42/23-572 EN Rev. 5
Operator’s Manual ACF-NT, ACF-NT V0309
35
FTIR Spectrometer Span Check
Correction Factor
Span calibration establishes a correction factor for each component in order to
assure the accuracy of the values displayed. This calibration is required since
there can be slight deviations between the optical components of various
analyzers. The correction factor is also known as measuring range amplification.
Span Calibration
In a span calibration the sample cell is filled with a known gas concentration and
analyzed. For this a gas having a concentration of the applicable component at
the upper end of the measuring range is recommended.
When should a span
calibration be
performed?
A span calibration must be performed on starting the analyzer system.
Since the factors involved in this calibration do not change over time, this cali-
bration only needs to be repeated if the optical components are changed during
maintenance (readjustment, change or cleaning of the optical components).
Calibration with
Steam Generator
Test containers cannot be filled with the H
2
O sample component. Thus a device
capable of producing a specific steam concentration in a continuous flow must be
used.
Since the calibration mix dew point is above room temperature, the calibration
gas must be supplied directly to the air injector in order to avoid noticeable
cooling of the H
2
O-air mix.
Step Action
1
Set the Maintenance Mode via the “Control Panel” screen and switch
the Flow control to either “Test gas local” or “Test gas probe” (see
page 14).
2
Make sure the proper calibration gas is connected to the test gas port
of the analyzer system.
3
Open test gas cylinder pressure reducer and check inlet pressure and
flow.
4
Wait until the sample cell is completely purged and the values have
stabilized between individual analyses. With a calibration gas flow rate
of 5 l/min. it will take approximately 5 minutes for the sample cell to
be completely purged.
5
Some components like NO
2
, HCl, HF and NH
3
need quite a long time
to reach equilibrium (30 to 90 minutes). Wait this time or use aqueous
solutions of HCl, HF or NH
3
with a water-evaporator to obtain shorter
times.
6
Note down the reading and compare it to the concentration on the
cylinder. The difference should be smaller than 4 %.
Procedure
7
If the reading factor is outside this range, the problem is either in the
calibration gas or in the sampling system.
Summary of Contents for ACF-NT
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