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Calibration Procedures Teledyne API T801 NDIR CO2 Analyzer Operation Manual
166
9.3. ASSESSING CALIBRATION QUALITY
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. 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 both test
functions (Section 3.4.2 or Appendix A-3), all of which are automatically stored
in the DAS channel CALDAT for data analys
is, documentation and archival.
Make sure that these parameters are within the limits listed below and frequently
compare them to those values on the Final Test and Checkout Sheet (PN
068340000) that came attached to your manual, which should not be significantly
different. If they are, refer to troubleshooting in Section 11.
Table 9-2: Calibration Data Quality Evaluation
FUNCTION
MINIMUM
VALUE
OPTIMUM
VALUE
MAXIMUM
VALUE
SLOPE
0.700 1.000 1.300
OFFSET
-0.500 0.000 0.500
These values should not be significantly different from the values recorded on the Teledyne API Final
Test and Validation Data Sheet that was shipped with your instrument.
If they are, refer to troubleshooting in
Section 11.
The default DAS configuration records all calibration values in channel
CALCO2 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 values (standard deviation of the CO
2
concentration) to assess whether the analyzer response has properly leveled
off during the calibration procedure.
9.4. CALIBRATING THE ELECTRONIC SUBSYSTEMS
9.4.1. PRESSURE CALIBRATION
A sensor in the sample path continuously measures the pressure of the sample
gas. This data is used to compensate the measured CO
2
concentration for
changes in atmospheric pressure and is stored in the CPU’s memory as the test
function PRES (also viewable via the front panel).
07274B DCN6418