第１超音波振動子２及び第２超音波振動子３を駆動する送信手段５と、受信側の超音波振動子で受信し切り替え手段４を通過した信号を所定の振幅まで増幅する増幅手段６と、増幅手段６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７とを備えている。
【０００３】
さらに、図１７に示すように基準比較手段７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９へ出力信号Ｄを出力する判定手段８と、この判定手段８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８からの信号を制御手段１２へ出力する繰り返し手段９と、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１０と、計時手段１０の計時した時間に応じて流量を算出する流量算出手段１１と、流量算出手段１１から算出された流量出力、繰り返し手段９からの信号を受け送信手段５の動作を制御する制御手段１２とから構成されている。
【０００４】
この装置は制御手段１２により送信手段５を動作させ超音波振動子２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３で受信され、増幅手段６で増幅後、基準比較手段７と判定手段８で信号処理され、繰り返し手段９を通り制御手段１２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１０により測定する。そして、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（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）。
【０００５】
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６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９に設定された回数の計測を繰り返し中に、図１８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１８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１８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）。
【０００６】
また、増幅手段６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７の基準電圧は判定手段８により検知するゼロクロス点の位置を決めるもので図１７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８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何らかの原因で受信信号の２波のピーク電圧の上昇、３波のピーク電圧の減少の双方に対してマージンをとれ、安定に判定手段８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。
【０００７】
【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、基準比較手段において所定の振幅レベルに増幅された受信信号と比較する基準電圧の電圧設定方法として、固定抵抗器と半固定抵抗器を用い抵抗分圧で設定することが多く用いられてきた。この方法では所定の電圧を発生するように基準電圧を監視しながら半固定抵抗器を手動で調節を行うので基準電圧設定に時間が掛かり、また、調整ミスの発生の可能性も有していた。
【０００８】
さらに機械振動、熱衝撃等を受けることによって調整位置が変化することもあった。また、温度変化や超音波振動子の経年変化等でその感度が変化した場合には基準電圧が不適当な電圧となっていても設定の変更が困難であ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、基準電圧の設定を迅速かつ、精度良く行い、常に最適な基準電圧に保つ流量計測装置を提供することを目的とする。
【０００９】
【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基準設定手段の基準電圧を最小から最大に変化させ、複数存在する出力幅計時手段の計時する出力幅の変曲点の分布状況に応じて、基準電圧を基準設定手段が設定するようにしたものである。
【００１０】
これによって、超音波の受信信号の電圧変動が発生しても、最も安定に超音波の受信信号の到達時期を検知出来る基準電圧を、出力幅計時手段の計時した値から判断できるので、基準電圧を人手を介することなく、迅速、かつ、精度良く、設定することが可能となる。
【００１１】
【発明の実施の形態】
請求項２に記載の発明は、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、前記基準比較手段の出力期間を計時する出力幅計時手段と、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、前記基準設定手段は、基準電圧を最小から最大に変化させたときの前記出力幅計時手段の計時する時間の変曲点の分布状況に応じて、基準電圧を設定する構成としているので、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することが出来る。
【００１２】
請求項３に記載の発明は、基準設定手段を、基準電圧を最小から最大に変化させたときの前記出力幅計時手段の計時する時間の変曲点の内、最大間隔の変曲点間の任意の点に基準電圧を設定する構成としているので、基準電圧の設定位置を最も細かく制御できる区間に定めることができる。
【００１３】
請求項４に記載の発明は、基準設定手段を、基準電圧を最小から最大に変化させたときの前記出力幅計時手段の計時する時間の変曲点の内、最大間隔の変曲点間の中点に基準電圧を設定する構成としているので、受信波形の変動に対して、最も余裕度の高い設定が可能となる。
【００１４】
請求項５に記載の発明は、基準設定手段を、基準電圧設定時の出力幅計時手段の計時値近傍に適正範囲を定めると共に、流量計測中に出力幅計時手段の計時した値が前記適正範囲から外れた場合に基準電圧を変更する構成としているので、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ができる。
【００１５】
請求項６に記載の発明は、第１および第２振動子間の相互の超音波送受信を複数回繰り返す繰り返し手段を備え、前記繰り返し手段による計測中に出力幅計時手段の計時した値が適正範囲を外れた回数に応じて基準電圧を変更する構成としているので、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ができる。
【００１６】
請求項７に記載の発明は、第１および第２振動子間の相互の超音波送受信を複数回繰り返す繰り返し手段を備え、前記繰り返し手段による計測中に出力幅計時手段の計時した値が適正範囲の上限および下限の両方を外れた場合には、基準電圧を再設定する構成としているので、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が出来る。
【００１７】
請求項８に記載の発明は、基準設定手段は、流量計測が終了する毎または流量計測を開始毎に基準電圧と出力幅計時手段の計時した値より変曲点を検出すると共に、検出した変曲点間の任意の点に基準電圧を設定する構成としているので、流量計測時に短時間で変曲点を検出し、できるので、常に最適な基準電圧に保つことが出来る。
【００１８】
請求項９に記載の発明は、基準設定手段により基準電圧を設定した時の出力幅計時手段の出力幅を記憶する出力幅記憶手段を備え、前記出力幅計時手段の計時する値と前記記憶手段の記憶した値との差に応じて基準電圧を設定する構成としているので、設定が迅速で常に最適な基準電圧に保つことが出来る。
【００１９】
請求項１０に記載の発明は、第１および第２の振動子の送受信を切り換える切替手段を備え、送受信の方向別に出力幅計時手段が計時した値の差が所定の値よりも大きい場合に方向別に基準電圧を設定する構成としているので、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の受信信号のバランス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最適に保つことが出来る。
【００２０】
請求項１１に記載の発明は、基準電圧を最小から最大に変化させたときの前記出力幅計時手段の計時する値が大きく変化し、かつ、計時手段の計時する値の変化量が超音波波形の１周期分である場合に変曲点と判断する構成としているので、変曲点の判定をより確実に行うことが可能となり、基準電圧の設定精度の向上を図ることができる。
【００２１】
請求項１２に記載の発明は、請求項１〜１０のいずれか１項記載の流量計測装置の手段の全てもしくは一部としてコンピュータを機能させるためのプログラムである。そして、プログラムであるのでマイコンなどを用いて本発明の流量計側装置の一部あるいは全てを容易に実現することができ超音波振動子の変更または経年変化等の特性の変化や動作を実現するための設定条件や定数の変更が柔軟に対応に出来る。また記録媒体に記録したり通信回線を用いてプログラムを配信したりすることでプログラムの配布が簡単にできる。
【００２２】
【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。
【００２３】
（実施例１）
図１は本発明の請求項１から６に係る第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及び図５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、及び図４は同装置の動作を説明する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。
【００２４】
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。
【００２５】
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は前記基準比較手段７の出力時間を計時する出力幅計時手段、１４は前記基準比較手段７の基準電圧を設定する基準設定手段である。
【００２６】
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、ゲイン調整は従来例で説明したのと同様の方法であるため説明は省略する。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３のステップ１）、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２）。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３）。
【００２７】
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（ステップ４）、その大小関係が反転した時点（タイミングｃ）で出力幅計時手段１３と判定手段８に出力信号Ｃを出力する。出力幅計時手段１３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５）、再度、増幅手段６の出力と基準電圧との大小関係が反転した時点（タイミングｅ）迄の基準比較手段７の出力時間を計時する（ステップ６、７）。
【００２８】
