JP2009257808A - Infrared gas analyzer - Google Patents

Infrared gas analyzer Download PDF

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JP2009257808A
JP2009257808A JP2008104289A JP2008104289A JP2009257808A JP 2009257808 A JP2009257808 A JP 2009257808A JP 2008104289 A JP2008104289 A JP 2008104289A JP 2008104289 A JP2008104289 A JP 2008104289A JP 2009257808 A JP2009257808 A JP 2009257808A
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gas
infrared light
measurement
infrared
cell
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Hitoshi Hara
仁 原
Naoteru Kishi
直輝 岸
Tetsuya Watanabe
哲也 渡辺
Kentaro Suzuki
健太郎 鈴木
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Yokogawa Electric Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared gas analyzer which is made compact, low priced, and maintenence-free by omitting a movable mechanism such as a motor. <P>SOLUTION: An infrared gas analyzer comprises an infrared light source which is electrically directly-modulated and driven in a blinking manner, a first gas chamber which is filled with a measurement gas and into which an output light from the infrared light source is input, a correlation cell having a second gas chamber which is filled with a reference gas that does not absorb an infrared light, and into which the output light from the infrared light source is input, a measurement cell into which a gas to be measured is introduced, a band path filter having a transmissive band which is a little broader than an infrared light absorption band of the measurement gas, and an infrared light detector for detecting the infrared light which passes through the band path filter, wherein the infrared light source and the correletaion cell are provided at one end of the measurement cell, the infrared light detector is provided at the other end of the measurement cell, and the band path filter is provided at either end of the measurement cell. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、赤外線ガス分析計に関し、詳しくは、赤外線を用いた大気中などのガス成分の濃度測定を行うガス分析計において、可動機構を省いたものである。   The present invention relates to an infrared gas analyzer, and more particularly, to a gas analyzer that measures the concentration of gas components such as in the atmosphere using infrared rays, omitting a movable mechanism.

図６は、従来のガス濃度測定装置の一例を示す構成図であり、ガス相関法を用いた例を示している。
赤外光源１の出力光は、チョッパ２→ガス相関セル３→バンドパスフィルタ４→測定セル５を経て赤外検出器６に入射される。 FIG. 6 is a block diagram showing an example of a conventional gas concentration measuring apparatus, showing an example using a gas correlation method.
The output light of the infrared light source 1 enters the infrared detector 6 through the chopper 2 → the gas correlation cell 3 → the band pass filter 4 → the measurement cell 5.

図７は、図６のチョッパ２とガス相関セル３の具体例を示す斜視図である。チョッパ２は円板状に形成されていて、円周方向に沿って光透過部２ａと遮光部２ｂが交互に設けられている。ガス相関セル３は円筒状に形成されていて、内部は、測定ガス室３ａと参照ガス室３ｂに仕切られている。測定ガス室３ａには被測定ガスであるたとえばＣＯ２ガスが高濃度で充填され、参照ガス室３ｂには赤外光を吸収しないガスとしてたとえばＮ２ガスが充填されている。 FIG. 7 is a perspective view showing a specific example of the chopper 2 and the gas correlation cell 3 of FIG. The chopper 2 is formed in a disk shape, and the light transmitting portions 2a and the light shielding portions 2b are alternately provided along the circumferential direction. The gas correlation cell 3 is formed in a cylindrical shape, and the inside is partitioned into a measurement gas chamber 3a and a reference gas chamber 3b. The measurement gas chamber 3a is filled with, for example, CO 2 gas, which is a gas to be measured, at a high concentration, and the reference gas chamber 3b is filled with, for example, N 2 gas as a gas that does not absorb infrared light.

再び図６において、チョッパ２およびガス相関セル３は、モータ６で回転駆動される。測定セル５には、試料ガスの入口５ａと出口５ｂが設けられている。入口５ａには、試料ガスとして、たとえばＣＯ２を含む大気ガスが導入され、出口５ｂから連続的に排気される。 In FIG. 6 again, the chopper 2 and the gas correlation cell 3 are rotationally driven by the motor 6. The measurement cell 5 is provided with an inlet 5a and an outlet 5b for sample gas. For example, atmospheric gas containing CO 2 is introduced into the inlet 5a as a sample gas, and is continuously exhausted from the outlet 5b.

