On Wed, 28 Feb 2001 18:49:01 -0100, Kuty <[log in to unmask]> wrote:

>At 11:01 28/02/01 -0500, Bob wrote:
>
>>The ORCA algorithm (for no-deco, no gas mix) is unquestionably
>>the MOST RELIABLE and TIME TESTED algorithm to date.
>
>This is a very interesting statement.  Can you back it up?

I started using dive computers (when they were new on the diving
scene for recreational divers), the choice was pretty much limited
to ORCA's EDGE (the Brick) Version IV and V which had been used many
years by professional divers, and the new SkinnyDipper, for rec
divers.  This was in the late 1980s.  When ORCA was updated to Version
VI (to rid the 1-ft ceiling problem) for some dives, the algorithm
became IDENTICAL among all EDGE, SD, and subsequent relatives of
the SD, namely SD-II, and Marathon, the latter is still widely used
today, mostly as "backup" of the fancier new generation of computers.

For those on this list, Crusty used it, I use it (actually as my PRIMARY)
for air-diving, Kelly Cunningham uses it, and some others I am sure.
A recent thread in rec.scuba showed that many are still using it,
because they were looking for batteries for them, as Kelly did here. :-)

So, it's in THIS sense I said it's time tested and reliable because
it already had millions of applications by divers before any of the
recent brands came on the scene.  It was the ORCA that enable me to
know ommediately how wrong Cochran's Nemesis Pro was in 1993-4.

>This question is not intended to be argumentative because I don't have any
>knowledge about the different algorithms that are used in different
>computers.  I even don't know who manufactures the ORCA because it has
>never been sold in Israel with this brand name.  Can you elaborate a little
>on this point?

See the above.

> Which computers are mostly used?

Over the entire history of dive computers, I would say the variants
of the ORCA computers and algorithm.  It was based on the Haldean
algorithm, and the work of Karl Huggins, who used to be on the
Scuba-L list.

Who manufactures them?

ORCA, which was bought by EIT.  I don't know if EIT has been eaten
by another company or not, but the companies that manufacture
and sell SkinnyDipper batteries come and go, but the EDGE (the
brick-size version) runs on standard 9-volt batteries.

>
>Another question Bob.  You wrote (in response to Don's question) that
>sometimes, relying on the manufacturer's statement about the algorithm, is
>not a clever thing to do (this is my interpretation of your explanation
>about the RGBM model).  Without any data, I tend to accept it because I
>tend to be quite suspicious about manufacturers' statements in general.
>The question is how do you know which algorithm is being used with the
>ORCA, as opposed to other computers?

You know because it is written in their manuals.  Just as Uwatec
describes its basic models are verious versions of Buhlmann, which
takes water TEMPERATURE into account.  For warm water diving, the
effect of temp is negligible, which was why when my Cochran computer
failed, but I had the detailed data (time/depth every 4 seconds over
the series of 6 repetitive dives that cause a gross blunder in
Cochran), the ORCA (Haldeanean model) and Uwatec (Buhlmann model)
simulation results for the 6 dives, done completely independently
and without each other's knowledge, by technicians of those
companies, turned out to be virtually identical, in their no-deco
verdict, against the Cochran error or a 55 minute deco required.

For MY type of simple style diving, I don't foresee I need a fancier
model than my original SkinnyDipper bought in 1988, and still use
on all my dives, while other fancier models tag alone just in case
THEY make errors, as Cochran's did.  :-)

I don't need any of the bells and whistles (can't hear them anyway :-),
and ultimately the ORCAS provide the BEST info for my computer between
the ears to make the ultimate decisions.

BTW, I could be wrong on this, but I believe the EDGE is STILL the
only dive computer that SHOWS simultaneously the N2 loadings in
EACH of all 12 compartments.  Other computers use that info in the
innerds of their algorithms but conceals all but the "controlling"
compartment to make their diagnosis.

At the time I purchase my first EDGE, the price was $400 MORE than
the SkinnyDipper, and the ONLY additional feature over the SD was
this graphical display of all compartment loadings.  I considered
it worth the $400 then.  I never regretted it since.  I purchase
a second ORCA recently (in case the first one croaks).  :-)

Hugh on the other list has a couple of EDGE (bought on bargain)
and SkinnyDs too.

-- Bob.