Teledyne 9110AH, Instruction Manual, Page: 33 / 181

TELEDYNE Model 9110AH NO
X
Analyzer Operator Manual, 01620, Rev. F
4-1
4 THE M9110AH NO
X
ANALYZER
4.1 Principle of Operation
The TELEDYNE Model 9110AH Analyzer is designed to measure the concentration of nitric
oxide [NO], total oxides of nitrogen [NO
x
] and, by calculation, nitrogen dioxide [NO
2
]. With
the proper setup, it can operate in any of three sampling modes.
Table 4-1: Sampling Modes of the M9110AH
Mode Description
NO/NO
X
switching mode Converter is switched, measures NO, NO
x
, and NO
2
NO only mode Converter is switched out of sample stream. Nitric Oxide is only gas
measured.
NO
x
only mode Converter is switched into the sample stream, NO
x
is only gas
measured.
Regardless of which sampling mode the instrument is operating in, the signal from the
M9110AH comes from the light emitted from the chemiluminescent gas phase reaction of nitric
oxide [NO] and ozone [O
3
] as follows:
2 2 3
O * NO O NO
+ ¾ ® ¾ +
hv NO * NO
2 2
+ ¾ ® ¾
The reaction of NO with ozone results in electronically excited NO
2
molecules as shown in the
first equation above. The excited NO
2
molecules release their excess energy by emitting a
photon and dropping to a lower energy level as shown in the second equation. It has been
shown that the light intensity produced is directly proportional to the [NO] concentration
present.
In the NO mode, the sample gas is routed directly into the reaction cell. Any NO gas present
reacts with ozone, producing light as described above.
In the NO
x
mode, the sample gas is routed through a NO
2
to NO converter, and any NO
2
present is reduced to NO. The NO initially present remains as NO, therefore the signal is the
sum of NO and NO
2
present in the sample gas stream.