JP2016200610A - Gas detector - Google Patents
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- JP2016200610A JP2016200610A JP2016177067A JP2016177067A JP2016200610A JP 2016200610 A JP2016200610 A JP 2016200610A JP 2016177067 A JP2016177067 A JP 2016177067A JP 2016177067 A JP2016177067 A JP 2016177067A JP 2016200610 A JP2016200610 A JP 2016200610A
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- 238000001514 detection method Methods 0.000 claims abstract description 64
- 239000004065 semiconductor Substances 0.000 claims abstract description 43
- 238000006243 chemical reaction Methods 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 description 161
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 60
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 15
- 230000035945 sensitivity Effects 0.000 description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003574 free electron Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
- 239000012855 volatile organic compound Substances 0.000 description 1
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Abstract
Description
本発明は、半導体式ガス検知素子を備えたガス検知装置に関する。 The present invention relates to a gas detection device including a semiconductor type gas detection element.
一般に、半導体式ガス検知素子は、例えば、清浄空気中等、検知対象となるガス（以下、「被検知ガス」と称する場合がある。）が存在しない雰囲気下では、表面に酸素が吸着した状態となっており、この吸着した酸素によって生じる空間電荷層が粒子内部に向かって広がるため、自由電子の伝導パスが狭くなり、電気抵抗が高くなる。一方、被検知ガスが存在する雰囲気下では、半導体式ガス検知素子は、吸着している酸素が被検知ガスとの酸化還元反応によって、その表面から脱離するため、電気抵抗が低くなる。半導体式ガス検知素子を備えたガス検知装置は、この電気抵抗の変化を出力値として取り出すことによって、被検知ガスを検知している。 In general, a semiconductor type gas detection element has a state in which oxygen is adsorbed on the surface in an atmosphere where there is no gas to be detected (hereinafter sometimes referred to as “detected gas”) such as in clean air. Since the space charge layer generated by the adsorbed oxygen spreads toward the inside of the particle, the conduction path of free electrons is narrowed and the electric resistance is increased. On the other hand, in an atmosphere in which a gas to be detected exists, the semiconductor gas detection element has a low electric resistance because adsorbed oxygen is desorbed from the surface by an oxidation-reduction reaction with the gas to be detected. A gas detection device including a semiconductor gas detection element detects a gas to be detected by taking out the change in electric resistance as an output value.
この種の半導体式ガス検知素子の出力値は、検知範囲の低濃度側で大きく変化し、高濃度になるほど濃度に対する出力値の変化量が小さくなる特性を有する。このため、このような半導体式ガス検知素子は、低濃度のガスを検知するのに適しており、特に高感度検知が要求されるガス警報器やガス漏洩検知装置などに多く利用されている。 The output value of this type of semiconductor gas detection element changes greatly on the low concentration side of the detection range, and the amount of change in the output value with respect to the concentration decreases as the concentration increases. For this reason, such a semiconductor gas detection element is suitable for detecting a low-concentration gas, and is often used particularly for a gas alarm or a gas leak detection device that requires high-sensitivity detection.
尚、本発明における従来技術となる半導体式ガス検知素子を備えたガス検知装置は、一般的な技術であるため、特許文献等の先行技術文献は記載しない。 In addition, since the gas detection apparatus provided with the semiconductor type gas detection element used as the prior art in this invention is a general technique, prior art documents, such as a patent document, are not described.
しかし、前記従来の半導体式ガス検知素子では、その出力値の特徴をセンサ出力値とガス濃度の対数との関係として図式化すると、非線形の関係になるが、この関係を単純な関数で表現する手法がなかった。このため、これまで半導体式ガス検知素子はガス濃度を計測する濃度計としての用途には活用されてこなかった。 However, in the conventional semiconductor type gas detection element, when the characteristic of the output value is graphed as the relationship between the sensor output value and the logarithm of the gas concentration, it becomes a non-linear relationship, but this relationship is expressed by a simple function. There was no method. For this reason, the semiconductor type gas detection element has not been used for the application as a concentration meter for measuring the gas concentration.
