Thermo Scientific 43iQ, Instruction Manual

Page: 150 / 284

Calibration
Equipment Required
4-4 43iQ Instruction Manual Thermo Scientific
The exact SO
2
concentration is calculated from:
F
+
F
F
x ]
SO
[
=
]
SO
[
SO
D
SO
STD
2
OUT
2
2
2
Where:
[SO
2
]
OUT
= diluted SO
2
concentration at the output manifold, ppm
[SO
2
]
STD
= concentration of the undiluted SO
2
standard, ppm
F
SO2
= flow rate of the SO
2
standard corrected to 25
°
C and 760 mm Hg
F
D
= flow rate of the dilution air corrected to 25
°
C and 760 mm Hg
Commercial precision dilution systems are available which reliably and
accurately dilute a high concentration gas mixture to provide a reliable span
gas. A high concentration (50 ppm) of SO
2
in air is precisely diluted to the
concentration range required.
The Thermo Scientific 146iQ Multi-gas Calibrator is one such system for
precision dilution.
Permeation tube systems which precisely maintain a set temperature to
within ±0.1
°
C and hold a zero air flow rate to within ±0.5% can be used
for generation of span gas. The flow rate of the permeation system must be
at least 0.5 LPM for proper operation.
A permeation tube system, shown in
Figure 4–2 can be constructed. All
connections between components in the system should be made with glass,
PTFE, or other non-reactive material.
The air flow controllers should be capable of maintaining a constant air
flow within ±2% of the required flow rate. Ensure all devices are properly
calibrated and that all flows are corrected to 25
°
C and 1 atm.
Commercial Precision
Dilution Systems
Permeation Tube System