Detector Drift - Micromeritics FlowSorb III 2305 Operator's Manual

FlowSorb III
TROUBLESHOOTING AND MAINTENANCE
This chapter contains:
common problems that may occur when operating the FlowSorb III, and
•
how you can resolve them
• instructions on replacing the septum
Contact your local Micromeritics service representative if additional assistance is
required.
Troubleshooting

Detector Drift

Some detector drift when first turning on the power is normal and to be ex-
pected. This type of drift is due to the detector system coming to its regulated
temperature and should disappear in approximately 30 minutes. The instrument is
generally usable after 10 minutes if it has been properly purged of air.
There are several likely causes for the detector indication (when on X1) not re-
turning to zero within ± 0.02 following a sample or calibration test with the DET.
pushbutton depressed.
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Aug 00
Using contaminated gas mixtures along with failure to keep the cold
trap properly submerged in liquid nitrogen. A decided shift of the
detector baseline occurs between the adsorption and desorption modes
when the gas contains impurities and the cold trap is ineffective.
Surprisingly small amounts of impurities can cause detector drift. A
contaminated pressure regulator, unclean metal connecting tubing, and
unclean non-metal tubing and connectors can contribute impurities to
an otherwise clean gas stream. Be sure one or more of these factors is
not responsible before proceeding further.
Using atmospheric air to perform calibrations can cause detector drift
because of its water vapor content which travels slowly through the
system. Using atmospheric air is discouraged and the procedure
described in Single-point Calibration in Chapter 3, is recommended.
Using too much liquid nitrogen in the Cold Trap Dewar. Too much
liquid nitrogen cools the metal fittings supporting the glass trap causing
moisture from the atmosphere to freeze. This leads to erratic gas
cooling. The liquid nitrogen level should be approximately one cm (0.5
in.) from the top of the Dewar.
Troubleshooting
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