Mailing List Archive Mailing List Archive
OOOOOPPPSSS
I'd say more but I'm busy inserting foot in mouth and
chewing vigorously. How about I'm sorry?
dive safe
Brock
<slinking off to the kitchen to prepare humble pie>
----- Original Message -----
From: <ScottBonis@ao*.co*>
To: <Bfrede1615@em*.ms*.co*>; <techdiver@aquanaut.com>
Sent: Sunday, August 20, 2000 6:47 PM
Subject: Re: Oxygen measuring (was "OMS Like" DIN flow regulator)
> Hi Brock,
>
> Don't feel so bad about TDI. I teach full cave and trimix for TDI myself.
> There are a number of good TDI instructors.
>
> Remember, depend primarily on the instructor, and secondarily on the
agency.
>
> Take care and dive safe, Scott
>
>
> In a message dated 8/20/00 12:22:01 PM, Bfrede1615@em*.ms*.co* writes:
> << Scott:
> I agree with you on the need to take at least some basic Nitrox
> course. With the slap-dash OW instruction nowadays, none of what I was
> reading here made full sense until I took a class and relearned what I
> vaguely picked up in AOW. After that my "DOH!" factor went down and my
"ahh
> gotchas" went up. My only regret was that it had to be a TDI ( I really
> resent giving Gilliam my money) course, but Rick turned it into a 2 day
> course to make sure we were getting things and threw in a couple of fills
> for us to practice our analysis skills on.
> I'm still sometimes fuzzy , but at least now I know what to ask
> (sorta) ;-)
>
> Dive safe
> Brock
>
> ----- Original Message -----
> From: <ScottBonis@ao*.co*>
> To: <techdiver@aquanaut.com>
> Sent: Saturday, August 19, 2000 10:09 PM
> Subject: Oxygen measuring (was "OMS Like" DIN flow regulator)
>
>
> > Hi Paul,
> >
> > You are correct in that if gas is flowing out to the ambient air, the
> > pressure must be somewhat above ambient. The trick is to make it as
> little
> > above ambient as possible and yet still have gas flowing. Many divers
> choose
> > to use some form of flow meter or flow control device while a bunch of
us
> > older guys simply turn the tank valve gradually closed until we can just
> > barely hear the gas flowing.
> >
> > Chris Elmore has mentioned that it is the partial pressure of oxygen
that
> the
> > sensor is responding to. And we know from Dalton's law that the PP(O2)
is
> > equal to the fraction of oxygen in a gas multiplied by the total
pressure
> of
> > the gas. So if the gas pressure at the sensor is above ambient and
> ambient
> > was the pressure at which the sensor was calibrated, the sensor will
> measure
> > a higher partial pressure of oxygen and will therefore display an
> > artificially high fraction of oxygen for the gas under analysis.
> >
> > If these terms are not familiar to you or this explanation is difficult
> for
> > you to understand, then I recommend strongly that you take a course in
> Nitrox
> > diving. It really is the best way to start learning about the use of
> gasses
> > other than air for diving. You can get some good information from these
> > lists, but occasionally you can get some bum dope also (of course never
on
> > "techdiver.")
> >
> > Take care and dive safe, Scott
> >
> >
> > In a message dated 8/18/00 1:10:30 PM, Bakalite@ba*.co* writes:
> > << I guess this doesn't make sense to me. If gas is flowing, how can
> > the pressure be ambient? What is the error induced by having a
> > higher PP due to a flow over the element versus a resing pressure.
> > It seems to me that if the flow is off by 10% you'd get a 10% reading
> > error, although in practice this doesn't seem to bear out. Sorry if
> > these are stupid questions, but I'd rather ask some of those than tox
> > on o2.
> >
> > Thanks.
> >
> > Chris Elmore wrote:
> > ~
> > >Paul,
> > > For flow rate, get a needle valve from the brass fittings
> > >section at Lowes and use a flow meter to calibrate it. Once it's
> > >calibrated epoxy the adjustment shaft and you're set to go- total
> > >cost: about $5. You can even oxygen clean it if that makes you
> > >happy. Flow rate doesn't really matter as long as you have enough to
> > >purge the lines and move the gas over the sensor but not enough to
> > >produce back pressure. Sensors measure partial pressure so you have
> > >to keep the pressure at ambient. If you can hear gas flowing that's
> > >enough.
> > >C.
> > --
> > Paul Braunbehrens mailto:Bakalite@ba*.co*
> > http://www.daw-mac.com Mailing list for digital audio on the mac >>
> > --
> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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