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Exhales gas first goes into the counter lung where there will be some
cooling and condensation, from there it is routed to the cannister.  At our
cannister the exhaled gas is mixed with the incoming feed gas near the
inlet.  Inside the cannister there is another cannister of smaller diameter
that is filled with sofnolime.  The gas travels between the inside of the
large outer cannister and the outside of the smaller inner cannister before
it enters the bottom of the inner cannister.  The gas then passes upward
through the 'sorb to finally exit the scrubber and flow to the diver's mouth.  

We plan to mount the sensor near the open end of the smaller inner cannister
that holds the 'sorb.  This area is heated by the reaction of the chemical
and the co2.  If we mount the sensor such that it has no connection to the
cold outer cannister and it is able to conduct heat away from the inner
cannister that should minimize condensation.

All rebreathers that operate at a loop temp below your body temp should
generate condensation so how do the big boys handle this?  Are sensors that
are in the CCRs, Cislunars, etc able to tolerate free water or do they also
use the scrubber heat to keep them dry.  I noticed the CCR has the sensor
pack inside their cannister is it for this reason?



>>Posted on 1 Mar 1996 at 07:46:48 by Barrie Kovish
>>
>>I checked the documentation on my teledyne sensor.  It had the following
>>to say:
>>
>>1.  The teledyne sensor is not affected by humidity.  However the
>>    ambient PO2 is reduced.  Free water condensing on the sensor
>>    is however a problem.
>>
>I'm becoming increasingly fascinated by rebreathers.
>First, I discuss this from a purely theoretical point of view.
>
>Your application is semiclosed I understand.  Seems to me
>that if the sensor is downstream of the point where sufficiently
>gas is added (enough to bring the dewpoint below sensor ambient)
>condensation might not be a problem.
>
>The other thing one could do is to heat the sensor to a
>certain number of Kelvins above ambient and calibrate it
>there but I wonder how stable it's reading will be
>as a function of the breathing rate (flowrate through
>the sensor)

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