JP4163887B2

JP4163887B2 - Flowmeter

Info

Publication number: JP4163887B2
Application number: JP2002093604A
Authority: JP
Inventors: 泰宏藤井; 忠幸南; 徹廣山; 徳行鍋島; 能章永田
Original assignee: Osaka Gas Co Ltd; Aichi Tokei Denki Co Ltd; Toho Gas Co Ltd
Current assignee: Osaka Gas Co Ltd; Aichi Tokei Denki Co Ltd; Toho Gas Co Ltd
Priority date: 2002-03-29
Filing date: 2002-03-29
Publication date: 2008-10-08
Anticipated expiration: 2022-03-29
Also published as: JP2003294509A

Description

【０００１】
【発明の属する技術分野】
本発明は、流量計に関するものである。
【０００２】
【従来の技術】
近年、ガスメータにおいてガスの使用量を計測するために超音波流量計を採用することが考えられている。超音波流量計は、図２に示すように、ガス流路上に設けた計測管１１の上流側と下流側とにそれぞれ超音波の送受波を行うための送受波器１２ａ，１２ｂを配置した瞬間流量計測部４を備える。流量の計測には、上流側の送受波器１２ａから下流側の送受波器１２ｂに向かって超音波を送波したときの超音波の伝播時間ｔ１と、下流側の送受波器１２ｂから上流側の送受波１２ａに向かって超音波を送波したときの超音波の伝播時間ｔ２とを計測し、両伝播時間ｔ１，ｔ２に基づいて流速を求める。流速が求まれば計測管１１の断面積と流速とを乗じた値が瞬間流量になる。
【０００３】
いま、送受波器１２ａ，１２ｂの間で送受される超音波の進行方向が計測管１１を通過するガスの流れる方向に一致しているものとする。送受波器１２ａ，１２ｂの間の距離をｄ、ガスの流速をＶ、音速をＣとすれば、伝播時間ｔ１，ｔ２はそれぞれ以下のように表すことができる。
ｔ１＝ｄ／（Ｃ＋Ｖ）
ｔ２＝ｄ／（Ｃ−Ｖ）
したがって、流速Ｖは以下のように表される。
Ｖ＝（ｄ／２）｛（１／ｔ１）−（１／ｔ２）｝
この計測技術では超音波の伝播時間ｔ１，ｔ２を求めるために、送信器１２ａ，１２ｂから超音波を間欠的に発生させる。ガスメータにおいては電池を電源としていることが多く超音波流量計を用いると電力を消費するから、超音波流量計を用いる場合には消費電力が増加しないように２〜３ｓｅｃの一定の計測周期で瞬間流量を計測する。
【０００４】
ところで、最近では都市ガスのような燃料ガスを用いてガスエンジンを駆動するガス使用機器がガスヒートポンプや発電機などの分野において普及してきている。この種のガスエンジンは吸気と排気とを繰り返しているから、燃料ガスの供給路の圧力に脈動（以下では、「圧力脈動」という）をもたらすことになる。また、一般にガスメータにおいて普及している膜式メータの動作によっても圧力脈動が生じることが知られている。このような圧力脈動があると流速Ｖにも脈動が生じる。一般に膜式メータでの圧力脈動の周波数は３〜６Ｈｚ程度であり、ガスエンジンによる圧力脈動の周波数は１０〜６０Ｈｚ程度になり、ガス使用機器の近傍では最大で２００Ｐａ（ピーク−ピークは４００Ｐａ）の振幅を有することが知られている。
【０００５】
ガスメータにおいてガスの使用量を計測するには瞬間流量を積算することになるから、上述のような圧力脈動が生じる環境下であっても多数個の瞬間流量を積算することによって脈動成分が相殺されれば、計測値に圧力脈動の影響が生じないと考えられる。つまり、多数個の瞬間流量の平均値は脈動成分を含まない値に収束すると考えられる。しかし、実際には計測周期が圧力脈動の脈動周期の整数倍にほぼ一致してしまう場合があり、このような場合に計測周期毎に得られる瞬時流量を積算しても脈動成分を相殺することができず、大きな計測誤差を生じることになる。
【０００６】
そこで、複数種類の計測周期を用意しておき、脈動周期の整数倍にほぼ一致するような計測周期が選択されているときには他の計測周期に切り換えることによって、計測誤差の発生を軽減する技術を先に提案した。実験結果によれば、計測周期を約３ｓｅｃとし、１／５１２ｓｅｃ単位で計測周期を変更可能であるものとし、以下の７種類のいずれかの計測周期を用意しておけば、計測周期が脈動周期の整数倍にほぼ一致するという事態を回避することができることがわかっている。すなわち、計測周期を（３＋ｎ／５１２）ｓｅｃと表すとき、ｎ＝３７，１９，４５，１０，−１１，−３０，５３から選択すればよい。また、計測周期を選択するにあたっては、まずすべての計測周期でそれぞれ一定回数ずつの計測を行い、各計測周期において得られる瞬間流量の最大値と最小値との間の計測回数が一定回数以下であるときに、当該計測周期を選択することが考えられている。
【０００７】
【発明が解決しようとする課題】
しかしながら、上述のように各計測周期で一定回数ずつ瞬間流量を計測した後に、どの計測周期を用いるかを判断すると計測周期の決定までに要する時間が長くなる。
【０００８】
本発明は上記事由に鑑みて為されたものであり、その目的は、圧力脈動が生じている環境下において脈動周期の整数倍ではない計測周期を比較的短時間で選択できる流量計を提供することにある。
【０００９】
【課題を解決するための手段】
請求項１の発明は、流体の流路に配設され通過する流体の瞬間流量を計測する瞬間流量計測部と、複数種類の計測周期を備え前記複数種類の計測周期から計測周期を択一的に選択し選択した計測周期で前記瞬間流量計測部に瞬間流量の計測を指示する計測タイミング生成部と、計測タイミング生成部に計測周期の変更を指示する同期判定部とを備え、前記同期判定部は、瞬間流量計測部で計測される瞬間流量の時系列から上側ピーク値と下側ピーク値とを求めるピーク検知手段と、前記上側ピーク値と前記下側ピーク値との間で中間値を設定する中間値設定手段と、瞬間流量の計測毎に計測した瞬間流量と中間値とを比較し連続した規定の複数回の計測を行う間において瞬間流量と中間値との大小関係が逆転しないときに計測周期を変更するように計測タイミング生成部に指示する計測周期変更手段とを備えることを特徴とする。
【００１０】
請求項２の発明は、請求項１の発明において、前記ピーク検知手段は、前回計測時の瞬間流量が中間値よりも小さい場合に、今回計測した瞬間流量が中間値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が下側ピーク値よりも小さければこの瞬間流量を下側ピーク値とする第１のピーク検知手段と、前回計測時の瞬間流量が中間値よりも大きい場合に、今回計測した瞬間流量が上側ピーク値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が中間値よりも小さければこの瞬間流量を下側ピーク値とする第２のピーク検知手段とを備えることを特徴とする。
【００１１】
請求項３の発明は、請求項１の発明において、前記ピーク検知手段は、設定された所定時間毎に計測された複数個の瞬間流量の最大値を上側ピーク値とするとともに最小値を下側ピーク値とすることを特徴とする。
【００１２】
請求項４の発明は、請求項１ないし請求項３の発明において、前記中間値設定手段は、前記上側ピーク値と前記下側ピーク値との平均値を中間値として設定することを特徴とする。
【００１３】
請求項５の発明は、流体の流路に配設され通過する流体の瞬間流量を計測する瞬間流量計測部と、複数種類の計測周期を備え前記複数種類の計測周期から計測周期を択一的に選択し選択した計測周期で前記瞬間流量計測部に瞬間流量の計測を指示する計測タイミング生成部と、計測タイミング生成部に計測周期の変更を指示する同期判定部とを備え、前記同期判定部は、設定された所定時間毎の瞬間流量の移動平均を中間値として設定する中間値設定手段と、瞬間流量の計測毎に計測した瞬間流量と中間値とを比較し連続した規定の複数回の計測を行う間において瞬間流量と中間値との大小関係が逆転しないときに計測周期を変更するように計測タイミング生成部に指示する計測周期変更手段とを備えることを特徴とする。
【００１４】
