JP4205243B2 - Temperature compensation method, temperature compensation circuit and sensor using the same - Google Patents

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となる。
【００１４】
したがって、この周囲温度Ｔ１においては両感熱素子１，２にはその出力電圧Ｖｏｕｔ１、Ｖｏｕｔ２にオフセットがある。このオフセットはオフセット調整回路５で調整される。オフセット調整回路５は可変抵抗８と増幅器９とを有しており、温度補償用感熱素子２の出力電圧Ｖｏｕｔ２は、両感熱素子１，２の抵抗値差（Ｒ１−Ｒ２）に相当する分をオフセット調整回路５の可変抵抗器８によって、また、両感熱素子１，２への通電電流比（Ｉ１／Ｉ２）に相当する分をオフセット調整回路５の増幅器９によって調整され、結果として、オフセット調整回路５によってＶｏｕｔ１と同一のＶｏｕｔ３に調整される。
【００１５】
周囲温度がＴ１で変化が無ければ、このオフセット調整によりオフセット調整回路５の出力電圧Ｖｏｕｔ３と検出用感熱素子１の出力電圧Ｖｏｕｔ１は互いに同一であるから、両出力電圧Ｖｏｕｔ１とＶｏｕｔ３とを差動増幅器７に入力することで、差動増幅器７の出力電圧Ｖｏｕｔ５がゼロとなり、検出用感熱素子１に対する温度補償がされることになる。
【００１６】
しかしながら、周囲温度がＴ１からΔＴだけ変化した場合、検出用感熱素子１の出力電圧Ｖｏｕｔ１が図２の特性▲１▼のように変化してＶｏｕｔ１’となるのに対し、オフセット調整回路５の出力電圧Ｖｏｕｔ３は特性▲２▼のように変化してＶｏｕｔ３’となるために、検出用感熱素子１の出力電圧Ｖｏｕｔ１’とオフセット調整回路５の出力電圧Ｖｏｕｔ３’とが一致しなくなる。これについて詳しく説明すると、検出用感熱素子１の抵抗Ｒ１はこのΔＴの温度変化に伴いΔＲ１だけその抵抗値が増加し、また、温度補償用感熱素子２の抵抗値Ｒ２は同様にΔＲ２だけ増加する。ここで、ΔＲ１／Ｒ１とΔＲ２／Ｒ２はほぼ同じ値になるため、この値をａとすると、

また、前記より

ここで、Ｖｏｕｔ３＝Ｖｏｕｔ１であることから、

また、Ｒ１＞Ｒ２であり、Ｉ１，Ｉ２，ａはすべて正の値であることから
Ｖｏｕｔ３’＜Ｖｏｕｔ１’となる。
【００１７】
そこで、この周囲温度Ｔ１＋ΔＴにおけるオフセット調整回路５の出力電圧Ｖｏｕｔ３’をゲイン調整回路６に入力し、ゲイン調整回路６の出力電圧Ｖｏｕｔ４がＶｏｕｔ１’となるようにゲイン調整するのである。このゲイン調整について説明する。まず、基準電圧Ｖｒｅｆを周囲温度Ｔ１における検出用感熱素子１の出力電圧Ｖｏｕｔ１に一致させるように可変抵抗１０で調整する。それから、ゲイン調整回路６の出力電圧Ｖｏｕｔ４が周囲温度がＴ１＋ΔＴのときの検出用感熱素子１の出力電圧Ｖｏｕｔ１’に一致させるように可変抵抗１１を調整する。これによって、ゲイン調整回路６の出力電圧Ｖｏｕｔ４は検出用感熱素子１の出力電圧Ｖｏｕｔ１’に一致するのである。その結果、差動増幅器７からは周囲温度の変化に依存することなく、検出用感熱素子１で検出した検出対象に対応した出力電圧Ｖｏｕｔ５が出力できることになる。
【００１８】
以上のような温度補償方法および回路において温度ゲイン調整後においても事前に調整したＶｏｕｔ３が変化しないことについて説明する。今、温度ゲイン調整後において周囲温度をＴ１に戻したとすると、検出用感熱素子１の抵抗値はＲ１となり、Ｖｏｕｔ１＝Ｉ１×Ｒ１でオフセット調整時の電圧Ｖｏｕｔ１に戻る。また、温度補償用感熱素子２の抵抗値はＲ２となり、Ｖｏｕｔ２＝Ｉ２×Ｒ２でＶｏｕｔ１と同様にオフセット調整時の電圧Ｖｏｕｔ２に戻る。ここで、オフセット調整回路５の各設定値はオフセット調整時のままなのでＶｏｕｔ３＝Ｖｏｕｔ１である。さてここで、温度ゲイン調整回路６の基準電圧Ｖｒｅｆは周囲温度Ｔ１における検出用感熱素子１の出力電圧Ｖｏｕｔ１に一致させるように既に可変抵抗器１１で調整されているため、オペアンプの動作原理にのっとってＶｏｕｔ４＝Ｖｒｅｆ＝Ｖｏｕｔ３となる。よって、Ｖｏｕｔ４＝Ｖｏｕｔ１となり、Ｖｏｕｔ５は周囲温度Ｔ１においてもゼロとなり、温度補償されるのが分かる。
【００１９】
なお、この実施の形態では、感熱素子を２つ用いたが、図３で示すように、感熱素子１３を１つとし、その感熱素子１３と定電流源３，４との間にスイッチ１４，１５を設け、このスイッチ１４，１５を制御部１６でオンオフすることで、定電流源３に接続された第１スイッチ１４がオン、定電流源４に接続された第２スイッチ１５がオフのときに定電流源３からは感熱素子１３に通電電流Ｉ１を、第１スイッチ１４がオフ、第２スイッチ１５がオンのときに定電流源４から通電電流Ｉ２を感熱素子１３に供給することで、１つの感熱素子１３を制御部１６で異なるタイミング（前記両スイッチ１４，１５のオンオフ）で異なる温度に制御処理し、この感熱素子１３の異なるタイミングにおけるそれぞれの出力電圧を前記オフセット調整回路５で任意の周囲温度のもとでオフセット調整し、感熱素子１３の前記異なるタイミングにおけるそれぞれの出力電圧を他の任意の周囲温度のもとでゲイン調整回路６でゲイン調整する温度補償方法として、上述と同様の温度補償を行わせることができる。
【００２０】
ここで異なるタイミングにおけるそれぞれの出力電圧は例えばサンプル・ホールド回路等を用いてそれぞれ保持する構成としてもよいし、マイクロコンピュータ等を用いて保持する構成としてもよい。
【００２１】
（実施の形態２）
上述した実施の形態１では、調整ステップが多いために手間がかかることが考えられること、また、検出対象を温度が異なる２つの環境下に置く必要があるので、そのための設備が必要となること、また、検出対象をそれぞれの温度環境下でなじませるための時間が必要となること、さらに、可変抵抗で調整する作業が大変である、いった問題がある。本発明の実施の形態２の温度補償方法においては、実施の形態１のそうした問題を解消している。
【００２２】
以下、説明すると、本発明の実施の形態２にかかる温度補償方法は、少なくとも２つの感熱素子のうちの一方を検出用感熱素子とし、他方を温度補償用感熱素子とし、前記両感熱素子それぞれを異なる加熱温度となるように処理する手段と、前記両感熱素子それぞれの出力電圧のうち、少なくともいずれか一方が他方に対する過不足分を加算または減算する手段とを少なくとも含むものであり、これについて図４ないし図６を参照して説明する。
【００２３】
まず、この実施の形態２の実施に用いられる温度補償回路は、例えば図４で示すように検出用感熱素子２１と、温度補償用感熱素子２２と、定電流源２３，２４と、調整回路２５と、加算回路２６と、差動増幅器２７とを備えて構成されている。 そして、本実施の形態２においては、実施の形態１と同様にして感熱素子が検出用感熱素子２１と温度補償用感熱素子２２との２つが使用されている。それぞれの感熱素子２１，２２は対応する定電流源２３，２４から通電電流Ｉ１，Ｉ２が供給される。ここでＩ１＞Ｉ２の関係である。ここで説明を簡単にするために、両感熱素子２１，２２それぞれの特性は同じとする。
【００２４】
