ZIROX SGM7.2, Руководство пользователя

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Oxygen Monitor SGM7.2 4 Functional Description
4.1.2 Gas flow quantity
At lower quantities, the measurement results become
distorted by contamination effects of the gas pipes
(leakages, permeability, desertions). If the gas flow trough
the sensor is too much, asymmetric cooling of the sensor
electrodes may cause additional measuring errors.
The constant flow of the measuring gas will be ensured by
internal pump. It can be chosen between
High (40 l/h) and
Low (5-10 l/h).
4.1.3 Precision of the measuring
The manufacturer guarantees a measuring error of less than
5% (relative error) only with measurements of oxygen
concentrations within a range of 2 · 10
5
... 10 ppm. For
measurements of oxygen concentrations of 10 ... 10
-3
ppm
the relative error is less than 5% if the gas inlet pipe has no
leakages or permeability’s.
For measurements of oxygen concentrations less than 10
ppm, the following aspects must be taken into account
during evaluation:
•
composition of the measured gas (e.g. presence of
burning gases)
•
specific characteristics of the production process (e.g.
material used)
•
temperature of the measured gas.
To reduce the measuring error at low oxygen concentrations,
the following advice must be considered:
•
The measuring gas must be taken from a location where
the measuring gas has a homogeneous concentration of
its substances.
•
The pipe from the measuring point to the SGM7.2 must
be as short as possible in order to avoid a change in the
chemical balance in the pipe.
•
All gas inlet and outlet pipes must be free of leakages.
•
For measurements of oxygen concentrations of less
than
1000 ppm, the use of steel pipes is necessary.
•
If the measured gas contains reducing components (e.g.
alcohol) the concentration of free oxygen cannot be
determined correctly as chemical reactions occur at the
electrode. In such cases the measured gas should be
filtered by an active charcoal filter before entering the
SGM7.2.
HB_SGM72_Rehm_eng.DOC
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