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Model 9110T NOx Analyzer Principles of Operation
Teledyne Analytical Instruments 321
Figure 13-1: Reaction Cell with PMT Tube and Optical Filter
The narrowness of this band of sensitivity allows the 9110T to ignore extraneous light and radiation that
might interfere with the 9110T’s measurement. For instance, some oxides of sulfur can also be
chemiluminescent emitters when in contact with O
3
but give off light at much shorter wavelengths
(usually around 260nm to 480nm).
0
20
40
60
80
100
120
140
0.5 0.9 1.1 1.3 1.5 1.7 1.9
Wavelength
(micrometers)
I
n
t
ens
it
y
(
arbitrary units
)
Optical Hi-Pass Filter Performance
NO + O
3
Emission Spectrum
Area of Sensitivity
Infrared
Visible
Spectrum
PMT
Response
0.7
Figure 13-2: 9110T Sensitivity Spectrum
13.1.3. NO
X
AND NO
2
DETERMINATION
The only gas that is actually measured by the 9110T is NO. NO
2
, and therefore NO
x
(which is defined
here as the sum of NO and NO
2
in the sample gas), contained in the gas is not detected because NO
2
does not react with O
3
to create chemiluminescence.