We have used O2 sensors for a couple of years and for a cumulative total
of over several hundred hours and have had no failures from the high
humidity in the center section during use. They will deterioriate in the
center section if you leave them unattended for several days in the
humidity. Most of you are simply parroting what Kellam has fed you about
sensors because of his aversion to using them on the Halcyon. O2 sensors
are not perfect but the technology is perfectly fine for now. The Halycon
will operate fine without sensors as long as the person mixing the gas is
competent and there is hard bottom at max pO2 or shallower. BioMarine
units use three which Kellam claims only proves his point about their
inherent unreliability. I think Kellam has made gigantic strides in his
unit and the Halcyon is light years ahead of the Odyssey and even Kellam
admits it. !3.5 K dollars is a lot to ask for the machine and I doubt
seriously that it will become a mass market unit. It is perfect for what
caves divers need. Given the choice between the BioMarine unit, the Cis
and Halcyon and unlimited resources I'd buy all three. They are all great
units for different applications. They BioMarine is the lightest and
sleekest, is electronic and has three sensors. The Cis has more
flexibility for on-the-fly changes in several parameters. It is electronic
and has sensors. The Halcyon has the fewest working parts, no electronics
to fail, and no O2 sensors. The Drager Atlantis is also good for me
because I can tear it down to its essential elements, put an adaptor on
its regulator and have a small bailout/deco unit for deep dives on the
BioMarine. Betwen BioMarine and Cis, the BioMarine has the deepest rating. 
The Cis -although it will dive to 500 feet- is rated only to 350, period. 
There is more breathing resistance diving the BioMarine units, the Cis and
Halycon apparently have little or none. The BioMarine unit is $5995; Cis
$15000, Halcyon $13500. It's better to have a sensor that fails than not
to have one at all. If it fails you are right where the people who say no
to sensors are anyway so whats the big deal. Give it a rest. The sensor
advocates will use them and the no-sensor folks will not.  Rod

On Mon, 13 Jan 1997, Barry Miller wrote:

> 
> Rich,
>     Are you saying that they have solved all the problems and that they now
have a waterproof O2 sensor that works. I want some of that Wonder Icing you
have on your cake. And to think just this past weekend there was no solution to
this fatal design flaw. The "Experts" at DEMA must be surprized.
> 
> Barry
> 
> ----------
> From: 	Richard Pyle[SMTP:deepreef@bi*.bi*.ha*.or*]
> Sent: 	Monday, January 13, 1997 6:43 AM
> To: 	George Irvine
> Cc: 	Chris Hellas; George Irvine; cavers@ge*.co*; techdiver@terra.net
> Subject: 	Re: D.E.M.A. SHOW
> 
> 
> 
> It seems like you think you understand everything about the unit, but you 
> don't.  Blowing water off the sensors is the icing on the cake.  The real 
> advantage is a method that, within the confidence levels of laws of 
> physics and the O2 content of your diluent, allows you to verify the 
> validity of the readings.  You might call a 10-second proceedure done 
> once every 15-20 minutes "task loading", but I would not.
> 
> Aloha,
> Rich
> 
> >   Chris - this is exactly true - the sensors do not like being in humid gas
(as 
> > in a rebreather), and Draeger recognizes this. Stone is still trying to
come  up 
> > with various Rube Goldberg schemes to deal with this, but the problem he is 
> > compounding in the process is the task loading, which is what kills
rebreather 
> > divers on closed circuit (even if the machine deos not get them) . Stone
has 
> > added audible warnings for this, but then you have to assume all of this
works, 
> > and all of it is getting its information from sensors that do not do well
in 
> > humidity, so we have nothing useful for cave diving other than our rig, and
it 
> > is quite obvious that we have proven that .
> > 
> >    What really amazes me is that the other manufacturers, who are really
just 
> > shade tree operators , keep pretending these things work. I am not
including 
> > Stone in that category, has the mere fact that he as tried to offer a sytem
to 
> > deal with the problem indiceates that he is firumly aware of it, while the 
> > others are rolling the dice. Just remember, Gavin wontl; dive one, and he
is the 
> > EX19 and MK 16 guy , and all of us will dive mine, so what does that tell
you.
> > 
> > On Mon, 13 Jan 1997, Chris Hellas <chris@de*.de*.co*.uk*> wrote:
> > >In message <199701121822.KAA22567@m2*.in*.co*>, George Irvine
> > ><gmiiii@in*.co*> writes
> > >
> > >Snip.....
> > >
> > >>
> > >>   We had the only new rebreather technology, Stone had the only new
attempt 
> > at 
> > >>solving the sensor problem (blowing dry gas over them - he used to heat
them, 
> > >>and before that he had Rosary Beads attached to them.
> > >
> > >G
> > >
> > >   Interesting that you point this out - I'm sure most people do not
> > >know the problems.
> > >
> > >As regards the use of active oxygen control systems on closed circuit
> > >rebreathers it's maybe worth remembering a conversation I had with
> > >Drager in mid 1996. 
> > >
> > >You may or may not know that they dabbled in electronic C2 a couple of
> > >years ago (SMS2000E) and decided not to persue the concept. They have a
> > >100 metre semi closed self mixing gas unit (military) - the M100M. It
> > >seemed a logical question as to why they never persued the electronic
> > >avenue. The answer was short but interesting.......
> > >
> > >        "until such time that we can develop a suitably moisture
> > >tolerant oxygen monitoring system we do not envisage entering the market
> > >with rebreathers that have electronic control systems"
> > >
> > >Food for thought........
> > >
> > >Regards
> > >
> > > 
> > >Chris Hellas         e-mail - chris@de*.de*.co*.uk*
> > >
> > >
> > 
> > 
> > George M. Irvine III
> > DIR WKPP
> > Woodville Karst Plain Project
> > 1400 SE 11 ST Ft Lauderdale, FL 33316
> > 954-493-6655 FAX 6698
> > Email gmiiii@in*.co*
> > 
> > 
> > --
> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> > Send subscription/archive requests to `techdiver-request@aquanaut.com'.
> > 
> 
> Richard Pyle
> Ichthyology, Bishop Museum
> 1525 Bernice St.
> Honolulu, HI 96817-0916
> PH: (808) 848-4115 / FAX: (808) 841-8968
> email: deepreef@bi*.bi*.ha*.or*
> 
> 
> 
> --
> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> Send subscription/archive requests to `techdiver-request@aquanaut.com'.
> 

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