Searching \ for 'carbon dioxide removal for life support' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/ios.htm?key=port
Search entire site for: 'carbon dioxide removal for life support'.

Truncated match.
PICList Thread
'carbon dioxide removal for life support'
1999\08\19@080621 by Russell McMahon

picon face
CC to PICList as of possible interest.


I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed like a
cheap way to make a sensor) and cell voltage seemed to be very insensitive
to Oxygen concentration (as you suggest it would be). Stored O2 appears to
be a major problem.  I'll be trying it again in due course with  a little
more finesses (hopefully). We bought a batch of "real" Oxygen sensors but
even in 100 volume (I think it was) they cost around $US45 AFAIR. These DO
produce a linear pO2 versus Voltage response. Being an electrochemical cell
they have a finite lifetime and they drift severely so you need to
calibrate them before every use. Fortunately there is an easy cheap and
fairly accurate source of 20.8%-Oxygen calibration gas available. (Or, if
you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
depends who you listen to :-)).

Diversion:

Q.:     Zinc Air cells have superb energy densities - about twice that of
Alkaline.Good for spacecraft?
A        :-(  - No




Russell McMahon

From: spam_OUTJimSwenTakeThisOuTspamaol.com <.....JimSwenKILLspamspam@spam@aol.com>
To: henryspamKILLspamspsystems.net <.....henryKILLspamspam.....spsystems.net>

>I have always thought that zinc-air hearing-aid batteries might make
decent
>pO2 sensors.
>
>Just looking at their voltage wouldn't work, of course.
>The voltage would be something like the log of pO2, a weak function, and
>subject to stored O2 every time it got a good exposure.
>
>But the sensor was run as a current source into a virtual-ground meter
input,
>with a small diffusive air leak,
>the current might be proportional to pO2 with a response time of under a
>minute.
>
>This might be useful for monitoring inert-gas vs oxygen.
>I never got around to trying it.
>Has anybody tried this or heard of it?
>
>Jim S

1999\08\19@082454 by paulb

flavicon
face
Russell McMahon wrote:

> Diversion:
> Q.:     Zinc Air cells have superb energy densities - about twice that
> of Alkaline.  Good for spacecraft?
> A        :-(  - No

 Of course not.  Mainly because that statement is not *actually* true.
They don't *really* have a good energy density.  It's a(n obvious sort
of) trick!
--
 Cheers,
       Paul B.

1999\08\19@204847 by admins

flavicon
face
Sounds like you were building a closed loop rebreather!  I agree, just
build the rebreather and monitor the scrubber.

good luck,
joe


"William M. Smithers" wrote:
{Quote hidden}

1999\08\19@222343 by William M. Smithers

flavicon
face
On Thu, 19 Aug 1999, Joe & Gladys Koontz wrote:

> Sounds like you were building a closed loop rebreather!  I agree, just
> build the rebreather and monitor the scrubber.

Gold Star for Joe!  Yes, I've done several PIC-based controllers
for closed-circuit rebreathers.  Of course, the absolute volume on
a rebreather isn't fixed, so you *do* need an O2 sensor.

Regards,

-Will


{Quote hidden}

1999\08\19@223429 by William M. Smithers

flavicon
face
On Thu, 19 Aug 1999, Joe & Gladys Koontz wrote:

> Sounds like you were building a closed loop rebreather!  I agree, just
> build the rebreather and monitor the scrubber.

BTW, (to whoemever posted that originally) - if you're having fantasies
about Space, you want Lithium Hydroxide instead of Calcium Hydroxide.
LiOH has a *vastly* superior weight/volume ratio, as well as a
moderately superior ratio of CO2 absorbency/volume.

It's rarely used in rebreather applications because it's also
reactive as hell in water...

