Newsgroup: it.hobby.scuba
Titolo: Aladin Air-x nitrox vs Oceanic Datatrans plus

Visto che l'argomento computer e' tra i piu' gettonati,
riporto la prova della prestigiosa rivista americana "SCUBA DIVING",
che mette in confronto i due migliori computer con sonda attualmente
in commercio.
A voi le conclusioni.
Dimenticavo una cosa e' in Inglese.
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 2 High-Tech Dive Computers
Two of today's most sophisticated dive computers go head-to-head,
algorithm-to-algorithm in our exclusive gear review. 
By Jon Hardy
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 It's simple: the greater the demands on the diver, the greater the
need for data to help the diver control the dive. And with the
increasing popularity of extended-range or technical diving - diving
beyond 130 feet, decompression diving, using mixed gases, cave, ice
and wreck diving, etc. - the push is on for more and better
information. This trend manifests itself here in two extremely
capable, feature-rich dive computers that provide extensive data
directly to the diver and interface with a personal computer. 
Every company known to distribute gas-integrated dive computers that
can handle air and nitrox and will interface with a PC was asked to
participate in this evaluation. Oceanic and UWATEC cooperated by
submitting the DataTrans Plus and the Aladin Air X Nitrox. Although
these computers are similar (both are gas-integrated and hoseless),
they are also very different. Depending on your needs and diving
activities, either can be an excellent choice for you. 
 While the Oceanic and the UWATEC computers both deserve the
"high-tech" label, they're also both fairly conservative (see Freedom
vs. Risk chart). Often, extended-range and tech divers need a liberal
dive computer that allows repetitive deep dives under demanding
conditions. For liberal dive computers useful in aggressive diving,
you have to turn primarily to computers distributed by Orca or Zeagle.
The Testing
During dive computer tests, we evaluate 10 different recreational dive
scenarios, including 16 different dives. These tests range in depth
from 60 to 130 feet; use standard air and three different oxygen
settings - 32, 36 and 50 percent. Tests include required decompression
stops, plus the violation of both the deco limits and oxygen limits of
the computer. Tests also include multilevel repetitive multiday dives
and sawtooth dives repeatedly going from 60 to 100 feet; and dives to
confirm each function and feature of each computer. 
The Evaluation:
Oceanic DataTrans Plus vs. UWATEC Aladin Air X Nitrox
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User-friendliness
As high-tech dive computers, both of these models receive high marks
for user-friendliness. During a dive, they are easy to see, read and
understand. Out of the water, they're a little trickier. The UWATEC
uses four electrical contacts; to operate, touch two at a time with
moist fingers. The Oceanic uses two push-button switches. Although the
Oceanic is somewhat more intuitive, both of these computers require
you to read the instructions carefully for full range of use. 
To further enhance user-friendliness, Oceanic uses graphic displays
with green, yellow and red zones for nitrogen loading, plus graphic
icons to identify data displayed digitally. Available air, breathing
rate, ascent rate and oxygen loading are also conveyed by graphics
plus digits as needed. 
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Adjusting No-Decompression Limits
Two completely different methods are used to change the
no-decompression limits on these two computers. With the DataTrans,
limits can be changed during a dive by simply backing off the graphic
display - staying out of both the red and yellow zones or allowing the
graph to return to a personally selected point in the green zone
before surfacing. 
UWATEC has taken a different approach to dive computer adjustments. By
sensing the water temperature, drops in gas pressure, ascent rates and
the pattern of ups and downs during the dive, the dive computer
applies these inputs to the program and cuts back the no-decompression
limits accordingly. All of these factors are known to affect the
likelihood of DCS, but available research does not provide enough data
to define how great the changes should be. Also, the currently
available methods of sensing these factors may not always give the
dive computer realistic data. For example, water temperature sensed by
the computer does not indicate diver body temperature, as the diver
could be in temperate water with an excellent dry suit or in cold
water with a poorly fitting wetsuit. Gas pressure drop is used as a
measure of breathing rate, therefore as an indicator of workload, but
it cannot tell the dive computer the tank size, performance
characteristics of the regulator or what the gas is actually being
used for (breathing, sharing air, inflation of BC, dry suit, lift bag,
etc.). 
The Oceanic computer also has a self-adjustment that operates as a
depth restriction. Medical research has indicated that several deep
dives made close together or progressively deeper dives increase the
likelihood of DCS. The key difficulty with this research is that it is
extremely limited, so there is no significant body of data on which to
base the cutoff points when programming dive computers. Therefore, the
Oceanic programmers have tended to put in conservative restrictions
for this behavior. Actual experience has shown these restrictions to
be too restrictive, so they have been somewhat relaxed over the years.
Current ScubaLab tests indicate that the restrictions are still
greater than necessary. 
These adjustments create an unusual dichotomy in these computers -
they're high-tech computers, but they do not allow aggressive diving. 
