Calibration
Pre-Calibration
Thermo Fisher Scientific
Model 48
i
Instruction Manual
4-3
A chamber constructed of glass, Teflon, or other nonreactive material, and
designed to provide thorough mixing of CO and diluent air for the
dilution method is required.
The output manifold should be constructed of glass, Teflon, or other
nonreactive material, and should be of sufficient diameter to ensure an
insignificant pressure drop at the analyzer connection. The system must
have a vent designed to ensure atmospheric pressure at the manifold and to
prevent ambient air from entering the manifold.
Prior to calibration, be sure the instrument is operating properly. Turn on
the instrument and allow it to stabilize for one hour. Perform the service
checks of the “
Preventive Maintenance
” chapter. Select the operating range
and the averaging time of the Model 48
i
.
Note
The averaging time should be less than the zero duration and less
than the span duration.
▲
Note
The calibration and calibration check duration times should be long
enough to account for the transition (purge) process when switching from
sample to zero and from zero to span. This transition time is the time
required to purge the existing air.
▲
Note
Depending on the plumbing configuration and the instrument, data
from approximately the first minute of a zero calibration or check should
be disregarded because of residual sample air. Also, data from
approximately the first minute of a span calibration or check should be
disregarded because the span is mixing with the residual zero air.
▲
Use the following procedure to calibrate the instrument.
Connect the instrument and the calibration equipment as shown in
Figure
4–1
. If an optional sample line filter is used, the calibration must be
performed through this filter. Ensure that the flow rate into the output
manifold is greater than the total flow required by the analyzer and any
other flow demand connected to the manifold.
Mixing Chamber
Output Manifold
Pre-Calibration
Calibration
Connect the Instrument