同一の周囲温度環境下であってこのような通電電流Ｉ１，Ｉ２において加熱された場合の検出用感熱素子２１と温度補償用感熱素子２２それぞれの抵抗値は図５で示すようにＲ１，Ｒ２（Ｒ２＜Ｒ１）となっている。このとき、検出用感熱素子２１と温度補償用感熱素子２２それぞれの出力電圧はＶｏｕｔ６，Ｖｏｕｔ７であり、調整回路２５の出力電圧はＶｏｕｔ８であり、加算回路２６の出力電圧はＶｏｕｔ９であり、差動増幅器２７の出力電圧はＶｏｕｔ１０であるが、以下の説明では容易な理解のため抵抗値で説明することにする。
【００２５】
そして、両感熱素子２１，２２の周囲温度がΔＴだけ変化した場合、それぞれの感熱素子２１，２２の抵抗値もそれぞれΔＲ１，ΔＲ２と変化するが、検出用感熱素子２１と温度補償用感熱素子２２の特性が同じであっても通電電流Ｉ１，Ｉ２によって抵抗値がＲ１，Ｒ２と異なるために、ΔＲ１＞ΔＲ２である。前述実施の形態１での説明においてΔＲ１／Ｒ１とΔＲ２／Ｒ２はほぼ同じと記したが、現実には若干の差異があり、この差異が正確な温度補償を行ううえで無視できない場合がある。例えば微流速を検出対象とする場合等である。ここではΔＲ１／Ｒ１＜ΔＲ２／Ｒ２の場合を例に挙げ、このときの抵抗値Ｒ１，ΔＲ１，Ｒ２，ΔＲ２の関係について図６を参照して説明する。
【００２６】
図６（ａ）には検出用感熱素子２１の抵抗値として、Ｒ１と前記周囲温度変化ΔＴによる抵抗値変化分であるΔＲ１との合計抵抗値ＴＲ１が示されている。また、図６（ｂ）には温度補償用感熱素子２２の抵抗値として、Ｒ２と前記周囲温度変化ΔＴによる抵抗値変化分であるΔＲ２との合計抵抗値ＴＲ２が示されている。ここで、調整回路２５で図６（ｃ）で示すように抵抗値変化分ΔＲ２をΔＲ１に一致させるようにΔＲ２’に調整して合計抵抗値をＴＲ２からＴＲ２’とする。このとき、抵抗値Ｒ２も調整回路２５で調整される結果、Ｒ２’となっているが、図６（ａ）の合計抵抗値ＴＲ１に対して、図６（ｃ）の合計抵抗値ＴＲ２’は抵抗値Ｒ３だけ小さい。そこで、あらかじめ実験等により抵抗値Ｒ３（加算電圧Ｖａｄｄ）を把握し、加算回路２６によって抵抗値Ｒ３分（加算電圧Ｖａｄｄ）だけ加算する回路構成とすることで、Ｒ２’＋Ｒ３＋ΔＲ２’に相当するＶｏｕｔ９がＲ１＋ΔＲ１に相当するＶｏｕｔ６に一致するように調整回路２５を調整するだけで差動増幅器２７には合計抵抗値が同じとなる電圧が入力されることになってその出力電圧Ｖｏｕｔ１０はゼロとなるのである。
【００２７】
つまり、Ｖｏｕｔ６，Ｖｏｕｔ７，Ｖｏｕｔ８，Ｖａｄｄ，Ｖｏｕｔ９を抵抗値関係であらわすと、

したがって、差動増幅器２７の一方の入力である前記式（１）と、他方の入力である前記式（５）とから明らかであるように、差動増幅器２７への両入力は同じであるから周囲温度に依存することなく、差動増幅器２７からは検出用感熱素子２１で検出した検出対象に対応した出力電圧Ｖｏｕｔ１０が出力できることになる。
【００２８】
また、ここでは抵抗値Ｒ３（加算電圧Ｖａｄｄ）をあらかじめ把握して設定しておき、調整回路２５を調整する例を説明したが、逆に、ΔＲ１／ΔＲ２に相当する値をあらかじめ把握して調整回路２５を固定値として設定しておき、抵抗値Ｒ３に相当する加算電圧Ｖａｄｄを調整するようにしてもよい。
【００２９】
また、ここではＴＲ２’にＲ３分を加算する形態で、温度補償用感熱素子側に加算回路を設けたが、逆に、ＴＲ１からＲ３分を減算する形態とし、検出用感熱素子側に減算回路を設けても同様の効果が得られる。
【００３０】
また、ここでは（ΔＲ１／Ｒ１）＜（ΔＲ２／Ｒ２）の場合を例に挙げて説明したが、（ΔＲ１／Ｒ１）＞（ΔＲ２／Ｒ２）の場合においては加減算の関係が逆になるだけで同様に温度補償できる。
【００３１】
また、感熱素子２１，２２の特性が違う場合においても感熱素子２１のΔＲ１／Ｒ１と感熱素子２２のΔＲ２／Ｒ２との関係を把握することで同様に温度補償可能である。
【００３２】
なお、この実施の形態２では、感熱素子を２つ用いたが、図３と同様にして感熱素子を１つとし、これを検出用感熱素子と温度補償用感熱素子とに用いるために異なるタイミングで異なる温度に制御処理し、この感熱素子を前記異なるタイミングそれぞれにおいて前記温度から同じ温度分で変化させ、この感熱素子を温度補償用感熱素子とするときにその出力電圧を調整し、前記調整された出力電圧を加算または減算する温度補償方法しても構わない。
【００３３】
なお、この実施の形態２では、加算回路２６を用いたが、調整の内容によっては減算回路を用いても構わない。
【００３４】
次にこの実施の形態２について具体数値例を挙げて説明することにする。
【００３５】
検出用感熱素子２１の出力電圧Ｖｏｕｔ６（通電電流Ｉ１×抵抗値Ｒ１）を１０Ｖ、補償用感熱素子２２の出力電圧Ｖｏｕｔ７（通電電流Ｉ２×抵抗値Ｒ２）を４Ｖとする。周囲温度ΔＴの変化で検出用感熱素子２１の抵抗値がＲ１→ＴＲ１（＝Ｒ１＋ΔＲ１）に、補償用感熱素子２２の抵抗値がＲ２→ＴＲ２（＝Ｒ２＋ΔＲ２）と変化し、これによって、Ｖｏｕｔ６がＩ１×Ｒ１＝１０ＶからＩ１×（Ｒ１＋ΔＲ１）＝Ｉ１×Ｒ１＋Ｉ１×ΔＲ１＝１０Ｖ＋２Ｖ＝１２Ｖに、Ｖｏｕｔ７がＩ２×Ｒ１＝４ＶからＩ２×（Ｒ２＋ΔＲ２）＝Ｉ２×Ｒ２＋Ｉ２×ΔＲ２＝４Ｖ＋１Ｖ＝５Ｖになったとすると、Ｖｏｕｔ６は周囲温度ΔＴの変化で２Ｖ上昇、Ｖｏｕｔ７は１Ｖ上昇したことになる。
【００３６】
Ｖｏｕｔ６についての電圧上昇分ΔＶｏｕｔ６（＝２Ｖ）はＩ１×ΔＲ１、Ｖｏｕｔ７についての電圧上昇分ΔＶｏｕｔ７（＝１Ｖ）はＩ２×ΔＲ２であるから、調整回路２５の増幅率にＩ１／Ｉ２を含めて設定することでそれ以降は抵抗値で説明され得る。
【００３７】
ここで、Ｖｏｕｔ７の電圧上昇分ΔＶｏｕｔ７＝１ＶをＶｏｕｔ６の電圧上昇分ΔＶｏｕｔ７＝２Ｖに等しくなるように調整回路２５の増幅率を２倍としたとき、Ｖｏｕｔ７はこの調整回路２５で２倍に増幅されるためにＶｏｕｔ８は周囲温度変化ΔＴに伴い８Ｖから１０Ｖに変化することになる。これをＶｏｕｔ６の電圧変化１０Ｖ→１２Ｖと比較すると、変化する電圧値は共に２Ｖで同じであるが、絶対値としては２Ｖ不足している。この不足電圧分をあらかじめ実験、計算等で求めておいて加算回路２６でこの不足電圧分が加算されるように設定、設計しておく。このようにすることにより、加算回路２６の出力電圧Ｖｏｕｔ９はΔＴの温度変化で１０Ｖから１２Ｖに変化することになる。
【００３８】
したがって、差動増幅器２７の両入力は周囲温度Ｔ１からΔＴの温度変化で１０Ｖから１２Ｖに変化することになり、温度補償されることになる。
【００３９】
なお、上述の各実施の形態における各回路は、定電流源および感熱素子を除いてはマイクロコンピュータによるプログラムを用い、ソフトウエア処理で演算させるようにしても構わない。
【００４０】
なお、例えば特開平７−３１８３６４号公報に記述のように感熱素子を１つ用い、この感熱素子を加熱、非加熱の処理をすることにより計測対象の検出信号と周囲温度の検出信号とを出力させるようにしたものがある。この公報に記述の方式では感熱素子が１つであるために上記感熱素子を２つ用いた方式のように２つの感熱素子の特性合わせは不要であり、制御が容易となる。
【００４１】
