> From:          "Capt. Jim Mims" <divetek@ic*.ne*>
> To:            "'Ted Green'" <scuba@md*.co*>,
>                "techdiver@aquanaut.com"
>                <techdiver@aquanaut.com>,
>                Mike Beresford <mikeb@gl*.co*.za*>
> Subject:       RE: O2 Analysers : Altitude Correction required?
> Date:          Sat, 19 Apr 1997 21:46:22 -0400

     Jim, 
       The question is : If you calibrated the analyser in the air 
plane at 19,000 feet to read 21.0 %, what would it read when you put 
it on 100% O2  at 19,000?
        Ted Green

> Mike,
> Analyzers will display the approximate O2 percentage of air at sea level to
be 20.9 (+/- 1%).
> When you take the analyzer to altitude however, (such as in an airplane that
is not equipped with a pressurized cabin) it will display the partial pressure
equivalent of air at a given altitude. i.e
> On a flight I made to Houston from Ft. Lauderdale in a Cessna 210 averaging
19,000ft altitude my mini-ox read 12.0  in the cabin. When I used the sensor in
my O2 mask to confirm a sufficient supply 
> the partial pressure for the altitude you are at you can get reliable
information. Underwater the partial pressure will increase quite rapidly with
your descent,  so the slight surface discrepancy s
> Use Voyager software to run some "what if" scenarios before you make any
decisions. If I can be of any other help feel free to contact me by e-mail : 
divetek@oc*.co* or call 800-874-6888.
> Sempre Deep,
> Capt. Jim Mims    
> IANTD/ B.O.A.
> -----Original Message-----
> From:	Ted Green [SMTP:scuba@md*.co*]
> Sent:	Thursday, April 17, 1997 1:25 PM
> To:	techdiver@aquanaut.com; Mike Beresford
> Subject:	Re: O2 Analysers : Altitude Correction required?
> 
> > Date:          Thu, 17 Apr 97 09:14:46 -0700
> > From:          Mike Beresford <mikeb@gl*.co*.za*>
> > To:            techdiver@aquanaut.com
> > Subject:       O2 Analysers : Altitude Correction required?
> 
>      Mike, 
>         Oxygen analysers don't require an altitude correction and 
> I am under the impression this is why:
>  The reason the analyser can read correctly regardless of altitude is because
> the fuel cell is a liquid filled cell with a flexible membrane where the gas
goes 
> through the fuel cell. When there is no gas flow the pressure on either 
> side of the membrane is the same because the liquid is not 
> compressable and the membrane is flexible. The calibrating of the 
> analyser is then just setting a reference point on a linear scale. 
> Once that is done, all readings should be correct and linear.
> 
>      Ted Green
Ted Green (owner)                
Tidewater Aquatics (Dive Store)  
Salisbury Maryland USA
TDI IT #029
SSI MI #178

The world contains but three types of people:
            1. Those who make things happen.
            2. Those who watch things happen.
            3. Those who wonder what happened.
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