請求項６の発明は、請求項１ないし請求項５の発明において、前記瞬時流量と前記計測周期とから積算流量を求める積算手段を備え、前記流体はガスであることを特徴とする。
【００１５】
【発明の実施の形態】
本実施形態では図２に示す構成のガスメータ１を想定する。ガスメータ１は、都市ガスのような燃料ガスの供給路（ガス流路）に配置された遮断弁２と、ガス流路において遮断弁の下流側に配置された圧力センサ３および瞬間流量計測部４とを備える。また、圧力センサ３および瞬間流量計測部４は、１チップマイクロコンピュータ（以下、「マイコン」と略称する）を主構成要素とする信号処理回路５に接続され、信号処理回路５では、圧力センサ３および瞬間流量計測部４の動作の制御、圧力センサ３および瞬間流量計測部４の出力による遮断弁２の制御、燃料ガスの流量の計測などを行う。燃料ガスの流量は図示しないカウンタにより表示される。瞬間流量計測部４には超音波流量計を用いており、従来の技術としても説明したように、ガス流路上に挿入した計測管１１と、計測管１１の上流側と下流側とにそれぞれ配置した送受波器１２ａ，１２ｂとを備える。
【００１６】
信号処理回路５は図１に示す構成を有し、送受波器１２ａ，１２ｂがそれぞれ接続される２個の送受信回路２１ａ，２１ｂを備え、送受信回路２１ａ，２１ｂは集積回路からなる計測制御回路２２に接続される。計測制御回路２２はマイコン２０により制御され、マイコン２０では計測制御回路２２から取得した情報に基づいてガス流量を計測する。また、マイコン２０の内部クロックを発生させるためにマイコン２０には水晶発振子のような発振子２３が接続される。信号処理回路５の電源はリチウム電池のような電池２４により供給される。
【００１７】
送受信回路２１ａ，２１ｂは送受波器１２ａ，１２ｂと計測制御回路２２との間の整合回路であって、計測制御回路２２は、各送受波器１２ａ，１２ｂを送波用と受波用とに切り換える機能と、送受波器１２ａ，１２ｂを駆動して超音波を間欠的に発生させるための高周波信号を生成する機能と、送受波器１２ａ，１２ｂにより受信した超音波に対応する信号を波形整形して出力する機能とを備える。
【００１８】
超音波の送波から受波までの伝播時間の計測はマイコン２０が行っている。すなわち、マイコン２０では以下に説明する機能がプログラムによって実現されている。マイコン２０には、流量計測のタイミングを指示する計測タイミング生成部２０ａが設けられ、計測タイミング生成部２０ａによって流量計測が指示されるとマイコン２０に設けられた瞬間流量演算部２０ｂから計測制御回路２２に対して計測が指示される。計測のタイミングについては後述する。計測制御回路２２は、上述したように、両送受波器１２ａ，１２ｂの一方から超音波を送波させ、他方での超音波の受信タイミングに対応する信号を出力する。したがって、瞬間流量演算部２０ｂは、超音波の送波から受波が予測される時間程度のゲート期間を設定し、ゲート期間内において超音波の受波に相当する信号が計測制御回路２２から入力されたタイミングを超音波の受波のタイミングとみなし、超音波の送波から受波までの伝播時間を計測する。ここに、ゲート期間の時限および超音波の送波から受波までの伝播時間の計測には、発振子２３により生成した高周波のクロック信号を用いる。つまり、クロック信号を瞬間流量演算部２０ｂの内蔵カウンタで計数することによって計時する。瞬間流量演算部２０ｂでは、１００〜２００μｓｅｃの残響時間を考慮した適宜の時間間隔で各送受波器１２ａ，１２ｂから超音波を送波し、超音波の送波毎に得られた超音波の伝播時間を瞬間流量に換算する。瞬間流量演算部２０ｂによって瞬間流量を求める処理が１回の流量計測であって、計測タイミング生成部２０ａが瞬間流量演算部２０ｂに対して流量計測を指示する時間間隔が計測周期になる。このように、瞬間流量演算部２０ｂによる流量計測は計測周期で間欠的に行われる。
【００１９】
マイコン２０には、瞬間流量演算部２０ｂで求めた瞬間流量を積算して積算流量を求める積算流量演算部２０ｃも設けられる。積算流量演算部２０ｃでは、瞬間流量演算部２０ｂで求めた瞬間流量に計測周期を乗じた値を当該時間の積算流量として求め、バッファ２０ｄに入力する。バッファ２０ｄは前記当該時間の積算流量を積算し、図示しないカウンタに表示させる。この動作によってガスメータとしてガスの使用量を計測することができる。すなわち、積算流量演算部２０ｃとバッファ２０ｄとにより積算手段が構成される。
【００２０】
ところで、従来構成において説明したように計測周期は複数種類から択一的に選択される。すなわち、計測タイミング生成部２０ａには複数種類の計測周期が用意されており、瞬間流量演算部２０ｂで求めた瞬間流量の変化を監視する同期判定部２５からの指示によって計測周期が選択される。計測周期を選択する処理手順を簡単に説明すると、図３に示すように、まず計測タイミング生成部２０ａでは選択されている計測周期から計測タイミングを決定し、瞬間流量演算部２０ｂに流量計測を指示する（Ｓ１）。瞬間流量演算部２０ｂでは瞬間流量を計測し（Ｓ２）、求めた瞬間流量に基づいて瞬間流量計測部４を通過するガスの圧力の脈動成分に関する脈動周期の整数倍と計測周期とが一致しているか否かを判定する（Ｓ３）。以下では、計測周期と脈動周期の整数倍とが一致する状態を計測周期の脈動周期に対する「同期」と呼び、脈動周期の整数倍と計測周期とが一致しているか否かを判定する処理を「同期判定ルーチン」と呼ぶ。ステップＳ３の同期判定ルーチンにおいて同期が検出されると、同期判定部２５では計測タイミング生成部２０ａに対して計測周期の変更を指示する（Ｓ４）。計測周期の変更が指示された場合には、計測タイミング生成部２０ａは他の計測周期を選択し（Ｓ５）、計測周期の変更が指示されなければ同じ計測周期を維持する。計測周期には適宜に優先順位が設定されており、優先順位に従って計測周期が順に選択される。計測周期が決定されると、先に瞬間流量演算部２０ｂで求めた瞬間流量から積算流量演算部２０ｃにおいて求めた積算流量をバッファ２０ｄに格納されている積算流量に積算する（Ｓ６）。以上の動作を繰り返すことによって、瞬間流量の計測を繰り返す間に、計測周期の脈動周期に対する同期の有無を判定するとともにガスの使用量を求めるのである。
【００２１】
次に、同期判定部２５における同期判定ルーチンについて説明する。同期判定部２５は、基本的には、瞬間流量の時系列から求められる上側ピーク値と下側ピーク値との平均値を中間値とする中間値設定手段２５ａと、１回前の計測時の瞬間流量が中間値よりも小さい場合に、今回計測した瞬間流量が中間値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が下側ピーク値よりも小さければこの瞬間流量を下側ピーク値とする第１のピーク検知手段２５ｂと、１回前の計測時の瞬間流量が中間値よりも大きい場合に、今回計測した瞬間流量が上側ピーク値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が中間値よりも小さければこの瞬間流量を下側ピーク値とする第２のピーク検知手段２５ｃと、連続した複数回（たとえば、４回）の計測において瞬間流量が中間値を横切らないときに計測周期を変更するように計測タイミング生成部２０ａに指示する計測周期変更手段２５ｄとからなる。
【００２２】
同期判定部２５の動作を、図４を用いて説明する。ここでは、過去の瞬間流量（つまり、瞬間流量の時系列）から後述する手順によって上側ピーク値Ｐｓ０と下側ピーク値Ｐｉ０とがすでに求められ、１回前の計測時における瞬間流量は中間値よりも小さいものとする。つまり、第１のピーク検知手段２５ｂを用い、第２のピーク検知手段２５ｃは用いない。また、瞬時流量の計測タイミングをｒ１，ｒ２，ｒ３とする。
【００２３】
計測タイミングｒ１において瞬時流量ｑ１を求めた時点では、中間値設定手段２５ａでは上側ピーク値Ｐｓ０と下側ピーク値Ｐｉ０との平均値を中間値ｍ１としており、瞬時流量ｑ１は中間値ｍ１よりも小さく、下側ピーク値Ｐｉ０よりも大きいから、第１のピーク検知手段２５ｂでは中間値ｍ１は変更しない。また、瞬時流量ｑ１が中間値ｍ１よりも小さいから依然として第１のピーク検知手段２５ｂを用いる。
【００２４】
