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Emerson Process Management GmbH & Co. OHG 7-21
Instruction Manual
HASAxE-IM-HS
05/2006
7 Maintenance
7-3-4 Auto Calibration
7-3-4 Auto Calibration
7-3-4-1 Additional Preparations for
Auto Calibration
As described in an earlier section autocal-
ibration is possible only with installed internal
and/or external valves.
In addition this requires all requested cali-
bration gases to be connected to the valves
and the valves to be software assigned to the
gases.
Why is assigning valves required?
X-STREAM gas analyzers support easy
system integration by offering variable instead
of fixed valve assignment. For autocalibrations
the analyzer controls the gas flow without
operator interaction and therefore needs to
"know" about the different valve functions - this
is done by valve assignment.
In addition variable valve assignment allows to
use one valve for different functions.
Example:
• Dual channel analyzer for measuring CO
and CO
2
.
• Spangases are CO and CO
2
, zero gas
for both channels is N
2
.
Without variable assignment one would need
to zero span channel 1 separately from channel
2. Taking into account the purges times before
a calibration calculation starts, to ensure the
measuring cells are filled with calibration gas,
the whole procedure takes a quite long time.
With variable valve assignment the operator
can specify e.g. the valve V1 to be the zero
gas valve for channel 1 AND channel 2. Now,
when starting a zero calibration, the analyzer
calculates the zero values for both channels
at a time!
Zero spanning with
fixed assignment
Zero spanning with
variable assignment
purge times
calibration
ch 1 ch 1 ch 1 ch 2 ch 2 ch 2
ch 1
&
ch2
ch 1
&
ch2
ch 1
&
ch2
improvement in
time
timeline
Fig. 7-3: Calibration improvement by variable valve assignments