本発明は、上記課題に鑑みてなされたものであり、半導体式ガス検知素子の出力値を被検知ガスの濃度として換算できるガス検知装置を提供することを目的とする。 This invention is made | formed in view of the said subject, and it aims at providing the gas detection apparatus which can convert the output value of a semiconductor type gas detection element as the density | concentration of to-be-detected gas.
上記目的を達成するための本発明に係るガス検知装置の特徴構成は、半導体式ガス検知素子と、当該半導体式ガス検知素子の出力値を下記（Ｉ）式に基づいてガスの濃度に換算する換算手段とを備えた点にある。
[数１]
Ｙ＝ａ・ｌｏｇ（Ｘ＋ｃ＋１）＋ｂ （Ｉ）
（式中、Ｘはガスの濃度、Ｙは出力値、ａ，ｂ，ｃはそれぞれ定数を示す。）
The characteristic configuration of the gas detection device according to the present invention for achieving the above object is to convert a semiconductor gas detection element and an output value of the semiconductor gas detection element into a gas concentration based on the following formula (I): It is in the point provided with the conversion means.
[Equation 1]
Y = a · log (X + c + 1) + b (I)
(In the formula, X is a gas concentration, Y is an output value, and a, b, and c are constants.)
本構成によれば、後述する実施例に示すように、雑ガス等による出力値を被検知ガスによる出力値とすることにより、半導体式ガス検知素子の出力値を清浄空気中における被検知ガスの濃度として換算することができる。
このため、清浄空気中に、被検知ガス、雑ガスを含めたガスがどれだけ存在するかを、被検知ガスの濃度を尺度として知ることができる。
According to this configuration, as shown in the examples to be described later, the output value of the miscellaneous gas or the like is set as the output value of the detected gas, so that the output value of the semiconductor type gas detection element is changed to the detected gas in the clean air. It can be converted as a concentration.
Therefore, it is possible to know how much gas including the gas to be detected and the miscellaneous gas exists in the clean air, using the concentration of the gas to be detected as a scale.
本発明に係るガス検知装置は、前記出力値が複数のガス種に基づく場合に好ましく適用できる。本構成によれば、被検知ガス、複数種類の雑ガス、水蒸気等が存在する環境下に
おいても、清浄空気中における被検知ガスの濃度として換算することができる。
The gas detector according to the present invention is preferably applicable when the output value is based on a plurality of gas types. According to this configuration, even in an environment where there is a gas to be detected, multiple types of miscellaneous gases, water vapor, and the like, it can be converted as the concentration of the gas to be detected in clean air.
本発明に係るガス検知装置において、前記ガスの濃度を所定のガス種の濃度とすることもできる。例えば、複数種類のガスが被検知ガスとなる場合のように出力値が複数種類の被検知ガスに基づく場合には、被検知ガスのうちの一つのガス種を予め決めて上記式（Ｉ）を設定しておくことで、そのガス種に対する濃度として換算することができる。 In the gas detection device according to the present invention, the concentration of the gas may be a concentration of a predetermined gas type. For example, in the case where the output value is based on a plurality of types of detected gases as in the case where a plurality of types of gases are detected gases, one gas type of the detected gases is determined in advance and the above formula (I) Can be converted as the concentration for the gas type.
本発明に係るガス検知装置は、前記所定のガス種の濃度を表示する表示手段をさらに備えることが好ましい。本構成によれば、清浄空気に対する濃度変化を表示できるので、工場、実験室、クリーンルーム等、仕切られた空間のガス濃度を監視するガス濃度表示装置として適用できる。 It is preferable that the gas detection device according to the present invention further includes display means for displaying the concentration of the predetermined gas type. According to this configuration, since the concentration change with respect to clean air can be displayed, it can be applied as a gas concentration display device that monitors the gas concentration in a partitioned space such as a factory, a laboratory, or a clean room.
