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Commercial Permeation
Calibration in Dual
Range and Auto
Range Mode
Set Background Readings
Thermo Scientific
Where:
[NO
P = permeation rate in μg/min
F
T
K (NO
Commercial permeation systems, such as the Thermo Scientific 146iQ
Multigas Calibration System, are available for this requirement. Refer to
Systems
the instrument instruction manual for more information.
In addition to the 146iQ and other commercial permeation systems, the
42iQTL can also be configured with an optional permeation oven to
supply calibration gas for the instrument. The operation of the internal
permeation oven is described in Chapter 9,
The dual/auto range calibration feature is used to calibrate the analyzer at
two different span levels (as opposed to a single span level in the standard
mode) generating a "tailored multi-point" calibration curve stored in the
analyzer's memory. This feature may be used:
When widely different gas levels are being monitored, such as a factor
●
of 10 or greater apart
If precision and span levels are being introduced using separate tanks
●
If more than one multi-component cylinder is being used to calibrate
●
the instrument
Properly designed chemiluminescence analyzers are inherently linear over a
wide dynamic range; and under normal U.S. EPA compliance situations
this feature is not required. Dual calibration may be used for span levels less
than a factor of 10 apart, however if this is done to correct for a significant
non-linearity, it may mask the problems causing the effect, such as, bad
calibration cylinder, leaks in sampling lines, or low ozonator output.
Use the following procedure to set the prereactor background reading to
zero. Both the NO and NO
to Zero
and the following procedure also applies to the NO and NO
screen.
Note The prereactor background should be zeroed first followed by the
NO, then the NO
]
= NO
output concentration in ppm
2
OUT
2
= total flow rate of gas after mixing chamber (F
) = 0.382 constant for NO
2
backgrounds screens operate the same way,
x
channels.
▲
x
Calibration in Dual Range and Auto Range Mode
+ F
) in liters/minute
P
D
permeant
2
"Optional
Equipment".
42iQTL Instruction Manual
Calibration
background
x
4-17
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