しかしながら、この公報に示される方式においては、感熱素子の非加熱処理に通電による温度上昇が無視可能な程度の通電電流を感熱素子に流す必要があるが、そのために、第１に、その通電の電流値が微小であるためにわずかな電流の変動でもそれが検出の大きな誤差要因となること、第２に、その微小な通電電流により感熱素子両端等に出力される電圧も微小となり、その後の信号処理系では非常に高精度の処理が必要となることである。そのために同公報の方式では感熱素子に通電する電流あるいは印加電圧等の設定回路、出力電圧の処理回路の構成の電子部品が非常に高価なものになる。
【００４２】
これに比較して、本実施の形態においては、１つの感熱素子を図３で示すようにスイッチでもって検出用感熱素子として用いるタイミングでは、感熱素子にその温度上昇が無視できない程度の通電電流を流して加熱処理し、温度補償用感熱素子としても用いるタイミングでも、その感熱素子にその温度上昇が無視できない程度の通電電流を流して加熱処理しても、実施できるものであるから、通電電流が微小であることによる誤差要因がなく、また、それに伴い、微小な通電電流による感熱素子出力電圧が微小となってその後の信号処理系で高精度な処理が要求されずに済み、簡易で低コストのものが容易に実現可能となる。
【００４３】
また、実施の形態１および２において感熱素子への通電方法として定電流方式を挙げたがこれを固定抵抗に代えて定電圧方式としても構わない。また、特開平４−１２２７８号公報の第１３図や前述の特開平７−３１８３６４号公報の第１７図に示すような定温度方式としても構わない。加えて、ここでは通電電流によって自己加熱する場合を例に挙げたが、検出用感熱素子を外部より加熱しても説明文中の抵抗値はＲ１，Ｒ２と異なった値が得られ、実現可能である。
【００４４】
ここで検出用感熱素子１と補償用感熱素子２を除く回路を処理回路とした場合に図７で示すように、処理回路そのもののオフセット調整およびゲイン調整を行うことで検出用感熱素子１に対するより適切な温度補償が行えるようにしても構わない。つまり、検出対象の温度に関する情報から検出用感熱素子１の温度補償を行う一方、検出用感熱素子１の温度補償のための処理および検出対象に対する所望の検出を行う処理回路に対してもそれ自身の温度に関する情報から温度補償を行うようにしても構わない。
【００４５】
図１で示される実施の形態１および図４で示される実施の形態２においては処理回路の周囲温度が変化しないことを前提にしているが、例えば上述の実施の形態をガス給湯器に適用した場合、ガス給湯器では両感熱素子１，２は空気流量、ガス流量の計測が目的だから検出対象である空気とかガスの管路のように給湯器内部に設置される。これに対して、処理回路は管路には設置されない。したがって、感熱素子１，２の周囲温度つまり管路内の空気やガス等の検出対象の温度とその変化は、処理回路の周囲温度とかその変化とは無関係に独立したものとなるから、処理回路のオフセットとかゲインとかの処理回路自身による温度の影響（変化）を無視したのでは、検出用感熱素子１の周囲温度の変化に対する適切な温度補償および検出対象に対する所望の検出を行う適切な処理とはならない。そこで、図７を参照して説明するように、処理回路そのものの周囲温度に対するオフセット調整をオフセット補償用感温素子である抵抗Ｒ９で行い、処理回路そのものの周囲温度の変化に対するゲイン調整をゲイン補償用感温素子である抵抗Ｒ２で行う。なお、図７において差動増幅器７は、増幅器Ａ１〜Ａ３と、抵抗Ｒ１〜Ｒ７で構成されている。このようにして検出用感熱素子１の処理回路によるオフセット調整およびゲイン調整と、処理回路そのもののオフセット調整およびゲイン調整とで、総合的な温度補償が可能となり、より適切な温度補償が可能となる。
【００４６】
なお、この場合、処理回路に対する温度補償はオフセット調整だけでもゲイン調整だけでもあるいはこの両調整で行っても構わない。
【００４７】
なお、この場合、オフセット調整、ゲイン調整は抵抗Ｒ２，Ｒ９のような感温素子で調整するのではなく温度変化を電流変化あるいは電圧変化で検出する感温素子でも構わないし、感温素子ではなく回路で行うようにしても構わない。
【００４８】
なお、上述の実施の形態の温度補償回路をチップ形態とかその他の形態の流速センサ、流量センサ、その他のセンサとしても構わない。
【００４９】
【発明の効果】
以上のように本発明によれば、１つの感熱素子のうちの一方を検出用感熱素子とし、他方を温度補償用感熱素子とし、前記両感熱素子それぞれを異なる加熱温度となるように処理し、前記両感熱素子の出力電圧が任意の周囲温度のもとで一致するようにオフセット調整し、前記両感熱素子の出力電圧が他の任意の周囲温度のもとで一致するようにゲイン調整するので、感熱素子のオフセットを調整したり、ゲイン調整する場合において、従来のようにオフセット調整後にゲイン調整する際に事前に調整したオフセット値がずれてしまうとか、ゲイン調整後に再度オフセット調整する工程を何度か繰り返して調整する必要とかがなくなり、温度補償が容易かつ正確になる。
【００５０】
また本発明によれば、２つの感熱素子のうちの一方を検出用感熱素子とし、他方を温度補償用感熱素子とし、前記両感熱素子それぞれを異なる加熱温度となるように処理し、前記両感熱素子それぞれの出力電圧のうち、少なくともいずれか一方が他方に対する過不足分を加算または減算することにより前記両感熱素子の出力電圧の差異がゼロとなるようにして温度補償するので、従来のように調整工程において感熱素子の周囲温度を変える必要がなくなり、したがって、そのための設備が不要となること、また、検出対象をそれぞれの温度環境下でなじませるための時間も不要となるなど、温度補償がきわめて容易になる。
【００５１】
上記の場合、前記２つの感熱素子に代えて、１つの感熱素子を異なるタイミングで切り替え、一方のタイミングでは前記検出用感熱素子とし、他方のタイミングでは前記温度補償用感熱素子とすると、感熱素子が少なくて済むだけでなく、２つの感熱素子を使用した際の両感熱素子間の相対的な特性のばらつきも感熱素子を１つとすることでほとんどなくなり、調整が容易になるばかりか、精度も向上する。
【図面の簡単な説明】
【図１】本発明の実施形態に係る温度補償方法に用いる温度補償回路の回路図
【図２】図１の回路において各部の電圧と周囲温度との関係を示す図
【図３】本発明の他の実施の形態に係る温度補償方法に用いる温度補償回路の要部回路図
【図４】本発明のさらに他の実施の形態に係る温度補償方法に用いる温度補償回路の回路図
【図５】図４の回路において感熱素子の抵抗値とその温度との関係の説明に供する図
【図６】図４の回路にて検出用感熱素子と温度補償用感熱素子それぞれの抵抗値の変化の説明に供する図
【図７】参考例に係る温度補償方法に用いる温度補償回路の要部の回路図
【符号の説明】
１ 検出用感熱素子
２ 温度補償用感熱素子
３，４ 定電流源
５ オフセット調整回路
６ ゲイン調整回路
７ 差動増幅器[0001]
BACKGROUND OF THE INVENTION
