New Cosmos Electric KS-7R, Инструкция по эксплуатации

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13. Detection Principle
Non-dispersive infrared sensor (NDIR)
Gas is molecules made of different chemical atoms. Each gas has a strong absorbance of infrared light
at specific wavelengths in the 1 to 20
μm Infrared spectrum, and the amount of absorbed infrared light is
proportional to its gas concentration according to the Beer-Lambert law. By using this characteristic, it is
possible to measure the gas concentration of a target gas based on the amount of infrared light
absorbed. Furthermore, the gas selectivity of the sensor can be enhanced by the addition of an optical
filter, which filters out all light outside of the wavelength that target gas molecules can absorb.
Typical model of NDIR is shown below.
The infrared radiation from the infrared light source (1) is chopped by the light regulator (2). The infrared
light passes thru the windows (3) and cell (4) to the optical filter (5), which allows only certain
wavelengths to pass to the infrared sensor (6), which then measures the amount of infrared absorbed by
the gas. The absorbed amount is converted to an electric signal, which is converted to a gas
concentration by the microcomputer (7).
②光源制御部
①赤外線光源
③窓
④セル
⑤光学フィルタ
⑥赤外線式センサ
⑦演算器
ＣＰＵ
(3) Window
(7) Microcomputer
(5) Optical filter
(6) Infrared sensor
(4) Cell
(2) Light generator
(1) Infrared light
source
CPU