バンドパスフィルタ４は、チョッパ２およびガス相関セル３を通過した赤外光源１の出力光のうち測定ガスの赤外線吸収帯より少し広い赤外光領域の光だけを通過させて、測定セル５に入射させる。測定セル５に入射された赤外光は、その一部が測定セル５中に導入された測定ガスによって吸収されて、赤外光検出器６に入射される。赤外光検出器６は、ＰｂＳｅ素子などの赤外光に感度を有する素子で構成されており、入射された赤外光の光強度が検出される。なお、この赤外光検出器６は、安定して赤外光の光強度を検出できるように図示しない恒温槽によって温度制御される。   The bandpass filter 4 allows only the light in the infrared region slightly wider than the infrared absorption band of the measurement gas among the output light of the infrared light source 1 that has passed through the chopper 2 and the gas correlation cell 3 to pass through the measurement cell 5. Make it incident. Part of the infrared light incident on the measurement cell 5 is absorbed by the measurement gas introduced into the measurement cell 5 and is incident on the infrared light detector 6. The infrared light detector 6 is composed of an element having sensitivity to infrared light, such as a PbSe element, and detects the light intensity of the incident infrared light. The infrared light detector 6 is temperature controlled by a thermostat (not shown) so that the light intensity of the infrared light can be detected stably.

特許第３４２４３６４号公報Japanese Patent No. 3424364 特開２００１−２２１７３７号公報JP 2001-221737 A

しかし、このような従来の赤外線ガス分析計は、赤外線を変調（チョッピング）するために、チョッパ２とガス相関セル３をモータ６で回転駆動させなければならず、小型、低価格、メンテナンスを不要（フリー）にすることが難しいという問題がある。   However, such a conventional infrared gas analyzer has to rotate and drive the chopper 2 and the gas correlation cell 3 with a motor 6 in order to modulate (chop) infrared rays, and is small, low cost, and does not require maintenance. There is a problem that it is difficult to make it (free).

本発明は、上記のような問題点を解決するものであり、モータなどの可動機構を省くことにより、小型、低価格、メンテナンスフリーを実現する赤外線ガス分析計を提供することを目的としたものである。   The present invention solves the above-described problems, and an object thereof is to provide an infrared gas analyzer that realizes a small size, low cost, and maintenance-free by omitting a movable mechanism such as a motor. It is.

上記のような目的を達成するために、本発明の請求項１では、電気的に直接変調され点滅駆動される赤外光源と、測定ガスが充填され前記赤外光源の出力光が入射される第１のガス室と赤外光を吸収しない参照ガスが充填され前記赤外光源の出力光が入射される第２のガス室を有する相関セルと、被測定ガスが導入される測定セルと、前記測定ガスの赤外線吸収帯域より少し広い透過帯域を有するバンドパスフィルタと、このバンドパスフィルタを透過する赤外線を検出する赤外光検出器を備え、
前記測定セルの一端には前記赤外光源と相関セルが設けられ、前記測定セルの他端には前記赤外光検出器が設けられ、前記バンドパスフィルタは前記測定セルのいずれかの端部に設けられたことを特徴とする。 In order to achieve the above object, in claim 1 of the present invention, an infrared light source that is directly modulated and driven to blink, and a measurement gas filled with output light from the infrared light source are incident. A correlation cell having a first gas chamber and a second gas chamber filled with a reference gas that does not absorb infrared light and into which the output light of the infrared light source is incident; a measurement cell into which a gas to be measured is introduced; A bandpass filter having a transmission band slightly wider than the infrared absorption band of the measurement gas, and an infrared light detector for detecting infrared light transmitted through the bandpass filter,
One end of the measurement cell is provided with the infrared light source and a correlation cell, the other end of the measurement cell is provided with the infrared light detector, and the bandpass filter is provided at one end of the measurement cell. It is characterized by being provided in.

請求項２では、請求項１の赤外線ガス分析計において、前記赤外光源が１つ設けられてその出力光は前記相関セルの第１のガス室と第２のガス室に共通に入射され、前記赤外光検出器は２つ設けられてこれらガス室を通過した赤外光を個別に検出することを特徴とする。   The infrared gas analyzer according to claim 1, wherein one infrared light source is provided, and the output light is incident on the first gas chamber and the second gas chamber of the correlation cell in common. Two infrared light detectors are provided to individually detect the infrared light that has passed through these gas chambers.

請求項３では、請求項１の赤外線ガス分析計において、前記赤外光源が２つ設けられてそれぞれの出力光は前記相関セルの第１のガス室と第２のガス室に個別に入射され、前記赤外光検出器は１つ設けられてこれらガス室を通過した赤外光を共通に検出することを特徴とする。   According to a third aspect of the present invention, in the infrared gas analyzer according to the first aspect, the two infrared light sources are provided, and the respective output lights are individually incident on the first gas chamber and the second gas chamber of the correlation cell. One infrared light detector is provided to commonly detect infrared light that has passed through these gas chambers.

モータなどの可動機構を省いたことにより、メンテナンスフリー、小型化、低価格化を実現できる。   By eliminating movable mechanisms such as motors, maintenance-free, downsizing, and low cost can be realized.

また、干渉成分の影響を受けにくいガス相関法を用い、電気的に直接変調ができて経時変化の小さい赤外光源と相関セルとを組み合わせることにより、干渉ガスの影響をほとんどなくすことができる。   Further, by using a gas correlation method that is not easily influenced by interference components, and combining an infrared light source that can be directly electrically modulated and has a small change with time, and a correlation cell, the influence of the interference gas can be almost eliminated.