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８）、出力信号Ｄを繰り返し手段９に出力する。出力幅計時手段１３は計時した出力幅を基準設定手段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９）。
【００２９】
制御手段１２は１回に設定された繰り返し回数が終了したことを繰り返し手段９より入力すると再度、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し、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。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（ステップ１０）、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出力幅計時手段１３の計時する出力幅が大きく変化する（例えば前回の出力幅と比較して２００ｎｓ以上変化する）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（ステップ１１）。この設定動作を図５を用いて説明する。図５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出力幅計時手段１３の計時した値を示した図である。出力幅計時手段１３の計時した値は図２に示すように基準比較手段１３の出力信号Ｃの時間幅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５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出力幅が最小（ｐ１、ｐ２、ｐ３．．．に対応してそれぞれＴｐ１、Ｔｐ２、Ｔｐ３．．．とする。）になり、その値は限りなくゼロに近くなる。
【００３０】
そこから基準電圧を増加させ、ピーク電圧を超えると出力幅計時手段１３の計時した出力幅は急に大きくなり図５に示すように出力幅の変曲点（出力幅の最小である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。）これは出力幅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。
【００３１】
図５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出力幅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の中点（図５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、受信信号の各波のピーク電圧差の一番大きい部分の中点の電圧となる。したがって、これは、電圧の設定分解能の最も高い区間（電圧差が最大の区間）であって、かつ、受信信号の電圧変動に最も強い点（電圧変動に対する余裕度が最も大きい点）に設定できるということを意味している。
【００３２】
したがって、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。なお、本実施例では、最大間隔の中点に基準電圧を設定する構成としているが、これは、中点に限定されるものではない。使用条件（温度や計測対象とする流体）に応じて適宜、最適な位置に設定する構成で良い。同様に、基準電圧の設定位置は、最大間隔の変曲点間に限定されるものではなく、例えば、時間幅の最大値が得られる変曲点の近傍に設けるなど、受信波形の特徴に応じて、最も適切な位置に設定する構成で良い。
【００３３】
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４を用いて説明する。流量計測を開始すると制御手段１２は、計時手段１０で伝搬時間の計時を開始する（図４のステップ１２）と共に、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（ステップ１３）、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１４）、その大小関係が反転した時点から出力幅計時手段１３で計時を開始し（ステップ１５）、再び、これら信号の大小関係が逆転するまで計時を続ける（ステップ１６、１７）。
【００３４】
一方、基準設定手段１４には、初期設定動作時に基準電圧（Ｖｒｅ）を印加した際の出力幅計時手段１３の出力値（６００ｎｓ）を中央値として、その近傍の値（例えば、５００〜７００ｎｓ）が出力幅の適正範囲として繰り返し計測の前に予め設定されている。そして、ゼロクロス点検知後、時間幅計時手段１３で計時した値が、適正範囲の下限値よりも短い値（５００ｎｓ未満）かどうかを判定し（ステップ１９）、短ければ基準電圧を１制御単位（２ｍＶ）分減少させる（ステップ２０）。次に、時間幅計時手段１３の計時した値が適正範囲の上限値を超えているかどうかを判定し（ステップ２１）、超えていれば、基準電圧を１制御単位（２ｍＶ）分増加させる（ステップ２２）。以上の判定の後、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。
【００３５】
この一連の動作を予め設定されたｎ回数繰り返しを行ない（ステップ２３）、所定の繰り返し終了後には、計時手段１０を停止して、伝搬時間の計測を終了する。そして、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、これらの出力幅より流量算出手段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。
【００３６】
また、図６を用いて基準設定手段１４の他の動作を説明する。図６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。図６に於いてゼロクロス点を検知するまでの動作、すなわちステップ２５〜３１は、図４のステップ１２〜１８と同様であるので説明は省略する。ゼロクロス点検知後、時間幅計時手段１３で計時した値が、適正範囲の下限値よりも短い値（３００ｎｓ未満）かどうかを判定し（ステップ３２）、短ければ下限値を下回った回数をカウントする（ステップ３３）。次に、時間幅計時手段１３の計時した値が適正範囲の上限値（４００ｎｓ以上）を超えているかどうかを判定し（ステップ３４）、超えていれば上限値を上回った回数をカウントする（ステップ３５）。
【００３７】
以上の動作を所定の繰り返し回数が終わるまで繰り返し（ステップ３６）、繰り返し終了後、計時手段１０による伝搬時間の計測を停止する（ステップ３７）。その後、基準設定手段１４は、繰り返し回数分の出力幅計時手段１３が計時した出力幅の内、適正範囲の上限下限両方の範囲外の出力幅が存在したかどうかを判定して（ステップ３８）、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した（ステップ３９）後、再度、繰り返し計測を始めからやり直す。存在していなかった場合は適正範囲の下限（３００ｎｓ）より短い出力幅だけが存在したかどうかを判定し（ステップ４０）、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４１）。所定の回数以上であれば基準電圧を２制御単位（４ｍＶ）分減少させる（ステップ４２）。所定の回数未満であれば基準電圧を１制御単位（２ｍＶ）分減少させる（ステップ４３）。そして同様に、適正範囲の下限（３００ｎｓ）より短い出力幅ではなく適正範囲の上限（４００ｎｓ）より長い出力幅だけが存在したかを判定し（ステップ４４）、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４５）。所定の回数以上であれば基準電圧を２制御単位（４ｍＶ）分増加させる（ステップ４６）。
【００３８】
所定の回数未満であれば基準電圧を１制御単位（２ｍＶ）分減少させる（ステップ４７）。そして範囲の下限との比較（ステップ４０）、上限との比較（ステップ４４）の結果、全ての出力幅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出力幅計時手段１３の計時する出力幅が基準電圧を設定した際の出力幅を基に決定される所定の出力幅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。
【００３９】
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、そのときの出力幅計時手段１３の計時する出力幅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、流量計測時の出力幅計時手段１３の計時する出力幅が基準電圧を設定した際の出力幅を基に決定される所定の出力幅の幅から逸脱した場合に基準電圧の再設定が行われる。
【００４０】
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が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。
【００４１】
また、本実施例の流量計測装置の動作を実行させるプログラムを格納した記録媒体とすることにより、制御手段１２や基準設定手段１４の所定比率や繰り返し手段９の繰り返し回数等の設定値の変更や超音波振動子の変更または経年変化等にも柔軟に対応できるものである。
【００４２】
（実施例２）
図７は本発明の請求項７に係る第２の実施例のフローチャートである。第２の実施例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。
【００４３】
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１と異なる基準設定手段１４の基準電圧設定動作後の動作、作用を説明する。繰り返し手段９に所定の繰り返し回数を設定することにより、流量計測が開始される。計時手段１０により伝搬時間の計時を開始した後（図７のステップ４８）、ゼロクロス点を検知する（ステップ５１）までは実施例１とは異なり、時間幅の計時は行なわない。所定の繰り返しが終了した（ステップ５２）後に、伝搬時間の計時を停止して（ステップ５３）、基準電圧の設定動作を行う。制御手段１２は繰り返し手段９の設定回数を１回に設定し、基準設定手段１４は基準電圧を増加させる（ステップ５４）。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（ステップ５５）、実施例１と同様に基準比較手段７において増幅手段６の出力と基準電圧とを比較し、その大小関係が反転した時点（ステップ５６）で出力幅計時手段１３が計時を開始して（ステップ５７）、再び、増幅手段６の出力と基準電圧の大小関係が反転した時点（ステップ５８）で出力幅計時手段１３が計時を停止する（ステップ５９）。
【００４４】
その後、判定手段８により超音波の到達ポイントを判定すると（ステップ６０）、送受信完了と判断する。制御手段１２は基準設定手段１４で出力幅計時手段１３が計時した出力幅の変曲点を検知する（ステップ６１）まで基準電圧を増加させながらステップ５４〜６１の一連の動作を繰り返す。変曲点が検知されると、基準設定手段１４は、基準電圧を初期値、すなわち伝搬時間計測（ステップ４８〜ステップ５３）で用いた値に設定後（ステップ６２）、ステップ５４〜６１と同様の処理を今度は基準電圧を下げながら実行する（ステップ６３〜７０）。以上の処理によって検出したふたつの変曲点の電圧を元に、基準設定手段１４は２変曲点間の中点の電圧に基準電圧を設定する（ステップ７１）。
【００４５】
以上のように本実施例においては流量計測終了後に基準電圧を増加もしくは減少させ、出力幅計時手段１３の計時した出力幅の変曲点間の中点の電圧に設定するので、基準電圧が初期設定動作に於いて設定された受信波との相対位置（受信波の２−３波または３−４波間等のどのピーク波の位置の間で設定されたか）で、出力幅の変曲点の中点の電圧に設定されるので設定に要する時間も短く、常に最適な基準電圧に保つことが出来る。なお、本実施例では、基準電圧の設定を流量計測後に行う構成としているが、流量計測の開始に先立って行う構成であっても良い。
