GE Analytical Instruments ©2006 16-11 DLM 14291 Rev. A
• Turn the NOA Power on and use a small screwdriver to turn the contrast
adjustment screw while viewing the LCD display. Adjust the screw to give a
clear display.
If the contrast cannot be adjusted, then the problem is with the display, the
power supply board or another electrical problem. Contact Sievers for assistance.
Cell Pressure too High or too Low
The NOA Cell Pressure should range from 4 to 7 torr. If the pressure is > 7 torr
(typically 12 torr) then the frit restrictor is not connected to the sample inlet. See
Frit Restrictor, page 4-12 for installation of the restrictor. If the Cell Pressure is <
4 torr, the restrictor may be clogged. See Testing and Cleaning the Flow Restrictor
Frit, page 15-13 for assistance.
Gas Sampling Problems
The most common problem encountered in gas-phase NO measurements is out of
range calibration. The ppm response factor should be in the range 0.09768 –
0.1465 and the ppb response factor should be in the range 0.1953 – 0.293. If the
response factors exceed the recommended limts, possible problems include:
• A dirty reaction chamber (see Cleaning the Chemiluminescence Reaction Cell,
page15-5).
• A clogged Frit Restrictor (see
Testing and Cleaning the Flow Restrictor Frit,
page
15-13).
• Calibration Gas flow rate is too low (make sure gas is venting out the open leg
of the tee).
• Incorrect concentration entered during calibration.
• Lower than expected NO concentration reaching the analyzer.
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