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From: "Thomas Tukker" <thomas@ha*.ne*>
To: "Ian Puleston" <DiverIan@pa*.ne*>, <techdiver@aquanaut.com>
Subject: RE: Oxygen Toxicity - using 100% in open water
Date: Tue, 13 Jun 2000 08:27:28 -0400
Same goes for one computer, you do not need it.

> -----Original Message-----
> From: Ian Puleston [mailto:DiverIan@pa*.ne*]
> Sent: Monday, June 12, 2000 9:34 PM
> To: thomas@ha*.ne*; techdiver@aquanaut.com
> Subject: RE: Oxygen Toxicity - using 100% in open water
>
>
> Who said anything about using two computers? Not me.
>
> This is a theoretical ideal tech diving computer that could (but probably
> wont) exist in the future. My point is that the arguments against using a
> computer are based on shortcomings of those currently in existence, and
> shouldn't preclude their use in future if those shortcomings could be
> overcome. "Current computers are not really suitable for deco diving" is a
> valid reasoned argument, but "Computers are a bad thing" (what started all
> this) is a short-sighted statement.
>
> Ian
>
> > -----Original Message-----
> > From: Thomas Tukker [mailto:thomas@ha*.ne*]
> > Sent: Monday, June 12, 2000 5:43 PM
> > To: Ian Puleston; techdiver@aquanaut.com
> > Subject: RE: Oxygen Toxicity - using 100% in open water
> >
> >
> > What if using two computers is convoluted solution to a non
> > existent problem
> > and thus makes you a stroke?
> >
> > THOMAS
> >
> > > -----Original Message-----
> > > From: Ian Puleston [mailto:DiverIan@pa*.ne*]
> > > Sent: Monday, June 12, 2000 1:18 PM
> > > To: techdiver@aquanaut.com
> > > Subject: RE: Oxygen Toxicity - using 100% in open water
> > >
> > >
> > > What if a battery dies? The separately powered redundant backup
> > > system takes
> > > over. What if the display dies? You flip it over and use the redundant
> > > display on the back. How does the backup know about your gas
> > switches? The
> > > primary passed that info to it whilst they were both
> > operational. What if
> > > you lose a gas? You hit the "Lost Gas" button. Pyle / WKPP
> > stops? Download
> > > the relevant software to the computer (note the Abyss Explorer
> > is going to
> > > be downloadable - hopefully it'll start a trend).
> > >
> > > All the problems you've brought up could be solved by a well designed
> > > computer today. Like I said - the right computer for tech diving
> > > doesn't yet
> > > exist, but that doesn't mean that it won't one day.
> > >
> > > > How useful are your 2 computers when the deco that the
> > > computers suggests
> > > > is wrong anyway?
> > >
> > > What's the alternative - cut tables using software on a PC.
> What if its
> > > wrong? What if you made an error copying the tables to your
> > slate? What if
> > > you lose your slate?
> > >
> > > > -----Original Message-----
> > > > From: ScottBonis@ao*.co* [mailto:ScottBonis@ao*.co*]
> > > > Sent: Sunday, June 11, 2000 4:28 PM
> > > > To: se2schul@uw*.ca*; donburke56@ya*.co*;
> > techdiver@aquanaut.com
> > > > Subject: Re: Oxygen Toxicity - using 100% in open water
> > > >
> > > >
> > > > In a message dated 6/11/00 3:03:53 PM, se2schul@uw*.ca* writes:
> > > > << Scott,
> > > >
> > > > What if you lose a gas?  You can't reprogram you computer in the
> > > > water.  You
> > > >
> > > > computer schedule becomes invalid.  What then? >>
> > > >
> > > > Hi Steve,
> > > > Thanks for raising some good points that are worth discussing.
> > > > If you loose
> > > > a gas during a dive, the situation is then the same as if you
> > > > lose a gas with
> > > > any predetermined dive plan.  You pull out the waterproof dive
> > > > tables, use
> > > > the computers as depth gauges / bottom timers, and figure a worst
> > > > case (depth
> > > > and time) plan for deco. with the gasses you have available.
> > > >
> > > >
> > > > << 2 computers sounds pretty expensive, and about as useful as
> > > > diving with 2
> > > >
> > > > wings.  You just fixed a problem (unreliable dive computer)
> > by adding a
> > > >
> > > > second computer.  Now the problems are compounded. >>
> > > >
> > > > I really don't think anything is compounded.  One computer can be
> > > > tucked away
> > > > in a pocket so it is not even seen unless it is needed.  And if
> > > > it is needed,
> > > > then the other computer has failed and so is ignored.  Both
> > > > computers contain
> > > > the same information so what's to compound?  And as far as
> expense is
> > > > concerned, when the cost of life support equipment becomes a strong
> > > > consideration in technical diving, then perhaps it's time to
> > > > consider some
> > > > other avocation.