【００４６】
また、本実施例の流量計測装置の動作を実行させるプログラムを格納した記録媒体とすることにより、制御手段１２や出力幅計時手段の所定時間や繰り返し手段９の繰り返し回数等の設定値の変更や超音波振動子の変更または経年変化等にも柔軟に対応できるものである。
【００４７】
（実施例３）
図８は本発明の請求項８に係る第３の実施例の流量計測装置のブロック図、図９は同装置のフローチャートである。
【００４８】
図８において１５は基準設定手段１４により基準電圧を設定した時の出力幅計時手段１３の出力幅を記憶する出力幅記憶手段である。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。
【００４９】
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。実施例１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出力幅計時手段１３の計時する出力幅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。そしてこの設定した基準電圧での出力幅計時手段１３の計時した出力幅を出力幅記憶手段１５に記憶する。
【００５０】
以上の初期設定動作終了後に、図９のフローチャートで示す計測処理が実行される。制御手段１２は実施例１の図４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う（ステップ７２〜８０）。そして流量計測後、出力幅計時手段１３が計時した出力幅の平均値を算出する（ステップ８１）。基準設定手段１４は算出した出力幅の平均値と出力幅記憶手段１５に記憶されている初期設定時に基準電圧を設定した際の出力幅とを比較し（ステップ８２、８４）、記憶していた値が平均値より所定値以上大きければ、基準電圧を減少し（ステップ８３）、平均値が記憶していた値より所定値以上大きければ、基準電圧を増加する（ステップ８４）。
【００５１】
以上のように本実施例においては流量計測後、基準設定手段１４により出力幅記憶手段１５に記憶されている初期設定時に基準電圧を設定した際の出力幅と、流量計測中の出力幅計時手段１３の出力幅の平均値とが比較され、その大小関係により基準電圧が調整されるものであり、これにより流量計測後、改めて出力幅を計時するための動作を必要とせずに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。
【００５２】
また、本実施例の流量計測装置の動作を実行させるプログラムを格納した記録媒体とすることにより、制御手段１２の所定時間や繰り返し手段９の繰り返し回数等の設定値の変更や超音波振動子の変更または経年変化等にも柔軟に対応できるものである。
【００５３】
（実施例４）
図１０は本発明の請求項９に係る第４の実施例の流量計測装置のブロック図、図１１は同装置のフローチャートである。
【００５４】
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１と異なるところであり、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。
【００５５】
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３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１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出力幅計時手段１３の計時する出力幅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、正流方向（流れの上流側から下流側へ向けての超音波伝搬）の流量計測を行うため、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（ステップ８６）を行う。なお、ステップ８６の動作は実施例３の図９におけるステップ７２からステップ８０までの一連の動作に相当する。
【００５６】
そして流量計測後、出力幅計時手段１３が計時した出力幅の平均値を算出する（ステップ８７）。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、逆流方向の流量計測を行い（ステップ８８）、その後、出力幅計時手段１３が計時した出力幅の平均値を算出する（ステップ８９）。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出力幅を比較し（ステップ９０）、所定の差より大きい場合（例えば片方の出力幅が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９１、９２）、以後方向に応じて別々の基準電圧を用いる。
【００５７】
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、出力幅計時手段が計時する出力幅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。
【００５８】
また、本実施例の流量計測装置の動作を実行させるプログラムを格納した記録媒体とすることにより、基準設定手段１４の所定の差や繰り返し手段９の繰り返し回数等の設定値の変更や超音波振動子の変更または経年変化等にもに柔軟に対応できるものである。
【００５９】
（実施例５）
図１２は本発明の請求項１０に係る第５の実施例の流量計測装置のブロック図、であり、図１３は本発明の第５の実施例の流量計測装置の動作説明図である。図１４は同装置のフローチャートである。第５の実施例の構成要素は実施例１と同じであり、図１４において基準設定手段１４が出力幅計時手段１３の計時する出力幅の変曲点を認識する際に計時手段１０が計時している超音波信号の送受信の累積時間も併せて用いるようにしたのが実施例１と異なるところである。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１と異なる基準設定手段１４の動作、作用を説明する。
【００６０】
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（ステップ９３）と基準電圧設定を行う。尚、本実施例の説明では実施例１と同様に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、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９４）。その後、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、計時手段１０により、超音波の伝搬時間の計測を開始する（ステップ９５）と同時に、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９６）。この後、ゼロクロス点を検出するまでの動作（ステップ９７からステップ１０１）までは、実施例１の図３と同様であるので、説明を省略する。
【００６１】
ゼロクロス点検出後、計時手段１０は伝搬時間の計時を停止する（ステップ１０２）。そして、基準電圧が最大電圧に達するまで同様に、時間幅と伝搬時間の計測を行う（ステップ１０３）。基準電圧が最大電圧に達した後、後述する方法により変曲点の判断を行い（ステップ１０４）、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１０５）。つづいて、図１３および、図１５を用いて変曲点の判定方法について説明する。図１３に示すＴｐ１等のように大きく（例えば２００ｎｓ以上）変化しているかどうかを判断し（ステップ１０６）、変化していれば計時手段１０が計時している超音波信号の伝搬時間が前回と比較して超音波の駆動周波数（例えば５００ＫＨｚ）の１周期分（２μｓ）変化があるかを判断する（ステップ１０７）。以上ふたつの条件を満たした時には、変曲点と認識し（ステップ１０８）、それ以外は、変曲点とは見なさない。図１３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出力幅計時手段１３の計時した出力幅と計時手段１０が計時する超音波信号の伝搬時間の前回との差を示した図である。
【００６２】
図のように出力幅の変曲点Ｔｐ１、Ｔｐ２．．．では計時手段１０の計時する超音波信号の伝搬時間の前回との差は超音波信号の駆動周波数の１周期分（２μｓ）異なる。つまり超音波信号の受信信号の各波のピーク電圧位置を検知するのに出力幅計時手段１３の計時する出力幅に加え、計時手段１０の計時時間とを併せて判定することにより出力幅だけで判定するよりもノイズ等、計時誤差に対して誤判断することなく、確実に変曲点を判定出来る。
【００６３】
以上のように本実施例においては基準設定手段は出力幅計時手段の計時する出力幅の変曲点を認識する際に計時手段が計時している超音波信号の送受信の累積時間も併せて用い、それにより認識した最大間隔の変曲点間の中点に基準電圧を設定することにより変曲点の判定を確実に行うことが出来、最適な基準電圧とすることが出来る。このように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、基準電圧が最適な電圧に設定出来る流量計測装置とすることが出来る。
【００６４】
また、本実施例の流量計測装置の動作を実行させるプログラムを格納した記録媒体とすることにより、制御手段１２の所定時間や繰り返し手段９の繰り返し回数等の設定値の変更や超音波振動子の変更または経年変化等にも柔軟に対応できるものである。
【００６５】
【発明の効果】
以上説明したように本発明に係る流量計測装置によれば、超音波の受信信号の電圧変動が発生しても、一番安定して超音波信号の到達時期を検知出来る点に基準電圧を設定することが出来る。
【００６６】
また、流量計測時の受信信号の変化に応じて、基準電圧の自動的に補正し、最適な電圧に保つことが出来る。
【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】同装置の基準電圧の設定動作を説明するフローチャート
【図４】同装置の動作を説明するフローチャート
【図５】同装置の流量計測の動作を説明する図
【図６】同装置の流量計測の他の動作を説明するフローチャート
【図７】本発明の実施例２における流量計測装置の動作を説明するフローチャート
【図８】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９】同装置のフローチャート
【図１０】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１１】同装置のフローチャート
【図１２】本発明の実施例５における流量計測装置のブロック図
【図１３】同装置の動作説明図
【図１４】同装置の動作を説明するフローチャート
【図１５】同装置の変曲点の判定方法を示すフローチャート
【図１６】従来の流量計測装置のブロック図
【図１７】同装置の動作説明図
【図１８】同装置の別の動作説明図
【符号の説明】
１　流路
２　第１超音波振動子
３　第２超音波振動子
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　出力幅計時手段
１４　基準設定手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flow rate measuring device that measures a flow rate of a gas or the like using ultrasonic waves.
