Siemens 7MB2041, Руководство по эксплуатации, Страница: 41 / 152

Commissioning
4.3 Commissioning and operation
OXYMAT 64
Operating Instructions, 06/2008, A5E00880383-03
39
4.3.2 Leak test
Sample gas must be passed through the sample gas path (including inlet pipe to analyzer,
see adjustment of sample gas flow). A meaningful measurement can only be carried out if
the sensor temperature has already been at its setpoint of 650 °C ± 0.1 K for more than
5 min.
The check is carried out as follows:
● Pass nitrogen at 7.5 l/h into the analyzer (flow over the sensor), and record the displayed
O
2
value after 5 minutes.
● Then reduce the flow to 6.9 l/h. Record the value again after 5 minutes. With this
reduction in flow, a leak would result in a larger O
2
value. There is a leak in the sample
gas path if the O
2
value deviates by more than +2% from the initial value.
● The opposite effect should occur if the sample gas flow is increased by a corresponding
amount.
● If the leak test indicates a fault, it must be repeated directly on the analyzer. This will then
indicate whether the leak is in the inlet pipe or in the analyzer itself.
See also
Adjusting the sample gas flow (Page 38)
4.3.3 Calibrate measuring ranges
Measuring ranges / spans
The desired spans (start-of-scale and full-scale values of measuring range) can be defined
using function 41. The start-of-scale / full-scale values are allocated to the analog current
values 0/2/4 mA to 20 mA.
If you enter the same values for the start-of-scale and full-scale of a measuring range, this
range is considered as non-existent. Allocate the smallest span (MS) to measuring range 1
and the respectively larger ones to ranges 2 – 4. In general, the following is true for the
allocation: MS1 < MS2 < MS3 < MS4 or MS1 > MS2 > MS3 > MS4.
The start-of-scale value must always be the same in all measuring ranges.
Technical zero
Since a zero point cannot be achieved because of the logarithmic measuring effect, the zero
adjustment is therefore carried out close to the start-of-scale value. This is defined as the
"Technical zero". An appropriate calibration gas must be selected as the "Zero gas" for this
purpose. Its O
2
concentration should always be < 30% of the smallest span to be adjusted.
Enter the zero setpoint using function 22.