JP4154274B2

JP4154274B2 - Gas concentration detection method and gas concentration detection device

Info

Publication number: JP4154274B2
Application number: JP2003105593A
Authority: JP
Inventors: 浩昭杉山; 康雄石川
Original assignee: Riken Keiki KK
Current assignee: Riken Keiki KK
Priority date: 2003-04-09
Filing date: 2003-04-09
Publication date: 2008-09-24
Anticipated expiration: 2023-04-09
Also published as: JP2004309391A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば、非分散型赤外線吸収法を利用した、ガス濃度検出方法およびガス濃度検出装置に関する。
【０００２】
【従来の技術】
現在、例えば、毒性ガスや可燃性ガスなどを検知するガス検知装置の一として、例えば、一定の光路長を有する測定用チャンバを備え、この測定用チャンバの一端側に赤外線発光素子が配置されると共に他端側に受光素子が配置されて構成されてなり、検知対象ガスによって赤外線が吸収されることによる赤外線光量の減衰の程度に応じて当該検知対象ガスの濃度を検出する、非分散型赤外線吸収法を利用した赤外線式ガス検知装置が用いられており、このような赤外線式ガス検知装置は多数提案されている（例えば、特許文献１等参照。）。
【０００３】
このような赤外線式ガス検知装置においては、例えば、濃度が既知であり、しかも互いに検知対象ガス（特定成分）の濃度が異なる複数の標準ガスを用いて、基準となる検量線データを予め取得しておき、この検量線データを実際の測定条件（例えば温度条件等）に即したものに校正し、これにより得られた検量線データに基づいて受光素子による出力値に応じた検知対象ガスの濃度が検出される。
【０００４】
【特許文献１】
特開平９−１９６８４６号公報
【０００５】
【発明が解決しようとする課題】
一般に、被検ガス中における検知対象ガスの濃度を検出するに際して用いられる検量線データは温度依存性を有し、被検ガスの温度によってその出力特性が異なり（出力波形が互いに相似形ではない）、しかも、例えば２つの温度値間の温度領域における平均出力変化率が濃度値によって異なることが知られている。
そのため、例えば、被検ガスの実測温度の、検量線データに係る基準温度に対する温度差のみを考慮して検量線データを一律の補正量で補正して検知対象ガスの濃度を検出する構成のものであれば、得られるガス濃度値は信頼性の低いものとなる。特に、高濃度の検知対象ガスに対しては、測定誤差が一層大きなものとなり、信頼性の高いガス検知を確実に行うことが困難である。
【０００６】
そこで、本発明は、検知対象ガスの濃度を、精確に、かつ、高い信頼性で検出することができる新規なガス濃度検出方法を提供することを目的とする。
また、本発明の他の目的は、信頼性の高いガス検知を確実に行うことができるガス濃度検出装置を提供することにある。
【０００７】
【課題を解決するための手段】
本発明のガス濃度検出方法は、ガスセンサーについて予め取得しておいた基準温度における出力値−ガス濃度値間の関係を示す検量線データを温度補正することにより被検ガスの実測温度における補正検量線データを取得し、ガスセンサーにより実際に得られる検出出力値を当該補正検量線データに対照することによりガス濃度値を得る方法であって、
補正検量線データは、基準温度における出力値を、当該出力値に応じた濃度値と、被検ガスの温度と前記基準温度との間の温度領域における平均出力変化率の大きさとによって定まる出力補正量で、補正することにより補正出力値を求める出力値補正処理が、前記基準温度における検量線データに係る測定レンジの濃度範囲について行われることにより取得されるものであることを特徴とする。
【０００８】
本発明のガス濃度検出方法においては、基準温度における出力値を補正するための出力補正量は、下記（１）、（２）の手順によって得ることができる。
（１）基準温度における出力値と、当該出力値に応じた濃度値を予め取得しておいた前記基準温度と異なる参照温度における検量線データに対照することにより求められる参照出力値との差分の大きさによる、前記基準温度と参照温度との間の温度領域における平均出力変化率を求める手順。
（２）この平均出力変化率に基づいて、前記基準温度または参照温度と被検ガスの温度との温度差の大きさに応じた出力補正量を求める手順。
【０００９】
また、本発明のガス濃度検出方法においては、基準温度における出力値を補正するための出力補正量は、下記（１）〜（４）の手順によって得ることもできる。
（１）基準温度における出力値と、当該出力値に応じた濃度値を予め取得しておいた前記基準温度より低い第１の参照温度における検量線データに対照することにより求められる第１の参照出力値との差分の大きさによる、前記基準温度と参照温度との間の第１の温度領域における第１の平均出力変化率を求める手順。
（２）前記濃度値を予め取得しておいた前記基準温度より高い第２の参照温度における検量線データに対照することにより求められる第２の参照出力値と、前記基準温度における出力値との差分の大きさによる、前記基準温度と第２の参照温度との間の第２の温度領域における第２の平均出力変化率を求める手順。
（３）第１の平均出力変化率と第２の平均出力変化率との総合平均出力変化率を求める手順。
（４）総合平均出力変化率に基づいて、前記基準温度、第１の参照温度または第２の参照温度と被検ガスの温度との温度差の大きさに応じた出力補正量を求める手順。
【００１０】
本発明のガス濃度検出方法においては、出力値補正処理を測定レンジの濃度範囲における複数の濃度値について行い、
ガスセンサーにより実際に得られる検出出力値を補正検量線データに対照するに際して、当該検出出力値と一致する補正出力値が存在しない場合には、当該検出出力値に隣接する２つの補正出力値間を補間することによりガス濃度値を得るよう設定されている。
【００１１】
さらに、本発明のガス濃度検出方法においては、基準温度における出力値を補正すべき出力補正量を、当該出力値に応じた濃度値と、被検ガスの温度と基準温度または参照温度との温度差の大きさとに基づいて、規格化した補正量データを設定しておき、
基準温度における出力値を補正するに際しては、当該出力値に応じた濃度値と、被検ガスの温度と基準温度との温度差の大きさとに応じて選定される出力補正量が用いられるよう設定することができ、補正量データは、被検ガスの温度と基準温度または参照温度との温度差の大きさに係る温度値が均一な大きさの温度幅で設定されたものであり、当該温度幅の大きさが０．１〜２℃であることが好ましい。
以上においては、参照温度がその基準温度に対する温度差が１０〜４０℃となる温度範囲内において設定されていることが好ましい。
【００１２】
本発明のガス濃度検出方法は、被検ガスが供給されたときに得られるガスセンサーの検出出力値を当該ガスセンサーについて予め取得しておいた基準温度における検出出力値−ガス濃度値間の関係を示す検量線データに対照することにより基準ガス濃度値を求め、この基準ガス濃度値を前記被検ガスの温度に基づいて補正することにより温度補正された補正ガス濃度値を得る方法であって、
前記基準ガス濃度値を、前記ガスセンサーの検出出力値の大きさと、前記被検ガスの温度と前記基準温度との間の温度領域における平均濃度変化率の大きさとによって定まる濃度補正量で補正することにより補正ガス濃度値を求めるガス濃度値補正処理が、前記基準温度における検量線データに係る測定レンジの濃度範囲について行われることを特徴とする。
【００１３】
本発明のガス濃度検出方法においては、基準ガス濃度値を補正するための濃度補正量は、下記（１）〜（３）の手順によって得ることができる。
（１）ガスセンサーの検出出力値を、当該ガスセンサーについて予め取得しておいた前記基準温度と異なる参照温度における検量線データに対照して参照ガス濃度値を求める手順。
（２）この参照ガス濃度値と基準ガス濃度値との差分の大きさによる、前記基準温度と参照温度との間の温度領域における平均濃度変化率を求める手順。
（３）この平均濃度変化率に基づいて、前記基準温度または参照温度と被検ガスの温度との温度差の大きさに応じた濃度補正量を求める手順。
【００１４】
また、本発明のガス濃度検出方法においては、基準ガス濃度値を補正するための濃度補正量は、下記（１）〜（３）の手順によって得ることもできる。
（１）ガスセンサーの検出出力値を、当該ガスセンサーについて予め取得しておいた前記基準温度より低い第１の参照温度における検量線データに対照して第１の参照ガス濃度値を求めると共に、
ガスセンサーの検出出力値を当該ガスセンサーについて予め取得しておいた前記基準温度より高い第２の参照温度における検量線データに対照して第２の参照ガス濃度値を求める手順。
（２）第１の参照ガス濃度値と基準ガス濃度値との差分の大きさによる、前記基準温度と第１の参照温度との間の第１の温度領域における第１の平均濃度変化率を求めると共に、
第２の参照ガス濃度値と基準ガス濃度値との差分の大きさによる、前記基準温度と第２の参照温度との間の第２の温度領域における第２の平均濃度変化率を求め、
更に、第１の平均濃度変化率と第２の平均濃度変化率との総合平均濃度変化率を求める手順。
（３）総合平均濃度変化率に基づいて、前記基準温度、第１の参照温度または第２の参照温度と被検ガスの温度との温度差の大きさに応じた濃度補正量を求める手順。
【００１５】
本発明のガス濃度検出方法においては、基準ガス濃度値を補正すべき濃度補正量を、基準温度における検出出力値と、被検ガスの温度と基準温度または参照温度との温度差の大きさとに基づいて、規格化した補正量データを設定しておき、基準ガス濃度値を補正するに際しては、基準温度における検出出力値と、被検ガスの温度と基準温度との温度差の大きさとに応じて選定される濃度補正量が用いられるよう設定することができ、補正量データは、被検ガスの温度と基準温度または参照温度との温度差の大きさに係る温度値が均一な大きさの温度幅で設定されたものであり、当該温度幅が０．１〜２℃であることが好ましい。
以上においては、参照温度がその基準温度に対する温度差が１０〜４０℃となる温度範囲内において設定されていることが好ましい。
【００１６】
本発明のガス濃度検出装置は、ガスセンサーと、このガスセンサーに供給される被検ガスの温度を検出する温度センサーと、当該ガスセンサーについて予め取得しておいた基準温度における検量線データを温度補正することにより被検ガスの温度における補正検量線データを取得し、ガスセンサーにより実際に得られる検出出力値を当該補正検量線データに対照することによりガス濃度値を得る出力値補正手段と、この出力値補正手段によって得られるガス濃度値を表示するガス濃度表示手段とを有してなり、
前記出力値補正手段は、基準温度における出力値を、当該出力値に応じた濃度値と、前記温度センサーからの被検ガスの検出温度値と基準温度との間の温度領域における平均出力変化率の大きさとによって定まる出力補正量で、補正することにより補正出力値を求める出力値補正処理を、基準温度における検量線データに係る測定レンジの濃度範囲について行うことにより補正検量線データを取得する機能を有するものであることを特徴とする。
【００１７】
本発明のガス濃度検出装置においては、少なくとも基準温度における検量線データが記憶された記憶部を備え、
当該記憶部には、基準温度における出力値を補正すべき出力補正量が、当該出力値に応じた濃度値と、被検ガスの温度と基準温度または参照温度との温度差の大きさとに基づいて、規格化された補正量データが記憶されており、
出力値補正手段は、基準温度における出力値を補正すべき出力補正量を、当該出力値に応じた濃度値と、被検ガスの温度と基準温度との温度差の大きさとに応じて、選定する機能を有する構成とすることができる。
【００１８】
本発明のガス濃度検出装置は、ガスセンサーと、このガスセンサーに供給される被検ガスの温度を検出する温度センサーと、前記ガスセンサーにおいて得られる検出出力値を、当該ガスセンサーについて予め取得しておいた基準温度における検出出力値−ガス濃度値間の関係を示す検量線データに対照することにより基準ガス濃度値を求め、この基準ガス濃度値を前記温度センサーからの検出温度値に応じて補正することにより温度補正された補正ガス濃度値を得る出力値補正手段と、この出力値補正手段によって得られる補正ガス濃度値を表示するガス濃度表示手段とを有してなり、
前記出力値補正手段は、基準ガス濃度値を、前記ガスセンサーからの検出出力値と、前記温度センサーからの検出温度値と前記基準温度との間の温度領域における平均濃度変化率の大きさとによって定まる濃度補正量で補正することにより補正ガス濃度値を求めるガス濃度値補正処理を、基準温度における検量線データに係る測定レンジの濃度範囲について行う機能を有するものであることを特徴とする。
【００１９】
本発明のガス濃度検出装置においては、少なくとも基準温度における検量線データが記憶された記憶部を備え、
当該記憶部には、基準ガス濃度を補正すべき濃度補正量が、基準温度における検出出力値と、被検ガスの温度と基準温度または参照温度との温度差の大きさとに基づいて、規格化された補正量データが記憶されており、
出力値補正手段は、基準ガス濃度を補正すべき濃度補正量を、検出出力値と、被検ガスの温度と基準温度との温度差の大きさとに応じて、選定する機能を有する構成とすることができる。
【００２０】
【作用】
本発明のガス濃度検出方法によれば、基準温度における出力値が、当該出力値に応じた濃度値と、被検ガスの温度と基準温度との温度差の大きさとによって定められた出力補正量で、補正されることにより、濃度値による出力補正量に対する影響の程度が補償された状態において、温度についての出力補正が行われるので、得られる補正検量線データは、精確で、かつ、高い信頼性を有するものとなり、従って、ガスセンサーにより実際に得られる検出出力値を補正検量線データに対照することにより、被検ガス中に含まれる検知対象ガスの濃度が精確に検出される。
【００２１】
また、本発明のガス濃度検出方法によれば、ガスセンサーにより実際に得られる検出出力値を基準温度における検量線データに対照することにより得られる基準ガス濃度値が、当該検出出力値と、被検ガスの温度と基準温度との温度差の大きさとによって定められた濃度補正量で、補正されることにより、検出出力値による濃度補正量に対する影響の程度が補償された状態において、温度についての濃度補正が行われるので、得られるガス濃度値は、精確で、かつ、高い信頼性を有するものとなる。
【００２２】
本発明のガス濃度検出装置によれば、特定のガス濃度検出方法が実行されることにより、被検ガス中に含まれる検知対象ガスの濃度が、精確に、かつ、高い信頼性で検出されるので、所期のガス検知を確実に行うことができる。
【００２３】
【発明の実施の形態】
以下、本発明について図面を参照して詳細に説明する。
＜第１実施形態＞
図１は、本発明に係る赤外線式ガス検知装置の一例における構成の概略を示す説明図である。
この赤外線式ガス検知装置は、目的とするガス検知が行われるべき被検ガス中に含まれる検知対象ガス（特定成分）についてのガス検知動作を行うガス検知部１０と、ガス検知部１０によるガス検知信号などの種々の信号に基づいて、赤外線式ガス検知装置における各構成部に適宜の動作指令信号を発する機能を有すると共にガス検知部１０によるガス検知信号に応じたガス濃度を検出する機能を有する制御処理部２０と、この制御処理部２０により検出された検知対象ガスの濃度が表示される表示部４０とを備えている。
【００２４】
ガス検知部１０は、ガス検知が行われるべき対象となる被検ガスが導入される例えば筒状の測定用チャンバ１１と、この測定用チャンバ１１の一端側（図１において左端側）に設けられた赤外線光源１２と、測定用チャンバ１１の他端側（図１において右端側）に赤外線光源１２と対向するよう設けられた、光学フィルタ１３Ｂが一端側に設けられてなる赤外線センサユニット１３とを有してなる。
測定用チャンバ１１には、ガス導入口１１Ａおよびガス排出口１１Ｂが互いに赤外線光源１２の光軸方向（図１において左右方向）に離間して並ぶよう形成されており、この例においては、検知対象ガスの流過方向（他端側から一端側に向かう方向）と、図１において矢印で示されている赤外線光源１２による赤外線の放射方向とが互いに対向する状態とされている。ここに、測定用チャンバ１１の光軸方向の長さ（セル長）は、目的に応じて適宜設定することができる。
【００２５】
赤外線光源１２は、後述する制御処理部２０における光源駆動回路２１によって、例えばパルス電流が供給されることにより点滅周期が制御された状態で、点滅駆動され、これにより、赤外線が周期的に赤外線センサユニット１３に供給される。
【００２６】
赤外線センサユニット１３を構成する赤外線センサ１３Ａは、例えば焦電型赤外線センサにより構成されており、赤外線光源１２からの赤外線が供給される周期を基準周期とする出力信号（以下、「ガス検知信号」ともいう。）を出力するものである。
赤外線センサユニット１３を構成する光学フィルタ１３Ｂは、検知対象ガスのガス分子固有の吸収波長域の赤外線に対してのみ高い透過率を有するものよりなり、例えばバンドパス・フィルターにより構成されている。
【００２７】
制御処理部２０は、上述したように、赤外線センサ１３Ａによるガス検知信号（検出出力値）に応じたガス濃度値を検出してその結果を表示部４０に出力する機能を有するものであり、例えば、赤外線光源１２を所定の周期で点滅駆動させる光源駆動回路２１と、赤外線センサ１３Ａによるガス検知信号を増幅させる増幅回路２２と、当該赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０における検量線データ（以下、「基準検量線データ」という。）が設定された記憶部２３と、赤外線式ガス検知装置を構成する各構成部の動作制御を行うと共に、基準検量線データを温度補正することにより補正検量線データを取得し、赤外線センサ１３Ａによる検出出力値を補正検量線データに対照することによりガス濃度値を検出する出力値補正手段として機能するＣＰＵ３０とを備えている。
【００２８】
記憶部２３に設定された基準検量線データは、次のようにして取得されたものである。すなわち、図２に示されているように、例えば２０℃を基準温度Ｔ０として設定し、この基準温度Ｔ０における、検知対象ガスの濃度が既知であり、しかも互いに濃度が異なる複数の標準ガス（例えば０〜１００体積％の濃度範囲（測定レンジ）内の例えば１０体積％毎の１０種類の標準ガス）の各々を、測定用チャンバ１１に順次に供給することによりガス濃度値と検出出力値との関係を示す実測値（１０ポイント）を取得すると共に、得られた実測値を例えば多項式で曲線近似し、これにより得られた近似曲線を用いて隣接する実測値間を補間することにより予測値を取得し、これにより、測定レンジの全濃度範囲における検量線データＫ０が取得される。
基準温度は、特に限定されるものではなく、例えばガス検知装置が使用される環境条件などによって適宜に設定することができる。
【００２９】
記憶部２３には、基準温度Ｔ０における任意の出力値を温度補正すべき出力補正量が、基準温度Ｔ０と温度検知手段により得られる温度値（被検ガスの実測温度）Ｔとの温度差の大きさと、出力値に応じた濃度値とに基づいて規格化された補正量データが設定されている。
【００３０】
補正量データは、被検ガスの温度と基準温度または参照温度との温度差の大きさに係る温度値が均一な大きさの温度幅で設定されると共に、濃度値が均一な大きさの濃度幅で設定されたものであり、温度幅の大きさおよび濃度幅の大きさは目的に応じて適宜に設定することができる。
補正量データにおける温度幅の大きさは０．１〜２℃であることが好ましく、また、濃度幅の大きさは、例えば０〜１００体積％の濃度範囲の測定レンジにおいては０．１〜１体積％であることが好ましい。これにより、精確で、高い信頼性を有する補正検量線データを確実に得ることができる。
【００３１】
出力補正量は、下記（１）〜（２）の手順により得られる。例えば、基準温度Ｔ０における出力値Ｃ０の出力補正量を取得する場合について、図２を参照して説明する。
【００３２】
手順（１）；基準温度Ｔ０における出力値Ｃ０に応じた濃度値Ｘを、赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０と異なる参照温度Ｔ１（例えば０℃）における検量線データＫ１に対照することにより参照温度Ｔ１における参照出力値Ｃ１を取得し、濃度値Ｘについての、基準温度Ｔ０における出力値Ｃ０と参照温度Ｔ１における参照出力値Ｃ１との差分ΔＣの大きさによる、基準温度Ｔ０（２０℃）と参照温度Ｔ１（０℃）との間の温度領域における平均出力変化率α１を求める手順。
手順（２）；この平均出力変化率α１に基づいて、基準温度Ｔ０または参照温度Ｔ１と、目的に応じて適宜に設定される温度値Ｔとの温度差の大きさΔＴに応じた出力補正量Ｒを下記式１により求める手順。
【００３３】
【数１】

