ABB AO2000 Series, Operating Instructions Manual

Page: 339 / 362

AO2000 CONTINUOUS GAS ANALYZERS | OI/AO2000-EN REV. B 339
Limas11 IR, Limas21 UV, Limas21 HW: Troubleshooting
Temperature problem
Connecting leads of the temperature sensor or the heater discon-
nected
•
Check the connecting leads and connectors.
•
Check the fit of the leads in the wire end ferrules.
Defective thermal link
•
Check thermal link for continuity and replace if necessary.
Measured value display is not stable
Leaks in the gas feed paths
•
Check the seal integrity (see page 268) of the analyzer module gas paths
and (if applicable) of the lines to the pneumatics module.
Beam intensity too low
•
Read the current intensity values using
Diagnostics/Test →
Module-specific → Lamp intensity
menu item (start the zero gas
supply for this) and compare this value with Init value displayed (the Init
values were stored following amplification optimization after installa-
tion of a new lamp). A significant decrease (by a factor of 10 or more) is
the probable cause of unstable measurement value readings.
Three different cases can be identified:
1 If only the two measurement detector values have dropped, there is
probably a contaminated sample cell. Clean the sample cell.
2 If all four values are have dropped by similar amounts then lamp in-
tensity has probably decreased. Perform an amplification optimiza-
tion (see page 310) or replace the lamp (see page 307).
3 For NO measurement only: If the reference receiver "Reference" value
has increased or not as markedly decreased as a percentage relative
to the reference receiver "Measurement" value and if at the same
time the sensitivity span has decreased (loss of sensitivity), aging of
the selectivity cell is the probable cause (see the service manual for
more information).
"Sample Value Overflow or Underflow" status signal
Drift or aging of optical components (lamp, sample cell, detector,
etc.)
• Determine the cause.
•
If required clean or replace the affected components.
•
Subsequently, perform an amplification optimization (see page 310), to
bring the receiver signal back to its optimal range.