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Violations
Another function of these dive computers that does not allow for
aggressive diving is the manner in which they violate and lock out if
a decompression stop is missed. UWATEC gives ample audio and visual
warnings, plus three minutes to correct a missed stop by going back
down. If you do not heed these warnings, it goes into lockout (called
"SOS" mode on this computer) for 24 hours, plus the addition of
increased desat time of up to 72 hours. In this SOS mode, none of the
computer's functions can be accessed by the user in the field. The
last dive is frozen on the screen. Data can be accessed by use of a
PC, but still the dive computer is non-operational. Another caution of
note is that if you have just decompressed or are very near
decompression and you violate the ascent rate, you may put yourself
unknowingly into decompression. This can also cause a violation and
lockout. 
Oceanic locks out if a decompression stop is violated, but in a
completely different manner. Again, plenty of visual and acoustic
warnings are given, plus a five-minute window to get back below the
stop level. If you do not correct the violation, the DataTrans will
lock out for 24 hours, but will still continue in gauge mode,
providing you depth, time, gas and related data without nitrogen or
oxygen information. If you dive with the computer during this time, it
will keep pushing the 24-hour period ahead until you've passed 24
hours with no dives. 
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Ascending
Both computers have well-conceived ascent-rate indicators (your
speedometer to the surface), but Oceanic's is easier to read and
follow. With the use of green, yellow and red zones with
triangle-shaped graphic indicators, you can monitor and adjust as
needed. If triangles show in the green, you are ascending at 11 to 40
feet per minute, if in the yellow, 41 to 60, and if in the red, you
are ascending at 61 to 120-plus feet per minute. 
UWATEC has, in the center of the computer face, a data box that
displays a percentage of the programmed ascent rate. This program is
not "buffered," so the numbers can change suddenly in short distances.
In deeper water, 67 feet per minute equals 100 percent, and in
shallower water, 23 feet per minute equals 100 percent. Decreasing
your ascent rate as you approach the surface is an excellent idea, but
it is difficult for most divers to go as slow as 23 feet per minute. 
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Oxygen Functions
The Aladin and the DataTrans both handle nitrox very well, but again
in very different ways. The Aladin can be set for standard air (21
percent oxygen), or for 22 percent to 50 percent oxygen in 2 percent
increments. This setting is made with relative ease on the dive
computer face and remains set until it is changed by the user. Oxygen
information displayed during the dive is clear and easy to read and is
shown only as needed. To change the cutoff point (oxygen partial
pressure) requires interfacing with a PC. It is unlikely that it would
need to be changed from its default of 1.5, but it does have an
adjustable range of 1.2 to 1.95. 
On the DataTrans Plus, the oxygen setting is even easier to follow,
but you need to be careful to set it before every dive once it has
been used for nitrox. It can be set for air or any percentage of
oxygen from 21 to 50 percent in 1 percent increments. Cutoff points
are built in as a caution warning at 1.4 and a danger warning at 1.6.
If you forget to check and set the oxygen percentage just before the
dive, the DataTrans will default to 50 percent oxygen and 79 percent
nitrogen, which is not only excessively conservative, but also
unacceptable for diving. You would then need to return to the surface
and wait 10 minutes before you could reset the oxygen percentage. This
may cause a situation that is simply embarrassing or one that's
impossible due to surface conditions or other dive plans. 
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Time to Fly
UWATEC has the best time-to-fly indicator of any dive computer now
available. It actually calculates and provides a useful number based
on the dives you have performed. If you often fly in conjunction with
your dive trips, this is a valuable feature. 
The time to fly on the DataTrans is simply two 12-hour countdowns; no
calculations are made based on prior dives. 
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PC Interfacing
The ability to interface with a PC, transfer data, record it and print
out profiles is one of the best innovations of modern dive equipment.
If you use this function, these computers are the two best available.
All such programs have their limits, but these are the most complete,
detailed and easiest to use. 
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Gas Functions
Ten years ago, remaining air (now gas) time and breathing rates on a
dive computer's display were thought to be nice novelties, but not of
any real use. Now we know these functions can significantly improve
the safety and efficiency of divers. Knowing how long your gas will
last, rather than just how much you have, can tell you if you can
complete the dive and return without surfacing. This is particularly
important if you need to decompress. You can also compare remaining
gas time with your buddy and make informed decisions about how the
dive plan should proceed. Breathing rate is a clear indication of work
load or stress, and can be monitored on both of these computers.
Oceanic shows this with its usual graphic display and the green,
yellow and red zones. This makes monitoring extremely easy. UWATEC
shows an icon of lungs when the computer senses you are breathing too
hard. This is not as easy to monitor and adjust for, because it is
either just off or on. For both of these computers, remaining gas time
is calculated to include ascent time with any required stops and your
preset reserve. Therefore, when the computer reads zero gas time
remaining, you still have your reserve and time to surface at your
current breathing rate. The Oceanic unit can be set directly on the
dive computer for a reserve of between 300 and 1,000 psi, while the
Aladin's reserve is set by interfacing with a PC to a pressure between
435 and 1,160 psi. It comes preset at 580 psi. 
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 © 1994-1998
Rodale Press Inc., All Rights Reserved

in commercio.
Grazie, molto interessante. Ora devo ancora leggere con attenzione, ma
da quello che ho scorso mi sembra di capire che l' Oceanic è
graficamente molto più comprensibile dell'Aladin, ma che quest'ultimo
è più restrittivo.
Bye.
Il sempre sguisciante "Worm"