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Maintenance Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 263
12.2. PREDICTING FAILURES USING THE TEST FUNCTIONS
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 12-3 can be used as a basis for
taking action as these values change with time. The internal data acquisition system (iDAS) is a convenient way
to record and track these changes. Use APICOM to download and review this data from a remote location.
Table 12-3: Predictive uses for Test Functions
FUNCTION CONDITION BEHAVIOR
INTERPRETATION
STABILITY
Zero Cal Increasing
Pneumatic Leaks – instrument & sample system
Detector deteriorating
CO MEAS
Zero Cal Decreasing
Source Aging
Detector deteriorating
Optics getting dirty or contaminated
MR RATIO
Zero Cal
Increasing
Source Aging
Detector deteriorating
Contaminated zero gas (H
2
O)
Decreasing
Source Aging
Detector deteriorating
GFC Wheel Leaking
Pneumatic Leaks
Contaminated zero gas (CO)
Span Cal
Increasing
Source Aging
Pneumatic Leaks – instrument & sample system
Calibration system deteriorating
GFC Wheel Leaking
Decreasing
Source Aging
Calibration system deteriorating
PRES
Sample
Increasing > 1”
Pneumatic Leak between sample inlet and Sample Cell
Change in sampling manifold
Decreasing > 1”
Dirty particulate filter
Pneumatic obstruction between sample inlet and
Sample Cell
Obstruction in sampling manifold
PHT DRIVE
Any, but with
Bench Temp at
48°C
Increasing
Mechanical Connection between IR-Detector and
Sample Cell deteriorating
IR-Photodetector deteriorating
OFFSET
Zero Cal
Increasing
See MR Ratio - Zero Cal Decreasing
above
Decreasing
See MR Ratio - Zero Cal Increasing
above
SLOPE
Span Cal
Increasing
See MR Ratio - Span Cal Decreasing
above
Decreasing
See MR Ratio – Span Cal Increasing
above