NDIR gas analysis NDIR气体分析

许多气体以一定特征吸收光谱吸收红外辐射，这是由各自气体的特定分子结构决定的。NDIR气体分析是一种相对便宜的方法，可用于精确测定单种气体的浓度，它利用待检测气体的单个物质典型吸收带。

Many gases absorb infrared radiation in a characteristic absorption spectrum, which is determined by the specific molecular structure of the respective gas. Non-dispersive infrared gas analysis (NDIR gas analysis) is a comparatively inexpensive method for an exact determination of the concentration of individual gases, which utilizes individual substance-typical absorption bands of the gases to be detected.

Principle of gas concentration measurement using NDIR gas analysis NDIR气体分析的气体浓度测量原理

待分析的混合气体位于宽带红外辐射器及红外探测器之间定义好的体积之内。吸收红外探测器的宽带备有一个窄带滤光片，其峰值传输正好位于待分析气体的典型吸收带。如果使用有多个光谱通道的红外探测器代替单元

红外探测器，则可以同时检测多个离散气体。红外辐射器的发射光谱必须至少覆盖所用吸收带的光谱范围。

如果在红外辐射器及红外探测器中没有检测到气体，辐射出来的辐射能量几乎可以毫无阻碍地击中该红外探测器，并在此生成最大可能的信号。随着待测气体的浓度增加，在其典型吸收光谱上的吸收会增加，于是带窄波段调谐的红外探测器会辐射一个较低的信号。如果还有其它气体通道的话，这些其它气体通道也会相应地对其它气体起作用。

The gas mixture to be analyzed is located in a defined volume between a broadband IR emitter and an infrared sensor. The broadband absorbing IR sensor is equipped with a narrowband filter which has its peak transmission exactly at a typical absorption band of the gas to be analyzed. If a sensor with multiple spectral channels is used instead of a single-element sensor, several discrete gases can be detected simultaneously. The emission spectrum of the emitter must cover at least the spectral range of the absorption bands used.
If there is no gas to be detected between the emitter and the sensor, the emitted radiation hits the sensor almost unhindered and generates the maximum possible signal there. With increasing concentration of a gas to be measured, the absorption on its typical absorption spectrum increases and thus the sensor with the narrowband filter tuned to it emits a lower signal. The other channels, if any, react accordingly only to other gases

Gas气体	Absorption band吸收带
CH4	3.33 µm
HC	3.40 µm
Reference基准气体	3.91 µm
CO2	4.26 µm & 4.43 µm
CO	4.64 µm
NO	5.30 µm
NO2	6.22 µm
SO2	7.30 µm
Freon R134a 氟利昂	10.27 µm
Freon R12 氟利昂	11.30 µm

对标准分析测量任务，红外探测器类型PYROSENSLTA 系列及LTM系列特别适合。而采用德国DIAS红外公司特别开发的PYROSENS LTMI系列及LTSI系列红外探测器系列，NDIR气体分析可以测量浓度很低的气体，其浓度最低可到一位数的ppm。相应的检测范围取决于测量单元的结构以及待测的气体。典型的光谱范围约为1μm至20μm，但我们的红外探测器甚至可以在远高于100μm的波长上使用。

PYROSENS红外探测器用于冰箱及空调系统的泄露检测或泄露测试，以及高精度及温度稳定的气体浓度测试，这些气体有CO、CO2及CH4，而CO及CO2间的交叉灵敏度比较低，常用于人类及兽医。

此外，在半导体行业，PYROSENS还可以用于半导体行业的真空室清洁过程的终端监控的气体监控。

For standard measurement tasks, the sensors of the type series PYROSENS LTA and LTM are perfectly suitable. With the type series PYROSENS LTMI and LTSI DIAS Infrared GmbH offers highly developed pyroelectric IR sensors which allow NDIR gas analysis even for lowest gas concentrations in the single digit ppm range. The respective detection limit depends on the construction of the measuring cell as well as on the gas to be detected. The typical spectral range is between approx. 1 µm and 20 µm, but our sensors can even be used at wavelengths far above 100 µm.

Für Standardmessaufgaben sind die Sensoren der Typenreihen PYROSENS LTA und LTM hervorragend geeignet. Mit den Typenreihen PYROSENS LTMI und LTSI bietet die DIAS Infrared GmbH hochentwickelte pyroelektrische IR-Sensoren an, mit denen NDIR-Gasanalyse auch für geringste Gaskonzentrationen im einstelligen ppm-Bereich möglich wird. Die jeweilige Nachweisgrenze ist dabei sowohl von der Konstruktion der Messzelle als auch vom zu detektierenden Gas abhängig. Der typische Spektralbereich liegt dabei zwischen ca. 1 µm und 20 µm, unsere Sensoren sind aber selbst bei Wellenlängen weit über 100 µm einsetzbar.

NDIR红外气体分析用德国DIAS红外探测器, 具有多种样式, 有单元红外探测器, 二元红外探测器，三元红外探测器, 四元红外探测器 — PYROSENS型系列红外探测器具有不同的样式

PYROSENS sensors are used for leak detection or leak testing of refrigerators and air conditioning systems as well as for highly accurate and temperature stable concentration measurements of gases such as CO, CO2 and CH4 with very low cross sensitivity between CO and CO2, which are used especially in human and veterinary medicine.

In the semiconductor industry, they are used, among other things, for gas monitoring in the end-point monitoring of vacuum chamber cleaning processes.

带德国DIAS红外探测器PYROSENS的NDIR气体传感模块 — 带PYROSENS的NDIR气体传感模块 (图片来源: 由制造商提供Photo: courtesy of the manufacturer)

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