[0002]
[Prior art]
A conventional flow measurement device of this type is generally as shown in FIG. This device switches between a first ultrasonic transducer 2 and a second ultrasonic transducer 3 installed in a flow path 1 through which a fluid flows, and a transmission / reception of the first ultrasonic transducer 2 and the second ultrasonic transducer 3. 4, a transmitting means 5 for driving the first ultrasonic transducer 2 and the second ultrasonic transducer 3, and a signal received by the ultrasonic transducer on the receiving side and passed through the switching means 4 is amplified to a predetermined amplitude. Amplifying means 6 and a reference comparing means 7 for comparing the voltage of the received signal amplified by the amplifying means 6 with a reference voltage are provided.
[0003]
Further, as shown in FIG. 17, the judgment means 8 outputs the output signal D to the repetition means 9 at the first zero-cross point a of the amplified signal after the magnitude relation is inverted by comparison with the reference voltage by the reference comparison means 7; The repetition means 9 counts the signal from the determination means 8 and counts the number of times set in advance, and outputs the signal from the determination means 8 to the control means 12. The transmission means 5 receives the signal from the repetition means 9 and the flow rate output calculated from the flow rate calculation means 11, the flow rate calculation means 11 for calculating the flow rate according to the time measured by the time measurement means 10, And control means 12 for controlling the operation.
[0004]
In this device, the transmitting means 5 is operated by the control means 12, and the ultrasonic signal transmitted by the ultrasonic transducer 2 propagates in the flow and is received by the second ultrasonic transducer 3, and is amplified by the amplifying means 6. The signal is processed by the reference comparing means 7 and the determining means 8, and is input to the control means 12 through the repeating means 9. This operation is repeated n times set in advance, and the time during this period is measured by the timer 10. Then, the first ultrasonic transducer 2 and the second ultrasonic transducer 3 are switched by the switching means 4 to perform the same operation, and from the upstream to the downstream of the fluid to be measured (this direction is defined as a positive flow) and the downstream. From the upstream (this direction is assumed to be a reverse flow), the flow time 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, and The measurement time for n times is t1, the measurement time for n times from the downstream to the 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).
[0005]
Q = S · v = S · L / 2 · cos φ ((n / t1) − (n / t2)) (Equation 1)
(Actually, the flow rate is calculated by multiplying Equation 1 by a coefficient corresponding to the flow rate.)
The gain of the amplification means 6 is adjusted so that the signal received by the ultrasonic transducer on the receiving side has a constant amplitude, and is adjusted 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 that the peak voltage 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. 18 during the measurement of the number of times set in the repeating means 9 is repeated. As shown by the reception signal c indicated by the dotted line in FIG. 18, the number of times exceeding the upper limit of the predetermined voltage range is counted, and the gain at the next flow rate measurement is adjusted based on the magnitude relationship (for example, the number of times the number falls below the lower limit is reduced). If it is larger, the gain is increased so as to fall within the upper and lower limits of the voltage range as shown by the reception signal a shown by the solid line in FIG. 18).
[0006]
Further, the reference voltage of the reference comparing means 7 for comparing with the voltage of the received signal amplified by the amplifying means 6 determines the position of the zero crossing point detected by the judging means 8. Is set to the midpoint voltage of the peak voltage of two waves and three waves of the received signal so that the determination means 8 detects the zero cross point a. By doing so, a margin is provided for both the rise of the peak voltage of the two waves of the received signal and the decrease of the peak voltage of the three waves for some reason, and the zero-cross point a of the third wave can be stably detected by the determination means 8. Things.
[0007]
[Problems to be solved by the invention]
However, the above-mentioned conventional flow rate measuring device sets the reference voltage to be compared with the received signal amplified to a predetermined amplitude level by the reference comparing means by using a fixed resistor and a semi-fixed resistor and setting the voltage by resistance division. Has been used a lot. In this method, since the semi-fixed resistor is manually adjusted while monitoring the reference voltage so as to generate a predetermined voltage, it takes time to set the reference voltage, and there is a possibility that an adjustment error may occur. .
[0008]
Further, the adjustment position may change due to mechanical vibration, thermal shock, or the like. Another problem is that when the sensitivity changes due to a temperature change or an aging of the ultrasonic transducer, it is difficult to change the setting even if the reference voltage is an inappropriate voltage. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a flow rate measuring device that quickly and accurately sets a reference voltage and always maintains an optimum reference voltage.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned conventional problems, the flow rate measuring device of the present invention changes the reference voltage of the reference setting means from the minimum to the maximum, and the distribution state of the inflection point of the output width measured by a plurality of output width timing means. , The reference voltage is set by the reference setting means.
[0010]
Accordingly, even if the voltage fluctuation of the ultrasonic reception signal occurs, the reference voltage that can detect the arrival time of the ultrasonic reception signal most stably can be determined from the value measured by the output width timer. Can be set quickly and accurately without manual intervention.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a second aspect of the present invention, there are provided a first vibrator and a second vibrator provided in a fluid conduit for transmitting and receiving an ultrasonic signal, transmitting means for driving the vibrator, and amplifying a received signal of the vibrator. Amplifying means, a time measuring means for measuring the time of transmission and reception of the ultrasonic signal, a flow rate calculating means for calculating a flow rate based on the time measured by the time measuring means, the first transducer and the second transducer Reference comparison means for comparing the voltage of the reception signal of the transducer on the reception side with a reference voltage, and determination means for determining the arrival time of the ultrasonic signal from the output of the reference comparison means and the amplification means, Output width timing means for measuring the output period of the reference comparison means, and reference setting means for setting a reference voltage of the reference comparison means, wherein the reference setting means changes the reference voltage from a minimum to a maximum. Timing of output width timing means The reference voltage is set in accordance with the distribution of the inflection points at different times, so that the reference voltage can be set quickly and accurately, and the reference voltage that is the most stable against fluctuations in the ultrasonic reception signal Can be set to
[0012]
According to a third aspect of the present invention, the reference setting means is provided between the inflection points of the maximum interval among the inflection points of the time measured by the output width timer when the reference voltage is changed from the minimum to the maximum. Since the configuration is such that the reference voltage is set at an arbitrary point, the setting position of the reference voltage can be set to a section where the finest control is possible.
[0013]
According to a fourth aspect of the present invention, the reference setting means is provided between the inflection points of the maximum interval among the inflection points of the time measured by the output width timer when the reference voltage is changed from the minimum to the maximum. Since the configuration is such that the reference voltage is set at the middle point, the setting with the highest margin is possible for the fluctuation of the received waveform.
[0014]
According to a fifth aspect of the present invention, the reference setting means sets an appropriate range in the vicinity of the time value of the output width timing means when the reference voltage is set, and the value measured by the output width timing means during the flow rate measurement is set in the appropriate range. Since the reference voltage is changed when the value deviates from the reference voltage, the reference voltage is automatically corrected, and the reference voltage can always be maintained at the optimum value.
[0015]
According to a sixth aspect of the present invention, there is provided a repetition means for repeating the mutual transmission and reception of ultrasonic waves between the first and second transducers a plurality of times, and the value measured by the output width timing means during the measurement by the repetition means is within an appropriate range. , The reference voltage is changed in accordance with the number of times the reference voltage is deviated, so that the reference voltage can be automatically corrected and always maintained at the optimum reference voltage.
[0016]
According to a seventh aspect of the present invention, there is provided a repetition means for repeating the mutual transmission and reception of the ultrasonic waves between the first and second transducers a plurality of times, and the value measured by the output width timing means during the measurement by the repetition means is within an appropriate range. When both the upper limit and lower limit are deviated, the reference voltage is reset, so it is detected that the magnitude relationship with the reference voltage has collapsed due to the fluctuation of the ultrasonic reception signal during the flow rate measurement. By resetting the reference voltage, the optimum reference voltage can be maintained.