次に、計測タイミングｒ２において得られる瞬間流量ｑ２は、下側ピーク値Ｐｉ０よりも小さいから下側ピーク値を瞬間流量ｑ２に変更する。つまり、下側ピーク値がＰｉ０からＰｉ２（＝ｑ２）に変更される。また、下側ピーク値Ｐｉ２の変更に伴って中間値設定手段２５ａでは中間値ｍ２（＜ｍ１）の変更を行う。ただし、瞬時流量ｑ２は中間値ｍ１よりも小さいから次の計測タイミングｒ３においても第１のピーク検知手段２５ｂを用いる。
【００２５】
図示例では計測タイミングｒ３で得られる瞬時流量ｑ３が中間値ｍ２よりも大きくなっているから、この場合には上側ピーク値を瞬時流量ｑ３に変更し、上側ピーク値がＰｓ０からＰｓ３（＝ｑ３）になる。また、上側ピーク値Ｐｓ３の変更に伴って中間値設定手段２５ａでは中間値ｍ３（＜ｍ２）の変更を行う。ここで、瞬時流量ｑ３は中間値ｍ２よりも大きいから次回の計測タイミングでは第１のピーク検知手段２５ｂではなく第２のピーク検知手段２５ｃを用いることになる。
【００２６】
以上説明した動作によって、上側ピーク値および下側ピーク値と中間値とを瞬時流量に応じて変化させることになる。図５は瞬間流量（各黒丸が瞬時流量を示す）と上側ピーク値Ｐｓおよび下側ピーク値Ｐｉと中間値ｍとの関係を示している。ここで、図５の左端部を除く部分では瞬時流量の１〜３回の計測毎に瞬時流量が中間値ｍを横切っており、このような状態であれば計測周期が脈動周期に同期していないと判断してよいという知見に基づいて本発明はなされている。一方、瞬時流量が４回連続して中間値を横切らない場合には計測周期が脈動周期に同期している可能性があるものとして、計測タイミング生成部２０ａに対して計測周期の変更を指示するのである。
【００２７】
同期判定部２５の具体的な処理は図６、図７のようになる。上述のように同期判定部２５は、前回の計測時に得られた瞬間流量と中間値との関係によって、第１のピーク検知手段２５ｂと第２のピーク検知手段２５ｃとのどちらを用いるかを選択するから、第１のピーク検知手段２５ｂと第２のピーク検知手段２５ｃとを選択するための状態フラグ（図示せず）を備えている。状態フラグが１であれば第１のピーク検知手段２５ｂを用い、状態フラグが２であれば第２のピーク検知手段２５ｃを用いる。そこで、まず状態フラグが１か２かが判定され（Ｓ１）、状態フラグが１であれば第１のピーク検知手段２５ｂを用いる図６の処理が行われる。また、瞬時流量が中間値を横切らない連続回数を計数するために同期判断カウンタ（図示せず）を備える。
【００２８】
すなわち、図６は前回の計測時の瞬間流量が中間値よりも小さかった場合であって、まず図３に示したステップＳ２で得られた瞬間流量を中間値と比較する（Ｓ２）。瞬間流量が中間値以下であれば、同期判断カウンタの計数値を１増加させる（Ｓ３）。また、瞬間流量と下ピーク値との大小を比較し（Ｓ４）、瞬間流量が下ピーク値よりも小さい場合には下ピーク値を瞬間流量に変更する（Ｓ５）。ここで、同期判断カウンタの計数値が閾値（たとえば３）を越えていれば（Ｓ６）、同期が生じているものと判断して計測周期の変更を指示し（Ｓ７）、瞬時流量を上側ピーク値として中間値を再度求める（Ｓ８）。さらに、状態フラグを２に設定して第２のピーク検知手段２５ｃを選択する（Ｓ９）とともに、同期判断カウンタの計数値をリセットする（Ｓ１０）。
【００２９】
ステップＳ２において瞬間流量が中間値よりも大きいときには、瞬間流量が中間値を横切ったことになるから、上ピーク値を瞬間流量に変更し（Ｓ１１）、同期判断カウンタの計数値をリセットする（Ｓ１２）。さらに、第２のピーク検知手段２５ｃを選択するために状態フラグを２にセットし（Ｓ１３）、現状の計測周期が維持されるように指示する（Ｓ１４）。また、ステップＳ６において同期判断カウンタの計数値が閾値以下である場合も現状の計測周期が維持されるように指示する（Ｓ１５）。
【００３０】
ステップＳ１において状態フラグが２である場合には第２のピーク検知手段２５ｃが用いられるほかは図６に示した動作と同様の動作になる。つまり、図７は前回の計測時の瞬間流量が中間値よりも大きかった場合であって、まず図３に示したステップＳ２で得られた瞬間流量を中間値と比較する（Ｓ１６）。瞬間流量が中間値以上であれば、同期判断カウンタの計数値を１増加させる（Ｓ１７）。また、瞬間流量と上ピーク値との大小を比較し（Ｓ１８）、瞬間流量が上ピーク値よりも大きい場合には上ピーク値を瞬間流量に変更する（Ｓ１９）。ここで、同期判断カウンタの計数値が閾値を越えていれば（Ｓ２０）、同期が生じているものと判断して計測周期の変更を指示し（Ｓ２１）、瞬時流量を上側ピーク値として中間値を再度求める（Ｓ２２）。さらに、状態フラグを１に設定して第１のピーク検知手段２５ｂを選択する（Ｓ２３）とともに、同期判断カウンタの計数値をリセットする（Ｓ２４）。
【００３１】
ステップＳ１６において瞬間流量が中間値よりも小さいときには、瞬間流量が中間値を横切ったことになるから、下ピーク値を瞬間流量に変更し（Ｓ２５）、同期判断カウンタの計数値をリセットする（Ｓ２６）。さらに、第１のピーク検知手段２５ｂを選択するために状態フラグを１にセットし（Ｓ２７）、現状の計測周期が維持されるように指示する（Ｓ２８）。また、ステップＳ２０において同期判断カウンタの計数値が閾値以下である場合も現状の計測周期が維持されるように指示する（Ｓ２９）。
【００３２】
図６および図７に示した処理手順での状態フラグおよび同期判断カウンタの計数値の推移の一例を図８に示す。図８は図５の動作に対応するものであって、破線が状態フラグの変化を示し、図の右側に状態フラグの値を示してある。また、図８の実線は同期判断カウンタの計数値の変化を示し、図の左側に計数値を示してある。図示例では左端部において状態フラグが４回連続して「１」であって、同期判断カウンタの計数値が閾値である３を越えて４になっているから、瞬間流量が４回連続して中間値を横切らなかったことを意味する。したがって、この時点で別の計測周期が選択されることになる。計測周期が変更された後は、同期判断カウンタの計数値が３を越えることがないから、計測周期が脈動周期に同期していないものとみなすことができる。つまり、積算流量演算部２０ｃの出力をバッファ２０ｄで積算することにより得られるガスの使用量から圧力脈動の影響を除去でき、ガスの使用量の計測誤差を抑制することができる。言い換えると、瞬間流量計測部４を通過するガスの圧力が周期的な脈動成分を含むときに脈動周期の非整数倍になる計測周期であって瞬間流量計測部４で計測される瞬間流量の平均値が時間経過に伴って収束する計測周期を選択したことになる。
【００３３】
ところで、上側ピーク値と下側ピーク値とは上述の方法以外の方法で設定してもよい。たとえば、設定された所定時間（たとえば、３０ｓｅｃ）毎に計測された複数個（たとえば、１０個）の瞬間流量の最大値を上側ピーク値とするとともに最小値を下側ピーク値として採用してもよい。この場合には上述したように第１のピーク検知手段２５ｂと第２のピーク検知手段２５ｃとを設ける代わりに、瞬間流量の最大値と最小値とを求めるピーク検知手段を設ければよい。ここに、上述した所定時間とは、中間値を求めることができる個数の瞬間流量を取得する時間であれば十分であり、瞬間流量のサンプリング数は１０〜２０個でよい。サンプリング間隔である測定周期は通常は１〜５ｓｅｃ程度であるから、上述した所定時間は１０〜１００秒の間の値になる。好ましい例としては測定周期は約３秒であるから、この場合には上述した所定時間は３０〜６０秒程度になる。
【００３４】
さらに、上述の実施形態では中間値を上側ピーク値と下側ピーク値との平均値と設定したが、設定された所定時間毎の瞬間流量の移動平均を中間値に用いてもよい。この場合の所定時間は、瞬間流量の最大値および最小値をそれぞれ上側ピーク値および下側ピーク値とする場合の所定時間と同程度に設定すればよい。また、移動平均を用いるから上側ピーク値および下側ピーク値を求める処理は不要になる。
【００３５】
なお、上述した実施形態において瞬間流量計測部４を超音波流量計で構成しているが、瞬間流量を計測することができるものであれば測定原理についてはとくに制限はない。また、超音波流量計を用いて瞬間流量を計測するにあたり、シングアラウンド法を用いてもよい。また、上述の実施形態ではガスの流量を計測する例を示したがガス以外の他の流体に本発明の技術を適用することも可能である。
【００３６】
【発明の効果】
