Thermo 48i - Span Adjust

Calibration
Calibration
Thermo Electron Corporation Model 48i Instruction Manual 4-5
Span Adjust 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:
Where:
[CO]
OUT
= diluted CO concentration at the output manifold, ppm
[CO]
STD
= concentration of the undiluted CO standard, ppm
F
CO
= flow rate of CO standard corrected to 25 °C and 760 mm Hg, LPM
F
D
= flow rate of dilution air corrected to 25 °C and 760 mm Hg, LPM
2. Allow the instrument to sample this CO concentration standard until a
stable response is obtained.
3. From the Main Menu, choose Calibration > Calibrate Span.
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, then
press to calibrate the CO reading to the CO calibration gas.
recorder response (percent scale) = (([CO]
OUT
x 100)/URL) + Z
CO
Where:
URL = nominal upper range limit of the instrument operating range
Z
CO
= instrument response to zero air, %scale
)
F
+
F
(
)
F
x
]
[CO (
=
]
[CO
COD
CO
STD
OUT
(1)