Specifications

S
TARTUP AND
O
PERATION
748410-A
August 1999
18
Chemiluminescense Detector Analyzer Module
Rosemount Analytical NGA 2000
3
It is recommended, after initial startup, that the CLD Analyzer Module is calibrated at least
once every eight hours. This practice should continue until experience indicates that some
other interval is more appropriate depending on the analytical accuracy required.
If the user is unable to calibrate the Analyzer Module (i.e., when ZERO or SPAN is initiated,
nothing happens), a possible solution relates to the use of an incorrect gas for zeroing or
spanning (e.g., using a high concentration gas to zero or a zero gas to span the Analyzer
Module). Simply recalibrating with the appropriate gas(es) will not correct the problem
because the ZERO OFFSET or SPAN FACTOR has been set to an extreme value in the
process.
To remedy the problem, do the following:
1. Select the following from the Main Menu: Expert Controls and Setup, Analyzer Module
Set Up, and Calibration Parameters.
2. Using the
↓
arrow, select Zero Ranges, press ENTER and, using the up/down arrows,
toggle to SEPARATE. Do the same for the Span Ranges selection. Do not press
ESCAPE at any time unless retention of prior settings is desired.
3. Return to the Main Menu and make the following selections: Expert Controls and Setup,
Expert Analyzer Controls, Zero/Span Calibration, FACTORS softkey, and Range 1 (2, 3,
4) Factors (do Steps 4 and 5 for each range).
4. Select Zero Offset, press ENTER, adjust the value to 32700 with the
↑
and
↓
arrow keys,
and press ENTER. Do not press ESCAPE at any time unless retention of prior settings is
desired.
5. Select Span Factor, press ENTER, adjust the value to 0.00015 with the
↑
and
↓
arrow
keys, and press ENTER. Do not press ESCAPE unless retention of prior settings is
desired.
6. Attempt to recalibrate the Analyzer Module according to the procedure outlined at the
beginning of Section 3.4. If recalibration fails, return to the Range Factors menu, readjust
Zero Offset and Span Factor values, and try calibrating again.
3.6 C
ONVERTER
T
EMPERATURE
A
DJUSTMENT
P
ROCEDURE
The vitreous carbon converter used in this analyzer module must be checked periodically to
assure that it is working at peak efficiency. The efficiency of the converter is typically 95% to
98%, that is, 95% to 98% of the nitrogen dioxide introduced to the module is reduced to
nitric oxide. That is well above the 90% minimum required by the Environmental Protection
Agency. (Refer to 40 CFR 60, App. A, Method 20, Paragraph 5.6.)
Two conditions reduce the efficiency of the converter:
•
the converter is operating at too low a temperature and the efficiency drops or