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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
6.3 Internal Zero/Span (IZS)
The IZS option includes the Zero/Span Valves described above, a temperature-controlled
permeation tube oven, and a rear panel mounted zero air scrubber. The IZS system is activated
by the same methods as described in Table 6-1 for the zero/span valves. The setup of the IZS is
the same as that of the valves and is described in Table 6-2.
The IZS system operation is similar to the zero/span valve operation, except that the source of
the zero air and span gas are supplied at the analyzer via a scrubber and permeation tube
respectively. See Section 7.1 - calibration for operational details. A continuous purge flow of
approximately 60 cc/min is drawn across the permeation tube to prevent span gas accumulation
when the permeation tube is not in use.
If the instrument is going to be turned off for more than 8 hours, the permeation tube must be
removed from the oven. The perm tube continues to release gas even while at room temp thus
causing high concentrations of NO
2
gas to accumulate. The high NO
2
levels cause high
background readings when operation is resumed.
6.4 Autocal - Setup of IZS and Zero/Span Valves
The Autocal system operates by executing SEQUENCES. It is possible to enable up to 3
sequences, each sequence operates in one of 4 MODES:
Table 6-6-2: IZS Sequence Modes
Mode No. Mode Name Action
1. Disabled Disables the Sequence
2. Zero Does a Zero Calibration
3. Zero-Span Does a Zero and Span Calibration
4. Span Does a Span Calibration
6-3
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