請求項１の発明の構成によれば、同期判定部では間欠的に計測される瞬間流量が規定の複数回の計測を行う間に中間値と瞬間流量との大小関係が逆転するか否かによって、瞬間流量の積算による圧力脈動の影響の除去が可能か否かを判断することができ、圧力脈動が生じている環境下において、複数種類の計測周期の中から脈動周期の整数倍ではない計測周期を瞬間流量が複数回計測される程度の比較的短い時間で選択することができるという利点を有する。すなわち、瞬間流量の計測毎に計測した瞬間流量と中間値とを比較し、連続した規定の複数回の計測を行う間において瞬間流量と中間値との大小関係が逆転しない場合は、計測周期が脈動周期に同期している可能性があるものと判断し、計測周期を変更することができる。しかも、実施形態で説明しているように瞬間流量を４回程度計測するだけで、計測周期と脈動周期との同期の可能性を判断することができるから、脈動周期に同期しない計測周期を短時間で選択することができる。
【００３７】
請求項２の発明は、請求項１の発明において、前記ピーク検知手段は、前回計測時の瞬間流量が中間値よりも小さい場合に、今回計測した瞬間流量が中間値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が下側ピーク値よりも小さければこの瞬間流量を下側ピーク値とする第１のピーク検知手段と、前回計測時の瞬間流量が中間値よりも大きい場合に、今回計測した瞬間流量が上側ピーク値より大きければこの瞬間流量を上側ピーク値とし、今回計測した瞬間流量が中間値よりも小さければこの瞬間流量を下側ピーク値とする第２のピーク検知手段とを備えるものであり、この構成によって上側ピーク値と下側ピーク値とを求めることによって、上側ピーク値と下側ピーク値との間で求める中間値が流量変動の中心付近の適正な値になる。要するに、このようにして求めた中間値に対する瞬間流量の変化を求めることによって、瞬間流量の積算による圧力脈動の影響の除去が可能か否かを正確に判断することができる。
【００３８】
請求項３の発明は、請求項１の発明において、前記ピーク検知手段は、設定された所定時間毎に計測された複数個の瞬間流量の最大値を上側ピーク値とするとともに最小値を下側ピーク値とするものであり、所定時間毎の瞬時流量の最大値と最小値とを求めるだけの簡単な処理で上側ピーク値と下側ピーク値とを決定することができる。
【００３９】
請求項４の発明は、請求項１ないし請求項３の発明において、前記中間値設定手段は、前記上側ピーク値と前記下側ピーク値との平均値を中間値として設定するものであり、中間値を設定する演算が容易である。
【００４０】
請求項５の発明の構成によれば、所定時間毎の瞬間流量の移動平均を中間値として設定するから、請求項１の発明と同様の効果に加えて、移動平均を用いることにより瞬間流量の突発的な変動による中間値の変動が防止される。
【００４１】
請求項６の発明は、請求項１ないし請求項５の発明において、前記瞬時流量と前記計測周期とから積算流量を求める積算手段を備え、前記流体はガスであって、ガスメータに適用可能な構成を提供できる。
【図面の簡単な説明】
【図１】本発明の実施の形態を示す要部ブロック図である。
【図２】同上を用いたガスメータを示すブロック図である。
【図３】同上の動作説明図である。
【図４】同上の動作説明図である。
【図５】同上の動作説明図である。
【図６】同上の動作説明図である。
【図７】同上の動作説明図である。
【図８】同上の動作説明図である。
【符号の説明】
４瞬間流量計測部
２０ａ計測タイミング生成部
２５同期判定部
２５ａ中間値設定手段
２５ｂ第１のピーク検知手段
２５ｃ第２のピーク検知手段
２５ｄ計測周期変更手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter.
[0002]
[Prior art]
In recent years, it has been considered to employ an ultrasonic flow meter to measure the amount of gas used in a gas meter. As shown in FIG. 2, in the ultrasonic flowmeter, the moment when transducers 12a and 12b for transmitting and receiving ultrasonic waves are respectively arranged on the upstream side and the downstream side of the measurement tube 11 provided on the gas flow path. A flow rate measuring unit 4 is provided. For the measurement of the flow rate, the propagation time t1 of the ultrasonic wave when the ultrasonic wave is transmitted from the upstream transducer 12a toward the downstream transducer 12b, and the upstream side from the downstream transducer 12b. The ultrasonic propagation time t2 when the ultrasonic wave is transmitted toward the transmission / reception wave 12a is measured, and the flow velocity is obtained based on both propagation times t1 and t2. When the flow velocity is obtained, a value obtained by multiplying the cross-sectional area of the measurement tube 11 and the flow velocity is the instantaneous flow rate.
[0003]
Now, it is assumed that the traveling direction of the ultrasonic waves transmitted and received between the transducers 12a and 12b coincides with the flowing direction of the gas passing through the measuring tube 11. If the distance between the transducers 12a and 12b is d, the gas flow velocity is V, and the sound velocity is C, the propagation times t1 and t2 can be expressed as follows.
t1 = d / (C + V)
t2 = d / (C−V)
Therefore, the flow velocity V is expressed as follows.
V = (d / 2) {(1 / t1)-(1 / t2)}
In this measurement technique, ultrasonic waves are intermittently generated from the transmitters 12a and 12b in order to obtain ultrasonic propagation times t1 and t2. A gas meter is often powered by a battery and consumes power when an ultrasonic flow meter is used. Therefore, when an ultrasonic flow meter is used, it is instantaneous at a constant measurement cycle of 2 to 3 seconds so that power consumption does not increase. Measure the flow rate.