The present invention provides a temperature compensation method, a temperature compensation circuit using the same, and a sensor using the temperature compensation so as to eliminate the influence of the ambient temperature when performing measurement by energizing the thermal element. To Related. Various sensors using thermal elements detect changes per unit time and unit area of the number of molecules of gas or liquid touching the thermal element, such as flow rate (including flow rate), type of gas or liquid, pressure, humidity, etc. If it does, it is contained in the sensor of this invention.
[0002]
[Prior art]
In a device that detects the flow velocity, pressure, humidity, etc. using the thermal element for various sensors such as a flow velocity (flow rate) sensor, the temperature compensation circuit should be temperature compensated to eliminate the ambient temperature dependence of the thermal element. There is something that has become.
[0003]
Conventionally, such a temperature compensation circuit uses two thermal elements, outputs one detection signal as a detection thermal element, and detects the ambient temperature with the other thermal element as a temperature compensation thermal element. There is a system that outputs a signal and compensates the ambient temperature dependency of the thermal element by the arithmetic processing of both outputs so that the detection target can be detected without being affected by the ambient temperature.
[0004]
[Problems to be solved by the invention]
However, in such a method, it is necessary to adjust the offset of the two thermosensitive elements or adjust the gain in advance, but the offset value adjusted in advance when adjusting the gain after adjusting the offset is It is necessary to repeat the process of adjusting the offset again and again after the gain adjustment, which is very time-consuming. In addition, it is necessary to change the ambient temperature of the thermosensitive element in the adjustment process, and there is a problem that it is necessary to have equipment for that purpose, and that it is necessary to adjust the detection target in each temperature environment. .
[0005]
[Means for Solving the Problems]
In order to solve the above problems,
In the present invention, one of the two thermal elements is a detection thermal element, the other is a temperature compensation thermal element, the two thermal elements are processed to have different heating temperatures, The offset adjustment is performed so that the output voltage is matched under an arbitrary ambient temperature, and the gain is adjusted so that the output voltages of the two thermal elements are matched under any other ambient temperature.
[0006]
In the present invention, one of the two thermosensitive elements is a detection thermosensitive element, the other is a temperature compensating thermosensitive element, the two thermosensitive elements are processed so as to have different heating temperatures, and the both thermosensitive elements are processed. Temperature compensation is performed such that at least one of the output voltages of each element adds or subtracts an excess or deficiency with respect to the other so that the difference between the output voltages of the two thermal elements becomes zero.
