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Emerson Process Management GmbH & Co. OHG 3-1
X-STREAM XE
Instruction Manual
HASXEE-IM-HS
04/2010
3
Principles
Chapter 3
Measuring Principles
3.1 Infrared Measurement (IR)
Ultraviolet Measurement (UV)
3.1.1 IntrinzX Technology
X-STREAM series analyzers support several
measuring principles depending on the gas
component of interest. This provides best
possible results, as the measurement can be
chosen to optimally t the characteristics of
the gas to be measured with respect to the
application. The following sections introduce
the available measuring principles highlighting
their specic characteristics.
The non-dispersive measurement methods
described in this section utilize gas specic
light absorption in order to discriminate bet-
ween different gases. This is possible, as
any gas possesses distinct absorption cha-
racteristics. Selective measurement of these
so called absorption lines can be used to
identify gas components: The amount of light
absorpted by the absorption lines, is a direct
measure of the gas concentration.
One can distinguish between two different
types of non-dispersive measurements, dif-
fering in the way, wavelength selectivity is
accomplished. It is essential for gas specic
concentration measurements, to selectively
detect only light of the absorption line wave-
lengths of the gas of interest. Typically a gas
selective detector is used for NDIR measure-
ments,
3-3. For NDUV the selectivity
is achieved by an additional optical lter, as
the detector itself is broadband sensitive. In
some applications, a pyrodetector is used for
NDIR measurements. This type of detectors
is not wavelength selective, hence these se-
tups also use an optical lter to narrow their
wavelength response function.
The assembly of a NDIR and NDUV channel
is shown in
Fig. 3-3. For NDIR a broad-
band IR light source is used to generate the
light, while NDUV measurements utilize a UV
narrowband uorescence source, already
adopted for the absorption lines of the gas
of interest. Part of this adoption is done by a
specially selected optical lter in the adaptor
cell.
The diameter of the light beam emitted from
the sources is adjusted to completely ll the
opening of the split analysis cell. After traver-
sing the analysis cell, the light passes through
a lter cell which adjusts the beam diameter
to the chopper opening and the diameter of
the active detector area. The chopper wheel
used is designed to allow an intrinsically re-
ferenced measurement. The details of this
new patent pending method are described in
section 3.1.1.
The decision, which measurement (UV / IR)
to use for a specic application depends on
the gas component to be measured, and the
required measurement performance.
The IntrinzX technology is an enhancement
of the well established “proof peak” techno-
logy with automatic sensitivity control, known
from the MLT gas analyzer series. While the
“proof peak” provided only one reference
measurement per chopper wheel revolution,
the IntrinzX technology provides four refe-
rence measurements per revolution. The
patent pending IntrinzX technology has been
introduced into the market with the launch of
the X-STREAM X2 gas analyzers.
Using the new IntrinzX chopper wheel, the
reference and the measurement signal are
modulated with 4 and 5 times the basic revo-