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EC9843 NOy ANALYZER OPERATION MANUAL
A built-in check verifies that the observed value is not different from the
calibration value by more than 25%. If it is, no correction is made and an
error message is sent to the EVENT LOG, setting the CALIBRATION ERROR flag.
8. The number displayed after NO SPAN RATIO and NO2 SPAN RATIO is the
factor by which the instrument gains are multiplied to cause the display and
output to agree with the span gas. You cannot set this number. This value is
set to 1.000 any time the span is set manually via the front panel. (The
assumption is that front panel adjustment is an instrument calibration, thus
preventing compound adjustments.)
3.9.4 Description of the AZS Process
The instrument will initiate a full zero/span cycle starting at the prescribed hour.
The valve to admit zero air will be opened and the sample valve closed. The
instrument will allow the cell to fill with the zero gas for 12 minutes. The display
and outputs are updated with the actual instrument reading during the entire zero
cycle. The zero value is for user reference only, and is never used by the analyzer
to compensate readings.
At the end of 12 minutes, the zero air valve is closed and the span gas valve is
opened, admitting the span gas for 12 minutes. The display and outputs are
updated with the actual instrument readings during the entire span cycle. The
current value at the end of the span cycle is used to calculate the compensation
value. If SPAN COMP is set to ENABLED, this is the value which is used to correct all
subsequent readings to the calibration.
The zero air valve is switched on for 3 minutes to purge the cell of span gas.
At the end of 28 minutes, monitoring resumes including putting data in the
average, etc. (The data averages are not updated during zero/span check.)
3.10 Calibration References
1. Quality Assurance Handbook for Air Pollution Measurement Systems.
Volume 11-Ambient Air Specific Methods, EPA-600/4-77-027a, U.S.
Environmental Protection Agency, Environmental Monitoring Systems
Laboratory (MD-77), Research Triangle Park, NC 27711, 1977.
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