-Will


{Quote hidden}

1999\08\19@225738 by Dennis Plunkett

flavicon
face
At 22:25 19/08/99 -0400, you wrote:
>On Thu, 19 Aug 1999, Joe & Gladys Koontz wrote:
>
>> Sounds like you were building a closed loop rebreather!  I agree, just
>> build the rebreather and monitor the scrubber.
>
>BTW, (to whoemever posted that originally) - if you're having fantasies
>about Space, you want Lithium Hydroxide instead of Calcium Hydroxide.
>LiOH has a *vastly* superior weight/volume ratio, as well as a
>moderately superior ratio of CO2 absorbency/volume.
>
>It's rarely used in rebreather applications because it's also
>reactive as hell in water...

Isn't that why they use a dehumidifier before being past into the scrubber?
Else Kaboomb! (Well at least a fizzle and quite a large amount of that user
friendly hydrogen being produced)


Dennis


{Quote hidden}

like a
>> > > cheap way to make a sensor) and cell voltage seemed to be very
insensitive
>> > > to Oxygen concentration (as you suggest it would be). Stored O2
appears to
>> > > be a major problem.  I'll be trying it again in due course with  a
little
>> > > more finesses (hopefully). We bought a batch of "real" Oxygen
sensors but
>> > > even in 100 volume (I think it was) they cost around $US45 AFAIR.
These DO
>> > > produce a linear pO2 versus Voltage response. Being an
electrochemical cell
>> > > they have a finite lifetime and they drift severely so you need to
>> > > calibrate them before every use. Fortunately there is an easy cheap and
>> > > fairly accurate source of 20.8%-Oxygen calibration gas available.
(Or, if
{Quote hidden}

function, and
>> > > >subject to stored O2 every time it got a good exposure.
>> > > >
>> > > >But the sensor was run as a current source into a virtual-ground meter
>> > > input,
>> > > >with a small diffusive air leak,
>> > > >the current might be proportional to pO2 with a response time of
under a
{Quote hidden}

1999\08\19@233150 by William M. Smithers
flavicon
face
On Fri, 20 Aug 1999, Dennis Plunkett wrote:

> >BTW, (to whoemever posted that originally) - if you're having fantasies
> >about Space, you want Lithium Hydroxide instead of Calcium Hydroxide.
> >LiOH has a *vastly* superior weight/volume ratio, as well as a
> >moderately superior ratio of CO2 absorbency/volume.
> >
> >It's rarely used in rebreather applications because it's also
> >reactive as hell in water...
>
> Isn't that why they use a dehumidifier before being past into the scrubber?
> Else Kaboomb! (Well at least a fizzle and quite a large amount of that user
> friendly hydrogen being produced)
>

No, actually, Hydrogen has nothing to do with it - the issues are purely
thermal.  But this is a list about PIC's, so I figure this thread
has probably extended as far as it properly should, without going
to private email...

-Will






{Quote hidden}

1999\08\21@093707 by Russell McMahon

picon face
Several times higher according to my tables for an equivalent sized
battery.

RM

+AD4APg-Q.:     Zinc Air cells have superb energy densities - about twice that o
f
+AD4APg-Alkaline.Good for spacecraft?
+AD4APg-A        :-(  - No
+AD4APg-
+AD4-
+AD4-Zinc air with more energy densities than alkaline, I don't think so+ACE- Th
e
+AD4-good thing about these cells is that they have a very long shelf life,
just
+AD4-pull the plug when you need them.
+AD4-
+AD4-Dennis
+AD4-

1999\08\22@180940 by Dennis Plunkett

flavicon
face
At 23:06 21/08/99 +1200, you wrote:
>Several times higher according to my tables for an equivalent sized
>battery.
>
>RM
>
>+AD4APg-Q.:     Zinc Air cells have superb energy densities - about twice
that of
>+AD4APg-Alkaline.Good for spacecraft?
>+AD4APg-A        :-(  - No
>+AD4APg-
>+AD4-
>+AD4-Zinc air with more energy densities than alkaline, I don't think
so+ACE- The
>+AD4-good thing about these cells is that they have a very long shelf life,
>just
>+AD4-pull the plug when you need them.
>+AD4-
>+AD4-Dennis
>+AD4-
>
>

I had better double check, last time I looked a alkaline cell (D) contained
22AH whereas an equivalent scaled zinc air has 28, but a very low discharge
rate and a high internal impedance.


Dennis

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...