前記（Ｉ）式において、cを０とし、bを検知するガスが存在しない場合の前記半導体式ガス検知素子の出力値とすることが好ましい。cを０とすれば、ガスの濃度Ｘが０のとき
、Ｙ＝ｂとなるため、清浄空気中の出力値としてbを予め設定しておくことができる。ま
た、aは、前記ガスの濃度と、当該濃度における前記半導体式ガス検知素子の出力値とに
基づき算出し、設定することができる。
In the formula (I), it is preferable that c is 0, and b is an output value of the semiconductor type gas detection element when there is no gas for detecting b. If c is 0, Y = b when the gas concentration X is 0, so that b can be set in advance as an output value in clean air. Further, a can be calculated and set based on the concentration of the gas and the output value of the semiconductor gas detection element at the concentration.
本発明に係るガス検知装置は、半導体式ガス検知素子と、当該半導体式ガス検知素子の出力値を下記（Ｉ）式に基づいてガスの濃度に換算する換算手段とを備えたものである。 The gas detection device according to the present invention includes a semiconductor gas detection element and conversion means for converting an output value of the semiconductor gas detection element into a gas concentration based on the following equation (I).
[数２]
Ｙ＝ａ・ｌｏｇ（Ｘ＋ｃ＋１）＋ｂ （Ｉ）
（式中、Ｘはガスの濃度、Ｙは出力値、ａ，ｂ，ｃはそれぞれ定数を示す。）
[Equation 2]
Y = a · log (X + c + 1) + b (I)
(In the formula, X is a gas concentration, Y is an output value, and a, b, and c are constants.)
本発明者らは、後述する実施例に示すように、環境中の雑ガス等の影響を実験的に確認し、半導体式ガス検知素子の出力値は、雑ガス等の種類に関わらず、被検知ガスの濃度として換算できることに着目し、上記（Ｉ）式を導き出した。 As shown in the examples described later, the present inventors have experimentally confirmed the effects of miscellaneous gases and the like in the environment, and the output value of the semiconductor gas detection element is not limited regardless of the type of miscellaneous gases. Focusing on the fact that it can be converted as the concentration of the detection gas, the above formula (I) was derived.
上記（Ｉ）式において、ａ、ｂ、ｃは定数であり、適宜設定することができる。一例として、センサを雑ガスがない清浄空気中で４ｍＡとなるように調整し、校正ガスとしてエタノール５０ｐｐｍで回路出力値が２０ｍＡとなるようにスパン調整をする場合で説明する。清浄空気中では、ガス濃度Ｘ=０、雑ガスによるノイズ分の校正ガス換算濃度ｃ=０であり、このときＹ=ｂ=４となる。次に清浄空気バランスのエタノール５０ｐｐｍ中で２０ｍＡとなるように調整する場合はＹ=２０、Ｘ=５０、ｃ=０、ｂ=４であるので、自ずとａ=９．３７が求まる。
このようにして調整したガスセンサを使用する通常の室内空気中におくと、雑ガスの影響でセンサの出力値Ｙは必ず４より大きな値となる。この清浄空気中と室内空気中とのセンサ出力の差がバックグラウンドノイズであり、この差の分を校正ガス濃度に換算してc
に代入する。仮にエタノール１ｐｐｍ相当分のバックグラウンドノイズがある環境でエタ
ノール濃度を計測する場合は、ａ=９．３７、ｂ=４、ｃ=１とし、環境中にエタノールに
よってセンサ出力Ｙの値が変化したとすると、Ｙの値からエタノールガス濃度Ｘが求まることになる。すなわち、室内に雑ガスが共存する環境中でもエタノールの濃度を求めることができる。
In the above formula (I), a, b, and c are constants and can be set as appropriate. As an example, a case will be described in which the sensor is adjusted to 4 mA in clean air with no miscellaneous gas, and span adjustment is performed so that the circuit output value is 20 mA with 50 ppm ethanol as the calibration gas. In clean air, the gas concentration X = 0, the calibration gas equivalent concentration c = 0 for noise due to miscellaneous gas, and Y = b = 4 at this time. Next, when adjusting to 20 mA in 50 ppm of ethanol with a clean air balance, since Y = 20, X = 50, c = 0, and b = 4, a = 9.37 is naturally obtained.
When the gas sensor adjusted in this way is placed in normal room air using the sensor, the output value Y of the sensor is always greater than 4 due to the influence of various gases. The difference in sensor output between clean air and indoor air is background noise, and this difference is converted to the calibration gas concentration.