さらに、電気的に直接変調ができて経時変化がない駆動電圧で赤外線を発光できる直接変調赤外光源を用いるため光量の経時変化がないこと、赤外光源が２つと赤外検出器が１つの場合には各出力信号を演算してセンサ出力を求めることから素子の経時変化や周囲温度変動を差動で除くことができる。   Furthermore, since a direct modulation infrared light source that can emit light with an electric voltage that can be directly electrically modulated and does not change with time is used, there is no change in the amount of light with time, two infrared light sources and one infrared detector. In this case, since the sensor output is obtained by calculating each output signal, the change with time of the element and the ambient temperature fluctuation can be removed differentially.

以下、図面を用いて、本発明の赤外線ガス分析計を説明する。図１は、本発明の赤外線ガス分析計の一実施例を示す構成図である。   Hereinafter, the infrared gas analyzer of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the infrared gas analyzer of the present invention.

図１において、光源部１１には発光特性の等しい２個の赤外光源１１ａと１１ｂが設けられている。これら赤外光源１１ａと１１ｂは、電気的に直接変調ができて経時変化がない駆動電圧で赤外線を発光できる直接変調赤外光源であり、交互に点滅駆動される。一方の赤外光源１１ａの出力光は相関セル１２の測定ガスとして被測定ガスであるたとえばＣＯ２ガスが高濃度で充填された測定ガス室１２ａに入射され、他方の赤外光源１１ｂの出力光は相関セル１２の赤外光を吸収しない参照ガスとしてたとえばＮ２ガスが充填された参照ガス室１２ｂに入射される。これら光源部１１と相関セル１２は、被測定ガスが導入される円筒状に形成された測定セル１３の一端に設けられている。 In FIG. 1, the light source unit 11 is provided with two infrared light sources 11a and 11b having the same light emission characteristics. These infrared light sources 11a and 11b are direct modulation infrared light sources that can emit infrared rays with a driving voltage that can be directly electrically modulated and do not change with time, and are alternately driven to blink. The output light from one infrared light source 11a is incident on a measurement gas chamber 12a filled with a high concentration of, for example, CO 2 gas, which is a measurement gas, as the measurement gas of the correlation cell 12, and the output light from the other infrared light source 11b. Enters the reference gas chamber 12b filled with, for example, N 2 gas as a reference gas that does not absorb the infrared light of the correlation cell 12. The light source unit 11 and the correlation cell 12 are provided at one end of a measurement cell 13 formed in a cylindrical shape into which a gas to be measured is introduced.

測定セル１３には、試料ガスの入口１３ａと出口１３ｂが設けられている。入口１３ａには、試料ガスとして、たとえばＣＯ２を含む大気ガスが導入され、出口１３ｂから連続的に排気される。なお、塵埃をフィルタで除去したりパーマピュアドライヤで赤外光を吸収する水分を除去するサンプリング装置など通した試料ガスを導入することもある。測定セル１３の他端には、バンドパスフィルタ１４と赤外光検出器１５が設けられている。バンドパスフィルタ１４は、測定ガスの赤外線吸収帯域よりも少し広い帯域の赤外線を通過させる特性を有する。赤外光検出器１５としては、サーモパイル、焦電素子、量子素子などが用いられる。 The measurement cell 13 is provided with an inlet 13a and an outlet 13b for sample gas. For example, atmospheric gas containing CO 2 is introduced into the inlet 13a as a sample gas, and is continuously exhausted from the outlet 13b. In some cases, a sample gas passed through a sampling device or the like that removes dust with a filter or removes moisture that absorbs infrared light with a perm pure dryer may be introduced. A band pass filter 14 and an infrared light detector 15 are provided at the other end of the measurement cell 13. The band-pass filter 14 has a characteristic of allowing infrared light in a band slightly wider than the infrared absorption band of the measurement gas to pass. As the infrared light detector 15, a thermopile, a pyroelectric element, a quantum element, or the like is used.

図１の動作について説明する。
相関セル１２の測定ガスが充填された測定ガス室１２ａを透過した赤外光源１１ａの赤外光ＩＲａは、試料ガス中の測定ガスの特性吸収の帯域をほとんど吸収しているので、測定セル１３内における測定ガスの濃度による光量変化はほとんどない。これに対して、参照ガスが充填された参照ガス室１２ｂを透過した赤外光源１１ｂの赤外光ＩＲｂは、測定セル１３内における試料ガス中の測定ガスの濃度に応じて光量が変化する。 The operation of FIG. 1 will be described.
Since the infrared light IRa of the infrared light source 11a that has passed through the measurement gas chamber 12a filled with the measurement gas of the correlation cell 12 absorbs almost the characteristic absorption band of the measurement gas in the sample gas, the measurement cell 13 There is almost no change in the amount of light due to the concentration of the measurement gas inside. On the other hand, the amount of light of the infrared light IRb of the infrared light source 11b transmitted through the reference gas chamber 12b filled with the reference gas changes according to the concentration of the measurement gas in the sample gas in the measurement cell 13.

