Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 206)

Model 9110TH NOx Analyzer Calibration Procedures
Teledyne Analytical Instruments 186
5.9. CALIBRATION QUALITY ANALYSIS
After completing one of the calibration procedures described above, it is important to
evaluate the analyzer’s calibration SLOPE and OFFSET parameters. These values
describe the linear response curve of the analyzer, separately for NO and NO
X
. The
values for these terms, both individually and relative to each other, indicate the quality
of the calibration. To perform this quality evaluation, you will need to record the values
of the following test functions (Section 4.2.1 or Appendix A-3), all of which are
automatically stored in the DAS channel CALDAT for data analysis, documentation
and archival.
 NO OFFS
 NO SLOPE
 NOX OFFS
 NOX SLOPE
Make sure that these parameters are within the limits listed in Table 5-5 and frequently
compare them to those values on the Final Test and Checkout Sheet that came attached
to your manual, which should not be significantly different. If they are, refer to the
troubleshooting Section 7.
Table 5-5: Calibration Data Quality Evaluation
FUNCTION MINIMUM VALUE OPTIMUM VALUE MAXIMUM VALUE
NOX SLOPE -0.700 1.000 1.300
NO SLOPE -0.700 1.000 1.300
NOX OFFS -20.0 mV 0.0 mV 150.0 mV
NO OFFS -20.0 mV 0.0 mV 150.0 mV
The default DAS configuration records all calibration values in channel CALDAT as
well as all calibration check (zero and span) values in its internal memory. Up to 200
data points are stored for up 4 years of data (on weekly calibration checks) and a lifetime
history of monthly calibrations. Review these data to see if the zero and span responses
change over time. These channels also store the STABIL value (standard deviation of
NO
X
concentration) to evaluate if the analyzer response has properly leveled off during
the calibration procedure. Finally, the CALDAT channel also stores the converter
efficiency for review and documentation.