[0007]
In this case, preferably, instead of the two thermosensitive elements, one thermosensitive element is switched at different timings, and the detection thermosensitive element is used at one timing and the temperature compensating thermosensitive element is used at the other timing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0009]
In the present invention, in order to simplify the description, an adjustment method in a state where the flow rate is zero will be described as an example as a detection target if the flow rate is, for example.
[0010]
(Embodiment 1)
In the temperature compensation method according to the first exemplary embodiment of the present invention, one of at least two thermal elements is a detection thermal element, the other is a temperature compensation thermal element, and the two thermal elements have different heating temperatures. A second step of adjusting the offset so that the output voltages of the two thermal elements coincide with each other under an arbitrary ambient temperature, and maintaining both of the thermal elements while maintaining the offset adjustment. And a third step of adjusting the gain so that the output voltage matches under any other ambient temperature. This temperature compensation method will be described based on the temperature compensation circuit shown in FIG. 1 and the output voltage characteristics of the thermal element with respect to the ambient temperature shown in FIG.
[0011]
First, the temperature compensation circuit of FIG. 1 includes a detection thermal element 1, a temperature compensation thermal element 2, constant current sources 3 and 4, an offset adjustment circuit 5, a gain adjustment circuit 6, and a differential amplifier 7. It is configured with.
[0012]
Here, in order to simplify the description, it is assumed that both the detection thermal element 1 and the temperature compensation thermal element 2 have the same characteristics. The temperature-compensating thermal element 2 is arranged in the same environment as the detection thermal element 1 with respect to a detection target (for example, a gas flow rate in a water heater). The detection thermosensitive element 1 generates an output voltage Vout1 corresponding to the energization current I1 from the constant current source 3 and the ambient temperature thereof. The temperature compensating thermosensitive element 2 generates an output voltage Vout2 corresponding to the energizing current I2 (<I1) from the constant current source 4 and the ambient temperature. The reason why the energization current I1 to the detection thermosensitive element 1 is larger than the energization current I2 to the temperature compensation thermosensitive element 2 is that the sensitivity of the temperature compensation thermosensitive element 2 to the detection target is detected by the detection thermosensitive element 1. This is because the sensitivity is lower than the target sensitivity.
[0013]
Here, when the ambient temperature is T1, the detection thermosensitive element 1 is supplied with the energizing current I1, and its output voltage is Vout1. The temperature compensation thermosensitive element 2 is supplied with an energization current I2 smaller than the energization current I1, so that its output voltage is Vout2 smaller than Vout1. That is, if both the thermosensitive elements 1 and 2 have the same characteristics as described above, the energization current I1 to the detection thermosensitive element 1 is larger than the energization current I2 to the temperature compensating thermosensitive element 2, so The amount of heat generated in the element 1 due to the above is larger than that in the element 2, and therefore the resistance value R1 of the thermal element 1 is larger than the resistance value R2 of the thermal element 2. So each output voltage is
Vout1 = I1 × R1
Vout2 = I2 × R2
And when this is transformed

It becomes.
[0014]
Therefore, at the ambient temperature T1, the output voltages Vout1 and Vout2 of the both thermal elements 1 and 2 have an offset. This offset is adjusted by the offset adjustment circuit 5. The offset adjustment circuit 5 has a variable resistor 8 and an amplifier 9, and the output voltage Vout2 of the temperature compensating thermal element 2 is equivalent to the resistance value difference (R1-R2) between the thermal elements 1 and 2. The variable resistor 8 of the offset adjustment circuit 5 and the amplifier 9 of the offset adjustment circuit 5 adjust the amount corresponding to the current ratio (I1 / I2) to both the thermosensitive elements 1 and 2 as a result. The circuit 5 adjusts to Vout3 which is the same as Vout1.
[0015]
If there is no change at the ambient temperature T1, the output voltage Vout3 of the offset adjustment circuit 5 and the output voltage Vout1 of the detection thermosensitive element 1 are the same with each other by this offset adjustment, so that both output voltages Vout1 and Vout3 are differential amplifiers. 7, the output voltage Vout5 of the differential amplifier 7 becomes zero, and the temperature compensation for the detection thermal element 1 is performed.
[0016]
However, when the ambient temperature changes by ΔT from T1, the output voltage Vout1 of the detection thermosensitive element 1 changes as shown by the characteristic (1) in FIG. 2 and becomes Vout1 ′, whereas the output of the offset adjustment circuit 5 Since the voltage Vout3 changes as indicated by characteristic (2) to become Vout3 ′, the output voltage Vout1 ′ of the detection thermosensitive element 1 and the output voltage Vout3 ′ of the offset adjustment circuit 5 do not match. This will be described in detail. The resistance value R1 of the detection thermal element 1 increases by ΔR1 as the temperature changes by ΔT, and the resistance value R2 of the temperature compensation thermal element 2 similarly increases by ΔR2. . Here, since ΔR1 / R1 and ΔR2 / R2 are substantially the same value, if this value is a,

Also, from the above

Here, since Vout3 = Vout1,

Since R1> R2 and I1, I2, and a are all positive values.
Vout3 ′ <Vout1 ′.
[0017]
Therefore, the output voltage Vout3 ′ of the offset adjustment circuit 5 at the ambient temperature T1 + ΔT is input to the gain adjustment circuit 6, and the gain is adjusted so that the output voltage Vout4 of the gain adjustment circuit 6 becomes Vout1 ′. This gain adjustment will be described. First, the reference voltage Vref is adjusted by the variable resistor 10 so as to coincide with the output voltage Vout1 of the detection thermosensitive element 1 at the ambient temperature T1. Then, the variable resistor 11 is adjusted so that the output voltage Vout4 of the gain adjusting circuit 6 matches the output voltage Vout1 ′ of the detection thermosensitive element 1 when the ambient temperature is T1 + ΔT. As a result, the output voltage Vout4 of the gain adjustment circuit 6 matches the output voltage Vout1 ′ of the detection thermosensitive element 1. As a result, the output voltage Vout5 corresponding to the detection target detected by the detection thermal element 1 can be output from the differential amplifier 7 without depending on the change in the ambient temperature.
[0018]
In the temperature compensation method and circuit as described above, it will be described that Vout3 adjusted in advance does not change even after temperature gain adjustment. Assuming that the ambient temperature is returned to T1 after the temperature gain adjustment, the resistance value of the detection thermosensitive element 1 is R1, and returns to the voltage Vout1 at the time of offset adjustment with Vout1 = I1 × R1. Further, the resistance value of the temperature compensating thermosensitive element 2 is R2, and Vout2 = I2 × R2 and returns to the voltage Vout2 at the time of offset adjustment similarly to Vout1. Here, since each set value of the offset adjustment circuit 5 remains at the time of offset adjustment, Vout3 = Vout1. Now, since the reference voltage Vref of the temperature gain adjusting circuit 6 has already been adjusted by the variable resistor 11 so as to coincide with the output voltage Vout1 of the detection thermosensitive element 1 at the ambient temperature T1, it follows the operational principle of the operational amplifier. Thus, Vout4 = Vref = Vout3. Therefore, Vout4 = Vout1, and Vout5 becomes zero even at the ambient temperature T1, and it can be seen that the temperature is compensated.
