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Theory of Operation Model 200E Instruction Manual
10.2.4. Ozone Gas Air Flow
The excess ozone needed for reaction with NO in the reaction cell is generated inside the
analyzer because of the instability and toxicity of ozone. Besides the ozone generator itself,
this requires a dry air supply and filtering of the gas before it is introduced into the reaction
cell. Due to its toxicity and aggressive chemical behavior, O
3
must also be removed from
the gas stream before it can be vented through the exhaust outlet.
In contrast to the sample flow, the ozone flow is measured with a mass flow sensor, which
is mounted on the pneumatic sensor board (Figure 11-5), just behind the PMT sensor
assembly. This mass flow sensor has a full scale range of 0-1000 cm³/min and can be
calibrated through software to its span point (Section 6.7.8). As the flow value displayed on
the front panel is an actual measurement (and not a calculated value), the flow variability
may be higher than that of the sample flow, which is based on a calculation from (more
stable) differential pressures. On the other hand, the drift, i.e. long-term change, in the
ozone flow rate may be higher and usually indicates a flow problem. As with all other test
parameters, we recommend to monitor the ozone flow over time for predictive diagnostics
and maintenance evaluation.
CAUTION
Ozone (O
3
) is a toxic gas. Obtain a Material and Safety Data Sheet
(MSDS) for this gas. Read and rigorously follow the safety guide-
lines described there. Always make sure that the plumbing of the
O
3
generation and supply system is maintained and leak-free.
10.2.5. O
3
Generator
The M200E uses a corona discharge (CD) tube for creating its O
3
. Corona discharge gener-
ation is capable of producing high concentrations of ozone efficiently and with low excess
heat. Although there are many cell designs, the fundamental principle remains the same
(Figure 10-6).
Figure 10-6: Ozone Generator Principle
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