図１の動作を、図２のガス相関法の測定原理図を用いて説明する。
（Ａ）は、赤外光源１１ｂから出力され参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過する測定光としての赤外光ＩＲｂの透過特性を示している。バンドパスフィルタ１４を透過した測定光は、バンドパスフィルタ１４の赤外線透過帯域のみが赤外光検出器１５に入射される。 The operation of FIG. 1 will be described using the measurement principle diagram of the gas correlation method of FIG.
(A) shows the transmission characteristics of infrared light IRb as measurement light output from the infrared light source 11b and transmitted through the reference gas chamber 12b filled with N 2 gas as the reference gas. The measurement light that has passed through the bandpass filter 14 is incident on the infrared light detector 15 only in the infrared transmission band of the bandpass filter 14.

（Ｂ）は、参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過しさらに測定セル１３を透過した測定光の透過特性を示している。測定セル１３の内部に測定ガスとしてたとえばＣＯ２が存在する場合、測定ガスＣＯ２の濃度に応じて赤外光が吸収される。バンドパスフィルタ１４では、測定ガスの赤外線吸収帯域より少し広い帯域を透過することにより、測定ガスＣＯ２の吸収分が差し引かれた赤外光ＩＲｂが赤外光検出器１５に入射される。 (B) shows the transmission characteristics of the measurement light that has passed through the reference gas chamber 12 b filled with N 2 gas as the reference gas and has further passed through the measurement cell 13. When, for example, CO 2 is present as a measurement gas inside the measurement cell 13, infrared light is absorbed according to the concentration of the measurement gas CO 2 . In the band pass filter 14, the infrared light IRb from which the absorption of the measurement gas CO 2 is subtracted is incident on the infrared light detector 15 by passing through a band slightly wider than the infrared absorption band of the measurement gas.

（Ｃ）は、赤外光源１１ａから出力され測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過する参照光としての赤外光ＩＲａの透過特性を示している。バンドパスフィルタ１４を透過した参照光は、バンドパスフィルタ１４における測定ガスＣＯ２の赤外線透過帯域より少し広い帯域を透過することにより、測定ガスＣＯ２の吸収分が差し引かれた赤外光ＩＲａが赤外光検出器１５に入射される。 (C) shows the transmission characteristics of infrared light IRa as reference light that is output from the infrared light source 11a and passes through the measurement gas chamber 12a filled with high-concentration CO 2 as the measurement gas. The reference light transmitted through the bandpass filter 14 passes through a band slightly wider than the infrared transmission band of the measurement gas CO 2 in the bandpass filter 14, so that the infrared light IRa from which the absorption of the measurement gas CO 2 has been subtracted. The light enters the infrared light detector 15.

（Ｄ）は、測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過しさらに測定セル１３を透過した参照光の透過特性を示している。（Ｄ）の透過特性から明らかなように、測定セル１３の内部に測定ガスとしてたとえばＣＯ２が存在していてその濃度が変化してもほとんど光量が変化しない赤外光ＩＲｂが赤外光検出器１５に入射される。 (D) shows the transmission characteristics of the reference light that has passed through the measurement gas chamber 12a filled with high-concentration CO 2 as the measurement gas and has further passed through the measurement cell 13. As is clear from the transmission characteristics of (D), infrared light IRb is detected by infrared light IRb, in which, for example, CO 2 exists as a measurement gas in the measurement cell 13 and the amount of light hardly changes even if its concentration changes. Is incident on the vessel 15.

赤外光源１１ａおよび１１ｂから出力され相関セル１２および測定セル１３を透過した赤外光ＩＲａおよびＩＲｂの光量を赤外光検出器１５で検出し、得られた信号に基づきガス相関法として従来から行われている所定の演算を行い、測定ガスたとえばＣＯ２の濃度を求める。 The amount of infrared light IRa and IRb output from the infrared light sources 11a and 11b and transmitted through the correlation cell 12 and the measurement cell 13 is detected by the infrared light detector 15, and based on the obtained signal, a gas correlation method has been conventionally used. The predetermined calculation being performed is performed to determine the concentration of the measurement gas, for example, CO 2 .