[0017]
In the invention described in claim 8, the reference setting means detects an inflection point from the reference voltage and the value measured by the output width timer at each time the flow measurement is completed or each time the flow measurement is started, and the detected inflection point is detected. Since the reference voltage is set at an arbitrary point between the inflection points, the inflection point can be detected in a short time when measuring the flow rate, so that the optimum reference voltage can always be maintained.
[0018]
The invention according to claim 9, further comprising output width storage means for storing an output width of the output width timing means when the reference voltage is set by the reference setting means, wherein the value measured by the output width timing means and the storage means are provided. Since the configuration is such that the reference voltage is set in accordance with the difference from the stored value, the setting is quick and the optimum reference voltage can always be maintained.
[0019]
The invention according to claim 10 is provided with switching means for switching between transmission and reception of the first and second vibrators, and when the difference between the values measured by the output width timer for each direction of transmission and reception is larger than a predetermined value, the direction is determined. Since the reference voltage is set separately, when the balance of the reception signal in each direction of transmission / reception of the ultrasonic signal is lost due to the influence of the flow rate of the fluid flowing through the flow path, the reference comparison is performed for each transmission / reception direction of the ultrasonic signal. The reference voltage of the means can be kept optimal.
[0020]
The invention according to claim 11, wherein when the reference voltage is changed from the minimum to the maximum, the value measured by the output width timer is greatly changed, and the amount of change in the value measured by the timer is an ultrasonic waveform. In this case, the inflection point is determined when the period is equal to one cycle, so that the inflection point can be determined more reliably, and the setting accuracy of the reference voltage can be improved.
[0021]
A twelfth aspect of the present invention is a program for causing a computer to function as all or a part of the means of the flow rate measuring device according to any one of the first to tenth aspects. And since it is a program, a part or all of the flow meter-side device of the present invention can be easily realized using a microcomputer or the like, and a change or operation of a characteristic such as a change or aging of the ultrasonic vibrator is realized. Settings and constants can be changed flexibly. Further, the program can be easily distributed by recording it on a recording medium or distributing the program using a communication line.
[0022]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
(Example 1)
FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention. 2 and 5 are explanatory views of the operation of the flow rate measuring device of the first embodiment, and FIGS. 3 and 4 are flowcharts for explaining the operation of the flow measuring device. In FIG. 1, a first ultrasonic vibrator 2 for transmitting ultrasonic waves and a second ultrasonic vibrator 3 for receiving ultrasonic waves are arranged at an angle φ in the flow direction in the middle of the flow path 1.
[0024]
Reference numeral 5 denotes a transmitting unit to the first ultrasonic vibrator 2, 4 denotes a switching unit for switching between transmission and reception of the first ultrasonic vibrator 2 and the second ultrasonic vibrator 3, and 6 denotes an ultrasonic vibrator on the receiving side. Amplifying means for amplifying the received signal with a gain according to an instruction from the control means 12; reference numeral 7 is a reference comparing means for comparing the signal amplified by the amplifying means 6 with a reference voltage; Judging means for judging the arrival time of the ultrasonic wave from the signal amplified by the amplifying means 6, and repetition means 9 for counting the signal of the judging means 8 and repeatedly outputting a signal to the control means 12 a predetermined number of times. .
[0025]
Reference numeral 10 denotes a timer for counting the time counted by the repetition unit 9 for a preset number of times, and 11 calculates the flow rate in consideration of the size of the pipeline and the state of the flow according to the time counted by the timer 10. Flow rate calculating means. Reference numeral 12 denotes a control unit that receives signals from the flow rate calculation unit 11 and the repetition unit 9 and controls the operations of the transmission unit 5 and the amplification unit 6. Reference numeral 13 denotes output width timing means for measuring the output time of the reference comparison means 7, and reference numeral 14 denotes reference setting means for setting the reference voltage of the reference comparison means 7.
[0026]
The operation and operation of the flow rate measuring device configured as described above will be described below. After turning on the power, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. Note that the gain adjustment is performed in the same manner as that described in the conventional example, and thus the description is omitted. 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 reference setting means 14 sets the reference voltage to the lowest voltage in the setting range (Step 1). Step 2). After setting to the lowest reference voltage, the control means 12 sets the number of repetitions of the repetition means 9 to one, activates the transmission means 5, and transmits an ultrasonic signal from the first ultrasonic transducer 2 (step 3). .
[0027]
The ultrasonic signal transmitted from the first ultrasonic transducer 2 propagates in the flow of the flow path 1, is received by the second ultrasonic transducer 3, is amplified by the amplification means 6, and is It is output to the judgment means 8. FIG. 2 shows the state of the received signal after amplification. That is, as shown in FIG. 2, the reference comparing means 7 compares the output of the amplifying means 6 (received signal A) with the reference voltage (step 4), and when the magnitude relation is inverted (timing c), the output width timing means 13 and an output signal C to the judgment means 8. The output width timing means 13 starts timing when the output signal C from the reference comparing means 7 is input (step 5), and again until the magnitude relationship between the output of the amplifying means 6 and the reference voltage is inverted (timing e). The output time of the reference comparing means 7 is measured (steps 6 and 7).
[0028]
The determining means 8 determines the first negative zero-cross point a at which the sign of the output of the amplifying means 6 changes from positive to negative after the timing c as the arrival point of the ultrasonic wave (step 8), and outputs the output signal D to the repeating means 9. I do. The output width timer 13 outputs the measured output width to the reference setting unit 14. The reference setting means 14 increases the reference voltage by one control unit (for example, 2 mV) of the variable range of the reference voltage (step 9).
[0029]
When the control means 12 inputs the end of the set number of repetitions from the repetition means 9, the control means 12 operates the transmission means 5 again to transmit an ultrasonic signal from the first ultrasonic vibrator 2, and the operation up to this point. Are repeated until the reference setting means 14 sets the maximum voltage in the setting range of the reference voltage. When the reference setting means 14 completes the setting up to the maximum voltage of the reference voltage (step 10), the reference setting means 14 greatly changes the output width measured by the output width timer 13 when the reference voltage is changed from the minimum to the maximum. The reference voltage is set at the midpoint between the inflection points at the maximum interval among a plurality of inflection points (for example, which change by 200 ns or more compared to the previous output width) (step 11). This setting operation will be described with reference to FIG. FIG. 5 is a diagram showing the value measured by the output width timing means 13 when the reference setting means 14 changes the reference voltage from the minimum to the maximum. Since the value measured by the output width timing means 13 is the time width of the output signal C of the reference comparing means 13 as shown in FIG. 2, the peak of each wave (one wave, two waves, three waves,...) Of the received signal is obtained. When there is a reference voltage near the voltage (in FIG. 5, p1, p2, p3,...), The output width is minimum (Tp1, Tp2, Tp3, respectively, corresponding to p1, p2, p3,. ...), and its value is infinitely close to zero.
[0030]
From there, the reference voltage is increased, and when the peak voltage is exceeded, the output width measured by the output width timer 13 suddenly increases, and the inflection points of the output width (Tp1, Tp2, which are the minimum output widths), as shown in FIG. , Tp3 ...). (For example, when the reference voltage is near the peak p2 of two waves (but does not exceed p2) and exceeds the peak voltage p2 of two waves, the inflection point is Tp2.) This is the inflection of the output width. This means that the reference voltage at the point 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 each wave of the received signal.
[0031]
In FIG. 5, the voltage difference between the inflection points Tp1 and Tp2 is the peak voltage difference between one and two waves of the received signal, and the voltage difference between the inflection points Tp2 and Tp3 is the peak voltage between two and three waves of the received signal. The difference is shown. As described above, there are a plurality of inflection points in the change of the output width when the reference voltage is changed from the minimum to the maximum, and the middle point of the reference voltage range having the widest width between the inflection points (FIG. In this case, if the reference voltage is set to the midpoint of the peak voltage of two or three waves (Vre), the voltage at the midpoint of the portion where the peak voltage difference between the waves of the received signal is the largest is obtained. Therefore, this can be set to a point where the voltage setting resolution is the highest (a section where the voltage difference is the largest) and which is strongest against the voltage fluctuation of the received signal (a point where the margin for the voltage fluctuation is the largest). It means that.
