Chapter 1
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BE6020-14
1316A-1 Multi Gas Monitor
LumaSense Technologies A/S
Instruction Manual
Page 13 of 98
1.4.3 The NDIR Module Building blocks
Infrared Source
A current-regulated infrared (IR) source provides a photon stream in
the range of 2 to 5 microns. Light is collimated and directed through
the sample cell to the optical block. The source is modulated at 1 Hz,
with a duty cycle of 50%.
Figure 1.4 The Optics of the NDIR Module.
Sample Cell
The sample cell is a gold-coated glass chamber that provides a
means for the infrared source to pass through the sample gas.
Infrared-transparent sapphire windows are provided at each end of
the cell. A microprocessor controlled transducer and thermistor
provide measurement compensation for sample gas temperature and
pressure variances. Sample gas exits the cell at the end opposite the
IR source and is
directed to the UA1372 manifold for O
2
or O
2
/NO
measurement
.
Optical Block
Infrared light not absorbed by the sample gas is transmitted to the
optical assembly. The remaining light is directed to the band pass
filters and on through to the quad detector.
The filter wavelengths are optimised to match the absorption spectra
of Hydrocarbons, Carbon Dioxide and Carbon Monoxide.
The filter associated with Hydrocarbons is centred on 3.46 µm (2889
cm
-1
), the filter associated with Carbon Dioxide is centred on 4.43
IR
SOURCE
SAMPLE CELL
BAND
PASS
FILTERS
ELECTRONICS