図３は、ガス相関法における干渉ガス補償の原理説明図である。
赤外線ガス分析計は、一般的に測定ガス以外のガスによって吸収されることにより干渉の影響が生じる。たとえば、測定ガスをＣＯ２、測定ガス以外のガスをＣＯとした場合、図２と同様に考えることができる。
（Ａ）は、赤外光源１１ｂから出力され参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過する測定光としての赤外光ＩＲｂの透過特性を示している。バンドパスフィルタ１４を透過した測定光は、バンドパスフィルタ１４の赤外線透過帯域のみが赤外光検出器１５に入射されるが、測定セル１３内に測定ガス以外のガスＣＯが存在するとＣＯによる吸収が生じるため、波形がわずかに削られてしまう。 FIG. 3 is a diagram for explaining the principle of interference gas compensation in the gas correlation method.
Infrared gas analyzers are generally affected by interference by being absorbed by a gas other than the measurement gas. For example, when the measurement gas is CO 2 and the gas other than the measurement gas is CO, it can be considered as in FIG.
(A) shows the transmission characteristics of infrared light IRb as measurement light output from the infrared light source 11b and transmitted through the reference gas chamber 12b filled with N 2 gas as the reference gas. Only the infrared transmission band of the bandpass filter 14 is incident on the infrared light detector 15 when the measurement light transmitted through the bandpass filter 14 is absorbed. If gas CO other than the measurement gas exists in the measurement cell 13, the measurement light is absorbed by the CO. As a result, the waveform is slightly cut.

（Ｂ）は、参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過しさらに測定セル１３を透過した測定光の透過特性を示している。測定セル１３の内部に測定ガスとしてたとえばＣＯ２が存在する場合、測定ガスＣＯ２の濃度に応じて赤外光が吸収される。バンドパスフィルタ１４では、測定ガスの赤外線吸収帯域より少し広い帯域を透過することにより、測定ガスＣＯ２および測定ガス以外のガスＣＯの吸収分が差し引かれた赤外光ＩＲｂが赤外光検出器１５に入射される。 (B) shows the transmission characteristics of the measurement light that has passed through the reference gas chamber 12 b filled with N 2 gas as the reference gas and has further passed through the measurement cell 13. When, for example, CO 2 is present as a measurement gas inside the measurement cell 13, infrared light is absorbed according to the concentration of the measurement gas CO 2 . In the band pass filter 14, the infrared light IRb from which the absorption of the measurement gas CO 2 and the gas CO other than the measurement gas is subtracted by passing through a band slightly wider than the infrared absorption band of the measurement gas is used as the infrared light detector. 15 is incident.

（Ｃ）は、赤外光源１１ａから出力され測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過する参照光としての赤外光ＩＲａの透過特性を示している。バンドパスフィルタ１４を透過した参照光は、バンドパスフィルタ１４における測定ガスＣＯ２の赤外線透過帯域より少し広い帯域を透過することにより、測定ガスＣＯ２の吸収分が差し引かれた赤外光ＩＲａが赤外光検出器１５に入射されるが、測定セル１３内に測定ガス以外のガスＣＯが存在するとＣＯによる吸収が生じるため、波形がわずかに削られてしまう。 (C) shows the transmission characteristics of infrared light IRa as reference light that is output from the infrared light source 11a and passes through the measurement gas chamber 12a filled with high-concentration CO 2 as the measurement gas. The reference light transmitted through the bandpass filter 14 passes through a band slightly wider than the infrared transmission band of the measurement gas CO 2 in the bandpass filter 14, so that the infrared light IRa from which the absorption of the measurement gas CO 2 has been subtracted. Although it is incident on the infrared light detector 15, if a gas CO other than the measurement gas is present in the measurement cell 13, the absorption by the CO occurs, and the waveform is slightly cut off.

（Ｄ）は、測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過しさらに測定セル１３を透過した参照光の透過特性を示している。（Ｄ）の透過特性から明らかなように、測定セル１３の内部に測定ガスとしてたとえばＣＯ２が存在していてその濃度が変化してもほとんど光量が変化しない赤外光ＩＲｂが赤外光検出器１５に入射されるが、測定セル１３内に測定ガス以外のガスＣＯが存在するとＣＯによる吸収が生じるため、波形がわずかに削られてしまう。 (D) shows the transmission characteristics of the reference light that has passed through the measurement gas chamber 12a filled with high-concentration CO 2 as the measurement gas and has further passed through the measurement cell 13. As is clear from the transmission characteristics of (D), infrared light IRb is detected by infrared light IRb, in which, for example, CO 2 exists as a measurement gas in the measurement cell 13 and the amount of light hardly changes even if its concentration changes. Although it is incident on the vessel 15, if a gas CO other than the measurement gas exists in the measurement cell 13, the absorption by the CO occurs, so that the waveform is slightly cut.

このように、測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過する参照光と参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過する測定光における干渉の影響が同程度になるため、図２（Ｂ）と（Ｄ）で検出された赤外光の演算値と、図３（Ｂ）と（Ｄ）で検出された赤外光の演算値とがほぼ同じなり、干渉の影響をほとんど受けないことがわかる。 Thus, there is an influence of interference between the reference light transmitted through the measurement gas chamber 12a filled with high concentration CO 2 as the measurement gas and the measurement light transmitted through the reference gas chamber 12b filled with N 2 gas as the reference gas. Since it becomes the same level, the calculated value of the infrared light detected in FIGS. 2B and 2D and the calculated value of the infrared light detected in FIGS. 3B and 3D are almost the same. Thus, it can be seen that it is hardly affected by interference.

