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Mixing Chamber
Output Manifold
Calibration Procedures
Connect to and Configure
the Calibration Gas System
Internal Valve System
Thermo Fisher Scientific
A chamber constructed of glass, Teflon®, or other nonreactive material, and
designed to provide thorough mixing of CO and diluent air for the
dilution needed.
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.
When using the gas dilution system, the total flow must exceed the total
demand of the analyzer(s) connected to the output manifold to ensure that
no ambient air is pulled into the manifold vent. The exact CO
concentration is calculated from:
[CO
Where:
[CO]
= diluted CO concentration at the output manifold, ppm
OUT
[CO]
= concentration of the undiluted CO standard, ppm
STD
F
= flow rate of CO standard corrected to 25 °C and 760 mmHg, LPM
CO
F
= flow rate of dilution air corrected to 25 °C and 760 mmHg, LPM
D
Use the following procedures to calibrate the instrument.
Connect the instrument and configure the calibration gas system per the
following.
In addition to the internal zero air scrubber, the Model 48i Trace Level-
Enhanced is shipped standard with internal switching valves that provide
the capability for fully automated calibration. The configuration of these
valves is illustrated schematically in Figure 4-2. When designing the
calibration system, it is important that the operator understand the
instrument's internal valve configuration. If the calibration and/or
sampling system is designed without considering the internal valves, there is
a possibility of calibration errors that would invalidate monitoring data.
(
[CO
x
]
F
CO
STD
]
=
OUT
(
+
)
F
F
D
CO
Model 48i Trace Level-Enhanced Instruction Manual
Calibration
Calibration Procedures
)
4-5
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