[0019]
In this embodiment, two heat sensitive elements are used. However, as shown in FIG. 3, one heat sensitive element 13 is provided, and a switch 14, between the heat sensitive element 13 and the constant current sources 3 and 4 is provided. 15, and when the switches 14 and 15 are turned on / off by the control unit 16, the first switch 14 connected to the constant current source 3 is turned on and the second switch 15 connected to the constant current source 4 is turned off. On the other hand, by supplying the energizing current I1 from the constant current source 3 to the thermal element 13 and the energizing current I2 from the constant current source 4 to the thermal element 13 when the first switch 14 is off and the second switch 15 is on, One thermal element 13 is controlled by the controller 16 at different temperatures at different timings (on / off of the switches 14 and 15), and the output voltage at different timings of the thermal element 13 is controlled by the offset adjustment circuit. As a temperature compensation method, the offset adjustment is performed under an arbitrary ambient temperature and the gain adjustment circuit 6 adjusts the gain of each output voltage at the different timing of the thermal element 13 under the other arbitrary ambient temperature. The same temperature compensation can be performed.
[0020]
Here, each output voltage at different timings may be held by using, for example, a sample / hold circuit or the like, or may be held by using a microcomputer or the like.
[0021]
(Embodiment 2)
In the first embodiment described above, it may be time-consuming because there are many adjustment steps, and it is necessary to place the detection target in two environments with different temperatures, so that equipment for that is required. In addition, there are problems that it takes time to adapt the detection target in each temperature environment, and that adjustment work with a variable resistor is difficult. In the temperature compensation method of the second embodiment of the present invention, such a problem of the first embodiment is solved.
[0022]
The temperature compensation method according to the second embodiment of the present invention will be described below. One of at least two thermal elements is a detection thermal element, the other is a temperature compensation thermal element, It includes at least a means for processing so as to have different heating temperatures, and a means for adding or subtracting the excess or deficiency of at least one of the output voltages of the two thermal elements with respect to the other. This will be described with reference to FIGS.
[0023]
First, as shown in FIG. 4, for example, the temperature compensation circuit used in the implementation of the second embodiment includes a detection thermal element 21, a temperature compensation thermal element 22, constant current sources 23 and 24, and an adjustment circuit 25. And an adder circuit 26 and a differential amplifier 27. In the second embodiment, as in the first embodiment, two thermal elements, that is, a detection thermal element 21 and a temperature compensation thermal element 22 are used. The thermal elements 21 and 22 are supplied with energization currents I1 and I2 from the corresponding constant current sources 23 and 24, respectively. Here, I1> I2. Here, in order to simplify the description, it is assumed that the characteristics of both the thermal elements 21 and 22 are the same.
[0024]
As shown in FIG. 5, the resistance values of the detection thermal element 21 and the temperature compensation thermal element 22 when heated at such energization currents I1 and I2 in the same ambient temperature environment are R1, R2 ( R2 <R1). At this time, the output voltages of the detection thermal element 21 and the temperature compensation thermal element 22 are Vout6 and Vout7, the output voltage of the adjustment circuit 25 is Vout8, the output voltage of the adder circuit 26 is Vout9, The output voltage of the amplifier 27 is Vout10. In the following description, the resistance value is used for easy understanding.
[0025]
When the ambient temperature of both the thermal elements 21 and 22 changes by ΔT, the resistance values of the thermal elements 21 and 22 also change to ΔR1 and ΔR2, respectively, but the detection thermal element 21 and the temperature compensation thermal element 22 Since the resistance value differs from R1 and R2 depending on the energization currents I1 and I2, ΔR1> ΔR2. In the description of the first embodiment, ΔR1 / R1 and ΔR2 / R2 are described as being substantially the same. However, in reality, there is a slight difference, and this difference may not be ignored for accurate temperature compensation. This is the case, for example, when the minute flow velocity is the detection target. Here, the case of ΔR1 / R1 <ΔR2 / R2 is taken as an example, and the relationship between the resistance values R1, ΔR1, R2, and ΔR2 at this time will be described with reference to FIG.
[0026]
FIG. 6A shows the total resistance value TR1 of R1 and ΔR1, which is a change in resistance value due to the ambient temperature change ΔT, as the resistance value of the detection thermal element 21. FIG. 6B shows the total resistance value TR2 of R2 and ΔR2, which is a resistance value change due to the ambient temperature change ΔT, as the resistance value of the temperature compensating thermosensitive element 22. Here, as shown in FIG. 6C, the adjustment circuit 25 adjusts the resistance value change ΔR2 to ΔR2 ′ so as to coincide with ΔR1, thereby changing the total resistance value from TR2 to TR2 ′. At this time, the resistance value R2 is also adjusted by the adjustment circuit 25, resulting in R2 ′. However, the total resistance value TR2 ′ in FIG. 6C is different from the total resistance value TR1 in FIG. The resistance value R3 is small. Therefore, by obtaining a resistance value R3 (added voltage Vadd) in advance through experiments or the like, and by adding a resistance value R3 (added voltage Vadd) by the adder circuit 26, Vout9 corresponding to R2 ′ + R3 + ΔR2 ′ is obtained. By simply adjusting the adjustment circuit 25 so as to match Vout6 corresponding to R1 + ΔR1, a voltage having the same total resistance value is input to the differential amplifier 27, and the output voltage Vout10 becomes zero. .
[0027]
That is, when Vout6, Vout7, Vout8, Vadd, and Vout9 are represented by a resistance value relationship,

Accordingly, as is clear from the equation (1) that is one input of the differential amplifier 27 and the equation (5) that is the other input, both inputs to the differential amplifier 27 are the same. The output voltage Vout10 corresponding to the detection target detected by the detection thermal element 21 can be output from the differential amplifier 27 without depending on the ambient temperature.
[0028]
Here, an example has been described in which the resistance value R3 (added voltage Vadd) is grasped and set in advance and the adjustment circuit 25 is adjusted, but conversely, a value corresponding to ΔR1 / ΔR2 is grasped and adjusted in advance. The circuit 25 may be set as a fixed value, and the added voltage Vadd corresponding to the resistance value R3 may be adjusted.
[0029]
In this example, R3 is added to TR2 ′, and an addition circuit is provided on the temperature compensation thermal element side. Conversely, R3 is subtracted from TR1, and a subtraction circuit is provided on the detection thermal element side. The same effect can be obtained even if the is provided.
