Oxygen Monitor SGM7.2.4/7.2.6
4 Functional description
12
4.2.2
Accuracy of the measurement
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 tube has no leaks or
permeability.
For measurements of oxygen concentrations less than 10 ppm, the following
aspects must be taken into account during evaluation:
•
composition of the measuring gas (e.g. presence of burning gases)
•
specific characteristics of the production process (e.g.
material used)
•
temperature of the measuring gas.
To reduce the measuring error in low oxygen concentrations, the following
conditions must be provided:
•
The measuring gas must be extracted where a formation of layers can
be avoided.
•
The tube from the measuring point to the SGM7.2.4 must be as short
as possible in order to avoid a change in the chemical balance in the
tube.
•
All gas inlet and outlet tubes must be free of leaks.
•
If the measuring 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
measuring gas should be filtered by an activated carbon filter before
entering the SGM7.2.4 (see chapter 10.1).
4.2.3
Special features (operating hours counter and maintenance interval)
Open the menu 'OPERATING HOURS' by pressing any key.
TOTAL TIME: 1234 h
CHANGE CARBON
FILTER IN: 0 h
MAINT.INTERVAL: 600 h
RESET
USER CODE
RETURN
First, enter the password, then set the time of the preset maintenance interval
to the next filter change (choose line 'RESET' and press 'Enter').
In pump mode HIGH the maintenance interval runs 3 times faster than
in mode LOW!
NOTE
