Ecotech Serinus 40 - Dryer; Ozone Generator; 2 To no Converter; Pressure Transducer Pcbs

Serinus 40 User Manual 2.2
Page 26
1.5.5 Dryer
The dryer is constructed of Nafion tubing, and is designed to remove water vapour from ambient air
that is used by the ozone generator. The water is absorbed and moves through the walls of the
tubing, evaporating into the surrounding air. The remaining gas is unaffected. The flow rate control
is performed by utilising a critical orifice.
1.5.6 Ozone Generator
The ozone generator is a corona discharge ozone source driven by an ignition coil. Dry air is drawn
into the discharge tube via an orifice and then ionised by a high voltage electrode. This yields O
3
from
the reaction 3O
2
→2O
3
. The ionisation takes place in the confines of a glass tube with the electrode
mounted on the outside. The amount of ozone generated is controlled by varying the energy to the
discharge tube. The ozone flow rate is approximately 80 cc/min with an ozone concentration of
6000-8000 ppm.
1.5.7 NO
2
to NO Converter
The NO
2
to NO converter uses high temperatures (325°C) and a catalyst to convert any NO
2
in the
sample to NO.
The NO
2
to NO converter assembly also houses a catalytic ozone destroyer that removes ozone from
the instrument exhaust.
To obtain accurate and stable results, the converter must operate at above 96% (US EPA/EN) or 95%
(Australian standard) efficiency.
1.5.8 Pressure Transducer PCBs
Two pressure transducers are used to check for flow and correct readings for pressure variations.
One is located upstream of the critical orifice (manifold pressure) and the other is located in the
reaction cell downstream of the critical orifice (cell pressure).
1.5.9 Optical Cell
Reaction Cell Assembly
The reaction cell is where O
3
and NO mix to create a chemiluminescence reaction which emits
photons. A portion of this light is filtered to a specific wavelength region (>665nm) and measured by
the PMT.
Optical Bandpass Filter
The optical bandpass filter is constructed of coloured glass that only allows the transmission of light
above 665nm. It is used to prevent measurement of interfering compounds.
Photomultiplier (PMT)
The PMT detects the amount of light reaching its sensors. The selective filtering of light reaching the
PMT allows direct measurement of NO in the cell.