[0030]
Further, here, the case of (ΔR1 / R1) <(ΔR2 / R2) has been described as an example, but in the case of (ΔR1 / R1)> (ΔR2 / R2), the addition / subtraction relationship is merely reversed. Similarly, the temperature can be compensated.
[0031]
Further, even when the characteristics of the thermal elements 21 and 22 are different, temperature compensation can be similarly performed by grasping the relationship between ΔR1 / R1 of the thermal element 21 and ΔR2 / R2 of the thermal element 22.
[0032]
In the second embodiment, two thermosensitive elements are used. However, in the same manner as in FIG. 3, one thermosensitive element is used, and different timings are used for using the thermosensitive element for detection and the thermosensitive element for temperature compensation. The thermal sensor is controlled to a different temperature, the thermal element is changed from the temperature by the same temperature at each of the different timings, and the output voltage is adjusted when the thermal element is used as a temperature-compensating thermal element. A temperature compensation method for adding or subtracting the output voltage may be used.
[0033]
Although the adder circuit 26 is used in the second embodiment, a subtractor circuit may be used depending on the contents of adjustment.
[0034]
Next, the second embodiment will be described with specific numerical examples.
[0035]
The output voltage Vout6 (energization current I1 × resistance value R1) of the detection thermal element 21 is 10V, and the output voltage Vout7 (energization current I2 × resistance value R2) of the compensation thermal element 22 is 4V. As the ambient temperature ΔT changes, the resistance value of the detection thermal element 21 changes from R1 → TR1 (= R1 + ΔR1), and the resistance value of the compensation thermal element 22 changes from R2 → TR2 (= R2 + ΔR2). If XR1 = 10V is changed to I1 × (R1 + ΔR1) = I1 × R1 + I1 × ΔR1 = 10V + 2V = 12V, and Vout7 is changed from I2 × R1 = 4V to I2 × (R2 + ΔR2) = I2 × R2 + I2 × ΔR2 = 4V + 1V = 5V Vout6 is increased by 2V due to the change of the ambient temperature ΔT, and Vout7 is increased by 1V.
[0036]
Since the voltage increase ΔVout6 (= 2V) for Vout6 is I1 × ΔR1, and the voltage increase ΔVout7 (= 1V) for Vout7 is I2 × ΔR2, the amplification factor of the adjustment circuit 25 is set to include I1 / I2. Then, it can be explained by the resistance value.
[0037]
Here, when the amplification factor of the adjustment circuit 25 is doubled so that the voltage increase ΔVout7 = 1V of Vout7 becomes equal to the voltage increase ΔVout7 = 2V of Vout6, Vout7 is amplified by the adjustment circuit 25 twice. Therefore, Vout8 changes from 8V to 10V with the ambient temperature change ΔT. When this is compared with the voltage change 10 V → 12 V of Vout 6, both the changing voltage values are the same at 2 V, but the absolute value is 2 V shortage. This undervoltage is obtained in advance by experiments, calculations, etc., and set and designed so that the undervoltage is added by the adder circuit 26. By doing so, the output voltage Vout9 of the adder circuit 26 changes from 10V to 12V with a temperature change of ΔT.
[0038]
Therefore, both inputs of the differential amplifier 27 change from 10 V to 12 V with a temperature change from the ambient temperature T1 to ΔT, and are temperature compensated.
[0039]
Each circuit in each of the above-described embodiments may be calculated by software processing using a program by a microcomputer except for the constant current source and the thermal element.
[0040]
For example, as described in JP-A-7-318364, one thermal element is used, and this thermal element is heated and unheated to output a detection signal for the measurement object and a detection signal for the ambient temperature. There is something to let you do. In the system described in this publication, since there is one thermal element, it is not necessary to match the characteristics of the two thermal elements as in the system using two thermal elements, and control is easy.
[0041]
However, in the method shown in this publication, it is necessary to pass an energizing current through the non-heating treatment of the thermosensitive element to such an extent that a temperature rise due to energization is negligible. Since the current value is very small, even a slight current fluctuation causes a large error in detection. Second, the voltage output to both ends of the thermal element is also small due to the small energization current. The signal processing system requires very high-precision processing. For this reason, in the method disclosed in this publication, electronic components having a configuration of a setting circuit for current or applied voltage to be applied to the thermosensitive element and a processing circuit for output voltage become very expensive.
[0042]
In contrast to this, in the present embodiment, at the timing when one thermal element is used as a thermal sensor for detection with a switch as shown in FIG. It is possible to carry out the heat treatment by applying a current that is not negligible to increase the temperature of the heat sensitive element even when it is used as a temperature compensating heat sensitive element. There is no error factor due to the minuteness, and the thermal sensor output voltage due to the minute energizing current is minute, so that the subsequent signal processing system does not require high precision processing, simple and low cost. Can be easily realized.
[0043]
In the first and second embodiments, the constant current method is used as a method for energizing the thermosensitive element. However, this may be replaced with a fixed resistor and a constant voltage method may be used. Further, a constant temperature system as shown in FIG. 13 of Japanese Patent Laid-Open No. 4-12278 or FIG. 17 of Japanese Patent Laid-Open No. 7-318364 described above may be used. In addition, although the case where self-heating is performed by energizing current is taken as an example here, the resistance value in the explanatory text is different from R1 and R2 even if the detection thermosensitive element is heated from the outside, which is feasible. is there.
[0044]
Here, when the circuit excluding the detection thermal element 1 and the compensation thermal element 2 is a processing circuit, as shown in FIG. Appropriate temperature compensation may be performed. That is, the temperature compensation of the detection thermosensitive element 1 is performed from the information regarding the temperature of the detection target, while the processing circuit for performing the temperature compensation of the detection thermosensitive element 1 and the desired detection for the detection target itself. You may make it perform temperature compensation from the information regarding temperature.
[0045]
In the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 4, it is assumed that the ambient temperature of the processing circuit does not change. For example, the above-described embodiment is applied to a gas water heater. In this case, since both the thermal elements 1 and 2 are intended to measure the air flow rate and the gas flow rate in the gas water heater, they are installed inside the water heater like the air or gas pipe to be detected. On the other hand, the processing circuit is not installed in the pipeline. Accordingly, the ambient temperature of the thermal elements 1 and 2, that is, the temperature of the detection target such as air or gas in the pipeline, and the change thereof are independent of the ambient temperature of the processing circuit or the change thereof. If the influence (change) of the temperature by the processing circuit itself such as offset and gain is ignored, appropriate temperature compensation for the change in ambient temperature of the detection thermal element 1 and appropriate processing for performing desired detection for the detection target Must not. Therefore, as will be described with reference to FIG. 7, the offset adjustment for the ambient temperature of the processing circuit itself is performed by the resistor R9 which is a temperature sensing element for offset compensation, and the gain adjustment for the change in the ambient temperature of the processing circuit itself is performed by gain compensation. This is performed by the resistor R2, which is a temperature sensing element for use. In FIG. 7, the differential amplifier 7 includes amplifiers A1 to A3 and resistors R1 to R7. In this way, the overall temperature compensation is possible by the offset adjustment and gain adjustment by the processing circuit of the detection thermosensitive element 1 and the offset adjustment and gain adjustment of the processing circuit itself, and more appropriate temperature compensation is possible. .