[0004]
By the way, recently, gas-using devices that drive a gas engine using a fuel gas such as city gas have been widely used in fields such as a gas heat pump and a generator. Since this type of gas engine repeats intake and exhaust, pulsation (hereinafter referred to as “pressure pulsation”) is caused in the pressure of the fuel gas supply path. It is also known that pressure pulsation is caused by the operation of a membrane meter that is generally used in gas meters. If there is such pressure pulsation, pulsation also occurs in the flow velocity V. In general, the frequency of pressure pulsation in a membrane meter is about 3 to 6 Hz, the frequency of pressure pulsation by a gas engine is about 10 to 60 Hz, and the maximum is 200 Pa (peak-peak is 400 Pa) in the vicinity of the gas using device. It is known to have an amplitude.
[0005]
In order to measure the amount of gas used in a gas meter, the instantaneous flow rate is integrated. Therefore, even in an environment where pressure pulsation as described above occurs, the pulsation component is canceled by integrating a number of instantaneous flow rates. If this is the case, it is considered that there is no effect of pressure pulsation on the measured value. That is, it is considered that the average value of a large number of instantaneous flow rates converges to a value that does not include a pulsating component. In practice, however, the measurement cycle may almost coincide with an integer multiple of the pulsation cycle of pressure pulsation. In such a case, even if the instantaneous flow rate obtained at each measurement cycle is integrated, the pulsation component is canceled out. This results in a large measurement error.
[0006]
Therefore, a technology that reduces the occurrence of measurement errors by preparing multiple types of measurement cycles and switching to another measurement cycle when a measurement cycle that approximately matches an integer multiple of the pulsation cycle is selected. Proposed earlier. According to the experimental results, the measurement cycle is about 3 seconds, and the measurement cycle can be changed in units of 1/512 sec. If any of the following seven measurement cycles is prepared, the measurement cycle is the pulsation cycle. It has been found that it is possible to avoid the situation of almost coincident with an integer multiple of. That is, when the measurement cycle is expressed as (3 + n / 512) sec, it may be selected from n = 37, 19, 45, 10, -11, -30, and 53. In addition, when selecting the measurement cycle, first, each measurement cycle is performed a fixed number of times, and the number of measurements between the maximum and minimum instantaneous flow rates obtained in each measurement cycle is less than the predetermined number. At some point, it is considered to select the measurement cycle.
[0007]
[Problems to be solved by the invention]
However, after measuring the instantaneous flow rate a certain number of times in each measurement cycle as described above, if it is determined which measurement cycle is used, the time required to determine the measurement cycle increases.
[0008]
The present invention has been made in view of the above-mentioned reasons, and an object thereof is to provide a flowmeter capable of selecting a measurement cycle that is not an integral multiple of the pulsation cycle in an environment where pressure pulsation occurs in a relatively short time. There is.
[0009]
[Means for Solving the Problems]
  The invention of claim 1 includes an instantaneous flow rate measurement unit that measures an instantaneous flow rate of a fluid that is disposed in a fluid flow path and a plurality of types of measurement cycles, and alternatively selects a measurement cycle from the plurality of types of measurement cycles. A measurement timing generation unit that instructs the instantaneous flow rate measurement unit to measure the instantaneous flow rate at a selected measurement cycle, and a synchronization determination unit that instructs the measurement timing generation unit to change the measurement cycle, the synchronization determination unit Is a peak detection means for obtaining the upper peak value and the lower peak value from the time series of the instantaneous flow rate measured by the instantaneous flow rate measuring unit, and sets an intermediate value between the upper peak value and the lower peak value. Intermediate value setting means,Compare the instantaneous flow rate measured for each instantaneous flow rate and the intermediate value.Consecutive prescribed multiple measurementsWhile doingInstantaneous flow rate atWhenIntermediate valueThe magnitude relationship with is not reversedMeasurement cycle changing means for instructing the measurement timing generation unit to change the measurement cycle sometimes.
[0010]
According to a second aspect of the present invention, in the first aspect of the invention, when the instantaneous flow rate at the time of the previous measurement is smaller than the intermediate value, the peak detecting means determines the instantaneous flow rate if the instantaneous flow rate measured this time is larger than the intermediate value. If the instantaneous flow rate measured this time is smaller than the lower peak value, the first peak detection means that uses this instantaneous flow rate as the lower peak value, and the instantaneous flow rate at the previous measurement is greater than the intermediate value In addition, if the instantaneous flow rate measured this time is larger than the upper peak value, the instantaneous flow rate is set as the upper peak value, and if the instantaneous flow rate measured this time is smaller than the intermediate value, the second peak detection is performed using the instantaneous flow rate as the lower peak value. Means.
[0011]
According to a third aspect of the present invention, in the first aspect of the present invention, the peak detecting means sets the maximum value of a plurality of instantaneous flow rates measured every set predetermined time as the upper peak value and sets the minimum value as the lower value. It is characterized by a peak value.
[0012]
According to a fourth aspect of the present invention, in the first to third aspects of the invention, the intermediate value setting means sets an average value of the upper peak value and the lower peak value as an intermediate value. .
[0013]
  The invention according to claim 5 includes an instantaneous flow rate measurement unit that measures an instantaneous flow rate of a fluid that is disposed in a fluid flow path and a plurality of types of measurement cycles, and alternatively selects a measurement cycle from the plurality of types of measurement cycles. A measurement timing generation unit that instructs the instantaneous flow rate measurement unit to measure the instantaneous flow rate at a selected measurement cycle, and a synchronization determination unit that instructs the measurement timing generation unit to change the measurement cycle, the synchronization determination unit Is an intermediate value setting means for setting, as an intermediate value, a moving average of the instantaneous flow rate set every predetermined time;Compare the instantaneous flow rate measured for each instantaneous flow rate and the intermediate value.Consecutive prescribed multiple measurementsWhile doingInstantaneous flow rate atWhenIntermediate valueThe magnitude relationship with is not reversedMeasurement cycle changing means for instructing the measurement timing generation unit to change the measurement cycle sometimes.
[0014]
According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, there is provided an integrating means for obtaining an integrated flow rate from the instantaneous flow rate and the measurement cycle, wherein the fluid is a gas.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present embodiment, a gas meter 1 having the configuration shown in FIG. 2 is assumed. The gas meter 1 includes a shutoff valve 2 disposed in a supply path (gas flow path) of a fuel gas such as city gas, a pressure sensor 3 disposed in the gas flow path downstream of the shutoff valve, and an instantaneous flow rate measuring unit 4. With. The pressure sensor 3 and the instantaneous flow rate measuring unit 4 are connected to a signal processing circuit 5 having a one-chip microcomputer (hereinafter abbreviated as “microcomputer”) as a main component. Further, the control of the operation of the instantaneous flow rate measuring unit 4, the control of the shutoff valve 2 by the outputs of the pressure sensor 3 and the instantaneous flow rate measuring unit 4, the measurement of the flow rate of the fuel gas, and the like are performed. The flow rate of the fuel gas is displayed by a counter (not shown). The instantaneous flow rate measuring unit 4 uses an ultrasonic flow meter, and as described in the prior art, is arranged on the measurement tube 11 inserted on the gas flow path and on the upstream side and the downstream side of the measurement tube 11 respectively. Transmitter / receiver 12a, 12b.
[0016]
The signal processing circuit 5 has the configuration shown in FIG. 1, and includes two transmission / reception circuits 21a and 21b to which the transducers 12a and 12b are connected, respectively. The transmission / reception circuits 21a and 21b are measurement control circuits 22 made of integrated circuits. Connected to. The measurement control circuit 22 is controlled by the microcomputer 20, and the microcomputer 20 measures the gas flow rate based on the information acquired from the measurement control circuit 22. In addition, an oscillator 23 such as a crystal oscillator is connected to the microcomputer 20 in order to generate an internal clock of the microcomputer 20. The signal processing circuit 5 is powered by a battery 24 such as a lithium battery.
