I'm not sure about the temperature actually being that much of an influence
on the ending reading. I have found that generally low O2 % mixes such as "deep"
Tri-Mix'es generally homogenize to the final desired analysis over a period of a
few hours.
     I've found that high O2 mixes that if filled with O2 and topped with air
and
allowed to sit without agitation, can render an inaccurate analysis a day later.
At that point, a simple "roll" around the garage will suffice to get you what
you
were looking for!

Jim Cobb wrote:

> 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
> >--
> >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
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> >--
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> >
>
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>
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