> > > >
> > > >
> > > > << How useful are your 2 computers when the deco that the
> > > > computers suggests
> > > > is
> > > >
> > > > wrong anyway?       Steve >>
> > > >
> > > > Remember please that I'm not proposing the use of wrist
> > > computers at this
> > > > time, for extended decompression diving.  I'm only pointing out
> > > > that a number
> > > > of the arguments against them are really not valid.  However, I
> > > > do completely
> > > > agree with this last point of yours in many cases.  But it
> has been my
> > > > experience that the wrist computers are simply more conservative,
> > > > rather than
> > > > being "wrong."   And as time goes on, I imagine the algorithms
> > > > employed in
> > > > these units will get more realistic and then perhaps the wrist
> > > > computers can
> > > > be useful.  I just don't like eliminating their use with a wave
> > > > of the hand
> > > > and a number of invalid arguments.
> > > >
> > > > Thanks for the response to my thoughts.
> > > >
> > > > Take care and safe diving,       Scott
> > > >
> > > >
> > > > ----- Original Message -----
> > > >
> > > > From: <ScottBonis@ao*.co*>
> > > >
> > > > To: <donburke56@ya*.co*>; <techdiver@aquanaut.com>
> > > >
> > > > Sent: Sunday, June 11, 2000 1:00 PM
> > > >
> > > > Subject: Re: Oxygen Toxicity - using 100% in open water
> > > >
> > > >
> > > >
> > > > > Hi Don, again,
> > > >
> > > > >
> > > >
> > > > > While I need to emphasize that I am definitely not recommending
> > > > the use of
> > > >
> > > > > wrist computers for extended decompression diving, the
> > reasons you are
> > > >
> > > > giving
> > > >
> > > > > for not using them are, IMHO, not valid reasons for eliminating
> > > > them from
> > > >
> > > > > consideration.  I say again that simply carrying a second
> > > computer will
> > > >
> > > > > protect against any possible failure of your primary unit.
> > > >
> > > > >
> > > >
> > > > > But "what about informing two computers of my gas changes
> > > > during the dive?"
> > > >
> > > > > you say.  Well actually, it is not necessary.  Consider for
> > > example, the
> > > >
> > > > > Cochran three gas computer.  It is not a trimix computer but
> > > will handle
> > > >
> > > > > three nitrox / air mixes and automatically switch to the deco
> > > > gasses at the
> > > >
> > > > > correct time.  All I need to do is to program into the computer
> > > > the depth at
> > > >
> > > > > which I plan to switch to my second deco. gas and the computer
> > > > then does the
> > > >
> > > > > rest.  In fact, I cannot change the programming of the computer
> > > > after I have
> > > >
> > > > > entered the water.
> > > >
> > > > >
> > > >
> > > > > Consider for example, a dive to say, 100 feet on air for a long
> > > > time and
> > > > EAN50
> > > >
> > > > > and O2 as the deco gasses.  I would need to program in 20
> > feet as the
> > > >
> > > > > depth to switch to my second deco gas (the O2).  The computer
> > > > would then do
> > > >
> > > > > the rest.
> > > >
> > > > >
> > > >
> > > > > "How does the computer know when to switch to the deco.
> > > > gasses?" you ask.
> > > >
> > > > > Good question.  Magic!!!  No not really, the computer is an air
> > > > integrated
> > > >
> > > > > unit connected to the back tanks.  It keeps track of my
> > breathing rate
> > > > during
> > > >
> > > > > the dive.  And when that breathing rate goes to zero, it knows
> > > > that I am no
> > > >
> > > > > longer breathing off of the back tanks so it switches to the
> > > > first deco. gas
> > > >
> > > > > (the EAN 50 in this example).  Then, later in the deco
> > > > schedule, when I have
> > > >
> > > > > progressed up to 20 feet, it knows to switch to the second
> > > > deco. gas (O2 in
> > > >
> > > > > this case).
