46 GMS800 · Operating Instructions · 8013025 V1.2 · © SICK MAIHAK GmbH
Adjustment
Subject to change without notice
6.3.4 Test gas feed with sample gas cooler
Only applicable for applications where a sample gas cooler is used.
Adjustment with “dry” test gases
In the method with “dry” test gases, the test gases flow from the source (pressure cylinder)
directly into the gas analyzer without flowing through the sample gas cooler.
Adjustment with “wet” test gases
The test gases are subjected to the same influences as the sample gas when the test
gases flow through the sample gas cooler before reaching the gas analyzer. The result is
“wet” test gases with the same H
2
O content as the sample gas.
Advantages: ● The physical conditions are identical during adjustment. This
means the adjustment results can be compared directly.
● This method allows following the gas analyzer drift.
Disadvantages: ● The influence of the sample gas cooler is not considered during
adjustment.
● It may be necessary to quantify the influence of the sample gas
cooler.
Possible methods to determine the sample gas cooler influence:
1 Feed a test gas directly into the gas analyzer (as during adjustment). Note
the measured value displayed for this test gas.
2 Feed the same test gas again through the sample gas cooler (as with the
sample gas) before it reaches the gas analyzer. Note the measured value.
3 Consider the difference between the two measured values during measur-
ing operation.
4 Possibly repeat this comparison measurement regularly.
Advantages: ● The actual influence of the sample gas cooler is recorded physi-
cally and considered in the adjustment.
Disadvantages: ● Because the physical conditions in the sample gas cooler are not
exactly constant, the results of single adjustments are also not
exactly identical. This must be considered when assessing the
drift.
● Due to the fact that adjustment gases from gas cylinders practi-
cally do not contain any H
2
O, the sample gas cooler can dry out
during the course of a long adjustment procedure. This would
neutralize the advantages of this method.
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