Assign to. If the ethanol concentration is measured in an environment with background noise equivalent to 1 ppm of ethanol, a = 9.37, b = 4, c = 1, and the value of the sensor output Y is changed by ethanol in the environment. Then, the ethanol gas concentration X is obtained from the value of Y. That is, the ethanol concentration can be obtained even in an environment where miscellaneous gases coexist in the room.
本発明に係るガス検知装置は、半導体式ガス検知素子の出力値が複数のガス種に基づいている場合に好ましく適用できる。例えば、環境中に複数種類の雑ガスや被検知ガス、水蒸気等が存在し、その濃度が変動する場合でも、清浄空気中における被検知ガスの濃度として、その変化を捉えることができる。特に、複数種類の被検知ガスが存在する場合には、そのうちの一つのガス種に対応するａを用いることにより、そのガス種の濃度として換算することができる。 The gas detection device according to the present invention is preferably applicable when the output value of the semiconductor gas detection element is based on a plurality of gas types. For example, even when there are a plurality of types of miscellaneous gases, detected gas, water vapor, and the like in the environment and the concentration thereof fluctuates, the change can be captured as the concentration of the detected gas in clean air. In particular, when there are a plurality of types of gas to be detected, by using a corresponding to one of the gas types, the concentration of the gas type can be converted.
本発明に係るガス検知装置は、ガスの濃度を表示する表示手段を設けることが好ましい。本発明に係るガス検知装置は、清浄空気中のガスの存在を、所定のガス種の濃度変化として表すことができるので、工場、実験室、クリーンルーム等、仕切られた空間のガス濃度を監視し、ユーザーに対してガスの濃度をリアルタイムで表示するガス濃度表示装置として適用できる。 The gas detection device according to the present invention is preferably provided with a display means for displaying the gas concentration. Since the gas detector according to the present invention can express the presence of gas in clean air as a change in concentration of a predetermined gas type, it monitors the gas concentration in partitioned spaces such as factories, laboratories, and clean rooms. The present invention can be applied as a gas concentration display device that displays the gas concentration to the user in real time.
本発明において使用する半導体式ガス検知素子は、特に限定されず、例えば、熱線型半導体式ガス検知素子、基板型半導体式ガス検知素子等が挙げられる。これらの半導体式ガス検知素子は、例えば、既知のガス検知回路等に組み込むことにより用いることができる。 The semiconductor gas detection element used in the present invention is not particularly limited, and examples thereof include a hot wire semiconductor gas detection element and a substrate type semiconductor gas detection element. These semiconductor gas detection elements can be used, for example, by being incorporated in a known gas detection circuit or the like.
本発明に係るガス検知装置は、被検知ガスの種類に応じて、半導体式ガス検知素子の種類を適宜選択することができる。このガス検知装置によって検知できるガス種としては、特に制限はなく、例えば、可燃性ガス、毒性ガス、不活性ガス、ＶＯＣ等が挙げられ、本発明に係るガス検知装置は、例えば、可燃性ガスセンサ、ガス漏れセンサ、ニオイセンサ等として用いることができる。 The gas detection device according to the present invention can appropriately select the type of semiconductor gas detection element according to the type of gas to be detected. The gas type that can be detected by the gas detector is not particularly limited, and examples thereof include flammable gas, toxic gas, inert gas, VOC, and the like. The gas detector according to the present invention includes, for example, a flammable gas sensor. It can be used as a gas leak sensor, an odor sensor or the like.
