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MEASURING PRINCIPLE
2 - 2
ETC00781(1) Series 100 e 10/2001
Fig. 2-1: Absorption Bands of Sample Gases and Transmittance of the
Interference Filters used
The signal generation happens by a pyroelectrical (solid-state) detector.
The detector records the incoming IR radiation. This radiation intensity is reduced by the
absorption of the gas at the corresponding wave lengths. By comparing the intensity at measuring
and reference wave length an alternating voltage signal is developed. This signal results from
cooling and heating of the pyroelectrical material of the detector.
IR MEASUREMENT
Transmittance [%]
Wave Length [nm]
4400 460042004000 48003000 3200 3400 3600 3800 5000 5200 5400 5600 5800 6000
CO
2
CO
Interference -
Filter
HC
CO
2
CO
18 36 54 72 900
Transmittance [%]
9075604530150
Reference
Absorption Band