【００３４】
上記のような処理を、例えば０〜１００体積％の濃度範囲の測定レンジ内において、目的に応じて適宜に設定される複数の濃度値、および目的に応じて適宜に設定される複数の温度値について行うことにより、補正量データを得ることができる。
【００３５】
参照温度Ｔ１は、その基準温度Ｔ０に対する温度差が１０〜４０℃となる温度範囲内において設定された温度値であることが好ましい。これにより、基準温度Ｔ０における出力値を補正すべき出力補正量を精確に取得することができる。
【００３６】
以上において、検知対象ガスの種類は特に限定されるものではなく、例えばＣＨ₄、ＣＯ₂、ＣＯ、ＣＦ₄、ＩＰＡ、メタノール、エタノール、Ｃ₃Ｈ₈、Ｃ₂Ｈ₆、Ｃ₅Ｈ₁₂、ｎ−Ｃ₆Ｈ₁₄等を例示することができ、目的とする検知対象ガスの種類に応じて光学フィルタ１３Ｂを適宜選択すると共に当該検知対象ガスについての基準検量線データを予め取得しておけばよい。
【００３７】
この赤外線式ガス検知装置においては、次のようにしてガス検知動作が行われる。すなわち、ガス検知動作を行うに際しては、赤外線光源１２がその点滅周期が制御された状態で光源駆動回路２１によって点滅駆動され、赤外線光源１２から放射された赤外線は、赤外線センサユニット１３における光学フィルタ１３Ｂにより検知対象ガスにより吸収される特定の波長領域以外の赤外線が除去された状態で、赤外線センサ１３Ａに周期的に受光され、これにより、赤外線センサ１３Ａにより検出される赤外線量に応じたガス検知信号が出力され、この状態において、例えば環境雰囲気の空気などの被検ガスが測定用チャンバ１１に導入される。そして、赤外線センサ１３Ａから出力されたガス検知信号は、増幅回路２２によって出力電圧値が増幅された状態でＣＰＵ３０に入力される。
一方、例えば測定用チャンバ１１の外面におけるガス導入口１１Ａの近傍に設けられた例えばサーミスタなどの温度センサー（図示せず）によってガス検知装置の周囲の温度が計測され、その検出温度値がＣＰＵ３０に入力される。ここに、ガス検知装置の周囲の温度は、測定用チャンバ１１に導入される被検ガスの温度と実質的に一致するものである。
【００３８】
そして、図３に示されているように、ＣＰＵ３０によって、赤外線センサ１３Ａによるガス検知信号に対して、赤外線光源１２の点滅周期よりも短い周期でデジタル変換して積分することにより出力単位（面積値）を算出する出力単位算出処理が行われ、これにより得られた出力単位を最大値が例えば１００体積％の測定レンジにおける出力値（フルスケール換算値）に換算する変換処理が行われ、その後、基準検量線データを温度補正して被検ガスの実測温度における補正検量線データを取得する出力値補正処理（検量線データ校正処理）が行われる。
この出力値補正処理においては、先ず、補正量データに係る各々の濃度値に応じた、基準温度Ｔ０における出力値の各々に対応する出力補正量が、温度センサーにより得られた被検ガスの検出温度値と基準温度Ｔ０との温度差の大きさΔＴに応じて選定され、基準温度Ｔ０における出力値が対応する出力補正量で補正されて補正検量線データが取得される。
【００３９】
そして、ガスセンサ１３Ａにより実際に得られる検出出力値（フルスケール換算値）を補正検量線データに対照する濃度算出処理が行われることによりガス濃度値が得られ、その結果が表示部４０に出力される。
【００４０】
以上のように、上記構成の赤外線式ガス検知装置によれば、基準温度Ｔ０における出力値が、当該出力値に応じた濃度値と、温度センサーにより得られる検出温度値（被検ガスの温度）Ｔと基準温度Ｔ０との温度差の大きさΔＴとによって定まる出力補正量で補正されることにより、濃度値による出力補正量に対する影響の程度が補償された状態において、温度についての出力補正が行われるので、精確で、かつ、高い信頼性を有する補正検量線データを得ることができ、従って、赤外線センサ１３Ａにより実際に得られる検出出力値を補正検量線データに対照することにより、被検ガス中に含まれる検知対象ガスの濃度を精確に検出することができ、所期のガス検知を確実に行うことができる。
【００４１】
また、ガス濃度による出力変化率に対する影響の程度が大きいガス、例えばイソブタンガス（ｉ−Ｃ₄Ｈ₁₀）、二酸化炭素ガス（ＣＯ₂）などが検知対象ガスとして設定される場合に極めて有用であるが、ガス濃度による出力変化率に対する影響の程度が小さいガス、すなわちガス濃度によって出力変化率に大きな差が生じないガスについても、検量線の傾きが比較的に大きい低温時および検量線の傾きが比較的小さい高温時において、検知対象ガスの濃度を高い精度で検出することができる。
また、ガス濃度による出力変化率に対する影響の程度が小さい測定レンジについても、低温時および高温時において、検知対象ガスの濃度を高い精度で検出することができる。
【００４２】
また、基準温度Ｔ０と参照温度Ｔ１との間の温度領域以外の外挿範囲、例えば０℃以下、あるいは２０℃以上においても、実際の検量線データに即した精確な補正検量線データを得ることができるので、ガス検知が行われるべき環境条件（温度条件）による影響を受けることがなく、信頼性の高いガス検知を確実に行うことができる。
【００４３】
以上においては、基準温度Ｔ０における検量線データを温度補正して補正検量線データを取得するに際しては、以下に示す（１）〜（４）の手順によって得られる出力補正量が、濃度値と、被検ガスの温度と基準温度、第１の参照温度または第２の参照温度との温度差の大きさとに基づいて、規格化された補正量データが用いられるよう設定されていてもよい。
【００４４】
手順（１）；図２に示されているように、基準温度Ｔ０における出力値Ｃ０に応じた濃度値Ｘを、赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０より低い第１の参照温度Ｔ１（例えば０℃）における検量線データＫ１に対照することにより第１の参照温度Ｔ１における第１の参照出力値Ｃ１を取得し、濃度値Ｘについての、基準温度Ｔ０における出力値Ｃ０と第１の参照温度Ｔ１における第１の参照出力値Ｃ１との差分ΔＣ１の大きさによる、基準温度Ｔ０（２０℃）と第１の参照温度Ｔ１（０℃）との間の第１の温度領域における第１の平均出力変化率α１を下記式２により求める手順。
【００４５】
【数２】