（実施例１）
半導体式ガス検知素子として、酸化スズを感応材料として用いた熱線型半導体式センサを用い、（１）清浄空気中、（２）実験室内の空気中、（３）雑ガス成分として水素を２００ｐｐｍ混入させた実験室内の空気中、（４）雑ガス成分としてトルエン１０ｐｐｍ混入させた実験室内の空気中、（５）雑ガス成分としてエタノールを１ｐｐｍ混入させた実験室内の空気中、のそれぞれの雰囲気下におけるエタノールの感度を調べ、図１に示した。その結果、低濃度側では環境中の雑ガス（バックグラウンドノイズ）による出力変動は大きいが、エタノールの濃度が高くなるとバックグラウンドノイズの影響が小さくなることが分かった。
Example 1
As a semiconductor gas detection element, a hot-wire semiconductor sensor using tin oxide as a sensitive material is used. (1) In clean air, (2) In the laboratory air, (3) 200 ppm of hydrogen as a miscellaneous gas component In the atmosphere of the laboratory, (4) in the laboratory air mixed with 10 ppm of toluene as a miscellaneous gas component, and (5) in the laboratory air mixed with 1 ppm of ethanol as the miscellaneous gas component, respectively. The ethanol sensitivity was examined and shown in FIG. As a result, it was found that the output fluctuation due to environmental miscellaneous gas (background noise) is large on the low concentration side, but the influence of the background noise becomes small as the ethanol concentration increases.
また、図１における清浄空気中のエタノールに対する感度を基準として、バックグラウンドノイズのレベルをエタノールの濃度に換算すると、室内空気中の２００ｐｐｍの水素に対する出力値はエタノールの濃度の約１ｐｐｍに相当し、室内空気中の１０ｐｐｍのトルエンに対する出力値はエタノールの濃度の約２ｐｐｍに相当することが分かった。すなわち、室内空気中における２００ｐｐｍの水素、及び１０ｐｐｍのトルエンが半導体式ガス検知素子に与える影響は、それぞれ清浄空気中のエタノール約１ｐｐｍ、及び約２ｐｐｍと同等と見なせることが分かる。したがって、室内空気中に水素２００ｐｐｍを含む雰囲気下でエタノールが１ｐｐｍ存在するときには、エタノールの濃度２ｐｐｍと同等であると考えることができ、同様にエタノール１０ｐｐｍ、５０ｐｐｍがそれぞれ存在するときには、エタノールの濃度１１ｐｐｍ、５１ｐｐｍと同等であると考えることができる。
これによれば、半導体式ガス検知素子において、エタノール濃度が高くなるほどバックグラウンドノイズの影響（比率）が小さくなることも説明できる。
この考えをもとに、バックグラウンドノイズ分をエタノール濃度に換算して加算し、プロットし直したときの感度特性を図２に示した。その結果、異なるバックグラウンドでもエタノール感度曲線が重なることから、環境中の雑ガス等の種類に関わらず、エタノールの濃度に換算して表すことができることが分かった。
Further, when the background noise level is converted into the concentration of ethanol based on the sensitivity to ethanol in clean air in FIG. 1, the output value for 200 ppm of hydrogen in the indoor air corresponds to about 1 ppm of the concentration of ethanol, It was found that the output value for 10 ppm toluene in room air corresponds to about 2 ppm ethanol concentration. That is, it can be seen that the effects of 200 ppm hydrogen and 10 ppm toluene in the room air on the semiconductor gas sensing element are equivalent to about 1 ppm and about 2 ppm of ethanol in clean air, respectively. Accordingly, when 1 ppm of ethanol is present in an atmosphere containing 200 ppm of hydrogen in the indoor air, it can be considered that the ethanol concentration is equivalent to 2 ppm. Similarly, when 10 ppm and 50 ppm of ethanol exist, respectively, the ethanol concentration of 11 ppm , 51 ppm.
This also explains that the influence (ratio) of the background noise decreases as the ethanol concentration increases in the semiconductor gas detection element.
Based on this idea, the sensitivity characteristic when the background noise was converted to ethanol concentration and added and plotted again is shown in FIG. As a result, since ethanol sensitivity curves overlap even in different backgrounds, it was found that it can be expressed in terms of ethanol concentration regardless of the type of miscellaneous gases in the environment.
上記結果から半導体式ガス検知素子の感度特性を数式で表すと、以下の近似式で表せることが分かった。
[数３]
Ｙ＝ａ・ｌｏｇ（Ｘ＋ｃ＋１）＋ｂ （Ｉ）
（式中、Ｘはガスの濃度、Ｙは出力値、ａ，ｂ，ｃはそれぞれ定数を示す。）
From the above results, it was found that the sensitivity characteristic of the semiconductor gas detection element can be expressed by the following approximate expression when expressed by a mathematical expression.