[0017]
The transmission / reception circuits 21a and 21b are matching circuits between the transducers 12a and 12b and the measurement control circuit 22, and the measurement control circuit 22 uses the transducers 12a and 12b for transmission and reception. A function for switching, a function for generating a high-frequency signal for intermittently generating ultrasonic waves by driving the transducers 12a and 12b, and a waveform shaping of signals corresponding to the ultrasonic waves received by the transducers 12a and 12b Output function.
[0018]
The microcomputer 20 measures the propagation time from ultrasonic wave transmission to wave reception. That is, in the microcomputer 20, the functions described below are realized by a program. The microcomputer 20 is provided with a measurement timing generation unit 20a for instructing the timing of flow measurement, and when the measurement of the flow rate is instructed by the measurement timing generation unit 20a, the measurement control circuit 22 is supplied from the instantaneous flow rate calculation unit 20b provided in the microcomputer 20. Is instructed to measure. The measurement timing will be described later. As described above, the measurement control circuit 22 transmits ultrasonic waves from one of the transducers 12a and 12b, and outputs a signal corresponding to the reception timing of the ultrasonic waves on the other side. Therefore, the instantaneous flow rate calculation unit 20b sets a gate period that is about the time during which reception is predicted from transmission of ultrasonic waves, and a signal corresponding to reception of ultrasonic waves is input from the measurement control circuit 22 within the gate period. The received timing is regarded as the timing of ultrasonic wave reception, and the propagation time from ultrasonic wave transmission to wave reception is measured. Here, a high-frequency clock signal generated by the oscillator 23 is used for the measurement of the time period of the gate period and the propagation time from ultrasonic wave transmission to wave reception. That is, the clock signal is counted by counting with the built-in counter of the instantaneous flow rate calculation unit 20b. In the instantaneous flow rate calculation unit 20b, ultrasonic waves are transmitted from each of the transmitters / receivers 12a and 12b at an appropriate time interval in consideration of a reverberation time of 100 to 200 μsec, and propagation of the ultrasonic waves obtained for each ultrasonic wave transmission is performed. Convert time to instantaneous flow rate. The process for obtaining the instantaneous flow rate by the instantaneous flow rate calculation unit 20b is a single flow rate measurement, and the time interval at which the measurement timing generation unit 20a instructs the instantaneous flow rate calculation unit 20b to measure the flow rate becomes the measurement cycle. Thus, the flow rate measurement by the instantaneous flow rate calculation unit 20b is intermittently performed at the measurement cycle.
[0019]
The microcomputer 20 is also provided with an integrated flow rate calculation unit 20c that integrates the instantaneous flow rate obtained by the instantaneous flow rate calculation unit 20b to obtain an integrated flow rate. In the integrated flow rate calculation unit 20c, a value obtained by multiplying the instantaneous flow rate obtained by the instantaneous flow rate calculation unit 20b by the measurement cycle is obtained as an integrated flow rate for the time and input to the buffer 20d. The buffer 20d accumulates the accumulated flow for the time and displays it on a counter (not shown). By this operation, the amount of gas used can be measured as a gas meter. In other words, the integrating flow rate calculation unit 20c and the buffer 20d constitute an integrating unit.
[0020]
Incidentally, as described in the conventional configuration, the measurement cycle is alternatively selected from a plurality of types. That is, a plurality of types of measurement cycles are prepared in the measurement timing generation unit 20a, and the measurement cycle is selected by an instruction from the synchronization determination unit 25 that monitors the change in the instantaneous flow rate obtained by the instantaneous flow rate calculation unit 20b. The processing procedure for selecting the measurement cycle will be briefly described. As shown in FIG. 3, the measurement timing generation unit 20a first determines the measurement timing from the selected measurement cycle, and instructs the instantaneous flow rate calculation unit 20b to measure the flow rate. (S1). The instantaneous flow rate calculation unit 20b measures the instantaneous flow rate (S2), and the measurement cycle coincides with the integral multiple of the pulsation cycle related to the pulsation component of the pressure of the gas passing through the instantaneous flow rate measurement unit 4 based on the obtained instantaneous flow rate. It is determined whether or not there is (S3). In the following, the state in which the measurement cycle and the integral multiple of the pulsation cycle match is referred to as “synchronization” with respect to the pulsation cycle of the measurement cycle, and the process of determining whether or not the integral multiple of the pulsation cycle and the measurement cycle match. This is called a “synchronization determination routine”. When synchronization is detected in the synchronization determination routine in step S3, the synchronization determination unit 25 instructs the measurement timing generation unit 20a to change the measurement cycle (S4). When the change of the measurement cycle is instructed, the measurement timing generator 20a selects another measurement cycle (S5), and maintains the same measurement cycle unless the change of the measurement cycle is instructed. Priorities are appropriately set for the measurement cycles, and the measurement cycles are sequentially selected according to the priorities. When the measurement cycle is determined, the integrated flow rate obtained by the integrated flow rate calculation unit 20c is integrated with the integrated flow rate stored in the buffer 20d from the instantaneous flow rate previously obtained by the instantaneous flow rate calculation unit 20b (S6). By repeating the above operation, while measuring the instantaneous flow rate, the presence or absence of synchronization with the pulsation cycle of the measurement cycle is determined and the amount of gas used is determined.
[0021]
Next, a synchronization determination routine in the synchronization determination unit 25 will be described. The synchronization determination unit 25 basically includes an intermediate value setting unit 25a having an average value of an upper peak value and a lower peak value obtained from a time series of instantaneous flow rates as an intermediate value, and at the time of the previous measurement. When the instantaneous flow rate is smaller than the intermediate value and the instantaneous flow rate measured this time is larger than the intermediate value, the instantaneous flow rate is set as the upper peak value, and when the instantaneous flow rate measured this time is lower than the lower peak value, the instantaneous flow rate is decreased. If the instantaneous flow rate measured this time is larger than the upper peak value when the instantaneous flow rate at the time of the first measurement is larger than the intermediate value, the instantaneous flow rate is set to the upper peak value. If the instantaneous flow rate measured this time is smaller than the intermediate value, the second peak detection means 25c that uses this instantaneous flow rate as the lower peak value and the instantaneous flow rate in a plurality of consecutive (for example, four) measurements. Comprising a measurement cycle changing means 25d to instruct measurement timing generator 20a so as to change the measurement cycle when not cross between values.
[0022]
  The operation of the synchronization determination unit 25 will be described with reference to FIG. Here, the upper peak value Ps0 and the lower peak value Pi0 are already obtained from the past instantaneous flow rate (that is, the time series of the instantaneous flow rate) by the procedure described later, and at the time of the previous measurementInThe instantaneous flow rate is assumed to be smaller than the intermediate value. That is, the first peak detector 25b is used and the second peak detector 25c is not used. The measurement timing of the instantaneous flow rate is r1, r2, r3.
[0023]
  At the time when the instantaneous flow rate q1 is obtained at the measurement timing r1, the intermediate value setting means 25a calculates the average value of the upper peak value Ps0 and the lower peak value Pi0 as the intermediate value m1.AndSince the instantaneous flow rate q1 is smaller than the intermediate value m1 and larger than the lower peak value Pi0, the first peak detection means 25b does not change the intermediate value m1. Further, since the instantaneous flow rate q1 is smaller than the intermediate value m1, the first peak detection means 25b is still used.
[0024]
Next, since the instantaneous flow rate q2 obtained at the measurement timing r2 is smaller than the lower peak value Pi0, the lower peak value is changed to the instantaneous flow rate q2. That is, the lower peak value is changed from Pi0 to Pi2 (= q2). Further, the intermediate value setting means 25a changes the intermediate value m2 (<m1) in accordance with the change of the lower peak value Pi2. However, since the instantaneous flow rate q2 is smaller than the intermediate value m1, the first peak detection means 25b is also used at the next measurement timing r3.