【００４６】
手順（２）；基準温度Ｔ０における出力値Ｃ０に応じた濃度値Ｘを、赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０より高い第２の参照温度Ｔ２（例えば４０℃）における検量線データＫ２に対照することにより第２の参照温度Ｔ２における第２の参照出力値Ｃ２を取得し、濃度値Ｘについての、基準温度Ｔ０における出力値Ｃ０と第２の参照温度Ｔ２における第２の参照出力値Ｃ２との差分ΔＣ２の大きさによる、基準温度Ｔ０（２０℃）と第２の参照温度Ｔ２（４０℃）との間の第２の温度領域における第２の平均出力変化率β１を下記式３により求める手順。
【００４７】
【数３】

【００４８】
手順（３）；濃度値Ｘについての、第１の平均出力変化率α１と、第２の平均出力変化率β１との総合出力平均変化率γ１を求める手順。
【００４９】
手順（４）；この総合平均出力変化率γに基づいて、基準温度Ｔ０、第１の参照温度Ｔ１または第２の参照温度Ｔ２と、目的に応じて適宜に設定される温度値Ｔとの温度差の大きさΔＴに応じた出力補正量Ｒを下記式４により求める手順。
【００５０】
【数４】

【００５１】
上記のような処理を、測定レンジ（０〜１００体積％）内において、目的に応じて適宜に設定される複数の濃度値、および目的に応じて適宜に設定される複数の温度値について行うことにより、補正量データを得ることができる。
【００５２】
補正量データは、被検ガスの温度と基準温度または参照温度との温度差の大きさに係る温度値が均一な大きさの温度幅で設定されると共に、濃度値が均一な大きさの濃度幅で設定されたものであり、温度幅の大きさおよび濃度幅の大きさは目的に応じて適宜に設定することができる。
補正量データにおける温度幅の大きさは０．１〜２℃であることが好ましく、また、濃度幅の大きさは、例えば０〜１００体積％の濃度範囲の測定レンジにおいては０．１〜１体積％であることが好ましい。これにより、精確で、高い信頼性を有する補正検量線データを確実に得ることができる。
【００５３】
第１の参照温度Ｔ１および第２の参照温度Ｔ２は、それぞれ、基準温度Ｔ０に対する温度差が１０〜４０℃となる温度範囲内において設定された温度値であることが好ましい。これにより、基準温度Ｔ０における出力値を補正すべき出力補正量を精確に設定することができる。
【００５４】
＜第２実施形態＞
上記第１実施形態においては、基準温度Ｔ０における出力値を温度補正することにより被検ガスの温度Ｔにおける補正検量線データを取得し、赤外線センサ１３Ａによる検出出力値を補正検量線データに対照することによりガス濃度値を得る構成とされているが、赤外線センサ１３Ａによる検出出力値を基準検量線に対照することにより得られる基準ガス濃度値を所定の濃度補正量で温度補正することにより、補正ガス濃度値を得る構成とすることができる。
【００５５】
具体的には、図１に示されるガス濃度検出装置において、制御処理部２０におけるＣＰＵ３０が、赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０における基準検量線データに対照することにより基準ガス濃度値Ｘ０を求め（図４参照）、この基準ガス濃度値Ｘ０を、所定の濃度補正量で補正するガス濃度値補正処理を行う機能を有するものとされており、記憶部２３には、基準ガス濃度値Ｘ０を補正すべき濃度補正量が測定レンジにおける出力値範囲について規格化された補正量データが設定されている。
【００５６】
補正量データにおける各々の濃度補正量は、基準温度Ｔ０と温度検知手段により得られる検出温度値（被検ガスの実測温度）Ｔとの温度差と、検出出力値Ｃとによって定まるものであり、下記（１）〜（３）の手順により得られる。
【００５７】
手順（１）；図４に示されているように、赤外線センサ１３Ａによる検出出力値Ｃを、当該赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０と異なる参照温度Ｔ１における検量線データＫ１に対照して参照ガス濃度値Ｘ１を求める手順。
【００５８】
手順（２）；この参照ガス濃度値Ｘ１と基準ガス濃度値Ｘ０との差分ΔＸの大きさによる、基準温度Ｔ０と参照温度Ｔ１との間の温度領域における平均濃度変化率α２を求める手順。
【００５９】
手順（３）；この平均濃度変化率α２に基づいて、基準温度Ｔ０または参照温度Ｔ１と被検ガスの温度Ｔとの温度差の大きさΔＴに応じた濃度補正量Ｄを下記式５により求める手順。
【００６０】
【数５】

【００６１】
また、基準ガス濃度値Ｘ０を温度補正して補正ガス濃度値を取得するに際して、以下に示す（１）〜（３）の手順によって得られる濃度補正量が測定レンジにおける所定の出力値範囲について規格化された補正量データが用いられるよう設定されていてもよい。
【００６２】
手順（１）；図４に示されているように、赤外線センサ１３Ａによる検出出力値Ｃを、この赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０より低い第１の参照温度Ｔ１における検量線データＫ１に対照して第１の参照ガス濃度値Ｘ１を求めると共に、
赤外線センサ１３Ａによる検出出力値Ｃをこの赤外線センサ１３Ａについて予め取得しておいた基準温度Ｔ０より高い第２の参照温度Ｔ２における検量線データＫ２に対照して第２の参照ガス濃度値Ｘ２を求める手順。
【００６３】
手順（２）；第１の参照ガス濃度値Ｘ１と基準ガス濃度値Ｘ０との差分ΔＸ１の大きさによる、基準温度Ｔ０と第１の参照温度Ｔ１との間の第１の温度領域における第１の平均濃度変化率α２を求めると共に、
第２の参照ガス濃度値Ｘ２と基準ガス濃度値Ｘ０との差分ΔＸ２の大きさによる、基準温度Ｔ０と第２の参照温度Ｔ２との間の第２の温度領域における第２の平均濃度変化率β２を求め、
更に、第１の平均濃度変化率α２と第２の平均濃度変化率β２との総合平均濃度変化率γ２を求める手順。
【００６４】
手順（３）；この総合平均濃度変化率γ２に基づいて、基準温度Ｔ０、第１の参照温度Ｔ１または第２の参照温度Ｔ２と被検ガスの温度Ｔとの温度差の大きさΔＴに応じた濃度補正量Ｄを下記式６により求める手順。
【００６５】
【数６】