[Equation 3]
Y = a · log (X + c + 1) + b (I)
(In the formula, X is a gas concentration, Y is an output value, and a, b, and c are constants.)
次に、上記の（Ｉ）式において、エタノールの濃度Ｘが０ｐｐｍ（清浄空気）のときの半導体式ガス検知素子の出力値Ｙが４ｍＶとなることを前提として、ｂ＝４、ｃ＝０とし、清浄空気中のエタノールの濃度が５０ｐｐｍのときの出力値が２０ｍＶであることに基づいてａを求め、この（Ｉ）式で近似したものと清浄空気中のエタノールの実測した感度とをプロットし、図３に示した。その結果、この近似式は実測の感度特性によく合っていることが分かった。 Next, in the above formula (I), assuming that the output value Y of the semiconductor gas detection element is 4 mV when the ethanol concentration X is 0 ppm (clean air), b = 4 and c = 0. Based on the fact that the output value when the concentration of ethanol in clean air is 50 ppm is 20 mV, a is obtained, and the approximation of this equation (I) and the measured sensitivity of ethanol in clean air are plotted. This is shown in FIG. As a result, it has been found that this approximate expression is in good agreement with the measured sensitivity characteristic.
（実施例２）
実施例１で説明した手順にてエタノールで校正したガスセンサのそのほかの各種ガスに対する感度も同じ近似式で表現できることを図４と図５に示す。図４は各種ガスに対する感度を雑ガスが存在しない清浄空気中で実際に確認した実測データである。式（Ｉ）のｂ＝４、ｃ＝０であるので、各種ガスの５０ｐｐｍ中の感度からａを求めることができる。そこで実測データから求めたａを式（Ｉ）に代入してガス濃度Ｘの値を適宜代入してセンサ出力値Ｙを求めてプロットしたものが図５である。両者を比較すると他のガスに対しても実測値とよく一致した結果が得られていることがわかり、式（Ｉ）の関数の妥当性が説明できる。このときの各ガスに対応するａの値は、感度の序列を表す指標として用いることができる。
(Example 2)
FIG. 4 and FIG. 5 show that the sensitivity of the gas sensor calibrated with ethanol according to the procedure described in the first embodiment can be expressed by the same approximate expression. FIG. 4 shows measured data obtained by actually confirming sensitivity to various gases in clean air in which no miscellaneous gas exists. Since b = 4 and c = 0 in the formula (I), a can be obtained from the sensitivity in 50 ppm of various gases. Accordingly, FIG. 5 shows a plot obtained by substituting a obtained from the actually measured data into the equation (I) and appropriately substituting the value of the gas concentration X to obtain the sensor output value Y. When both are compared, it can be seen that the results of the other gases are in good agreement with the actual measurement values, and the validity of the function of formula (I) can be explained. The value of a corresponding to each gas at this time can be used as an index representing the order of sensitivity.
したがって、半導体式ガスセンサを用いて環境中の低濃度のガスを連続的にモニタリングする用途において、予め清浄空気中で任意の校正ガスで調整して、式（Ｉ）の定数ａとｂを決めておき、ｃを０として、センサ出力値Ｙを式（Ｉ）に代入すれば、環境中の不特定のガス濃度を校正ガスの濃度に換算して表現することができる。これにより、例えば校正ガスをトルエンとすれば、環境中に存在するＶＯＣの濃度レベルをトルエン濃度に換算してＴＶＯＣとして表現することが可能となる。 Therefore, in an application where a low concentration gas in the environment is continuously monitored using a semiconductor gas sensor, the constants a and b of the formula (I) are determined by adjusting with an arbitrary calibration gas in clean air in advance. If c is set to 0 and the sensor output value Y is substituted into the formula (I), an unspecified gas concentration in the environment can be converted into a calibration gas concentration and expressed. Thus, for example, if the calibration gas is toluene, the concentration level of VOC existing in the environment can be converted to toluene concentration and expressed as TVOC.