[0032]
Therefore, the determination means 8 can detect the arrival time of the ultrasonic reception signal most stably with respect to the voltage fluctuation of the reception signal. In this embodiment, the reference voltage is set at the midpoint of the maximum interval. However, the present invention is not limited to the midpoint. The configuration may be such that the position is appropriately set according to the use condition (temperature or fluid to be measured). Similarly, the setting position of the reference voltage is not limited to the inflection point at the maximum interval. For example, the reference voltage is set near the inflection point at which the maximum value of the time width is obtained. In this case, the most appropriate position may be set.
[0033]
When the reference setting means 14 sets the reference voltage as described above, the control means 12 sets the regular number of repetitions (for example, 256 times) in the repetition means 9 and starts the flow rate measurement. The operation of the reference setting means 14 after starting the flow measurement will be described with reference to FIG. When the flow rate measurement is started, the control means 12 starts the measurement of the propagation time by the time measurement means 10 (step 12 in FIG. 4), and operates the transmission means 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2. (Step 13) The ultrasonic signal amplified by the amplifying means 6 and received by the second ultrasonic transducer 3 is output to the reference comparing means 7 and the judging means 8, and the received signal, the reference voltage and (Step 14), and when the magnitude relationship is inverted, the output width timing means 13 starts timekeeping (Step 15), and continues counting until the magnitude relationship of these signals is reversed (Steps 16 and 17). ).
[0034]
On the other hand, the output value (600 ns) of the output width timer 13 when the reference voltage (Vre) is applied at the time of the initial setting operation is set to the reference setting means 14 as a central value, and a value in the vicinity thereof (for example, 500 to 700 ns). Is set in advance as an appropriate range of the output width before repeated measurement. After detecting the zero-cross point, it is determined whether or not the value measured by the time width timer 13 is shorter than the lower limit of the appropriate range (less than 500 ns) (step 19). 2mV) (step 20). Next, it is determined whether or not the value measured by the time width measuring means 13 exceeds the upper limit value of the appropriate range (step 21). If it exceeds, the reference voltage is increased by one control unit (2 mV) (step 21). 22). After the above determination, the control unit 12 operates the transmission unit 5 again to transmit an ultrasonic signal from the ultrasonic transducer 2.
[0035]
This series of operations is repeated a preset number of times n (step 23). After the predetermined repetition is completed, the timer 10 is stopped and the measurement of the propagation time is completed. The first ultrasonic vibrator 2 and the second ultrasonic vibrator 3 are switched by the switching means 4 and the same operation is performed to measure the respective propagation times of the fluid to be measured from upstream to downstream and from downstream to upstream. Then, from these output widths, the flow rate calculating means 11 determines the flow rate value in consideration of the size of the flow path and the state of the flow.
[0036]
Another operation of the reference setting unit 14 will be described with reference to FIG. FIG. 6 is a flowchart illustrating another operation of the reference setting unit 14. The operation up to the detection of the zero cross point in FIG. 6, that is, steps 25 to 31, is the same as steps 12 to 18 in FIG. After detecting the zero-cross point, it is determined whether or not the value measured by the time width timer 13 is shorter than the lower limit of the appropriate range (less than 300 ns) (step 32), and if shorter, the number of times below the lower limit is counted. (Step 33). Next, it is determined whether or not the value measured by the time width timer 13 exceeds the upper limit of the appropriate range (400 ns or more) (step 34), and if it exceeds, the number of times exceeding the upper limit is counted (step 34). 35).
[0037]
The above operation is repeated until the predetermined number of repetitions is completed (step 36). After the repetition is completed, the measurement of the propagation time by the timer 10 is stopped (step 37). Thereafter, the reference setting means 14 determines whether or not there is an output width out of both upper and lower limits of the appropriate range among the output widths counted by the output width timing means 13 for the number of repetitions (step 38). If it is present, the reference voltage setting operation performed in the initial setting operation is executed again (step 39), and then the measurement is repeated again from the beginning. If not, it is determined whether only an output width shorter than the lower limit of the appropriate range (300 ns) exists (step 40). If there is, the number of times is equal to or more than a predetermined number (for example, 10). Is determined (step 41). If the number is equal to or more than the predetermined number, the reference voltage is reduced by two control units (4 mV) (step 42). If it is less than the predetermined number, the reference voltage is reduced by one control unit (2 mV) (step 43). Similarly, it is determined whether or not only an output width shorter than the lower limit (300 ns) of the appropriate range but longer than the upper limit (400 ns) of the appropriate range exists (step 44). It is determined whether or not the number of times (for example, 10 times) has been exceeded (step 45). If the number is equal to or more than the predetermined number, the reference voltage is increased by two control units (4 mV) (step 46).
[0038]
If the number is less than the predetermined number, the reference voltage is reduced by one control unit (2 mV) (step 47). Then, as a result of comparison with the lower limit of the range (step 40) and comparison with the upper limit (step 44), if all output widths are within the range, the process ends without changing the reference voltage. In this manner, the reference voltage is reset in accordance with the number of times that the output width measured by the output width timing means 13 during the flow rate measurement deviates from the predetermined output width determined based on the output width when the reference voltage is set. The settings are made.
[0039]
As described above, in this embodiment, the reference voltage is changed from the minimum to the maximum at the time of the initial setting, and the maximum interval of the plurality of inflection points at which the output width measured by the output width timer 13 greatly changes is set. Since the reference voltage is set at the midpoint between the inflection points, the reference voltage is set most stably with respect to the voltage fluctuation of the received signal in the received wave of the ultrasonic wave by the reference voltage. A predetermined output that can be set to a voltage that can detect the timing, and that after the reference voltage is set, the output width measured by the output width timing means 13 when measuring the flow rate is determined based on the output width when the reference voltage is set. When the width deviates from the width, the reference voltage is reset.
[0040]
Thereby, the reference voltage can be set quickly without manual intervention, and after the setting, the flow rate measuring device can maintain the reference voltage at the optimum voltage when measuring the flow rate.
[0041]
Further, by using a recording medium storing a program for executing the operation of the flow rate measuring device of the present embodiment, it is possible to change a set value such as a predetermined ratio of the control means 12 or the reference setting means 14 or the number of repetitions of the repetition means 9. It is possible to flexibly cope with a change of ultrasonic transducer or aging.
[0042]
(Example 2)
FIG. 7 is a flowchart of the second embodiment according to claim 7 of the present invention. Since the components of the second embodiment are the same as those of the first embodiment, the description is omitted.
[0043]
The operation and operation of the flow rate measuring device configured as described above after the reference voltage setting operation of the reference setting means 14 different from the first embodiment will be described below. The flow rate measurement is started by setting a predetermined number of repetitions in the repetition means 9. After the time of the propagation time is started by the time measuring means 10 (step 48 in FIG. 7), until the zero-cross point is detected (step 51), unlike the first embodiment, the time width is not measured. After the predetermined repetition ends (step 52), the measurement of the propagation time is stopped (step 53), and the setting operation of the reference voltage is performed. The control means 12 sets the number of times of setting of the repetition means 9 to one, and the reference setting means 14 increases the reference voltage (step 54). The control means 12 operates the transmission means 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 55), and the reference comparison means 7 compares the output of the amplification means 6 with the reference voltage in the same manner as in the first embodiment. When the magnitude relationship is inverted (step 56), the output width timing means 13 starts counting (step 57), and again when the magnitude relationship between the output of the amplifying means 6 and the reference voltage is inverted (step 56). At 58), the output width timing means 13 stops timing (step 59).