【００６６】
以上において、補正量データは、被検ガスの温度と基準温度または参照温度との温度差の大きさに係る温度値が均一な大きさの温度幅で設定されると共に、検出出力値が均一な大きさの出力幅で設定されたものであり、温度幅の大きさおよび出力幅の大きさは目的に応じて適宜に設定することができる。
補正量データにおける温度幅の大きさは０．１〜２℃であることが好ましい。これにより、精確で、高い信頼性を有する補正検量線データを確実に得ることができる。
【００６７】
上記構成のガス濃度検出装置によれば、赤外線センサ１３Ａにより実際に得られる検出出力値Ｃを基準温度Ｔ０における基準検量線データに対照することにより得られる基準ガス濃度値Ｘ０が、当該検出出力値Ｃと、被検ガスの温度Ｔと基準温度Ｔ０、第１の参照温度Ｔ１または第２の参照温度Ｔ２との温度差の大きさΔＴとによって定められた濃度補正量で、補正されることにより、検出出力値による濃度補正量に対する影響の程度が補償された状態において、温度についての濃度補正が行われるので、精確で、かつ、高い信頼性を有する補正ガス濃度値を得ることができ、従って、所期のガス検知を確実に行うことができる。
【００６８】
以上、本発明の実施形態について説明したが、本発明は上記の態様に限定されるものではなく、以下に示すような種々の変更を加えることができる。
【００６９】
（１）上記第１実施形態においては、基準温度（例えば２０℃）における出力値を温度補正することにより補正検量線データを取得するよう設定されているが、参照温度（例えば０℃または４０℃）における検量線データを温度補正して補正検量線データを取得するよう設定されていてもよい。
【００７０】
（２）第１の参照温度Ｔ１および第２の参照温度Ｔ２における検量線データが予め取得されている場合において、基準温度Ｔ０における出力値または基準ガス濃度値を補正すべき補正量は、基準温度Ｔ０と第１の参照温度Ｔ１との間の温度領域における平均変化率αと、基準温度Ｔ０と第２の参照温度Ｔ２との間の温度領域における平均変化率βとの総合平均変化率γを用いる代わりに、各々の平均変化率を用いて算出されてもよい。
例えば、第１実施形態において、２５℃（基準温度との温度差５℃）における出力補正量を取得するに際しては、２０℃および４０℃（第２の参照温度）の温度値間における温度領域に係る平均出力変化率β１を用いて、測定レンジにおける所定の濃度値毎に出力補正量が算出される。このような濃度検出方法によれば、一層、実際の検量線データに即した補正検量線データが得られる。
【００７１】
（３）基準温度における出力値または基準ガス濃度値を補正すべき出力補正量または濃度補正量を、予め算出しておいた規格化された補正量データより選定することに代えて、出力補正量または濃度補正量をガス検知動作中に演算するよう設定されていてもよく、この場合には、制御処理部におけるＣＰＵに演算機能を付与すればよい。
【００７２】
（４）基準温度または参照温度における検量線データを取得するに際しては、０〜１００体積％の濃度範囲（測定レンジ）において１０体積％毎の１０種類のガス濃度の標準ガスを用いて１０ポイントの検量線データを取得することにより行ったが、用いられる標準ガスの種類の数（取得されるべき実測値の数）は、特に制限されるものではなく適宜設定することが可能である。
また、補正量を取得するに際して用いられる、予め取得しておくべき検量線データの数、および基準温度または参照温度の温度値についても、特に制限されるものではなく、目的に応じて適宜設定することができる。
さらに、測定レンジは特に限定されるものではなく、目的とするガス検知（例えば検知対象ガスの種類等の測定条件）に応じて適宜設定することができる。
【００７３】
（５）本発明のガス濃度検出方法においては、例えば図５に示されるように、複数種類の検知対象ガスを同時に検出することが可能に構成されたものについても適用することができ、この場合には、目的とする検知対象ガスの各々について、上記と同様に、基準温度における基準検量線データを予め設定しておくと共に、補正量データを設定しておけばよい。
図５に示される赤外線式ガス検知装置は、主光路軸Ｌ１に一致する貫通孔５１の一端に集光面５２が形成されると共にこの主光路軸Ｌ１に直交する透光用通孔５３が形成された基台５０と、透光用通孔５３に発光領域が位置されるよう貫通孔５１に配置された発光手段５５と、基台５０における集光面５２に対向する位置に配置された第１チャンバ５６Ａと、透光用通孔５３に対向する位置に配置された第２チャンバ５６Ｂと、第１チャンバ５６Ａおよび第２チャンバ５６Ｂの各々の出射口側に配置された受光手段５８Ａ、５８Ｂとにより構成されている。図５において、６０Ａおよび６０Ｂは、それぞれ、第１チャンバ５６Ａおよび第２チャンバ５６Ｂに被検ガスを導入するためのガス導入口、６１Ａおよび６１Ｂは、それぞれ、第１チャンバ５６Ａおよび第２チャンバ５６Ｂから被検ガスを排出するためのガス排出口である。
【００７４】
（６）ガス濃度検出装置においては、検出される検知対象ガスの濃度が一定の基準レベル以上であることが検知された場合にＣＰＵにより警報信号が発せられる警報報知機能を備えたものとして構成することができる。
【００７５】
以下、本発明の効果を確認するために行った実験例について説明する。
＜実験例１＞
図１に示す構成に従って、試験用の赤外線式ガス検知装置を製造した。各構成部の具体的な構成は、次に示す通りである。
〔１〕測定用チャンバ（１１）；セル長が２ｍｍの円筒状のもの
〔２〕赤外線光源（１２）；１．５ｓｅｃの周期で点滅駆動されるもの
〔３〕赤外線センサ（１３Ａ）；焦電型赤外線センサ
〔４〕光学フィルタ（１３Ｂ）；下記に示す実験用ガスを構成するガス分子固有の吸収波長域の赤外線を透過するもの
〔５〕実験用ガス；イソブタンガス（ｉ−Ｃ₄Ｈ₁₀）が８０体積％（ｖｏｌ％）の割合で室内空気に含有されてなるもの
【００７６】
２０℃を基準温度（Ｔ０）、０℃を第１の参照温度（Ｔ１）、４０℃を第２の参照温度（Ｔ２）として設定し、０〜１００体積％の濃度範囲において１０体積％毎に濃度が異なる１０種類の濃度（０、１０、２０、・・・・・・、９０、１００体積％）のイソブタンガス（標準ガス）の各々を用いて１０ポイントの実測値を取得すると共に、これらの実測値を曲線近似して実測値間における０．１体積％毎の濃度値についての予測値を補間することにより取得する操作を行うことにより、０℃、２０℃、および４０℃の各々における検量線データを得た。
そして、０℃および２０℃の温度値間の第１の温度領域における平均出力変化率α１と、２０℃および４０℃の温度値間の第２の温度領域における平均出力変化率β１との総合平均変化率γ１を、０〜１００体積％の濃度範囲における０．１体積％毎の濃度値の各々について別個に算出し、その後、０．１℃毎の温度値の各々について、基準温度に対する温度差の大きさに応じた出力補正量を算出することにより、０．１℃の温度幅および０．１体積％の濃度幅で、基準温度に対する温度差の大きさと濃度値とに基づいて規格化された補正量データを得た。
以上のようにして取得された、基準温度（２０℃）における検量線データおよび補正量データを記憶部に設定した。
【００７７】
そして、１０℃の環境条件下（実験用ガスの温度が１０℃）において、基準温度に対する温度差−１０℃に応じた出力補正量を選定し、０．１体積％毎の濃度値の各々に応じた、２０℃における出力値の各々（検量線データ）を対応する出力補正量で補正して補正検量線データを取得し、赤外線センサにより実際に得られるガス検知信号に応じた検出出力値を補正検量線データに対照することによりガス濃度値を算出するよう制御処理部の動作を制御して、ガス濃度検出テストを実施したところ、検出された実験用ガスの濃度は平均値で７９．５体積％（測定誤差０．５％Ｆ．Ｓ．）であり、検知対象ガスの濃度を精確に検出することができることが確認された。ここに、測定誤差が５％Ｆ．Ｓ．の範囲内であれば、実用上問題ないものといえる。
【００７８】
＜実験例２＞
実験例１において、下記（１）、（２）のように設定を変更したことの他は実験例１と同様のガス濃度検出テストを実施したところ、検出された実験用ガスの濃度は平均値で７９．５体積％（測定誤差０．５％Ｆ．Ｓ．）であり、検知対象ガスの濃度を精確に検出することができることが確認された。
【００７９】
（１）最大値が１００体積％の測定レンジにおける任意の出力単位（面積値）毎の出力値の各々について、０℃および２０℃の温度値間の第１の温度領域における平均濃度変化率α２と、２０℃および４０℃の温度値間の第２の温度領域における平均濃度変化率β２との総合平均濃度変化率γ２を算出し、０．１℃毎の温度値の各々について、基準温度に対する温度差に対応する濃度補正量を算出することにより、０．１℃の温度幅で、基準温度に対する温度差の大きさに係る温度値と検出出力値とに基づいて規格化された補正量データを得、基準温度（２０℃）における検量線データおよび補正量データを記憶部に設定した。
（２）赤外線センサによる検出出力値を２０℃における検量線データに対照することにより基準ガス濃度値を取得し、この基準ガス濃度を当該検出出力値と、被検ガスの温度と基準温度との温度差（−１０℃）と応じた濃度補正量で補正して補正ガス濃度を算出するよう制御処理部の動作を制御した。
【００８０】
【発明の効果】
本発明のガス濃度検出方法によれば、基準温度における出力値が、当該出力値に応じた濃度値と、被検ガスの温度と基準温度との温度差の大きさとによって定められた出力補正量で補正されることにより、濃度値による出力補正量に対する影響の程度が補償された状態において、温度についての出力補正が行われるので、精確で、かつ、高い信頼性を有する補正検量線データを得ることができ、従って、ガスセンサーにより実際に得られる検出出力値を補正検量線データに対照することにより、被検ガス中に含まれる検知対象ガスの濃度を精確に検出することができる。
【００８１】
また、本発明のガス濃度検出方法によれば、ガスセンサーにより実際に得られる検出出力値を基準温度における検量線データに対照することにより得られる基準ガス濃度値が、当該検出出力値と、被検ガスの温度と基準温度との温度差とによって定められた出力補正量で、補正されることにより、検出出力値による濃度補正量に対する影響の程度が補償された状態において、温度についての濃度補正が行われるので、精確で、かつ、高い信頼性を有する補正ガス濃度値を得ることができ、被検ガス中に含まれる検知対象ガスの濃度を精確に検出することができる。
【００８２】
本発明のガス濃度検出装置によれば、特定のガス濃度検出方法が実行されることにより、被検ガス中に含まれる検知対象ガスの濃度が、精確に、かつ、高い信頼性で検出されるので、所期のガス検知を確実に行うことができる。
【図面の簡単な説明】
【図１】本発明に係る赤外線式ガス検知装置の一例における構成の概略を示す説明図である。
【図２】第１実施形態における検知対象ガスの濃度を算出するための検量線データを示す説明図である。
【図３】図１に示す赤外線式ガス検知装置の制御処理部による信号処理を示す動作フローチャート図である。
【図４】第２実施形態における検知対象ガスの濃度を算出するための検量線データを示す説明図である。
【図５】本発明に係るガス濃度検出装置の他の例における構成の概略を示す説明用断面図である。
【符号の説明】
１０ガス検知部
１１測定用チャンバ
１１Ａガス導入口
１１Ｂガス排出口
１２赤外線光源
１３赤外線センサユニット
１３Ａ赤外線センサ
１３Ｂ光学フィルタ
２０制御処理部
２１光源駆動回路
２２増幅回路
２３記憶部
３０ＣＰＵ
４０表示部
Ｋ０２０℃における検量線データ
Ｋ１０℃における検量線データ
Ｋ２４０℃における検量線データ
５０基台
５１貫通孔
５２集光面
５３透光用通孔
５５発光手段
５６Ａ第１チャンバ
５６Ｂ第２チャンバ
５８Ａ、５８Ｂ受光手段
６０Ａ、６０Ｂガス導入口
６１Ａ、６１Ｂガス排出口
Ｌ１主光路軸[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas concentration detection method and a gas concentration detection device using, for example, a non-dispersive infrared absorption method.
[0002]
[Prior art]
At present, for example, as a gas detection device that detects toxic gas, flammable gas, and the like, for example, a measurement chamber having a certain optical path length is provided, and an infrared light emitting element is disposed on one end side of the measurement chamber. In addition, a non-dispersive infrared ray is configured to detect the concentration of the detection target gas according to the degree of attenuation of the amount of infrared light due to the absorption of the infrared ray by the detection target gas. An infrared gas detector using an absorption method is used, and many such infrared gas detectors have been proposed (see, for example, Patent Document 1).
[0003]
In such an infrared gas detector, for example, a standard curve data is acquired in advance using a plurality of standard gases whose concentrations are known and whose concentrations of detection target gases (specific components) are different from each other. The calibration curve data is calibrated to the actual measurement conditions (for example, temperature conditions), and the concentration of the detection target gas according to the output value from the light receiving element based on the calibration curve data obtained thereby. Is detected.
[0004]
[Patent Document 1]
JP-A-9-196846
[0005]
[Problems to be solved by the invention]
In general, calibration curve data used for detecting the concentration of the detection target gas in the test gas has temperature dependence, and its output characteristics vary depending on the temperature of the test gas (the output waveforms are not similar to each other). Moreover, for example, it is known that the average output change rate in the temperature region between two temperature values varies depending on the concentration value.
Therefore, for example, a configuration in which the concentration of the detection target gas is detected by correcting the calibration curve data with a uniform correction amount considering only the temperature difference between the measured temperature of the test gas and the reference temperature related to the calibration curve data. If so, the obtained gas concentration value is low in reliability. In particular, for a high concentration gas to be detected, the measurement error becomes even larger, and it is difficult to reliably perform highly reliable gas detection.
[0006]
Therefore, an object of the present invention is to provide a novel gas concentration detection method capable of accurately and reliably detecting the concentration of a detection target gas.
Another object of the present invention is to provide a gas concentration detection device capable of reliably performing gas detection with high reliability.
[0007]
[Means for Solving the Problems]
In the gas concentration detection method of the present invention, calibration calibration at the measured temperature of the test gas is performed by correcting the temperature of calibration curve data indicating the relationship between the output value at the reference temperature and the gas concentration value acquired in advance for the gas sensor. A method for obtaining a gas concentration value by acquiring line data and comparing a detection output value actually obtained by a gas sensor with the corrected calibration curve data,
The corrected calibration curve data includes the output value at the reference temperature, the concentration value corresponding to the output value, the temperature of the test gas, and the reference temperature. Average output change rate in the temperature range An output value correction process for obtaining a corrected output value by performing correction with an output correction amount determined by the magnitude of the measurement value is obtained by performing the concentration range of the measurement range related to the calibration curve data at the reference temperature. It is characterized by that.
[0008]
In the gas concentration detection method of the present invention, the output correction amount for correcting the output value at the reference temperature can be obtained by the following procedures (1) and (2).
(1) The difference between the output value at the reference temperature and the reference output value obtained by comparing the calibration curve data at the reference temperature different from the reference temperature obtained in advance with the concentration value corresponding to the output value. A procedure for obtaining an average output change rate in a temperature region between the reference temperature and the reference temperature according to the magnitude.
(2) A procedure for obtaining an output correction amount in accordance with the temperature difference between the reference temperature or reference temperature and the temperature of the test gas based on the average output change rate.
[0009]
In the gas concentration detection method of the present invention, the output correction amount for correcting the output value at the reference temperature can also be obtained by the following procedures (1) to (4).
(1) The first reference obtained by comparing the output value at the reference temperature and the calibration curve data at the first reference temperature lower than the reference temperature obtained in advance with the concentration value corresponding to the output value. A procedure for obtaining a first average output change rate in a first temperature region between the reference temperature and the reference temperature based on the magnitude of the difference from the output value.
(2) A second reference output value obtained by comparing the concentration value with calibration curve data at a second reference temperature higher than the reference temperature acquired in advance, and an output value at the reference temperature A procedure for obtaining a second average output change rate in a second temperature region between the reference temperature and the second reference temperature according to the magnitude of the difference.
(3) A procedure for obtaining an overall average output change rate of the first average output change rate and the second average output change rate.
(4) A procedure for obtaining an output correction amount corresponding to the temperature difference between the reference temperature, the first reference temperature or the second reference temperature and the temperature of the test gas, based on the total average output change rate.
[0010]
In the gas concentration detection method of the present invention, the output value correction process is performed for a plurality of concentration values in the concentration range of the measurement range,
When the detected output value actually obtained by the gas sensor is compared with the corrected calibration curve data, if there is no corrected output value that matches the detected output value, the interval between the two corrected output values adjacent to the detected output value. Is set to obtain a gas concentration value by interpolating.
[0011]
Furthermore, in the gas concentration detection method of the present invention, the output correction amount to be corrected for the output value at the reference temperature is the concentration value corresponding to the output value, the temperature of the test gas and the reference temperature or reference temperature. Based on the magnitude of the difference, set standardized correction amount data,
When correcting the output value at the reference temperature, the output correction amount selected according to the concentration value according to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature is used. The correction amount data is obtained by setting a temperature value related to the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature in a uniform temperature range, and the temperature The width is preferably 0.1 to 2 ° C.
In the above, it is preferable that the reference temperature is set within a temperature range in which the temperature difference with respect to the reference temperature is 10 to 40 ° C.
[0012]
According to the gas concentration detection method of the present invention, the relationship between the detection output value at the reference temperature and the gas concentration value obtained in advance for the gas sensor is the detection output value of the gas sensor obtained when the test gas is supplied. A reference gas concentration value is obtained by contrasting with calibration curve data indicating a correction gas concentration value whose temperature is corrected by correcting the reference gas concentration value based on the temperature of the test gas. ,
The reference gas concentration value is obtained by calculating the magnitude of the detection output value of the gas sensor, the temperature of the test gas, and the reference temperature. Average concentration change rate in the temperature range between Correct with the density correction amount determined by the size of Thus, the gas concentration value correction process for obtaining the corrected gas concentration value is performed for the concentration range of the measurement range related to the calibration curve data at the reference temperature. It is characterized by that.
[0013]
In the gas concentration detection method of the present invention, the concentration correction amount for correcting the reference gas concentration value can be obtained by the following procedures (1) to (3).
(1) A procedure for obtaining a reference gas concentration value by comparing a detection output value of a gas sensor with calibration curve data at a reference temperature different from the reference temperature acquired in advance for the gas sensor.
(2) A procedure for obtaining an average concentration change rate in a temperature region between the reference temperature and the reference temperature based on the difference between the reference gas concentration value and the reference gas concentration value.
(3) A procedure for obtaining a concentration correction amount according to the temperature difference between the reference temperature or reference temperature and the temperature of the test gas based on the average concentration change rate.
[0014]
In the gas concentration detection method of the present invention, the concentration correction amount for correcting the reference gas concentration value can also be obtained by the following procedures (1) to (3).