[0025]
In the illustrated example, the instantaneous flow rate q3 obtained at the measurement timing r3 is larger than the intermediate value m2. In this case, the upper peak value is changed to the instantaneous flow rate q3, and the upper peak value is changed from Ps0 to Ps3 (= q3). become. Further, the intermediate value setting means 25a changes the intermediate value m3 (<m2) in accordance with the change of the upper peak value Ps3. Here, since the instantaneous flow rate q3 is larger than the intermediate value m2, the second peak detection means 25c is used instead of the first peak detection means 25b at the next measurement timing.
[0026]
  By the operation described above, the upper peak value, the lower peak value, and the intermediate value are changed according to the instantaneous flow rate. FIG. 5 shows the relationship between the instantaneous flow rate (each black circle indicates the instantaneous flow rate), the upper peak value Ps, the lower peak value Pi, and the intermediate value m. Here, in the portion excluding the left end portion of FIG. 5, the instantaneous flow rate crosses the intermediate value m every 1 to 3 times of measurement of the instantaneous flow rate. In such a state, the measurement cycle is synchronized with the pulsation cycle. The present invention has been made based on the knowledge that it may be determined that there is no.on the other hand,When the instantaneous flow rate does not cross the intermediate value four times in succession, it is assumed that the measurement cycle may be synchronized with the pulsation cycle, and the measurement timing generator 20a is instructed to change the measurement cycle. .
[0027]
Specific processing of the synchronization determination unit 25 is as shown in FIGS. As described above, the synchronization determination unit 25 selects which of the first peak detection unit 25b and the second peak detection unit 25c to use depending on the relationship between the instantaneous flow rate obtained during the previous measurement and the intermediate value. Therefore, a state flag (not shown) for selecting the first peak detection means 25b and the second peak detection means 25c is provided. If the status flag is 1, the first peak detection means 25b is used, and if the status flag is 2, the second peak detection means 25c is used. Therefore, it is first determined whether the status flag is 1 or 2 (S1). If the status flag is 1, the processing of FIG. 6 using the first peak detection means 25b is performed. In addition, a synchronization determination counter (not shown) is provided for counting the number of consecutive times that the instantaneous flow rate does not cross the intermediate value.
[0028]
That is, FIG. 6 shows a case where the instantaneous flow rate at the previous measurement is smaller than the intermediate value. First, the instantaneous flow rate obtained in step S2 shown in FIG. 3 is compared with the intermediate value (S2). If the instantaneous flow rate is equal to or less than the intermediate value, the count value of the synchronization determination counter is incremented by 1 (S3). Further, the magnitudes of the instantaneous flow rate and the lower peak value are compared (S4), and if the instantaneous flow rate is smaller than the lower peak value, the lower peak value is changed to the instantaneous flow rate (S5). Here, if the count value of the synchronization determination counter exceeds a threshold value (for example, 3) (S6), it is determined that synchronization has occurred and a change in the measurement cycle is instructed (S7), and the instantaneous flow rate is increased to the upper peak. The intermediate value is obtained again as a value (S8). Further, the status flag is set to 2 and the second peak detecting means 25c is selected (S9), and the count value of the synchronization determination counter is reset (S10).
[0029]
When the instantaneous flow rate is larger than the intermediate value in step S2, the instantaneous flow rate has crossed the intermediate value, so the upper peak value is changed to the instantaneous flow rate (S11), and the count value of the synchronization determination counter is reset (S12). ). Further, in order to select the second peak detecting means 25c, the status flag is set to 2 (S13), and an instruction is given to maintain the current measurement cycle (S14). In addition, when the count value of the synchronization determination counter is equal to or smaller than the threshold value in step S6, the current measurement cycle is instructed (S15).
[0030]
When the status flag is 2 in step S1, the operation is the same as that shown in FIG. 6 except that the second peak detection means 25c is used. That is, FIG. 7 shows a case where the instantaneous flow rate at the previous measurement is larger than the intermediate value. First, the instantaneous flow rate obtained in step S2 shown in FIG. 3 is compared with the intermediate value (S16). If the instantaneous flow rate is greater than or equal to the intermediate value, the count value of the synchronization determination counter is incremented by 1 (S17). Further, the magnitudes of the instantaneous flow rate and the upper peak value are compared (S18). If the instantaneous flow rate is larger than the upper peak value, the upper peak value is changed to the instantaneous flow rate (S19). Here, if the count value of the synchronization determination counter exceeds the threshold value (S20), it is determined that synchronization has occurred, and a change in the measurement cycle is instructed (S21), and the intermediate value is set with the instantaneous flow rate as the upper peak value. Is obtained again (S22). Further, the status flag is set to 1 to select the first peak detecting means 25b (S23), and the count value of the synchronization determination counter is reset (S24).
[0031]
When the instantaneous flow rate is smaller than the intermediate value in step S16, the instantaneous flow rate has crossed the intermediate value, so the lower peak value is changed to the instantaneous flow rate (S25), and the count value of the synchronization determination counter is reset (S26). ). Further, in order to select the first peak detecting means 25b, the status flag is set to 1 (S27), and an instruction is given to maintain the current measurement cycle (S28). In addition, when the count value of the synchronization determination counter is equal to or smaller than the threshold value in step S20, an instruction is given to maintain the current measurement cycle (S29).
[0032]
FIG. 8 shows an example of the transition of the status flag and the count value of the synchronization determination counter in the processing procedure shown in FIGS. FIG. 8 corresponds to the operation of FIG. 5, and the broken line indicates the change of the status flag, and the value of the status flag is shown on the right side of the figure. Further, the solid line in FIG. 8 shows the change in the count value of the synchronization determination counter, and the count value is shown on the left side of the figure. In the illustrated example, the status flag is “1” four times continuously at the left end, and the count value of the synchronization determination counter is 4 beyond the threshold value of 3, so the instantaneous flow rate is four times consecutively. It means that the intermediate value was not crossed. Therefore, another measurement cycle is selected at this time. After the measurement cycle is changed, the count value of the synchronization determination counter does not exceed 3, so that it can be considered that the measurement cycle is not synchronized with the pulsation cycle. That is, the influence of pressure pulsation can be removed from the gas usage obtained by integrating the output of the integrated flow rate calculation unit 20c with the buffer 20d, and the measurement error of the gas usage can be suppressed. In other words, when the pressure of the gas passing through the instantaneous flow rate measuring unit 4 includes a periodic pulsation component, the average of the instantaneous flow rate measured by the instantaneous flow rate measuring unit 4 is a measurement cycle that is a non-integer multiple of the pulsation cycle. The measurement cycle in which the value converges with time has been selected.
[0033]
Incidentally, the upper peak value and the lower peak value may be set by a method other than the method described above. For example, even if the maximum value of a plurality of (for example, 10) instantaneous flow rates measured every predetermined time (for example, 30 sec) is set as the upper peak value and the minimum value is adopted as the lower peak value. Good. In this case, instead of providing the first peak detection means 25b and the second peak detection means 25c as described above, a peak detection means for obtaining the maximum value and the minimum value of the instantaneous flow rate may be provided. Here, the predetermined time described above is sufficient as long as it is a time for acquiring the number of instantaneous flow rates for which the intermediate value can be obtained, and the sampling number of the instantaneous flow rates may be 10 to 20. Since the measurement cycle, which is a sampling interval, is usually about 1 to 5 seconds, the above-mentioned predetermined time is a value between 10 and 100 seconds. As a preferred example, the measurement cycle is about 3 seconds. In this case, the above-mentioned predetermined time is about 30 to 60 seconds.
[0034]
Furthermore, in the above-described embodiment, the intermediate value is set as an average value of the upper peak value and the lower peak value, but a moving average of the instantaneous flow rate set every predetermined time may be used as the intermediate value. The predetermined time in this case may be set to be approximately the same as the predetermined time when the maximum value and the minimum value of the instantaneous flow rate are the upper peak value and the lower peak value, respectively. Further, since the moving average is used, the processing for obtaining the upper peak value and the lower peak value is not necessary.
