What I think could be a possibility for checking if a scrubber is warm
     (working or not) is an array of temp sensors and an ambient gas temp
     sensor.  If you are able to determine the difference in ambient gas
     going into the scrubber and the active zone of the scrubber, then the
     array could be connected so that a red LED comes on when the is no
     warmer scrubber area.  Green would be displayed on power on if there
     is a warm area, red if not.  If you wanted to "prebreathe" the
     scrubber to warm it up for cold water diving, you just prebreathe and
     watch until the light switches red to green.

     A second red could be set up on a separate temp sensor near the end of
     the scrubber stack to light up when it gets warm.  This would indicate
     nearing the end of the scrubber life if your scrubber acts like
     Barrie's with the disk traveling thru the tube.  If the temp is always
     warmer downstream of the active region or a pratical resolution is too
     difficult, then the "almost gone" LED could be set to go off when two
     particular probes in diffent sections of the scrubber develop a
     different temp indicating the active zone has passed the upstream
     scrubber probe.

     On the subject of rebreather electronics, if you set up a 9 volt
     battery, a LED and some probes inside the scrubber and a one-way
     switch (manual reset), you maybe able to have a red idiot light that
     shows when water makes a connection between probes.  Lot's of testing
     and now real guarantees for these ideas, but still means to let you
     know something is wrong.

     John, I've a buddy who wants an O2 meter with only one nine volt
     battery and the changes to the offset that I suggested so it is less
     sensitive as well as the 5K pot on the external gain adjustment.  He
     is very interested, but wants to hear more about it before coughing
     dough.  Drop me a line on what you can do with the single battery
     issue as I want to have a backup meter too.--DD

David Drake             EDS/SATURN Infrastructure 8-320-4190 on GMnet
Spring Hill, TN  USA    Internet: saturn.ddrake05@gm*.co*

______________________________ Forward Header __________________________________
Subject: Re: Physiologic safety parameters for SC rebre
Author:  owner-techdiver (INET.OWNERTE7) at DIAMOND
Date:    6/13/96 1:19 PM


>John wrote:
>
>My speculation is that the output of the array, after subtraction
>of the water temp would display an approximate profile of the
>currently most active region of the scrubber.
>I have no idea how linear it would scale with temp variations.
>This is one of the tings I attempted to get Barrie excited about
>seeing as I am years from diving a rebreather myself :-).

From our observations I think that you are right.  One could tell if the
scrubber is working by checking the temperature at various positions
in the bed.  This would not tell you your FiCO2 but assuming that the
scrubber design was "known" to be effective you would at least be able
to detect when the scrubber was exhausted.  This would take a fair amount
of research to establish the actual "signature" of a dead vs live
scrubber under various conditions.  Currently we're having a hard time
just finding the time to complete our next version of the "Black Widow"!

Barrie



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