(1) The first reference gas concentration value is obtained by comparing the detected output value of the gas sensor with the calibration curve data at the first reference temperature lower than the reference temperature acquired in advance for the gas sensor,
A procedure for obtaining a second reference gas concentration value in contrast to calibration curve data at a second reference temperature higher than the reference temperature obtained in advance for the gas sensor for the detection output value of the gas sensor.
(2) A first average concentration change rate in a first temperature region between the reference temperature and the first reference temperature, based on a difference between the first reference gas concentration value and the reference gas concentration value. Asking
Obtaining a second average concentration change rate in a second temperature region between the reference temperature and the second reference temperature according to a difference between the second reference gas concentration value and the reference gas concentration value;
Further, a procedure for obtaining a total average density change rate of the first average density change rate and the second average density change rate.
(3) A procedure for obtaining a concentration correction amount according to the temperature difference between the reference temperature, the first reference temperature, or the second reference temperature and the temperature of the test gas based on the total average concentration change rate.
[0015]
In the gas concentration detection method of the present invention, the concentration correction amount for correcting the reference gas concentration value is determined based on the detection output value at the reference temperature and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature. Based on the standardized correction amount data, the reference gas concentration value is corrected according to the detected output value at the reference temperature and the magnitude of the temperature difference between the detected gas temperature and the reference temperature. The concentration correction amount selected can be set so that the temperature value related to the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature is uniform. The temperature range is set, and the temperature range is preferably 0.1 to 2 ° C.
In the above, it is preferable that the reference temperature is set within a temperature range in which the temperature difference with respect to the reference temperature is 10 to 40 ° C.
[0016]
The gas concentration detection apparatus according to the present invention includes a gas sensor, a temperature sensor for detecting the temperature of a test gas supplied to the gas sensor, and calibration curve data at a reference temperature acquired in advance for the gas sensor. Correction value curve correction means for obtaining a gas concentration value by acquiring correction calibration curve data at the temperature of the test gas by correcting, and comparing the detection output value actually obtained by the gas sensor with the correction calibration curve data; Gas concentration display means for displaying the gas concentration value obtained by the output value correction means,
The output value correcting means calculates an output value at a reference temperature, a concentration value corresponding to the output value, a detected temperature value of a test gas from the temperature sensor, and a reference temperature. Average output change rate in the temperature range A function for obtaining corrected calibration curve data by performing output value correction processing for obtaining a corrected output value by performing correction on the concentration range of the measurement range related to the calibration curve data at the reference temperature with an output correction amount determined by the magnitude of It is characterized by having.
[0017]
In the gas concentration detection device of the present invention, at least a calibration part data at a reference temperature is stored, and a storage unit is stored.
In the storage unit, the output correction amount for correcting the output value at the reference temperature is based on the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature. Standardized correction amount data is stored,
The output value correction means selects the output correction amount to be corrected for the output value at the reference temperature according to the concentration value according to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. It can be set as the structure which has a function to do.
[0018]
The gas concentration detection device of the present invention acquires in advance for a gas sensor, a temperature sensor for detecting the temperature of the gas to be supplied to the gas sensor, and a detection output value obtained by the gas sensor for the gas sensor. The reference gas concentration value is obtained by comparing with the calibration curve data indicating the relationship between the detected output value at the reference temperature and the gas concentration value, and the reference gas concentration value is determined according to the detected temperature value from the temperature sensor. An output value correcting means for obtaining a corrected gas concentration value whose temperature is corrected by correcting, and a gas concentration display means for displaying a corrected gas concentration value obtained by the output value correcting means,
The output value correction means calculates a reference gas concentration value between a detected output value from the gas sensor, a detected temperature value from the temperature sensor, and the reference temperature. Average concentration change rate in the temperature range between Correct with the density correction amount determined by the size of Gas concentration value correction processing is performed for the concentration range of the measurement range related to the calibration curve data at the reference temperature. It has a function.
[0019]
In the gas concentration detection device of the present invention, at least a calibration part data at a reference temperature is stored, and a storage unit is stored.
In the storage unit, the concentration correction amount for correcting the reference gas concentration is normalized based on the detected output value at the reference temperature and the magnitude of the temperature difference between the detected gas temperature and the reference temperature or reference temperature. Stored correction amount data,
The output value correcting means has a function of selecting a concentration correction amount for correcting the reference gas concentration according to the detected output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. be able to.
[0020]
[Action]
According to the gas concentration detection method of the present invention, the output correction value determined by the output value at the reference temperature determined by the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. As a result of the correction, the temperature correction is performed in a state where the degree of the influence of the concentration value on the output correction amount is compensated, so that the corrected calibration curve data obtained is accurate and highly reliable. Therefore, the concentration of the detection target gas contained in the test gas is accurately detected by comparing the detection output value actually obtained by the gas sensor with the corrected calibration curve data.
[0021]
Further, according to the gas concentration detection method of the present invention, the reference gas concentration value obtained by comparing the detection output value actually obtained by the gas sensor with the calibration curve data at the reference temperature, In the state in which the degree of influence on the concentration correction amount by the detected output value is compensated by the concentration correction amount determined by the temperature difference between the detected gas temperature and the reference temperature, Since concentration correction is performed, the obtained gas concentration value is accurate and has high reliability.
[0022]
According to the gas concentration detection device of the present invention, the concentration of the detection target gas contained in the test gas is accurately and reliably detected by executing the specific gas concentration detection method. Therefore, the desired gas detection can be performed reliably.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 is an explanatory diagram showing an outline of a configuration in an example of an infrared gas detection device according to the present invention.
The infrared gas detection apparatus includes a gas detection unit 10 that performs a gas detection operation on a detection target gas (specific component) contained in a target gas to be detected, and a gas generated by the gas detection unit 10. Based on various signals such as detection signals, it has a function of issuing an appropriate operation command signal to each component in the infrared gas detection device and a function of detecting a gas concentration according to the gas detection signal from the gas detection unit 10. And a display unit 40 on which the concentration of the detection target gas detected by the control processing unit 20 is displayed.
[0024]
The gas detection unit 10 is provided, for example, in a cylindrical measurement chamber 11 into which a target gas to be subjected to gas detection is introduced, and one end side (left end side in FIG. 1) of the measurement chamber 11. An infrared light source 12 and an infrared sensor unit 13 provided on the other end side (right end side in FIG. 1) of the measurement chamber 11 so as to face the infrared light source 12 and having an optical filter 13B provided on one end side. Have.
In the measurement chamber 11, a gas inlet 11 </ b> A and a gas outlet 11 </ b> B are formed so as to be spaced apart from each other in the direction of the optical axis of the infrared light source 12 (left and right direction in FIG. 1). The gas flow direction (the direction from the other end side toward the one end side) and the infrared radiation direction by the infrared light source 12 indicated by an arrow in FIG. Here, the length (cell length) of the measurement chamber 11 in the optical axis direction can be appropriately set according to the purpose.
[0025]
The infrared light source 12 is driven to blink by a light source driving circuit 21 in a control processing unit 20 to be described later in a state where the blinking period is controlled, for example, by supplying a pulse current. It is supplied to the unit 13.
[0026]
The infrared sensor 13A constituting the infrared sensor unit 13 is constituted by, for example, a pyroelectric infrared sensor, and an output signal (hereinafter referred to as “gas detection signal”) having a reference period as a period in which infrared rays from the infrared light source 12 are supplied. Is also output).
The optical filter 13B that constitutes the infrared sensor unit 13 has a high transmittance only with respect to infrared rays in the absorption wavelength range unique to the gas molecules of the detection target gas, and is constituted by, for example, a bandpass filter.
[0027]
As described above, the control processing unit 20 has a function of detecting a gas concentration value corresponding to a gas detection signal (detection output value) from the infrared sensor 13A and outputting the result to the display unit 40. The light source driving circuit 21 that drives the infrared light source 12 to blink at a predetermined cycle, the amplification circuit 22 that amplifies the gas detection signal from the infrared sensor 13A, and the calibration curve at the reference temperature T0 acquired in advance for the infrared sensor 13A. By performing operation control of the storage unit 23 in which data (hereinafter referred to as “reference calibration curve data”) is set and each component constituting the infrared gas detection device, the reference calibration curve data is temperature-corrected. The correction calibration curve data is acquired, and the gas concentration value is detected by comparing the detection output value of the infrared sensor 13A with the correction calibration curve data. And a CPU30 which functions as a value correcting means.
[0028]
The reference calibration curve data set in the storage unit 23 is acquired as follows. That is, as shown in FIG. 2, for example, 20 ° C. is set as the reference temperature T0, and the concentration of the detection target gas at the reference temperature T0 is known and the concentrations are different from each other. By sequentially supplying each of 10 kinds of standard gases in the concentration range (measurement range) of 0 to 100% by volume to the measurement chamber 11, the gas concentration value and the detection output value are obtained. The actual measurement value (10 points) indicating the relationship is acquired, and the obtained actual measurement value is approximated by a curve, for example, using a polynomial. Thus, calibration curve data K0 in the entire concentration range of the measurement range is acquired.
The reference temperature is not particularly limited, and can be appropriately set depending on, for example, environmental conditions in which the gas detection device is used.
[0029]
In the storage unit 23, an output correction amount for correcting an arbitrary output value at the reference temperature T0 is a temperature difference between the reference temperature T0 and a temperature value (measured temperature of the test gas) T obtained by the temperature detecting means. Normalized correction amount data is set based on the size and the density value corresponding to the output value.
[0030]
In the correction amount data, the temperature value related to the temperature difference between the temperature of the test gas and the reference temperature or reference temperature is set to a uniform temperature range, and the concentration value is a uniform concentration. The temperature range and the concentration range can be appropriately set according to the purpose.
The magnitude of the temperature width in the correction amount data is preferably 0.1 to 2 ° C., and the magnitude of the density width is 0.1 to 1 in a measurement range of a concentration range of 0 to 100% by volume, for example. It is preferable that it is volume%. As a result, accurate calibration curve data having high reliability can be obtained with certainty.
[0031]
The output correction amount is obtained by the following procedures (1) to (2). For example, a case where the output correction amount of the output value C0 at the reference temperature T0 is acquired will be described with reference to FIG.
[0032]
Procedure (1): Concentration value X corresponding to output value C0 at reference temperature T0 is compared with calibration curve data K1 at reference temperature T1 (for example, 0 ° C.) different from reference temperature T0 acquired in advance for infrared sensor 13A. As a result, the reference output value C1 at the reference temperature T1 is obtained, and the reference temperature T0 (for the concentration value X, which is based on the difference ΔC between the output value C0 at the reference temperature T0 and the reference output value C1 at the reference temperature T1). 20 ° C.) and the average output change rate α1 in the temperature region between the reference temperature T1 (0 ° C.).
Step (2): Based on the average output change rate α1, the output correction amount according to the magnitude ΔT of the temperature difference between the standard temperature T0 or the reference temperature T1 and the temperature value T set appropriately according to the purpose Procedure for obtaining R by the following formula 1.
[0033]
[Expression 1]

