42/24-10 EN Rev. 9
Chapter 8: Gas Analyzer Calibration
8-C-13
Uras26: Notes for Calibrating
Calibration
Calibration can be performed in range 1 and range 2 for each sample component.
It is always a common calibration and thus affects both ranges.
For additional information on measurement ranges, please refer to “Limas11,
Uras26: Notes for Changing Measurement Range Limits” section, page 7-A-3.
Calibration Cells
The use of calibration cells allows the Uras26 analyzer module to be calibrated
without using test gas containers.
A calibration cell can be installed in each of the analyzer module’s beam paths.
Each calibration cell is filled with a test gas matched to the sample components
and measurement ranges set up in the corresponding beam path.
Test Gases for Zero
Calibration
A zero gas is required for each zero calibration.
In addition to nitrogen, ambient air can be used for zero calibration. Water vapor
must be absorbed using a cooler. If the ambient air contains sample gas compo-
nents, these must be removed with a suitable absorber (for CO: HOPCALIT
®
,
for CO
2
: Sodium hydroxide on substrate).
Test Gases for Span
Calibration without
Calibration Cells
A test gas is required for each detector for span calibration without calibration
cells. In the case of automatic and externally controlled calibration, a test gas
mixture is required for all detectors since all are calibrated simultaneously. The
span gas concentration should be 70-80% of the end value of the largest
measurement range.
Test Gases for Span
Calibration of
Suppressed Ranges
For suppressed ranges, the span gas concentration must be within the suppressed
range. If possible, it should be equal to the end value of the suppressed range (and
thus the end value of the larger measurement range).
Test Gas for
Automatic Calibration
In principle a test gas for each sample component is required for the internally or
externally controlled automatic calibration.
A test gas mixture containing each sample component in the appropriate con-
centration may be used only when all sample components have no mutual cross-
sensitivity and / or carrier gas influences.
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