また、たとえば水のように広い帯域で吸収特性があり、ベースラインに影響を及ぼすガスにおいても、その干渉の影響を少なくすることができる。   Further, for example, gas having a wide band such as water and having an influence on the base line can reduce the influence of the interference.

図４は、ＣＯ２濃度と赤外光検出器１５の出力信号と演算の関係を示す説明図であり、たとえば、測定セル１３内のＣＯ２濃度が変化する場合の赤外光検出器１５の信号変化をモデル化して示している。図１のように２つの赤外光源１１ａと１１ｂと１つの赤外光検出器１５を設けたことにより、測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過した参照光の出力信号Ａと、参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過した測定光の出力信号Ｂが交互に得られる場合、出力信号ＡはＣＯ２の濃度が変化しても変動なく、出力信号ＢはＣＯ２の濃度が高くなると共に出力信号が小さく変化している。 FIG. 4 is an explanatory diagram showing the relationship between the CO 2 concentration and the output signal of the infrared light detector 15 and the calculation. For example, the infrared light detector 15 in the case where the CO 2 concentration in the measurement cell 13 changes. The signal change is modeled. As shown in FIG. 1, by providing two infrared light sources 11a and 11b and one infrared light detector 15, the reference light transmitted through the measurement gas chamber 12a filled with high-concentration CO 2 as the measurement gas. When the output signal A and the output signal B of the measurement light transmitted through the reference gas chamber 12b filled with N 2 gas as the reference gas are alternately obtained, the output signal A does not change even if the CO 2 concentration changes. In the output signal B, the CO 2 concentration increases and the output signal changes small.

また、赤外光源１１を１つ、赤外光検出器１５を２つ設けた場合は、測定ガスとして高濃度のＣＯ２が充填された測定ガス室１２ａを透過した参照光の出力信号Ａと、参照ガスとしてＮ２ガスが充填された参照ガス室１２ｂを透過した測定光の出力信号Ｂを同時に得ることができる。出力信号Ａと出力信号Ｂを演算してセンサ出力Ｓｏｕｔを求め、あらかじめ求めておいた検量線、つまりＣＯ２濃度Ｃｃとセンサ出力Ｓｏｕｔの関係から、測定セル１３内のＣＯ２濃度Ｃｃを求める。 Further, when one infrared light source 11 and two infrared light detectors 15 are provided, the output signal A of the reference light transmitted through the measurement gas chamber 12a filled with high concentration CO 2 as the measurement gas and The output signal B of the measurement light transmitted through the reference gas chamber 12b filled with N 2 gas as the reference gas can be obtained at the same time. The sensor output Sout is obtained by calculating the output signal A and the output signal B, and the CO 2 concentration Cc in the measurement cell 13 is obtained from the calibration curve obtained in advance, that is, the relationship between the CO 2 concentration Cc and the sensor output Sout.

また、赤外光源１１を３つ設けた場合は２種類の成分を検出し、赤外光源１１を２つ設けた場合は１種類の成分を検出する。つまり、赤外光源１１をｎ個設けた場合は（ｎ−１）種類の成分を検出することができる。   When three infrared light sources 11 are provided, two types of components are detected, and when two infrared light sources 11 are provided, one type of component is detected. That is, when n infrared light sources 11 are provided, (n-1) types of components can be detected.

なお、図１の実施例では、光源部１１と相関セル１２を一体化して被測定ガスが導入される円筒状に形成された測定セル１３の一端に設け、測定セル１３の他端にバンドパスフィルタ１４と赤外光検出器１５を一体化して設ける例を示したが、この組み合わせに限るものではなく、赤外光源１１と赤外光検出器１５との間に相関セル１２と測定セル１３とバンドパスフィルタ１４が配置される組み合わせであればよく、図５（Ａ）〜（Ｃ）に示すように組み合わせることもできる。なお、図５において図１と共通する部分には同一符号を付して示す。   In the embodiment of FIG. 1, the light source unit 11 and the correlation cell 12 are integrated and provided at one end of a measurement cell 13 formed into a cylindrical shape into which a gas to be measured is introduced, and a bandpass is provided at the other end of the measurement cell 13. Although an example in which the filter 14 and the infrared light detector 15 are integrally provided has been shown, the present invention is not limited to this combination, and the correlation cell 12 and the measurement cell 13 are interposed between the infrared light source 11 and the infrared light detector 15. And the band pass filter 14 may be combined, and may be combined as shown in FIGS. 5 that are the same as those in FIG. 1 are denoted by the same reference numerals.

（Ａ）は、赤外光源１１と相関セル１２をそれぞれ個別に形成して測定セル１３の一端に設け、測定セル１３の他端にバンドパスフィルタ１４と赤外光検出器１５を一体化して設けた構成例である。   (A) Infrared light source 11 and correlation cell 12 are individually formed and provided at one end of measurement cell 13, and bandpass filter 14 and infrared light detector 15 are integrated at the other end of measurement cell 13. It is the provided structural example.

