System Description
NO2-to-NO Converter
8-2
Model 42
i
Trace Level Instruction Manual
Thermo Fisher Scientific
Flow
Transducer
Converter
PMT Assembly
Prereactor
Fan
Power Supply
Thermistor
Measurement
Interface Board
Pressure Transducer
Input Board
Capillaries (2)
Figure 8–1.
Hardware Components
The NO
2
-to-NO converter heats molybdenum to approximately 325 °C in
order to convert and detect NO
2
. The converter consists of an insulated
housing, heater, replaceable cartridge, and a type K thermocouple sensor.
The mode solenoid valve switches analyzer operation between the NO
mode and NO
x
mode. It routes the ambient air sample either through the
reaction chamber (NO mode) or through the NO
2
-to-NO converter and
then to the reaction chamber (NO
x
mode).
The reaction chamber is where the sample reacts with ozone and produces
excited NO
2
that gives off a photon of energy when it decays.
The reaction chamber is heated and controlled to approximately 50 °C in
order to ensure the greatest instrument stability. The sample and ozone
flow capillaries and a thermistor sensor are also housed in/on the reaction
chamber assembly.
NO
2
-to-NO
Converter
Mode Solenoid
Reaction Chamber
Ozonator Solenoids (3) Motherboard Digital Output Board
Transformer
I/O Expansion
Board (Opt)
Flow
Switch
Reaction
Chamber