I don't know about you guys but I think the problem we are dealing with 
here is the temperature of the mix rather than stratification. As the mix 
cools off the reading becomes more accurate.

   Jim

Sender: Steve Hogan  Date: 4/8/99 6:53 PM

>
>I have run into this and have modified my mixing procedures 
>so that after I add the O2 to the helium I wait 1 day (I 
>usually mix at night so waiting around is not appealing)
>before measuring the O2 % (O2 & He). It is not hard to figure
>out what percentage I expect after mixing O2 with He.
>Next step is to add air, wait a few hours (usually doing 
>something else) and then measure again. 
>I fill about 50 psi/min so I expect to not get much mixing from 
>Brownian motion.
>
>Steve
>
>-----Original Message-----
>From: Patricia Disler [mailto:pdisler@io*.ne*]
>Sent: Friday, April 09, 1999 1:14 PM
>To: S I L E N T I M M E R S I O N
>Cc: techdiver@aquanaut.com
>Subject: Re: Trimix Question
>
>
>
>
>
>At 09:16 AM 4/8/99 -0700, you wrote:
>>Frank,
>>
>>>Not me, but I do let the filled tanks rest a day before analyzing. An if
>>>you want to tell me
>>>thats not neseccary I recommend that you try this: Fill oxygen, top with
>>>air, wait a minute,
>>>analyze mix, turn the tank so that the valve faces ground, wait another
>>>minute and than
>>>re-analyze the mix.
>>
>>And it's the same... or not?
>>When filling a tank the temperature and pressure are high which in turn
>>gives a high diffusion coefficient. Makes the mix homogeneous almost
>>instantaneoulsy (couple of seconds).
>>What kind of differences do you get?
>>What kind of analyser do you use, are you sure the hoses are drained when
>>using a regulator or something?
>>
>>Regards,>
>>THOMAS
>
>I have witnessed Nitrox mixtures take a while to fully homogenize. Several
>years ago while mixing 80/20, (Yeah I know don't start) it came out 63% O2
>approx 30 min after the very s-l-o-w top off to fill pressure. Yes I
>checked the calibration of the aynalizer (Teledyne TD-50). Each time I
>would check the O2 reading would climb. I did this over a period of several
>hours. Later it was right on 80%.
>I'd have to say stratification can and does occur, esp. if there is not
>enough turbulence during top off.
>I have never seen this with Trimix as the fill rates are much higher.
>However I suppose it could occur if they too were topped slowly.
>At any rate I never seem to dive my gas until they show the correct mixture.
>
>
>
>"SILT HAPPENS"JD   JEFF DISLER
>  SAFE CAVING       NSS 26000
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