（Ｂ）は、赤外光源１１と相関セル１２とバンドパスフィルタ１４とを一体化して測定セル１３の一端に設け、測定セル１３の他端に設けられている赤外光検出器１５と赤外線の透過率の高い赤外窓材１６を一体化した構成例である。   (B) shows that the infrared light source 11, the correlation cell 12, and the band pass filter 14 are integrated and provided at one end of the measurement cell 13, and the infrared light detector 15 and infrared light provided at the other end of the measurement cell 13. This is a configuration example in which an infrared window material 16 having a high transmittance is integrated.

（Ｃ）は、赤外光源１１と相関セル１２とバンドパスフィルタ１４をそれぞれ個別に形成して測定セル１３の一端に設け、測定セル１３の他端に設けられている赤外光検出器１５と赤外線の透過率の高い赤外窓材１６を一体化した構成例である。   (C) Infrared light source 11, correlation cell 12, and bandpass filter 14 are individually formed and provided at one end of measurement cell 13, and infrared light detector 15 provided at the other end of measurement cell 13. And an infrared window material 16 having a high infrared transmittance.

また、赤外光源１１と相関セル１２の組み合わせを増やすことにより、複数のガス成分を測定することができる。   Moreover, a plurality of gas components can be measured by increasing the combination of the infrared light source 11 and the correlation cell 12.

なお、これら図１および図５は、左から右へ赤外光源１１→相関セル１２→測定セル１３→バンドパスフィルタ１４→赤外光検出器１５または赤外光源１１→相関セル１２→バンドパスフィルタ１４→測定セル１３→赤外窓材１６→赤外光検出器１５の順に構成されているが、右から左へ赤外光源１１→相関セル１２→測定セル１３→バンドパスフィルタ１４→赤外光検出器１５または赤外光源１１→相関セル１２→バンドパスフィルタ１４→測定セル１３→赤外窓材１６→赤外光検出器１５の順に構成してもよい。   1 and 5 show from left to right the infrared light source 11 → correlation cell 12 → measurement cell 13 → bandpass filter 14 → infrared light detector 15 or infrared light source 11 → correlation cell 12 → bandpass. The filter 14 → the measurement cell 13 → the infrared window material 16 → the infrared light detector 15 are configured in this order. From the right to the left, the infrared light source 11 → the correlation cell 12 → the measurement cell 13 → the bandpass filter 14 → red. The external light detector 15 or infrared light source 11 → correlation cell 12 → bandpass filter 14 → measurement cell 13 → infrared window material 16 → infrared light detector 15 may be configured in this order.

これらの実施例から明らかなように、相関セル１２を固定化しているため、モータなどの可動機構を省くことができ、メンテナンスフリーにすることができる。そして、モータなどの可動機構を省くことにより部品数を削減できるため、小型化および低価格化を実現できる。   As is clear from these embodiments, since the correlation cell 12 is fixed, a movable mechanism such as a motor can be omitted and maintenance-free can be achieved. Since the number of parts can be reduced by omitting a movable mechanism such as a motor, downsizing and cost reduction can be realized.

また、電気的に直接変調ができて経時変化がない赤外光源１１と固定化された相関セル１２とを組み合わせた光学系と干渉成分の影響を受けにくいガス相関法を用いたことにより、干渉ガスの影響をほとんどなくすことができる。   Further, by using an optical system in which an infrared light source 11 that can be directly electrically modulated and does not change with time and a fixed correlation cell 12 and a gas correlation method that is not easily affected by interference components are used, interference is prevented. The effect of gas can be almost eliminated.

また、電気的に直接変調ができて経時変化がない駆動電圧で赤外線を発光できる赤外光源１１を用いるため、光量の経時変化を無くすことができる。   In addition, since the infrared light source 11 that can be electrically directly modulated and emits infrared light with a drive voltage that does not change with time, the change in the amount of light with time can be eliminated.

また、測定セル１３を多重反射するような構造にする場合には、赤外光源１１と赤外光検出器１５を同一の基板上に配置することができるので、高精度で小型化にすることができる。   Further, when the measurement cell 13 is structured to be multiple-reflected, the infrared light source 11 and the infrared light detector 15 can be arranged on the same substrate, so that the size can be reduced with high accuracy. Can do.

さらに、赤外光源１１を２つ、赤外光検出器１５を１つ設けて、測定ガスが充填された測定ガス室１２ａを透過した参照光の出力信号Ａと参照ガスが充填された参照ガス室１２ｂを透過した測定光の出力信号Ｂを演算してセンサ出力Ｓｏｕｔを求めることにより、素子の経時変化や周囲温度変動を差動で除くことができる。   Further, two infrared light sources 11 and one infrared light detector 15 are provided, and an output signal A of the reference light transmitted through the measurement gas chamber 12a filled with the measurement gas and a reference gas filled with the reference gas. By calculating the output signal B of the measurement light that has passed through the chamber 12b and obtaining the sensor output Sout, it is possible to differentially remove changes in the elements over time and ambient temperature fluctuations.

