Appendix C-2 | Model 888 ATEX IECEx Tail Gas Analyzer
The analyzer performs a zero calibration at this time. It will also adjust the
lamp flash count for each of the detectors during the zero process. At the
end of Period 2, the detector readings are saved and the analyzer advanc-
es to Period 3. The data valid contact will be open.
If there is a system alarm during the normal operation of the analyzer (i.e.
Periods 3 through 11), the current period will transition back to Period 2
until the alarm condition is cleared.
Period 3 – Sample Flush
The analyzer flows process gas through the sample system. The timer
ensures that the sample system is flushed with gas before advancing to
Period 4. The analog outputs are held at the last valid reading and the
data valid contact will be open.
Period 4 – Measure
The analyzer remains in Period 4 indefinitely until a system alarm, zero,
or calibration event occurs. The concentration readings are updated once
per second. The data valid relay contact will be closed and analog outputs
will be active.
Zero and Photo-Span Calibration
A zero or photo-span can be initiated either automatically or manually.
Manual initiation is accomplished either by using the local display or from
the remote input.
A photo-span calibration sequence is always preceded by a zero cali-
bration sequence.
Once time in Period 8 elapses, the period will continue either revert to
Period 3 or continue to Period 9.
Only analyzers equipped with the steam blowback option, can be con-
figured to advance to Period 9.
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