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6.2. PREDICTING FAILURES USING THE TEST FUNCTIONS
Table 6-3:
Predictive Uses for Test Functions
FUNCTION
CONDITION
Zero Cal
STABILITY
Zero Cal
CO2 MEAS
Zero Cal
MR RATIO
Span Cal
Sample
PRES
Any, but
with Bench
PHT DRIVE
Temp at
48°C
Zero Cal
OFFSET
Span Cal
SLOPE
07272B DCN6552
The Test Functions can be used to predict failures by looking at how their values
change over time. Initially it may be useful to compare the state of these Test
Functions to the values recorded on the printed record of the final calibration
performed on your instrument at the factory, p/n 04307. Table 6-3 can be used as
a basis for taking action as these values change with time. The internal data
acquisition system (DAS) is a convenient way to record and track these changes.
Use APICOM to download and review this data from a remote location.
BEHAVIOR
Pneumatic Leaks – instrument & sample system
Increasing
Detector deteriorating
Source Aging
Decreasing
Detector deteriorating
Optics getting dirty or contaminated
Source Aging
Increasing
Detector deteriorating
Contaminated zero gas (H2O)
Source Aging
Detector deteriorating
Decreasing
GFC Wheel Leaking
Pneumatic Leaks
Contaminated zero gas (CO
Source Aging
Increasing
Pneumatic Leaks – instrument & sample system
Calibration system deteriorating
Source Aging
Decreasing
GFC Wheel Leaking
Calibration system deteriorating
Pneumatic Leak between sample inlet and Sample Cell
Increasing > 1"
Change in sampling manifold
Dirty particulate filter
Decreasing > 1"
Pneumatic obstruction between sample inlet and Sample Cell
Obstruction in sampling manifold
Mechanical Connection between IR-Detector and Sample Cell
deteriorating
Increasing
IR-Photodetector deteriorating
Increasing
See MR Ratio - Zero Cal Decreasing above
Decreasing
See MR Ratio - Zero Cal Increasing above
Increasing
See MR Ratio - Span Cal Decreasing above
Decreasing
See MR Ratio – Span Cal Increasing above
INTERPRETATION
)
2
189
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