B28050-410-000-RC (MANUAL FOR XD-I).doc
4
Procedure
Remove electronics module for pulling wires and reinstall for connection. Undo
the centre nut and disconnect the sensor wire from the jack. Pull outward.
3.
FILTERS AND SENSOR POISONS
Catalytic bead sensors such as are used in these instruments are subject to certain poisoning effects from
some gases. Some gas classes, notably silicones are permanent poisons: they coat the surface of the
sensor, preventing the sensor from interacting with the hydrocarbon gases being measured. There is no
"cure" for sensors poisoned with silicones.
There are other gases which have similar effects, but which are to some degree reversible. These are
Chlorinated solvents, sulphur based products and some others. The symptoms are the same, in that the
sensor becomes non-responsive; however, it is possible to "burn off" the coating by applying an
"overdose" by, for instance a short exposure to pure butane. The procedure is always slightly damaging to
the sensor, so it should not be done indiscriminately, and the sensor should be recalibrated afterwards.
It is important to note that THE ONLY WAY TO DETERMINE WHETHER A SENSOR IS POISONED
Figure 2 Enclosure Access
