Calibration
Pre-Calibration
Thermo Electron Corporation Model 48i Instruction Manual 4-3
Pressure Regulator for CO
Standard Cylinder
The regulator used must have a nonreactive diaphragm and internal parts,
as well as a suitable delivery pressure.
Mixing Chamber 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.
Output Manifold 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.
Pre-Calibration 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 48i.
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.
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.
Calibration Use the following procedure to calibrate the instrument.
Connect 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.
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