[0034]
For example, within the measurement range of the concentration range of 0 to 100% by volume, a plurality of concentration values that are appropriately set according to the purpose and a plurality of temperature values that are appropriately set according to the purpose. By performing the above, correction amount data can be obtained.
[0035]
The reference temperature T1 is preferably a temperature value set within a temperature range in which the temperature difference with respect to the reference temperature T0 is 10 to 40 ° C. As a result, the output correction amount for correcting the output value at the reference temperature T0 can be accurately acquired.
[0036]
In the above, the kind of detection object gas is not specifically limited, For example, CH _Four , CO ₂ , CO, CF _Four , IPA, methanol, ethanol, C _Three H ₈ , C ₂ H ₆ , C _Five H ₁₂ , N-C ₆ H ₁₄ The optical filter 13B may be appropriately selected according to the type of target detection target gas, and the reference calibration curve data for the detection target gas may be acquired in advance.
[0037]
In this infrared type gas detection device, the gas detection operation is performed as follows. That is, when performing the gas detection operation, the infrared light source 12 is driven to blink by the light source driving circuit 21 in a state in which the blinking period is controlled, and the infrared rays emitted from the infrared light source 12 are optical filters 13B in the infrared sensor unit 13. In the state where infrared rays other than the specific wavelength region absorbed by the detection target gas are removed, the infrared sensor 13A periodically receives the light, and thereby the gas detection signal corresponding to the amount of infrared rays detected by the infrared sensor 13A In this state, a test gas such as air in an ambient atmosphere is introduced into the measurement chamber 11. The gas detection signal output from the infrared sensor 13 </ b> A is input to the CPU 30 with the output voltage value amplified by the amplifier circuit 22.
On the other hand, for example, a temperature sensor (not shown) such as a thermistor provided in the vicinity of the gas inlet 11A on the outer surface of the measurement chamber 11 measures the ambient temperature of the gas detector, and the detected temperature value is sent to the CPU 30. Entered. Here, the temperature around the gas detector substantially matches the temperature of the test gas introduced into the measurement chamber 11.
[0038]
Then, as shown in FIG. 3, the CPU 30 converts the gas detection signal from the infrared sensor 13 </ b> A into a digital unit at a cycle shorter than the blinking cycle of the infrared light source 12 and integrates the output unit (area value). ) Is calculated, the output unit obtained thereby is converted into an output value (full scale conversion value) in a measurement range where the maximum value is, for example, 100% by volume, An output value correction process (calibration curve data calibration process) is performed in which the temperature of the reference calibration curve data is corrected to obtain corrected calibration curve data at the actually measured temperature of the test gas.
In this output value correction process, first, an output correction amount corresponding to each output value at the reference temperature T0 corresponding to each concentration value related to the correction amount data is detected by the temperature sensor. Selection is made according to the magnitude ΔT of the temperature difference between the temperature value and the reference temperature T0, and the output value at the reference temperature T0 is corrected with the corresponding output correction amount to obtain corrected calibration curve data.
[0039]
A gas concentration value is obtained by performing a concentration calculation process in which the detection output value (full scale conversion value) actually obtained by the gas sensor 13A is compared with the corrected calibration curve data, and the result is output to the display unit 40. The
[0040]
As described above, according to the infrared gas detection device having the above configuration, the output value at the reference temperature T0 is the concentration value corresponding to the output value and the detected temperature value (temperature of the test gas) obtained by the temperature sensor. By correcting with the output correction amount determined by the magnitude of the temperature difference ΔT between T and the reference temperature T0, the output correction for the temperature is performed in a state where the degree of the influence of the density value on the output correction amount is compensated. Therefore, it is possible to obtain accurate and highly reliable corrected calibration curve data. Therefore, by comparing the detected output value actually obtained by the infrared sensor 13A with the corrected calibration curve data, The concentration of the detection target gas contained therein can be accurately detected, and the intended gas detection can be reliably performed.
[0041]
Further, a gas having a large influence on the output change rate due to the gas concentration, for example, isobutane gas (i-C _Four H _Ten ), Carbon dioxide gas (CO ₂ ) Is set as the detection target gas, but calibration is also possible for gases that have a small effect on the output change rate due to the gas concentration, that is, gases that do not cause a large difference in the output change rate due to the gas concentration. The concentration of the detection target gas can be detected with high accuracy at low temperatures where the slope of the line is relatively large and at high temperatures where the slope of the calibration curve is relatively small.
Further, even in a measurement range in which the degree of influence on the output change rate due to gas concentration is small, the concentration of the detection target gas can be detected with high accuracy at low temperatures and high temperatures.
[0042]
Also, accurate calibration curve data can be obtained in conformity with actual calibration curve data even in an extrapolation range other than the temperature range between the reference temperature T0 and the reference temperature T1, for example, 0 ° C. or less, or 20 ° C. or more. Therefore, it is possible to reliably perform highly reliable gas detection without being affected by environmental conditions (temperature conditions) in which gas detection should be performed.
[0043]
In the above, when the calibration curve data at the reference temperature T0 is temperature-corrected to obtain the corrected calibration curve data, the output correction amount obtained by the following procedures (1) to (4) is the concentration value, The standardized correction amount data may be used based on the temperature of the test gas and the reference temperature, and the magnitude of the temperature difference between the first reference temperature or the second reference temperature.
[0044]
Procedure (1): As shown in FIG. 2, the first reference temperature lower than the reference temperature T0 acquired in advance for the infrared sensor 13A, the concentration value X corresponding to the output value C0 at the reference temperature T0. The first reference output value C1 at the first reference temperature T1 is obtained by comparing with the calibration curve data K1 at T1 (for example, 0 ° C.), and the output value C0 at the reference temperature T0 and the first value for the concentration value X In the first temperature region between the reference temperature T0 (20 ° C.) and the first reference temperature T1 (0 ° C.) due to the magnitude of the difference ΔC1 from the first reference output value C1 at the reference temperature T1. A procedure for obtaining an average output change rate α1 of 1 by the following formula 2.
[0045]
[Expression 2]

