Thermo Scientific 48i Instruction Manual page 139

Span Adjust
Thermo Fisher Scientific
Use the following procedure to adjust the span.
1. Adjust the zero air flow and the CO flow from the standard CO
cylinder to provide a diluted CO concentration of approximately 80%
of the upper range limit (URL) of the analyzer.The total air flow must
exceed the total demand of the analyzer 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, L/min
CO
F = flow rate of dilution air corrected to 25 °C and 760 mmHg, L/min
D
2. Allow the instrument to sample this CO concentration standard until a
stable response is obtained.
3. From the Main Menu, choose Calibration > Cal Coef.
The first line of the display shows the current CO concentration
reading. The second line of the display shows the CO range and the
third line is where the CO concentration is entered.
4. Enter the CO calibration gas concentration using the pushbuttons, and
then press to calibrate the CO reading to the CO calibration gas.
recorder response (percent scale) = (([CO]
Where:
URL = nominal upper range limit of the instrument operating range
Z = instrument response to zero air, %scale
CO
5. Record the CO concentration and the instrument's response.
( [CO x
]
F
CO
STD
] =
OUT
( + )
F F
D CO
OUT
Calibration
Calibration
)
x 100)/URL) + Z
CO
Model 48i Instruction Manual 4-5