[0046]
In this case, temperature compensation for the processing circuit may be performed by only offset adjustment, gain adjustment, or both adjustments.
[0047]
In this case, the offset adjustment and gain adjustment are not adjusted by the temperature sensitive elements such as the resistors R2 and R9, but may be temperature sensitive elements that detect a temperature change by a current change or a voltage change. It may be performed by a circuit.
[0048]
The temperature compensation circuit of the above-described embodiment may be a chip form or other forms of flow velocity sensor, flow sensor, or other sensor.
[0049]
【The invention's effect】
As described above, according to the present invention, one of the thermosensitive elements is used as a thermosensitive element for detection, the other is used as a thermosensitive element for temperature compensation, and both the thermosensitive elements are processed so as to have different heating temperatures, Since the offset adjustment is performed so that the output voltages of the two thermal elements coincide with each other under an arbitrary ambient temperature, and the gain is adjusted so that the output voltages of the two thermal elements coincide with each other under an arbitrary ambient temperature. When adjusting the offset of the thermal element or adjusting the gain, the offset value adjusted in advance when the gain is adjusted after the offset adjustment as in the past is shifted, or what is the process of adjusting the offset again after the gain adjustment? This eliminates the need for repeated adjustments and makes temperature compensation easy and accurate.
[0050]
Further, according to the present invention, one of the two thermosensitive elements is a detecting thermosensitive element, the other is a temperature compensating thermosensitive element, the two thermosensitive elements are processed to have different heating temperatures, and the both thermosensitive elements are processed. Since the temperature compensation is performed so that the difference between the output voltages of the two thermal elements becomes zero by adding or subtracting the excess or deficiency of the output voltage of each element relative to the other, as in the conventional case. It is no longer necessary to change the ambient temperature of the thermal element in the adjustment process, so that no equipment is required for this, and there is no need for time to adapt the detection target under each temperature environment. It becomes extremely easy.
[0051]
In the above case, instead of the two thermal elements, if one thermal element is switched at different timings, the thermal element for detection is used at one timing and the thermal element for temperature compensation is used at the other timing. Not only can it be reduced, but there is almost no variation in relative characteristics between the two thermal elements when two thermal elements are used, making it easier to adjust and improving accuracy. To do.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a temperature compensation circuit used in a temperature compensation method according to an embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the voltage of each part and the ambient temperature in the circuit of FIG.
FIG. 3 is a main circuit diagram of a temperature compensation circuit used in a temperature compensation method according to another embodiment of the present invention.
FIG. 4 is a circuit diagram of a temperature compensation circuit used in a temperature compensation method according to still another embodiment of the present invention.
FIG. 5 is a diagram for explaining the relationship between the resistance value of a thermal element and its temperature in the circuit of FIG. 4;
6 is a diagram for explaining changes in resistance values of the detection thermal element and the temperature compensation thermal element in the circuit of FIG. 4;
[Fig. 7] Reference example The circuit diagram of the principal part of the temperature compensation circuit used for the temperature compensation method concerning
[Explanation of symbols]
1 Thermal element for detection
2 Thermosensitive element for temperature compensation
3, 4 Constant current source
5 Offset adjustment circuit
6 Gain adjustment circuit
7 Differential amplifier

Claims (11)

One of the two thermosensitive elements is a detection thermosensitive element, the other is a temperature-compensating thermosensitive element, and both the thermosensitive elements are processed to have different heating temperatures,
Adjust the offset so that the output voltages of the two thermal elements coincide under an arbitrary ambient temperature,
Adjusting the gain so that the output voltages of the two thermal elements are matched under any other ambient temperature;
And a temperature compensation method. The temperature compensation method according to claim 1,
A temperature compensation method characterized in that, instead of the two thermal elements, one thermal element is switched at different timings, the thermal sensor for detection is used at one timing, and the thermal sensor for temperature compensation is used at the other timing. . One of the two thermosensitive elements is a detection thermosensitive element, the other is a temperature-compensating thermosensitive element, and both the thermosensitive elements are processed to have different heating temperatures,
Temperature compensation so that the difference between the output voltages of the two thermal elements becomes zero by adding or subtracting the excess or deficiency of at least one of the output voltages of the two thermal elements to the other,
And a temperature compensation method. The temperature compensation method according to claim 3, wherein
A temperature compensation method characterized in that, instead of the two thermal elements, one thermal element is switched at different timings, the thermal sensor for detection is used at one timing, and the thermal sensor for temperature compensation is used at the other timing. . At least two thermal elements;
One of the thermosensitive elements is a detecting thermosensitive element, the other is a temperature compensating thermosensitive element, and each of the thermosensitive elements is processed at different heating temperatures;
Means for adjusting the offset so that the output voltages of the two thermal elements are matched under an arbitrary ambient temperature;
Means for adjusting the gain so that the output voltages of the two thermal elements are matched under any other ambient temperature;
A temperature compensation circuit comprising: The temperature compensation circuit according to claim 5,
Instead of the two thermosensitive elements, the thermosensitive element has one thermosensitive element, and the one thermosensitive element is switched at different timings, and is used as the thermosensitive element for detection at one timing, and the thermosensitive element for temperature compensation at the other timing. And a temperature compensation circuit. At least two thermal elements;
Means for treating one of the thermal elements to have a different heating temperature with one thermal element as the detection thermal element and the other thermal element as the temperature compensating thermal element;
Means for compensating for temperature so that the difference between the output voltages of the two thermal elements becomes zero by adding or subtracting the excess or deficiency of at least one of the output voltages of the two thermal elements to the other; and
A temperature compensation circuit comprising: The temperature compensation circuit according to claim 7,
Instead of the two thermosensitive elements, the thermosensitive element has one thermosensitive element, and the one thermosensitive element is switched at different timings, and is used as the thermosensitive element for detection at one timing, and the thermosensitive element for temperature compensation at the other timing. And a temperature compensation circuit. The temperature compensation circuit according to claim 5 or 6,
Having a reference voltage,
Means for amplifying or calculating an output voltage of at least one of the detection thermal element and the temperature compensation thermal element based on the reference voltage;
A temperature compensation circuit comprising: The temperature compensation circuit according to claim 7 or 8,
Have a preset or adjustable reference voltage,
Means for adding / subtracting the reference voltage to / from an output voltage of at least one of the thermal element for detection or the thermal element for temperature compensation;
A temperature compensation circuit comprising: 11. A sensor comprising the temperature compensation circuit according to claim 5.

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