Thermo 42i - Page 135

Calibration
Calibration
Thermo Electron Corporation Model 42i Low Source Instruction Manual 4-7
d. Press to return to the Calibration menu and repeat this
procedure to set the NO
x
background to zero.
e. Record the stable zero air responses as Z
NO
, Z
NOX
, and Z
NO2
(recorder response, percent scale).
3. Adjust the NO flow from the standard NO cylinder to generate a NO
concentration of about 80% of the upper range limit (URL) of the NO
range. The exact NO concentration is calculated from:
Where:
•[NO]
OUT
= Diluted NO concentration at the output manifold,
ppm
•NO
STD
= No feed concentration
•F
NO
= No flow
•F
O
= Ozone flow
•F
D
= Dilution flow
4. Allow the analyzer to sample the NO calibration gas until the NO,
NO
2
and NO
x
readings stabilize.
5. When the responses stabilize, from the Main Menu, choose Calibration
> Calibrate NO Coefficient.
The NO line of the Calibrate NO screen displays the current NO
concentration. The SPAN CONC line of the display is where you enter
the NO calibration gas concentration.
Use and to move the cursor left and right and use
and to increment and decrement each digit.
6. Press to calculate and save the new NO coefficient based on the
entered span concentration.
F
+
F
+
F
NO
x
F
=
]
[NO
DONO
STD
NO
OUT