Specifications

I
NTRODUCTION
748410-A
August 1999
2
Chemiluminescense Detector Analyzer Module
Rosemount Analytical NGA 2000
1
NO + O
3
→
NO2* + O
2
NO
2
*
→
NO
2
+ red light
As NO and O3 mix in the reaction chamber, the intensity of the emitted red light is
measured by a photodiode and is proportional to the concentration of NO in the original gas
sample.
To measure NOx (NO + NO
2
), any NO
2
in the sample is reduced to NO (at <95% efficiency)
by being continuously passed through a heated bed of vitreous carbon (this occurs before
the sample gas is presented to the ozone). Any NO initially present in the sample passes
through this converter stage unchanged before being routed to the reaction chamber.
The photodiode generates a DC current, which is then amplified, conditioned and expressed
on the network as the Primary Variable.
1.4 F
EATURES
Among the features included in the CLD Analyzer Module are: 1) ozonator air loss shutoff
and 2) NO/NOx mode capability.