[0044]
Then, when the arrival point of the ultrasonic wave is judged by the judging means 8 (step 60), it is judged that the transmission and reception are completed. The control means 12 repeats a series of operations of steps 54 to 61 while increasing the reference voltage until the reference setting means 14 detects an inflection point of the output width measured by the output width timing means 13 (step 61). When the inflection point is detected, the reference setting unit 14 sets the reference voltage to the initial value, that is, the value used in the propagation time measurement (steps 48 to 53) (step 62), and then performs the same as steps 54 to 61. Is executed while lowering the reference voltage (steps 63 to 70). Based on the voltages at the two inflection points detected by the above processing, the reference setting means 14 sets the reference voltage to the voltage at the midpoint between the two inflection points (step 71).
[0045]
As described above, in the present embodiment, the reference voltage is increased or decreased after the flow rate measurement is completed, and is set to the voltage at the midpoint between the inflection points of the output width measured by the output width timing means 13, so that the reference voltage is initially set. The inflection point of the output width is determined by the relative position with respect to the received wave set in the setting operation (which peak wave position is set, such as between 2-3 waves or 3-4 waves of the received wave). Since the voltage is set to the midpoint voltage, the time required for the setting is short, and the reference voltage can always be maintained at the optimum value. In this embodiment, the reference voltage is set after the flow rate measurement, but may be performed before the start of the flow rate measurement.
[0046]
Further, by using a recording medium storing a program for executing the operation of the flow rate measuring device of the present embodiment, it is possible to change a set value such as a predetermined time of the control means 12 or the output width timing means or the number of repetitions of the repetition means 9. It is possible to flexibly cope with a change of ultrasonic transducer or aging.
[0047]
(Example 3)
FIG. 8 is a block diagram of a flow rate measuring device according to a third embodiment of the present invention, and FIG. 9 is a flowchart of the device.
[0048]
In FIG. 8, reference numeral 15 denotes an output width storage means for storing the output width of the output width timer 13 when the reference voltage is set by the reference setting means 14. Other components are the same as those in the first embodiment, and a description thereof will be omitted.
[0049]
The operation and operation of the flow rate measuring device configured as described above will be described below. After turning on the power, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. Similarly to the first embodiment, in the reference voltage setting operation, among a plurality of inflection points at which the output width measured by the output width timer 13 when the reference setting unit 14 changes the reference voltage from the minimum to the maximum greatly changes, The reference voltage is set at the midpoint between the inflection points at the maximum interval. Then, the output width measured by the output width timer 13 at the set reference voltage is stored in the output width storage 15.
[0050]
After the end of the above initial setting operation, the measurement processing shown in the flowchart of FIG. 9 is executed. The control means 12 transmits and receives the ultrasonic waves the number of times set in the repetition means 9 as in FIG. 4 of the first embodiment (steps 72 to 80). Then, after measuring the flow rate, the average value of the output width measured by the output width timing means 13 is calculated (step 81). The reference setting means 14 compares the calculated average value of the output width with the output width when the reference voltage is set at the time of the initial setting stored in the output width storage means 15 (steps 82 and 84) and stores the result. If the value is greater than the average by a predetermined value, the reference voltage is decreased (step 83). If the average is greater than the stored value by a predetermined value, the reference voltage is increased (step 84).
[0051]
As described above, in the present embodiment, after the flow rate measurement, the output width when the reference voltage is set at the time of the initial setting stored in the output width storage means 15 by the reference setting means 14 and the output width timing means during the flow rate measurement. 13 is compared with the average value of the output width, and the reference voltage is adjusted according to the magnitude relationship. Thus, after measuring the flow rate, the reference voltage is optimized without the need for another operation for measuring the output width again. It can be a flow rate measuring device that keeps the voltage at an appropriate level.
[0052]
Further, by using a recording medium storing a program for executing the operation of the flow rate measuring device of the present embodiment, it is possible to change a set value such as a predetermined time of the control means 12 and the number of repetitions of the repetition means 9 and to set the ultrasonic vibrator. It can respond flexibly to changes or aging.
[0053]
(Example 4)
FIG. 10 is a block diagram of a flow rate measuring apparatus according to a fourth embodiment of the present invention, and FIG. 11 is a flowchart of the apparatus.
[0054]
10 is different from the first embodiment in that the reference setting unit 14 receives a signal from the control unit 12 in the direction of transmitting the ultrasonic wave from the first transducer and the second transducer to change the reference voltage to be set. Since the other components are the same as those in the first embodiment, description thereof will be omitted.
[0055]
The operation and operation of the reference setting means 14 different from the third embodiment will be described below for the flow rate measuring device configured as described above. After turning on the power, the control means 12 first performs gain adjustment and reference voltage setting as an initial setting operation. Similarly to the first embodiment, in the reference voltage setting operation, among a plurality of inflection points at which the output width measured by the output width timer 13 when the reference setting unit 14 changes the reference voltage from the minimum to the maximum greatly changes, The reference voltage is set at the midpoint between the inflection points at the maximum interval. Then, the control means 12 performs transmission and reception of ultrasonic waves for the number of times set in the repetition means 9 in order to measure the flow rate in the forward direction (propagation of ultrasonic waves from the upstream side to the downstream side of the flow). 86) is performed. The operation of step 86 corresponds to a series of operations from step 72 to step 80 in FIG. 9 of the third embodiment.
[0056]
After the flow rate measurement, the average value of the output width measured by the output width timing means 13 is calculated (step 87). Then, the control means 12 switches the first ultrasonic transducer 2 and the second ultrasonic transducer 3 by the switching means 4 to measure the flow rate in the reverse flow direction (step 88). An average value of the measured output width is calculated (step 89). The reference setting means 14 compares the average output widths of the first ultrasonic transducer 2 and the second ultrasonic transducer 3 for each transmission direction (step 90). If the average output widths are larger than a predetermined difference (for example, one output width is 600 ns) In the case where the other has a difference of 670 ns and 10% or more), a reference voltage setting operation is performed for each transmission direction (steps 91 and 92), and thereafter different reference voltages are used according to the directions.
[0057]
As described above, in the present embodiment, a difference in sensitivity of the received signal occurs in the direction of transmitting the ultrasonic signal from the upstream to the downstream of the fluid to be measured and the downstream to the upstream by 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, as a result, when the output width measured by the output width timer differs in the direction in which the ultrasonic signal is transmitted, the optimal reference voltage setting in each direction is determined. it can. In this way, even if a difference occurs in the voltage of the received signal in the transmission direction of the ultrasonic signal, the flow rate measuring device can maintain the reference voltage at the optimum voltage.
[0058]
Further, by using a recording medium storing a program for executing the operation of the flow rate measuring device of the present embodiment, it is possible to change the set value such as the predetermined difference of the reference setting means 14 and the number of repetitions of the repetition means 9 and to reduce the ultrasonic vibration. It can flexibly respond to changes in the child or aging.
[0059]
(Example 5)
FIG. 12 is a block diagram of a flow rate measuring device according to a fifth embodiment of the present invention, and FIG. 13 is an operation explanatory diagram of the flow rate measuring device according to the fifth embodiment of the present invention. FIG. 14 is a flowchart of the apparatus. The components of the fifth embodiment are the same as those of the first embodiment. In FIG. 14, when the reference setting means 14 recognizes the inflection point of the output width measured by the output width time counting means 13, the time counting means 10 measures the time. The difference from the first embodiment is that the accumulated transmission / reception time of the ultrasonic signal is also used. The operation and operation of the reference setting means 14 different from the first embodiment will be described below for the flow rate measuring device configured as described above.
[0060]
After turning on the power, the control means 12 performs gain adjustment (step 93) and reference voltage setting as an initial setting operation. In the description of the present embodiment, the description of the gain adjustment is omitted as in the first embodiment. First, after adjusting the gain so that the signal received by the ultrasonic transducer on the receiving side has a constant amplitude, the reference setting means 14 sets the reference voltage to the lowest voltage in the setting range (step 94). Thereafter, the control means 12 sets the number of repetitions of the repetition means 9 to one, starts the measurement of the propagation time of the ultrasonic wave by the timer means 10 (step 95), and at the same time, operates the transmission means 5 to perform the first operation. An ultrasonic signal is transmitted from the ultrasonic transducer 2 (step 96). Thereafter, the operation up to the detection of the zero-cross point (from step 97 to step 101) is the same as that of FIG. 3 of the first embodiment, and thus the description is omitted.