なお、上記各実施例では、測定セルが円筒形に形成されている例について説明したが、測定セルは円筒形に限るものではなく、用途に応じて適宜の形状に形成してもよい。   In each of the above-described embodiments, an example in which the measurement cell is formed in a cylindrical shape has been described. However, the measurement cell is not limited to a cylindrical shape, and may be formed in an appropriate shape depending on the application.

以上説明したように、本発明によれば、モータなどの回転機構を省くことができ、小型で低価格でメンテナンスがフリーの赤外線ガス分析計を実現できる。   As described above, according to the present invention, a rotating mechanism such as a motor can be omitted, and an infrared gas analyzer that is small, inexpensive, and free of maintenance can be realized.

本発明の一実施例を示す構成図である。It is a block diagram which shows one Example of this invention. 本発明で用いるガス相関法の測定原理である。This is the measurement principle of the gas correlation method used in the present invention. 本発明で用いるガス相関法における干渉ガス補償の原理説明図である。It is principle explanatory drawing of interference gas compensation in the gas correlation method used by this invention. 本発明のＣＯ２濃度と赤外光検出器１５の出力信号と演算の関係を示す説明図である。The CO 2 concentration and the infrared light detector 15 output signal and calculating the relationship of the present invention; FIG. 本発明の他の実施例を示す構成図である。It is a block diagram which shows the other Example of this invention. 従来のガス濃度測定装置の一例を示す構成図である。It is a block diagram which shows an example of the conventional gas concentration measuring apparatus. 図６のチョッパ２とガス相関セル３の具体例を示す斜視図である。It is a perspective view which shows the specific example of the chopper 2 and the gas correlation cell 3 of FIG.

符号の説明Explanation of symbols

１１ 光源部
１２ 相関セル
１３ 測定セル
１４ バンドパスフィルタ
１５ 赤外光検出器
１６ 赤外窓材 DESCRIPTION OF SYMBOLS 11 Light source part 12 Correlation cell 13 Measurement cell 14 Band pass filter 15 Infrared light detector 16 Infrared window material

Claims (3)

電気的に直接変調され点滅駆動される赤外光源と、測定ガスが充填され前記赤外光源の出力光が入射される第１のガス室と赤外光を吸収しない参照ガスが充填され前記赤外光源の出力光が入射される第２のガス室を有する相関セルと、被測定ガスが導入される測定セルと、前記測定ガスの赤外線吸収帯域より少し広い透過帯域を有するバンドパスフィルタと、このバンドパスフィルタを透過する赤外線を検出する赤外光検出器を備え、
前記測定セルの一端には前記赤外光源と相関セルが設けられ、前記測定セルの他端には前記赤外光検出器が設けられ、前記バンドパスフィルタは前記測定セルのいずれかの端部に設けられたことを特徴とする赤外線ガス分析計。 An infrared light source that is electrically directly modulated and driven to blink, a first gas chamber that is filled with a measurement gas and into which the output light of the infrared light source is incident, and a reference gas that does not absorb infrared light is filled with the red light source. A correlation cell having a second gas chamber into which output light of an external light source is incident, a measurement cell into which a gas to be measured is introduced, a bandpass filter having a transmission band slightly wider than the infrared absorption band of the measurement gas, It has an infrared light detector that detects infrared rays that pass through this bandpass filter,
One end of the measurement cell is provided with the infrared light source and a correlation cell, the other end of the measurement cell is provided with the infrared light detector, and the bandpass filter is provided at one end of the measurement cell. An infrared gas analyzer characterized by being provided in 前記赤外光源が１つ設けられてその出力光は前記相関セルの第１のガス室と第２のガス室に共通に入射され、前記赤外光検出器は２つ設けられてこれらガス室を通過した赤外光を個別に検出することを特徴とする請求項１記載の赤外線ガス分析計。   One infrared light source is provided, and its output light is incident on the first gas chamber and the second gas chamber of the correlation cell in common, and two infrared light detectors are provided, and these gas chambers are provided. The infrared gas analyzer according to claim 1, wherein infrared light that has passed through is individually detected. 前記赤外光源が２つ設けられてそれぞれの出力光は前記相関セルの第１のガス室と第２のガス室に個別に入射され、前記赤外光検出器は１つ設けられてこれらガス室を通過した赤外光を共通に検出することを特徴とする請求項１記載の赤外線ガス分析計。   Two infrared light sources are provided, and each output light is individually incident on the first gas chamber and the second gas chamber of the correlation cell, and one infrared light detector is provided for these gases. The infrared gas analyzer according to claim 1, wherein infrared light passing through the chamber is commonly detected.
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