Teledyne 200E, Instruction Manual, Page: 175 / 302

Theory of Operation Model 200E Instruction Manual
The influence of water vapor on the M200E measurement can be eliminated with an
optional, internal sample gas dryer. The concentrations of N
2
and O
2
are virtually constant
in ambient air measurements, hence provide a constant amount of quenching and the
interference of varying CO
2
amounts is negligible at low concentrations.
Table 10-1: List of Interferents
Gas Interference Type Rejection Method
Dilution: Viscosity of CO
2
molecules causes
them to collect in aperture of Critical Flow
Orifice altering flow rate of NO.
CO
2
3
rd
Body Quenching: CO
2
molecules collide
with NO
2
* molecules absorbing excess energy
kinetically and preventing emission of
photons.
If high concentrations of CO
2
are suspected,
special calibration methods must be
performed to account for the affects of the
CO
2
.
Contact T-API Customer Service depart-
ment for details.
Some SO
X
variants can also initiate a
chemiluminescence reaction upon exposure to
O
3
producing excess light.
Wavelengths of light produced by
chemiluminescence of SO
X
are screened out
by the Optical Filter.
Chemically reacts with NH
3
, O
2
and H
2
O in O
3
generator to create (NH
3
)
2
SO
4
(ammonium
sulfate) and NH
3
NO
2
(ammonium nitrate)
which form opaque white deposits on optical
filter window. Also forms highly corrosive
HNO
3
(Nitric Acid)
Most of the ammonium sulfate and
ammonium nitrate produced is removed
from the sample gas by an air purifier
located between the O
3
Generator and the
reaction cell.
SO
X
3
rd
Body quenching: SO
X
molecules collide
with NO
2
* molecules absorbing excess energy
kinetically and preventing emission of
photons.
If high concentrations of SO
X
are suspected,
special calibration methods must be
performed to account for the affects of the
SO
2
.
Contact T-API Customer Service depart-
ment for details.
3
rd
Body quenching: H
2
O molecules collide
with NO
2
* molecules absorbing excess energy
kinetically and preventing emission of
photons.
Analyzer’s operating in high humidity areas
must have some method of drying applied
to the sample gas supply (Section 5.7 for
more details).
H
2
0
Chemically reacts with NH
3
and SO
X
in O
3
generator to create (NH
3
)
2
SO
4
(ammonium
sulfate) and NH
3
NO
2
(ammonium nitrate)
which form opaque white deposits on optical
filter Window. Also forms highly corrosive
HNO
3
(nitric acid)
Removed from the O
3
gas stream by the
Perma Pure
®
Dryer (Section 10.2.6 for
more details).
NH
3
Direct Interference: NH
3
is converted to H
2
O
and NO by the NO
2
converter. Excess NO
reacts with O
3
in reaction cell creating excess
chemiluminescence.
If a high concentration of NH
3
is suspected,
steps must be taken to remove the NH
3
from the sample gas prior to its entry into
the NO
2
converter.
Chemically reacts with H
2
O, O
2
and SO
X
in O
3
generator to create (NH
3
)
2
SO
4
(ammonium
sulfate) and NH
3
NO
2
(ammonium nitrate)
which form opaque white deposits on optical
filter window. Also forms highly corrosive
HNO
3
(nitric acid).
The Perma Pure
®
dryer built into the M200E
is sufficient for removing typical ambient
concentration levels of NH
3
.
In cases with excessively high CO
2
concentrations (larger than 0.5%), the effect can be
calibrated out by using calibration gases with a CO
2
content equal to the measured air. Only
very high and highly variable CO
2
concentrations will then be cause of measurable interfer-
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