> > > >
> > > > >
> > > >
> > > > > As you can see, no "informing the computer" during the dive is
> > > > necessary, so
> > > >
> > > > > a second computer stowed away conveniently, serves well as a
> > > > backup should a
> > > >
> > > > > failure occur in the primary unit.  Of course a set of
> > waterproof deco
> > > > tables
> > > >
> > > > > must be taken also (with the computers serving as depth
> > > gauges / bottom
> > > >
> > > > > timers), to serve as a second backup should something unusual
> > > > occur during
> > > >
> > > > > the dive.  After all, the well trained and experienced human
> > > > brain is still
> > > >
> > > > > the best dive computer around, by far.
> > > >
> > > > >
> > > >
> > > > > So as I said previously, I need to emphasize that I am
> certainly not
> > > >
> > > > > recommending using wrist dive computers for extended
> > > > decompression dives at
> > > >
> > > > > this time.  But I believe the reasons you are stating for not
> > > > using them are
> > > >
> > > > > not valid reasons to preclude their use.  I do agree with you
> > > > however, that
> > > >
> > > > > sometime in the future these computers may have reached
> the state of
> > > > maturity
> > > >
> > > > > where we will be able to depend on them for extended
> > > > decompression dives.
> > > >
> > > > >
> > > >
> > > > > Take care and safe diving,     Scott
> > > >
> > > > >
> > > >
> > > > >
> > > >
> > > > >
> > > >
> > > > > In a message dated 6/11/00 8:08:25 AM,
> donburke56@ya*.co* writes:
> > > >
> > > > >
> > > >
> > > > > << DB>A computer failure on a deco stop dive isn't nearly
> > > >
> > > > > that easy in that vital information about your deco
> > > >
> > > > > obligation went away with the computer.  Perhaps one
> > > >
> > > > > day there will be a computer with an independent,
> > > >
> > > > > redundant system that can fix this properly.  There
> > > >
> > > > > are other issues as well.
> > > >
> > > > >
> > > >
> > > > > SB> I can't speak to the "other issues", but this one
> > > >
> > > > > is a non-problem.  Simply take a second computer.  And
> > > >
> > > > > remember, there may be no significant difference
> > > >
> > > > > between the failure rate of dive computers and the
> > > >
> > > > > failure rate of the electronic depth gauges / bottom
> > > >
> > > > > timers commonly used in technical diving.
> > > >
> > > > >
> > > >
> > > > >
> > > >
> > > > > Scott,
> > > >
> > > > >   The rub here is the gas changes.  The Nitrex (I
> > > >
> > > > > think that was the name) computer needs to be told
> > > >
> > > > > about each gas change.  IMO doing this on two
> > > >
> > > > > computers during a dive is a bit much.  Two computers
> > > >
> > > > > in the same case, (but independent pressure housings)
> > > >
> > > > > operated by a double set of switches might fill the
> > > >
> > > > > bill.
> > > >
> > > > >
> > > >
> > > > >   Make no mistake, I _really_ like the display on my
> > > >
> > > > > Oceanic but I have been screwed by electronic devices
> > > >
> > > > > too often to bet my life on one.
> > > >
> > > > >
> > > >
> > > > >   The digital depth guages can be backed up with your
> > > >
> > > > > reel and bottom timers can be backed up with your
> > > >
> > > > > watch.  It's also pretty easy to find a home for an
> > > >
> > > > > extra watch or an extra depth guage (like maybe on
> > > >
> > > > > your buddy).  Since you don't need to look at these
> > > >
> > > > > devices until the primary fails, they can be stashed
> > > >
> > > > > away.  Not so with a computer that must be informed of
> > > >
> > > > > gas changes.
> > > >
> > > > >
> > > >
> > > > > There are some watches out there that can give you
> > > >
> > > > > depth, so there's a possible backup to backup.
> > > >
> > > > >
> > > >
> > > > > The fact that I'm paranoid doesn't mean these devices
> > > >
> > > > > aren't out to get me. :)
> > > >
> > > > >
> > > >
> > > > > SB>Take care and safe diving
> > > >
> > > > >
> > > >
> > > > > Same to ya >> >>
> > > >
> > > > --
> > > > Send mail for the `techdiver' mailing list to
> > `techdiver@aquanaut.com'.
> > > > Send subscribe/unsubscribe requests to
> > `techdiver-request@aquanaut.com'.
> > > >
> > >
> > > --
> > > Send mail for the `techdiver' mailing list to
> `techdiver@aquanaut.com'.
> > > Send subscribe/unsubscribe requests to
> `techdiver-request@aquanaut.com'.
> > >
> >
> >
>
>

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