[0035]
In the above-described embodiment, the instantaneous flow rate measuring unit 4 is configured by an ultrasonic flow meter. However, the measurement principle is not particularly limited as long as the instantaneous flow rate can be measured. Further, when measuring the instantaneous flow rate using an ultrasonic flow meter, a single-around method may be used. Moreover, although the example which measures the flow volume of gas was shown in the above-mentioned embodiment, it is also possible to apply the technique of this invention to fluids other than gas.
[0036]
【The invention's effect】
  Invention of Claim 1According to the configuration ofInstantaneous flow rate measured intermittently in the synchronization judgment unitIs a ruleMultiple timesMeasureBetweenDepending on whether the magnitude relationship between the intermediate value and the instantaneous flow rate is reversed,It is possible to determine whether or not the influence of pressure pulsation can be eliminated by integrating instantaneous flow rate, and in an environment where pressure pulsation occurs, a measurement cycle that is not an integral multiple of the pulsation cycle among multiple types of measurement cycles Can be selected in a relatively short time such that the instantaneous flow rate is measured a plurality of times.That is, the instantaneous flow rate measured for each instantaneous flow rate is compared with the intermediate value, and if the magnitude relationship between the instantaneous flow rate and the intermediate value does not reverse during the continuous multiple measurements, the measurement cycle is The measurement cycle can be changed by determining that there is a possibility of synchronization with the pulsation cycle. In addition, as described in the embodiment, the possibility of synchronization between the measurement period and the pulsation period can be determined by measuring the instantaneous flow rate about four times. Therefore, the measurement period that is not synchronized with the pulsation period can be shortened. You can choose by time.
[0037]
According to a second aspect of the present invention, in the first aspect of the invention, when the instantaneous flow rate at the time of the previous measurement is smaller than the intermediate value, the peak detecting means determines the instantaneous flow rate if the instantaneous flow rate measured this time is larger than the intermediate value. If the instantaneous flow rate measured this time is smaller than the lower peak value, the first peak detection means that uses this instantaneous flow rate as the lower peak value, and the instantaneous flow rate at the previous measurement is greater than the intermediate value In addition, if the instantaneous flow rate measured this time is larger than the upper peak value, the instantaneous flow rate is set as the upper peak value, and if the instantaneous flow rate measured this time is smaller than the intermediate value, the second peak detection is performed using the instantaneous flow rate as the lower peak value. The intermediate value obtained between the upper peak value and the lower peak value is the center of the flow rate fluctuation by obtaining the upper peak value and the lower peak value by this configuration. Made to an appropriate value in the near. In short, by determining the change in the instantaneous flow rate with respect to the intermediate value thus determined, it is possible to accurately determine whether or not the influence of the pressure pulsation by the integration of the instantaneous flow rate can be removed.
[0038]
According to a third aspect of the present invention, in the first aspect of the present invention, the peak detecting means sets the maximum value of a plurality of instantaneous flow rates measured every set predetermined time as the upper peak value and sets the minimum value as the lower value. The peak value is used, and the upper peak value and the lower peak value can be determined by a simple process of simply obtaining the maximum value and the minimum value of the instantaneous flow rate for each predetermined time.
[0039]
According to a fourth aspect of the present invention, in the first to third aspects of the invention, the intermediate value setting means sets an average value of the upper peak value and the lower peak value as an intermediate value. Calculation to set a value is easy.
[0040]
  Invention of Claim 5According to the configurationSet the moving average of instantaneous flow rate every hour as an intermediate valueFromIn addition to the effect similar to that of the first aspect of the invention, the use of the moving average prevents the fluctuation of the intermediate value due to the sudden fluctuation of the instantaneous flow rate.
[0041]
A sixth aspect of the present invention is the invention according to any one of the first to fifth aspects, further comprising an integrating means for obtaining an integrated flow rate from the instantaneous flow rate and the measurement cycle, wherein the fluid is a gas and is applicable to a gas meter. Can provide.
[Brief description of the drawings]
FIG. 1 is a principal block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a gas meter using the same as above.
FIG. 3 is an operation explanatory diagram of the above.
FIG. 4 is an operation explanatory view of the above.
FIG. 5 is an operation explanatory view of the above.
FIG. 6 is an operation explanatory view of the above.
FIG. 7 is an operation explanatory diagram of the above.
FIG. 8 is an operation explanatory view of the above.
[Explanation of symbols]
4 Instantaneous flow rate measurement unit
20a Measurement timing generator
25 Synchronization judgment part
25a Intermediate value setting means
25b First peak detecting means
25c Second peak detecting means
25d Measuring cycle changing means

Claims

An instantaneous flow rate measurement unit that measures the instantaneous flow rate of the fluid that is disposed in the fluid flow path, and a measurement cycle that includes a plurality of types of measurement cycles and selectively selects the measurement cycle from the plurality of types of measurement cycles. A measurement timing generation unit that instructs the instantaneous flow rate measurement unit to measure the instantaneous flow rate, and a synchronization determination unit that instructs the measurement timing generation unit to change the measurement cycle,
The synchronization determination unit includes a peak detection unit for obtaining an upper peak value and a lower peak value from a time series of the instantaneous flow rate measured by the instantaneous flow rate measurement unit, and between the upper peak value and the lower peak value. The intermediate value setting means for setting the intermediate value and the instantaneous flow rate measured for each instantaneous flow rate are compared with the intermediate value, and the magnitude relationship between the instantaneous flow rate and the intermediate value is measured during continuous multiple measurements. A flow meter comprising: a measurement cycle changing unit that instructs the measurement timing generation unit to change the measurement cycle when not reversing .

When the instantaneous flow rate at the time of the previous measurement is smaller than the intermediate value, the peak detection means sets the instantaneous flow rate as the upper peak value if the instantaneous flow rate measured this time is larger than the intermediate value, and the instantaneous flow rate measured this time is the lower peak value. If the instantaneous flow rate measured this time is larger than the upper peak value when the instantaneous flow rate at the previous measurement is larger than the intermediate value when the instantaneous flow rate at the previous measurement is larger than the intermediate value, 2. The second peak detecting means according to claim 1, further comprising: a second peak detection unit that sets the instantaneous flow rate as an upper peak value and sets the instantaneous flow rate as a lower peak value if the instantaneous flow rate measured this time is smaller than an intermediate value. Flowmeter.

2. The peak detecting means according to claim 1, wherein a maximum value of a plurality of instantaneous flow rates measured at a set predetermined time is set as an upper peak value and a minimum value is set as a lower peak value. Flowmeter.

The flowmeter according to any one of claims 1 to 3, wherein the intermediate value setting means sets an average value of the upper peak value and the lower peak value as an intermediate value.

An instantaneous flow rate measurement unit that measures the instantaneous flow rate of the fluid that is disposed in the fluid flow path, and a measurement cycle that includes a plurality of types of measurement cycles and selectively selects the measurement cycle from the plurality of types of measurement cycles. The measurement timing generation unit that instructs the instantaneous flow rate measurement unit to measure the instantaneous flow rate, and the synchronization determination unit that instructs the measurement timing generation unit to change the measurement cycle. instantaneous flow rate between performing an intermediate value setting means for setting a moving average of instantaneous flow rate of each as an intermediate value, a plurality of measurements of provisions for comparing the instantaneous flow rate instantaneous flow rate and an intermediate value measured for each measurement of continuous And a measurement cycle changing means for instructing the measurement timing generation unit to change the measurement cycle when the magnitude relationship between the intermediate value and the intermediate value is not reversed .

The flowmeter according to claim 1, further comprising an integrating unit that obtains an integrated flow rate from the instantaneous flow rate and the measurement cycle, wherein the fluid is a gas.