[0046]
Procedure (2); calibration curve data at a second reference temperature T2 (for example, 40 ° C.) that is higher than the reference temperature T0 acquired in advance for the infrared sensor 13A with the concentration value X corresponding to the output value C0 at the reference temperature T0. The second reference output value C2 at the second reference temperature T2 is obtained by comparing with K2, and the output value C0 at the reference temperature T0 and the second reference output at the second reference temperature T2 for the concentration value X are obtained. The second average output change rate β1 in the second temperature region between the reference temperature T0 (20 ° C.) and the second reference temperature T2 (40 ° C.) depending on the magnitude of the difference ΔC2 from the value C2 is expressed by the following equation: Procedure obtained by 3.
[0047]
[Equation 3]

[0048]
Procedure (3): A procedure for obtaining a total output average change rate γ1 of the first average output change rate α1 and the second average output change rate β1 for the density value X.
[0049]
Procedure (4): Based on the total average output change rate γ, the temperature of the reference temperature T0, the first reference temperature T1, or the second reference temperature T2, and the temperature value T set appropriately according to the purpose A procedure for obtaining the output correction amount R according to the difference ΔT according to the following equation 4.
[0050]
[Expression 4]

[0051]
The above processing is performed for a plurality of concentration values appropriately set according to the purpose and a plurality of temperature values appropriately set according to the purpose within the measurement range (0 to 100% by volume). Thus, correction amount data can be obtained.
[0052]
The correction amount data is set with a temperature range in which the temperature value related to the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature is uniform. With The density value is set with a uniform density range, and the temperature range and the density range can be appropriately set according to the purpose.
The magnitude of the temperature width in the correction amount data is preferably 0.1 to 2 ° C., and the magnitude of the density width is 0.1 to 1 in a measurement range of a concentration range of 0 to 100% by volume, for example. It is preferable that it is volume%. As a result, accurate calibration curve data having high reliability can be obtained with certainty.
[0053]
Each of the first reference temperature T1 and the second reference temperature T2 is preferably a temperature value set within a temperature range in which a temperature difference with respect to the reference temperature T0 is 10 to 40 ° C. As a result, the output correction amount for correcting the output value at the reference temperature T0 can be accurately set.
[0054]
Second Embodiment
In the first embodiment, the corrected calibration curve data at the temperature T of the test gas is obtained by correcting the output value at the reference temperature T0, and the detection output value by the infrared sensor 13A is compared with the corrected calibration curve data. Thus, the gas concentration value is obtained by correcting the temperature of the reference gas concentration value obtained by comparing the detection output value of the infrared sensor 13A with the reference calibration curve by a predetermined concentration correction amount. The gas concentration value can be obtained.
[0055]
Specifically, in the gas concentration detection apparatus shown in FIG. 1, the CPU 30 in the control processing unit 20 compares the reference gas concentration by comparing the reference calibration curve data at the reference temperature T0 acquired in advance for the infrared sensor 13A. A value X0 is obtained (see FIG. 4), and this reference gas concentration value X0 is corrected by a predetermined concentration correction amount. Perform gas concentration correction processing In the storage unit 23, correction amount data in which the concentration correction amount for correcting the reference gas concentration value X0 is normalized with respect to the output value range in the measurement range is set.
[0056]
Each concentration correction amount in the correction amount data is determined by the temperature difference between the reference temperature T0 and the detected temperature value (measured temperature of the detected gas) T obtained by the temperature detecting means, and the detected output value C. It is obtained by the following procedures (1) to (3).
[0057]
Procedure (1): As shown in FIG. 4, the detection output value C from the infrared sensor 13A is converted into calibration curve data K1 at a reference temperature T1 different from the reference temperature T0 acquired in advance for the infrared sensor 13A. In contrast, a procedure for obtaining the reference gas concentration value X1.
[0058]
Procedure (2): A procedure for obtaining an average concentration change rate α2 in a temperature region between the reference temperature T0 and the reference temperature T1, based on the difference ΔX between the reference gas concentration value X1 and the reference gas concentration value X0.
[0059]
Step (3): Based on this average concentration change rate α2, a concentration correction amount D corresponding to the magnitude ΔT of the temperature difference between the reference temperature T0 or the reference temperature T1 and the temperature T of the test gas is obtained by the following equation 5. procedure.
[0060]
[Equation 5]

[0061]
Further, when the correction gas concentration value is obtained by correcting the temperature of the reference gas concentration value X0, the concentration correction amount obtained by the following procedures (1) to (3) is specified for a predetermined output value range in the measurement range. It may be set so that the normalized correction amount data is used.
[0062]
Procedure (1): As shown in FIG. 4, the calibration curve at the first reference temperature T1 that is lower than the reference temperature T0 acquired in advance for the infrared sensor 13A is the detected output value C from the infrared sensor 13A. A first reference gas concentration value X1 is obtained in contrast to the data K1, and
The second reference gas concentration value X2 is obtained by comparing the detection output value C by the infrared sensor 13A with the calibration curve data K2 at the second reference temperature T2 higher than the reference temperature T0 acquired in advance for the infrared sensor 13A. procedure.
[0063]
Procedure (2): The first in the first temperature region between the reference temperature T0 and the first reference temperature T1 according to the difference ΔX1 between the first reference gas concentration value X1 and the reference gas concentration value X0. And calculating the average density change rate α2 of
The second average concentration change rate in the second temperature region between the reference temperature T0 and the second reference temperature T2 depending on the difference ΔX2 between the second reference gas concentration value X2 and the reference gas concentration value X0. Find β2,
Further, a procedure for obtaining a total average density change rate γ2 of the first average density change rate α2 and the second average density change rate β2.
[0064]
Procedure (3): Based on the total average concentration change rate γ2, according to the magnitude ΔT of the temperature difference between the reference temperature T0, the first reference temperature T1, or the second reference temperature T2 and the temperature T of the test gas A procedure for obtaining the obtained density correction amount D by the following equation 6.
[0065]
[Formula 6]

[0066]
In the above, the correction amount data is set such that the temperature value related to the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature is set to a uniform temperature range, and the detected output value is uniform. The output width is set in accordance with the size, and the temperature width and the output width can be appropriately set according to the purpose.
The magnitude of the temperature width in the correction amount data is preferably 0.1 to 2 ° C. As a result, accurate calibration curve data having high reliability can be obtained with certainty.
[0067]
According to the gas concentration detection apparatus having the above configuration, the reference gas concentration value X0 obtained by comparing the detection output value C actually obtained by the infrared sensor 13A with the reference calibration curve data at the reference temperature T0 is the detected output value. By being corrected by a concentration correction amount determined by C and the magnitude ΔT of the temperature difference between the temperature T of the test gas and the reference temperature T0, the first reference temperature T1, or the second reference temperature T2. In the state where the degree of the influence of the detected output value on the concentration correction amount is compensated, the concentration correction with respect to the temperature is performed, so that an accurate and highly reliable correction gas concentration value can be obtained. The expected gas detection can be performed reliably.
[0068]
As mentioned above, although embodiment of this invention was described, this invention is not limited to said aspect, A various change as shown below can be added.
[0069]
(1) In the first embodiment, the calibration curve data is set to be acquired by correcting the output value at the reference temperature (for example, 20 ° C.), but the reference temperature (for example, 0 ° C. or 40 ° C.) is set. The calibration curve data in (1) may be set so as to obtain a corrected calibration curve data by correcting the temperature.
[0070]
(2) When calibration curve data at the first reference temperature T1 and the second reference temperature T2 is acquired in advance, the correction amount for correcting the output value or the reference gas concentration value at the reference temperature T0 is the reference temperature. An overall average change rate γ of an average change rate α in the temperature region between T0 and the first reference temperature T1 and an average change rate β in the temperature region between the reference temperature T0 and the second reference temperature T2 Instead of using, each average change rate may be used for calculation.
For example, in the first embodiment, when acquiring the output correction amount at 25 ° C. (temperature difference 5 ° C. from the reference temperature), the temperature range between the temperature values of 20 ° C. and 40 ° C. (second reference temperature) is obtained. Using the average output change rate β1, the output correction amount is calculated for each predetermined density value in the measurement range. According to such a concentration detection method, corrected calibration curve data that further conforms to actual calibration curve data can be obtained.
[0071]
(3) Instead of selecting the output correction amount or concentration correction amount for correcting the output value or reference gas concentration value at the reference temperature from the standardized correction amount data calculated in advance, the output correction amount Alternatively, the concentration correction amount may be set to be calculated during the gas detection operation. In this case, a calculation function may be added to the CPU in the control processing unit.
[0072]
(4) When the calibration curve data at the standard temperature or the reference temperature is acquired, 10 points of standard gas having 10 kinds of gas concentrations every 10% by volume in a concentration range (measurement range) of 0 to 100% by volume Although it was performed by acquiring calibration curve data, the number of types of standard gas used (the number of actually measured values to be acquired) is not particularly limited and can be set as appropriate.
Further, the number of calibration curve data to be acquired in advance and the temperature value of the reference temperature or reference temperature used when acquiring the correction amount are not particularly limited, and are appropriately set according to the purpose. be able to.
Furthermore, the measurement range is not particularly limited, and can be set as appropriate according to the target gas detection (for example, measurement conditions such as the type of detection target gas).
[0073]
(5) In the gas concentration detection method of the present invention, for example, as shown in FIG. 5, the gas concentration detection method can be applied to those configured to be able to detect a plurality of types of detection target gases at the same time. For each target gas to be detected, the reference calibration curve data at the reference temperature may be set in advance and the correction amount data may be set in the same manner as described above.
In the infrared gas detection device shown in FIG. 5, a condensing surface 52 is formed at one end of a through hole 51 that coincides with the main optical path axis L1, and a light transmitting through hole 53 that is orthogonal to the main optical path axis L1 is formed. The base 50, the light emitting means 55 disposed in the through hole 51 so that the light emitting region is positioned in the light transmitting through hole 53, and the first disposed in the position facing the light collecting surface 52 in the base 50. A first chamber 56A, a second chamber 56B disposed at a position facing the light transmitting through-hole 53, and light receiving means 58A and 58B disposed on the emission port side of each of the first chamber 56A and the second chamber 56B. It is comprised by. In FIG. 5, 60A and 60B are gas inlets for introducing the test gas into the first chamber 56A and the second chamber 56B, respectively, and 61A and 61B are from the first chamber 56A and the second chamber 56B, respectively. This is a gas outlet for discharging the test gas.
[0074]
(6) The gas concentration detection device is configured to have an alarm notification function for generating an alarm signal by the CPU when it is detected that the concentration of the detection target gas to be detected is equal to or higher than a certain reference level. be able to.
[0075]
Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.
<Experimental example 1>
A test infrared gas detector was manufactured according to the configuration shown in FIG. The specific configuration of each component is as follows.
[1] Measuring chamber (11): cylindrical with a cell length of 2 mm
[2] Infrared light source (12); driven to blink at a cycle of 1.5 sec
[3] Infrared sensor (13A); pyroelectric infrared sensor
[4] Optical filter (13B); one that transmits infrared rays in the absorption wavelength range unique to the gas molecules constituting the experimental gas shown below
[5] Experimental gas; isobutane gas (i-C _Four H _Ten ) Is contained in room air at a rate of 80% by volume (vol%)
[0076]
20 ° C. is set as the standard temperature (T0), 0 ° C. is set as the first reference temperature (T1), and 40 ° C. is set as the second reference temperature (T2). Every 10% by volume in the concentration range of 0 to 100% by volume. 10 points of actual measurement values are obtained using each of 10 different concentrations (0, 10, 20,..., 90, 100% by volume) of isobutane gas (standard gas). By approximating the actual measured value of the curve and interpolating the predicted value for the concentration value for each 0.1% by volume between the actual measured values, the operation is performed at 0 ° C., 20 ° C., and 40 ° C. Calibration curve data was obtained.
And the total average of the average output change rate α1 in the first temperature range between the temperature values of 0 ° C. and 20 ° C. and the average output change rate β1 in the second temperature range between the temperature values of 20 ° C. and 40 ° C. The rate of change γ1 is calculated separately for each concentration value of 0.1% by volume in the concentration range of 0 to 100% by volume, and then the temperature difference from the reference temperature for each of the temperature values every 0.1 ° C. By calculating the output correction amount according to the magnitude of the temperature, it is normalized based on the magnitude of the temperature difference with respect to the reference temperature and the density value with a temperature range of 0.1 ° C. and a concentration range of 0.1% by volume. Correction amount data was obtained.
Calibration curve data and correction amount data at the reference temperature (20 ° C.) acquired as described above were set in the storage unit.
[0077]
Then, under an environmental condition of 10 ° C. (the temperature of the experimental gas is 10 ° C.), an output correction amount corresponding to a temperature difference of −10 ° C. with respect to the reference temperature is selected, and a concentration value for each 0.1% by volume is selected. Accordingly, each of the output values at 20 ° C. (calibration curve data) is corrected by the corresponding output correction amount to obtain corrected calibration curve data, and the detection output value corresponding to the gas detection signal actually obtained by the infrared sensor is obtained. When the gas concentration detection test was performed by controlling the operation of the control processing unit so as to calculate the gas concentration value by comparing with the corrected calibration curve data, the detected concentration of the experimental gas was 79.5 as an average value. It was volume% (measurement error 0.5% FS), and it was confirmed that the concentration of the detection target gas could be accurately detected. Here, the measurement error is 5% F.V. S. If it is in the range, it can be said that there is no practical problem.
[0078]
<Experimental example 2>
In Experimental Example 1, the same gas concentration detection test as in Experimental Example 1 was performed except that the settings were changed as in the following (1) and (2). It was 79.5 volume% (measurement error 0.5% FS), and it was confirmed that the concentration of the detection target gas can be accurately detected.
[0079]
(1) The average concentration change rate α2 in the first temperature region between the temperature values of 0 ° C. and 20 ° C. for each output value for each arbitrary output unit (area value) in the measurement range where the maximum value is 100% by volume. And a total average density change rate γ2 with an average density change rate β2 in the second temperature range between the temperature values of 20 ° C. and 40 ° C., and for each of the temperature values every 0.1 ° C. with respect to the reference temperature, By calculating the density correction amount corresponding to the temperature difference, the correction amount data normalized based on the temperature value and the detected output value related to the temperature difference with respect to the reference temperature within a temperature range of 0.1 ° C. The calibration curve data and the correction amount data at the reference temperature (20 ° C.) were set in the storage unit.
(2) The reference gas concentration value is obtained by comparing the detection output value by the infrared sensor with the calibration curve data at 20 ° C., and the reference gas concentration is calculated from the detection output value, the temperature of the test gas, and the reference temperature. The operation of the control processing unit was controlled so as to calculate a corrected gas concentration by correcting with a concentration correction amount corresponding to the temperature difference (−10 ° C.).
[0080]
【The invention's effect】
According to the gas concentration detection method of the present invention, the output correction value determined by the output value at the reference temperature determined by the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. As a result of the correction, the output correction for temperature is performed in a state where the degree of influence on the output correction amount due to the density value is compensated, so that accurate and highly reliable correction calibration curve data is obtained. Therefore, the concentration of the detection target gas contained in the test gas can be accurately detected by comparing the detection output value actually obtained by the gas sensor with the corrected calibration curve data.
[0081]
Further, according to the gas concentration detection method of the present invention, the reference gas concentration value obtained by comparing the detection output value actually obtained by the gas sensor with the calibration curve data at the reference temperature, Concentration correction for temperature in a state where the degree of influence on the concentration correction amount by the detected output value is compensated by the output correction amount determined by the temperature difference between the detected gas temperature and the reference temperature. Therefore, an accurate and highly reliable correction gas concentration value can be obtained, and the concentration of the detection target gas contained in the detection gas can be accurately detected.
[0082]
According to the gas concentration detection device of the present invention, the concentration of the detection target gas contained in the test gas is accurately and reliably detected by executing the specific gas concentration detection method. Therefore, the desired gas detection can be performed reliably.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a configuration in an example of an infrared gas detection device according to the present invention.
FIG. 2 is an explanatory diagram showing calibration curve data for calculating a concentration of a detection target gas in the first embodiment.
FIG. 3 is an operation flowchart showing signal processing by a control processing unit of the infrared gas detection device shown in FIG. 1;
FIG. 4 is an explanatory diagram showing calibration curve data for calculating the concentration of a detection target gas in the second embodiment.
FIG. 5 is an explanatory sectional view showing an outline of a configuration in another example of a gas concentration detection device according to the present invention.
[Explanation of symbols]
10 Gas detector
11 Measuring chamber
11A Gas inlet
11B Gas outlet
12 Infrared light source
13 Infrared sensor unit
13A Infrared sensor
13B Optical filter
20 Control processor
21 Light source drive circuit
22 Amplifier circuit
23 Memory unit
30 CPU
40 display section
Calibration curve data at K0 20 ° C
Calibration curve data at K10 0 ℃
Calibration curve data at K2 40 ℃
50 base
51 Through hole
52 Condensing surface
53 Light transmission hole
55 Light emitting means
56A first chamber
56B Second chamber
58A, 58B Light receiving means
60A, 60B gas inlet
61A, 61B Gas outlet
L1 Main optical axis