尚、各種ガスのａの値は、表１に示す通りである。
また、半導体式ガスセンサを用いて低濃度のガス濃度を計測する用途において、予め清浄空気中で任意の被検知ガスで校正して、式（Ｉ）の定数ａとｂを決めておき、測定環境
中での被検知ガスが存在しない場合（Ｘ＝０）のセンサ出力値をバックグラウンドノイズと見なしてcを求めてから、ａ、ｂ、ｃおよびＹを式（Ｉ）に代入すれば、水蒸気や雑ガ
スが存在する環境中であっても、センサ出力の変化分を被検知ガスの濃度に換算して表現できるようになる。これにより例えば携帯型のガス濃度計において、屋外などでゼロ調整（ｃを求めて式（Ｉ）に代入する操作）し、室内の空気を計測すれば屋外と室内の空気の清浄の違いを被検知ガスの濃度として表現することが可能となる。
Further, in an application for measuring a low concentration gas concentration using a semiconductor type gas sensor, the constants a and b in the formula (I) are determined in advance by calibrating with an arbitrary gas to be detected in clean air. If the sensor output value in the case where there is no gas to be detected (X = 0) is regarded as background noise, c is obtained, and if a, b, c and Y are substituted into equation (I), water vapor Even in an environment where various gases exist, the change in sensor output can be expressed by converting it to the concentration of the gas to be detected. As a result, for example, in a portable gas concentration meter, if zero adjustment is performed outdoors (an operation for obtaining c and substituting it into equation (I)), and the indoor air is measured, the difference in cleanness between the outdoor and indoor air can be measured. It can be expressed as the concentration of the detection gas.
本発明に係るガス検知装置は、半導体式ガス検知素子の出力値を被検知ガスの濃度として換算できるため、ガス濃度計、ガス警報器、ガス漏れ検知装置等に適用することができる。 The gas detection device according to the present invention can be applied to a gas concentration meter, a gas alarm device, a gas leak detection device and the like because the output value of the semiconductor gas detection element can be converted as the concentration of the gas to be detected.
上記目的を達成するための本発明に係るガス検知装置の特徴構成は、半導体式ガス検知素子と、当該半導体式ガス検知素子の出力値を下記（Ｉ）式に基づいてガスの濃度に換算する換算手段とを備えた点にある。
［数１］
Ｙ＝ａ・ｌｏｇ（Ｘ＋ｃ＋１）＋ｂ （Ｉ）
（式中、Ｘはガスの濃度、Ｙは出力値、ａ，ｂはそれぞれ定数を示し、ｃは外乱要因によって設定される定数を示す。）
The characteristic configuration of the gas detection device according to the present invention for achieving the above object is to convert a semiconductor gas detection element and an output value of the semiconductor gas detection element into a gas concentration based on the following formula (I): It is in the point provided with the conversion means.
[Equation 1]
Y = a · log (X + c + 1) + b (I)
(Wherein, X is the concentration of gas, Y is the output value, a, b will indicate constants respectively, c is shown to the constants set by the disturbance factor.)
前記（Ｉ）式において、ｃを外乱要因による前記半導体式ガス検知素子の出力変動分の濃度換算値とすることができる。In the formula (I), c can be a concentration converted value corresponding to the output fluctuation of the semiconductor type gas detection element due to a disturbance factor.
前記（Ｉ）式において、Ｘを被検知ガスの濃度とし、ｃを外乱要因による半導体式ガス検知素子の出力変動分を前記被検知ガスの濃度に換算した値とすることができる。In the formula (I), X can be a concentration of the gas to be detected, and c can be a value obtained by converting the output fluctuation of the semiconductor gas detection element due to a disturbance factor into the concentration of the gas to be detected.
Claims (6)
[数１]
Ｙ＝ａ・ｌｏｇ（Ｘ＋ｃ＋１）＋ｂ （Ｉ）
（式中、Ｘはガスの濃度、Ｙは出力値、ａ，ｂ，ｃはそれぞれ定数を示す。） A gas detection device comprising: a semiconductor gas detection element; and a conversion means for converting an output value of the semiconductor gas detection element into a gas concentration based on the following formula (I).
[Equation 1]
Y = a · log (X + c + 1) + b (I)
(In the formula, X is a gas concentration, Y is an output value, and a, b, and c are constants.)
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