[0061]
After detecting the zero-crossing point, the timer 10 stops measuring the propagation time (step 102). Then, similarly, the time width and the propagation time are measured until the reference voltage reaches the maximum voltage (step 103). After the reference voltage reaches the maximum voltage, an inflection point is determined by a method described later (step 104), and the reference setting means 14 determines the maximum inflection point when the reference voltage is changed from the minimum to the maximum. A reference voltage is set at a middle point between the inflection points of the interval (step 105). Next, a method of determining an inflection point will be described with reference to FIGS. It is determined whether there is a large change (for example, 200 ns or more) such as Tp1 shown in FIG. 13 (step 106). In comparison, it is determined whether there is a change (2 μs) for one cycle of the ultrasonic drive frequency (for example, 500 KHz) (step 107). When the above two conditions are satisfied, it is recognized as an inflection point (step 108), and otherwise, it is not regarded as an inflection point. FIG. 13 shows the difference between the output width measured by the output width timer 13 and the propagation time of the ultrasonic signal measured by the timer 10 when the reference setting unit 14 changes the reference voltage from the minimum to the maximum. FIG.
[0062]
As shown in the figure, the inflection points Tp1, Tp2. . . In this case, the difference between the propagation time of the ultrasonic signal measured by the timer 10 and the previous time differs by one cycle (2 μs) of the driving frequency of the ultrasonic signal. That is, in order to detect the peak voltage position of each wave of the reception signal of the ultrasonic signal, in addition to the output width measured by the output width timer 13 and the time measured by the timer 10, it is determined only by the output width. The inflection point can be determined more reliably without erroneous determination of a timing error such as noise than determination.
[0063]
As described above, in the present embodiment, the reference setting means also uses the accumulated time of transmission and reception of the ultrasonic signal which is measured by the time counting means when recognizing the inflection point of the output width measured by the output width time counting means. By setting the reference voltage at the midpoint between the inflection points at the maximum interval recognized thereby, the inflection point can be reliably determined, and the optimum reference voltage can be obtained. As described above, the reference voltage can be set quickly without any manual operation, and the flow rate measuring device can set the reference voltage to an optimum voltage.
[0064]
Further, by using a recording medium storing a program for executing the operation of the flow rate measuring device of the present embodiment, it is possible to change a set value such as a predetermined time of the control means 12 and the number of repetitions of the repetition means 9 and to set the ultrasonic vibrator. It can respond flexibly to changes or aging.
[0065]
【The invention's effect】
As described above, according to the flow rate measuring device of the present invention, the reference voltage is set at a point where the arrival time of the ultrasonic signal can be detected most stably even if the voltage fluctuation of the ultrasonic reception signal occurs. You can do it.
[0066]
Further, the reference voltage can be automatically corrected in accordance with the change of the received signal at the time of the flow rate measurement, and the optimum voltage can be maintained.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow measurement 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 for explaining a reference voltage setting operation of the apparatus.
FIG. 4 is a flowchart illustrating the operation of the apparatus.
FIG. 5 is a view for explaining the flow measurement operation of the apparatus.
FIG. 6 is a flowchart for explaining another operation of the flow rate measurement of the apparatus.
FIG. 7 is a flowchart illustrating an operation of the flow rate measuring device according to the second embodiment of the present invention.
FIG. 8 is a block diagram of a flow rate measuring device according to a third embodiment of the present invention.
FIG. 9 is a flowchart of the apparatus.
FIG. 10 is a block diagram of a flow rate measuring device according to a fourth embodiment 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 a fifth embodiment of the present invention.
FIG. 13 is an explanatory diagram of the operation of the apparatus.
FIG. 14 is a flowchart illustrating the operation of the apparatus.
FIG. 15 is a flowchart showing a method of determining an inflection point of the apparatus.
FIG. 16 is a block diagram of a conventional flow measurement device.
FIG. 17 is an explanatory diagram of the operation of the apparatus.
FIG. 18 is another operation explanatory view of the apparatus.
[Explanation of symbols]
1 channel
2 First ultrasonic transducer
3 Second ultrasonic 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 Output width timing means
14 Standard setting means

Claims

At least one pair of transducers provided in the fluid conduit for transmitting and receiving ultrasonic signals, reference comparison means for comparing a voltage of a received signal of a reception-side transducer with a reference voltage, the reference comparison means and the amplification means Determining means for determining the arrival time of the ultrasonic signal from the output of the reference signal, output width timing means for timing the output period of the reference comparison means, and reference setting means for setting a reference voltage of the reference comparison means, The flow rate measuring device sets the reference voltage in accordance with a distribution state of an inflection point of a time measured by the output width timer when the reference voltage is changed from a minimum to a maximum.

A first vibrator and a second vibrator provided in a fluid conduit for transmitting and receiving an ultrasonic signal, transmitting means for driving the vibrator, amplifying means for amplifying a received signal of the vibrator, and the ultrasonic signal A timer for measuring the time of transmission / reception of the data, a flow rate calculator for calculating a flow rate based on the time measured by the timer, and reception of a transducer on the receiving side among the first transducer and the second transducer. Reference comparing means for comparing the voltage of the signal with a reference voltage; determining means for determining the arrival time of the ultrasonic signal from the outputs of the reference comparing means and the amplifying means; and measuring the output period of the reference comparing means. Output width timing means, and reference setting means for setting a reference voltage of the reference comparison means, wherein the reference setting means measures the time measured by the output width timing means when the reference voltage is changed from minimum to maximum. Inflection point distribution Flow rate measuring device which sets a reference voltage corresponding to the.

The reference setting means sets the reference voltage at an arbitrary point between the inflection points at the maximum interval among the inflection points of the time measured by the output width timing means when the reference voltage is changed from the minimum to the maximum. The flow measurement device according to claim 1.

The reference setting means sets the reference voltage at a midpoint between the inflection points at the maximum interval among the inflection points of the time measured by the output width timing means when the reference voltage is changed from the minimum to the maximum. Item 3. The flow measurement device according to item 1 or 2.

The reference setting means determines an appropriate range near the time value of the output width timing means at the time of setting the reference voltage, and changes the reference voltage when the value measured by the output width timing means deviates from the appropriate range during the flow rate measurement. The flow measurement device according to any one of claims 1 to 4, wherein:

A repetition unit that repeats mutual transmission and reception of ultrasonic waves between transducers a plurality of times, wherein the reference voltage is changed according to the number of times that a value measured by an output width timer is out of an appropriate range during measurement by the repetition unit. 6. The flow measurement device according to 5.

A repetition unit that repeats mutual ultrasonic transmission and reception between the transducers a plurality of times is provided.If the value measured by the output width timing unit deviates from both the upper limit and the lower limit of the appropriate range during measurement by the repetition unit, a reference is provided. The flow measuring device according to claim 5, wherein the voltage is reset.

The reference setting means searches for an inflection point from the reference voltage and the value measured by the output width timing means every time the flow rate measurement ends or the flow rate measurement starts, and at any point between the searched inflection points. The flow measurement device according to any one of claims 1 to 4, wherein the reference voltage is set.

A storage means for storing the time of the output width timing means when the reference voltage is set by the reference setting means, according to a difference between a value measured by the output width timing means at the time of flow rate measurement and a value stored in the storage means. The flow measurement device according to any one of claims 1 to 4, wherein the reference voltage is set by using a reference voltage.

5. A switching device for switching between transmission and reception of the vibrator, wherein a reference voltage is set for each direction when a difference between values measured by the output width timer for each direction of transmission and reception is larger than a predetermined value. 3. The flow measurement device according to 1.

When the reference voltage is changed from the minimum to the maximum, the value measured by the output width timer changes greatly, and the amount of change in the value measured by the timer measures one cycle of the ultrasonic waveform. The flow rate measuring device according to any one of claims 1 to 4, wherein it is determined that the point is an inflection point.

A program for causing a computer to function as all or a part of the flow rate measuring device means according to any one of claims 1 to 11.