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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
6-2
Zero/Span valves have 3 operational states:
1. Sample mode. Here both valves are un-energized and sample gas passes through the
sample/cal valve and into the analyzer for analysis.
2. Zero mode. The sample/cal valve is energized to the cal mode. The zero/span valve is un-
energized in the zero mode, thus allowing zero gas to be admitted through the rear panel
bulkhead fitting into the analyzer.
3. Span mode. The sample/cal and the zero/span valves are both energized and in the cal mode.
With both valves on, span gas is admitted through a rear panel bulkhead fitting into the
analyzer.
Zero air and span gas inlets should supply their respective gases in excess of the 1000 cc/min
demand of the Analyzer. Supply and vent lines should be of sufficient length and diameter to
prevent back diffusion and pressure effects. See Figure 2-3 for fitting location and tubing
recommendations.
Zero air for this instrument should have less than 1 ppt (.001 ppb) NO and have various
interferent gas concentrations such that they produce less than 1 ppt total interferent. We
recommend a tank of Ultra Zero Air commonly used in gas chromatographic applications as a
reliable and constant source of zero air. Another source of zero air is the Model 701 zero air
module.
6.3 Autocal - Setup Zero/Span Valves
The Autocal system operates by executing SEQUENCES. It is possible to enable 0-3 sequences,
each sequence operates in one of 4 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