Thermo 42i - Page 138

Calibration
Calibration
4-10 Model 42i Low Source Instruction Manual Thermo Electron Corporation
of the URL of the NO
2
range. The decrease must not exceed 90% of the
NO concentration determined in Steps 5 and 6 above.
8. When the analyzer responses stabilize, record the resultant NO
concentrations as [NO]
REM
.
9. From the Main Menu choose Calibration > Calibrate NO
2
Coefficient.
The NO
2
line of the Calibrate NO
2
screen displays the current NO
2
concentration. The SPAN CONC line of the display is where you enter
the NO
2
calibration gas concentration.
10. Set the NO
2
calibration gas concentration to reflect the sum of the
following: the NO
2
concentration generated by GPT, ([NO]
ORIG
-
[NO]
REM
), and any NO
2
impurity.
Use to move the cursor left and right and use
to increment and decrement the numeric character at the cursor.
Where:
NO
2
]
OUT
= diluted NO
2
concentration at the output manifold, ppm
[NO]
ORIG
= original NO concentration, prior to addition of O
3
, ppm
[NO]
REM
= NO concentration remaining after addition of O
3
, ppm
11. Press to calculate and save the new NO
2
coefficient based on the
entered span concentration.
The analyzer does a one point NO
2
span coefficient calculation, corrects
the NO
2
reading for converter inefficiency, and then adds the corrected
NO
2
to the NO signal to give a corrected NO
x
signal.
If the analyzer calculates a NO
2
span coefficient of less than 0.96, either
the entered NO
2
concentration is incorrect, the converter is not being
heated to the proper temperature, the instrument needs servicing (leak
F
+
F
+
F
]
NO
[ x
F
+)
]
[NO-
]
([NO=
]
NO
[
DONO
IMP
2
NO
REMORIGOUT
2