SICK DEFOR, Supplementary Operating Instructions, Page: 9 / 30

Product Description
DEFOR · Supplementary Operating Instructions · 8013029 V2.0 · © SICK AG 9
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2.1
Measuring system
Measuring principle
The Analyzer module DEFOR uses the fact that some gases have a specific absorption
characteristic in the ultraviolet light range. For this purpose, UV light is radiated through the
sample gas. The concentration of a gas component in a gas mixture can be determined
through suitable selection of the light wavelength and selective absorption measurement.
The Analyzer module DEFOR can, in this way, analyze the concentration of the gases Cl
2
,
H
2
S, NO, NO
2
, NH
3
, SO
2
and further gases.
The Analyzer module DEFOR can simultaneously measure up to 3 gas components.
Measuring method
● The Analyzer module DEFOR uses interference filter correlation (IFC) for most gas com-
ponents. Measuring and reference radiation are created alternately by swiveling two dif-
ferent interference filters into the beam path (filter wheel [2a]).
● Gas filter correlation (UVRAS) is used for NO. This method creates the reference radia-
tion by swiveling a gas filter filled with the relevant gas into the beam path (filter wheel
[2b]).
● Both measuring methods are combined for joint measurement of NO and other gases
(both filter wheels [2a]+[2b] are used).
● The physical state of the measuring system is captured and compensated using a refer-
ence beam path through a reference cuvette.
Analyzer module layout
– Beam source is a special UV gas discharge lamp ( → p. 8, Fig. 1 [1]) that emits both broad-
band as well as NO-specific radiation components.
– Thermostat-controlled filter wheel unit [2] keeps the optic filters at a constant tempera-
ture. This minimizes the influence of external temperature changes.
– Lenses [3][8], beam splitter [4] and mirror [5] direct the beam path.
– Sample gas flows through sample cuvette [6]. Reference cuvette [7] is either filled with
a neutral gas or has span gas flowing through (option).
– Detectors [9] capture the radiation intensity created with the various filters.
– Measurement signals are amplified electronically and digitally evaluated. The structure
symmetry compensates proportional and symmetric signal drifts in the best possible
way.
– The measuring system can be fitted with an adjustment unit ([10] → p. 10, §2.2.1 ).
The specific properties of the desired measuring components and the desired
physical measuring range each demand an individual metrological concept for
the Analyzer module.