Claims

Corrected calibration curve data at the measured temperature of the test gas is obtained by correcting the temperature of the calibration curve data indicating the relationship between the output value at the reference temperature and the gas concentration value acquired in advance for the gas sensor. A method of obtaining a gas concentration value by comparing the actually obtained detection output value with the corrected calibration curve data,
The corrected calibration curve data is an output correction determined based on the output value at the reference temperature based on the concentration value corresponding to the output value and the magnitude of the average output change rate in the temperature region between the temperature of the test gas and the reference temperature. The gas concentration is obtained by performing an output value correction process for obtaining a corrected output value by correcting with a quantity for the concentration range of the measurement range related to the calibration curve data at the reference temperature. Detection method.

The gas concentration detection method according to claim 1, wherein the output correction amount for correcting the output value at the reference temperature is obtained by the following procedures (1) and (2).
(1) The difference between the output value at the reference temperature and the reference output value obtained by comparing the calibration curve data at the reference temperature different from the reference temperature obtained in advance with the concentration value corresponding to the output value. A procedure for obtaining an average output change rate in a temperature region between the reference temperature and the reference temperature according to the magnitude.
(2) A procedure for obtaining an output correction amount in accordance with the temperature difference between the reference temperature or reference temperature and the temperature of the test gas based on the average output change rate.

The gas concentration detection method according to claim 1, wherein the output correction amount for correcting the output value at the reference temperature is obtained by the following procedures (1) to (4).
(1) The first reference obtained by comparing the output value at the reference temperature and the calibration curve data at the first reference temperature lower than the reference temperature obtained in advance with the concentration value corresponding to the output value. A procedure for obtaining a first average output change rate in a first temperature region between the reference temperature and the reference temperature based on the magnitude of the difference from the output value.
(2) A second reference output value obtained by comparing the concentration value with calibration curve data at a second reference temperature higher than the reference temperature acquired in advance, and an output value at the reference temperature A procedure for obtaining a second average output change rate in a second temperature region between the reference temperature and the second reference temperature according to the magnitude of the difference.
(3) A procedure for obtaining an overall average output change rate of the first average output change rate and the second average output change rate.
(4) A procedure for obtaining an output correction amount corresponding to the temperature difference between the reference temperature, the first reference temperature or the second reference temperature and the temperature of the test gas, based on the total average output change rate.

Perform output value correction processing for multiple density values in the density range of the measurement range,
When the detected output value actually obtained by the gas sensor is compared with the corrected calibration curve data, if there is no corrected output value that matches the detected output value, the interval between the two corrected output values adjacent to the detected output value. The gas concentration detection method according to claim 1, wherein a gas concentration value is obtained by interpolating.

Standardized output correction amount for correcting the output value at the reference temperature based on the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or reference temperature Set quantity data,
When correcting the output value at the reference temperature, the output correction amount selected according to the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature is used. The gas concentration detection method according to any one of claims 1 to 4, characterized in that:

In the correction amount data, the temperature value related to the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature is set with a uniform temperature range. It is 0.1-2 degreeC, The gas concentration detection method of Claim 5 characterized by the above-mentioned.

The reference temperature is set within a temperature range in which a temperature difference with respect to the reference temperature is 10 to 40 ° C, and the reference temperature is any one of claims 2, 3, 5, and 6 . Gas concentration detection method.

Contrast the detected output value of the gas sensor obtained when the test gas is supplied with the calibration curve data indicating the relationship between the detected output value at the reference temperature and the gas concentration value acquired in advance for the gas sensor. A method for obtaining a corrected gas concentration value corrected for temperature by obtaining a reference gas concentration value by correcting the reference gas concentration value based on the temperature of the test gas,
The reference gas concentration value is corrected by a concentration correction amount determined by the magnitude of the detection output value of the gas sensor and the average concentration change rate in the temperature region between the temperature of the test gas and the reference temperature. A gas concentration detection method , wherein a gas concentration value correction process for obtaining a corrected gas concentration value is performed for a concentration range of a measurement range related to calibration curve data at the reference temperature .

9. The gas concentration detection method according to claim 8, wherein the concentration correction amount for correcting the reference gas concentration value is obtained by the following procedures (1) to (3).
(1) A procedure for obtaining a reference gas concentration value by comparing a detection output value of a gas sensor with calibration curve data at a reference temperature different from the reference temperature acquired in advance for the gas sensor.
(2) A procedure for obtaining an average concentration change rate in a temperature region between the reference temperature and the reference temperature based on the difference between the reference gas concentration value and the reference gas concentration value.
(3) A procedure for obtaining a concentration correction amount according to the temperature difference between the reference temperature or reference temperature and the temperature of the test gas based on the average concentration change rate.

9. The gas concentration detection method according to claim 8, wherein the concentration correction amount for correcting the reference gas concentration value is obtained by the following procedures (1) to (3).
(1) The first reference gas concentration value is obtained by comparing the detected output value of the gas sensor with the calibration curve data at the first reference temperature lower than the reference temperature acquired in advance for the gas sensor,
A procedure for obtaining a second reference gas concentration value in contrast to calibration curve data at a second reference temperature higher than the reference temperature obtained in advance for the gas sensor for the detection output value of the gas sensor.
(2) A first average concentration change rate in a first temperature region between the reference temperature and the first reference temperature, based on a difference between the first reference gas concentration value and the reference gas concentration value. Asking
Obtaining a second average concentration change rate in a second temperature region between the reference temperature and the second reference temperature according to a difference between the second reference gas concentration value and the reference gas concentration value;
Further, a procedure for obtaining a total average density change rate of the first average density change rate and the second average density change rate.
(3) A procedure for obtaining a concentration correction amount according to the temperature difference between the reference temperature, the first reference temperature, or the second reference temperature and the temperature of the test gas based on the total average concentration change rate.

Concentration correction amount that should be corrected for the reference gas concentration value is standardized correction amount data based on the detected output value at the reference temperature and the temperature difference between the detected gas temperature and the reference temperature or reference temperature. Set it,
When correcting the reference gas concentration value, a concentration correction amount selected according to the detection output value at the reference temperature and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature is used. The gas concentration detection method according to claim 9 or 10.

In the correction amount data, the temperature value related to the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature is set with a uniform temperature range, and the temperature range is 0.1. The gas concentration detection method according to claim 11, wherein the gas concentration detection method is ˜2 ° C.

The gas concentration detection method according to any one of claims 9 to 12, wherein the reference temperature is set within a temperature range in which a temperature difference with respect to the reference temperature is 10 to 40 ° C.

The temperature of the gas to be detected by correcting the temperature of the gas sensor, the temperature sensor for detecting the temperature of the gas to be supplied to the gas sensor, and the calibration curve data at the reference temperature acquired in advance for the gas sensor The correction value curve means for obtaining the gas concentration value by obtaining the corrected calibration curve data and comparing the detected output value actually obtained by the gas sensor with the corrected calibration curve data, and the gas obtained by this output value correction means Gas concentration display means for displaying the concentration value,
The output value correcting means converts the output value at the reference temperature into a concentration value corresponding to the output value and an average output change rate in a temperature region between the detected temperature value of the test gas from the temperature sensor and the reference temperature. A function for obtaining corrected calibration curve data by performing output value correction processing for obtaining a corrected output value by performing correction on the concentration range of the measurement range related to the calibration curve data at the reference temperature with an output correction amount determined by the magnitude of A gas concentration detecting device characterized by comprising:

A storage unit storing at least calibration curve data at a reference temperature;
In the storage unit, the output correction amount for correcting the output value at the reference temperature is based on the concentration value corresponding to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature or the reference temperature. Standardized correction amount data is stored,
The output value correction means selects the output correction amount to be corrected for the output value at the reference temperature according to the concentration value according to the output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. The gas concentration detection device according to claim 14, which has a function of

A gas sensor, a temperature sensor for detecting the temperature of the test gas supplied to the gas sensor, and a detection output value obtained at the gas sensor, a detection output value at a reference temperature acquired in advance for the gas sensor. -Correction for temperature correction by obtaining a reference gas concentration value by comparing with calibration curve data indicating the relationship between gas concentration values and correcting this reference gas concentration value according to the detected temperature value from the temperature sensor. An output value correcting means for obtaining a gas concentration value, and a gas concentration display means for displaying a corrected gas concentration value obtained by the output value correcting means,
The output value correction means determines the reference gas concentration value based on the detected output value from the gas sensor and the average concentration change rate in the temperature region between the detected temperature value from the temperature sensor and the reference temperature. A gas concentration having a function of performing a gas concentration value correction process for obtaining a corrected gas concentration value by correcting with a fixed concentration correction amount with respect to a concentration range of a measurement range related to a calibration curve data at a reference temperature. Detection device.

A storage unit storing at least calibration curve data at a reference temperature;
In the storage unit, the concentration correction amount for correcting the reference gas concentration is normalized based on the detected output value at the reference temperature and the magnitude of the temperature difference between the detected gas temperature and the reference temperature or reference temperature. Stored correction amount data,
The output value correction means has a function of selecting a concentration correction amount for correcting the reference gas concentration according to the detected output value and the magnitude of the temperature difference between the temperature of the test gas and the reference temperature. The gas concentration detection device according to claim 16.