COMPUTERS SUUNTO VYPER AIR & COBRA 3

They share basically the same functions, but the Cobra 3 sits inside a very sexy-looking console and employs a quick-release high-pressure hose to get tank pressure information, whereas the Vyper Air is wrist-mounted and uses the same (optional) transmitter that plugs into any regulator first stage, just like the D9 and Vytec DS computers.
The Vyper 2 may have won the DIVER Award for Innovation of the Year last year, but it has fallen by the wayside. The Vyper Air replaces it on the Suunto product line-up.
Both new computers are full-function decompression models, with the ability to monitor and display remaining tank pressure, track the rate of gas consumption and continuously calculate remaining air-time.
Both have a new 3D compass that can be used up to 45° from horizontal without impairing the ability to read the figures clearly and accurately. You can choose to keep the compass display for up to five minutes at one time, subject to no important change in deco obligation, which of course takes precedence. You have the option to lock a bearing, too.
Both computers allow you to switch between nitrox mixes during a dive, presetting a primary mix between 21 and 99% and switching to a second richer mix as long as you are within the maximum operating depths. Maximum ppO2 settings can be varied between 0.5 and 1.6 bar.

Algorithm
As I get older, my record for never suffering any ill-effects from spending time under pressure grows more precious to me. I have great faith in the RGBM decompression model, developed for Suunto by Bruce Wienke. I read on a well-known UK Internet forum that Suunto didn't use his algorithm, but only paid to use the name. That's the great mis-information super-highway for you. It's rubbish, of course.
The Suunto-Wienke algorithm uses nine model-tissue compartments with M values tracked for 100 hours after the dive. The oxygen toxicity calculations and nitrox calculations are based on those of Bill Hamilton.
You can choose to add some personal caution to what is already quite a cautious program when it comes to repeat diving, and you can also adjust it manually for altitude. There is the option of adding in "deep stops" too, should you so wish. These are iterative, in that, should you choose to miss one, you are not punished with added stops in the shallows.
Deep stops can be set at one- or two-minute durations. Choosing to use deep stops does not disable the automatic safety-stop display, which comes into effect once you are shallower than 6m. Safety-stop durations are added to the Time To Surface display, which explains why one moment you're in no-stop diving, and the next you have apparently notched up more stop-time than you were expecting.

Settings
I was diving with someone recently who used a computer with wet-finger contacts. Remember those? Seeing him at the surface prior to submerging, trying to set his computer, reminded me of how wonderful it was when Suunto introduced buttons with the first Vyper and immediately became brand-leader - probably as a direct result. Other manufacturers soon followed suit.
The four buttons of each of these computers are quite intuitive to use, and the displays are easily set up.
Once you have set the time and date, the choice of algorithm (RGBM50 or the full RGBM100), the sampling rate (normally every 20 seconds), metric or imperial measurements and personal caution settings, you can choose to set things like dive-time and maximum depth alarms if you wish.
The backlight can be set to stay on in five stages, from five seconds to a minute. All this done, I found that the only setting I needed to change regularly was the actual nitrox percentage once I had analysed my gas, and this is done in a moment, once you know how.
Of course, it's best to pair the Vyper Air with its transmitter immediately before diving. You do this by holding it alongside the transmitter with the computer in Dive mode, and opening the tank valve.
You can choose different channels if it clashes with another diver's transmitter on your boat.
I used one transmitter successfully with both a Vyper Air and the D9 I wore alongside it.
The Cobra 3 is attached via a quick-fitting bayonet mount to a high-pressure hose. Of course, it doesn't work very well if you forget and leave it in your cabin!
If you are using a mix other than nitrox or straight air, you can choose to use these computers in Gauge mode, whereby only depth and time and maximum depth are displayed. Then they are good for 150m, and there is no ascent-rate monitoring.
You need to calibrate the electronic compass for your particular part of the world, and this is a straightforward procedure.
If you want to be accurate enough to allow for the difference between magnetic north and true north, you can set the declination too, though I have never found this to be important for a diver. Once set it's self-calibrating, unless you go to a very different part of the world.

Display Legibility
The dot matrix display now adopted by Suunto makes it very legible, because real words can easily be formed up. Everything is clear, and there are no icons that leave you scratching your head.
I read in the US diving press about divers getting into trouble because they didn't understand what their computers were telling them. I can't believe there would be any risk of that with one of these Suuntos. The LCD sits behind a protective anti-scratch plastic screen.

In the Water
Decreasing no-stop time is displayed alongside an estimate of your remaining "air-time". Tank pressure is permanently displayed, too. If you miss a deep stop, the computer doesn't go into a sulk.
These stops are computed on the fly. Once you reach the appropriate depth they are counted down in figures next to the words. The three-minute safety stop is counted down in big figures, once you reach 6m.
If you ascend too quickly (at more than 10m/min) the backlight is activated and the ascent-rate indicator blinks.
Once you get into deco stops, a total ascent time is displayed, along with the depth of the first stop. Miss a stop and the "Er" sign is displayed, alongside a downward arrow. I never saw this on either computer.
If you want to change to a tank containing a different nitrox mix, you simply scroll using the bottom buttons and select what you want with the left-side button. It's simple, and it won't let you choose a predetermined mix if you are below its maximum operating depth.
The good thing about the new electronic compass is that not only can you use it when it's way out of horizontal, but you can elect to have it stay on the screen for one, three or five minutes. I found the older version irritating because it used to disappear just when I was getting the feel for using it.
Previous Suunto users of recent models will find all the controls exactly the same. It's merely a question of whether you prefer a wrist-mounted or console-style computer. n

Comparable computers to consider:
Mares Nemo Air, £380
Uwatec Galileo Sol (with accessories), £869
Suunto Vytec DS, £329

SPECS
PRICE Cobra 3 £679; Vyper Air £399 (plus £260 for the transmitter)
FAST ASCENT WARNING Yes
NORMAL IN-WATER DISPLAY Depth, remaining air-time, remaining no-stop time, tank pressure, dive time, ascent rate, O2 exposure
ALTERNATIVE DISPLAYS Nitrox mix, set ppO2, OLF (oxygen limiting fraction), maximum depth, current time, water temperature
DECO INFO Full
MAX DEPTH Deco computed to 100m
DIVE PLANNING Yes (including dive simulation)
LOGBOOK Recording interval adjustable between every one and 60sec with up to 42 hours (Cobra 3) or 80 hours (Vyper Air) of diving recorded
PC INTERFACE Suunto Dive Manager
MODES Air/Nitrox/Gauge
BATTERY User-replaceable CR2450 lithium
CONTACT www.suunto.com/diving
DIVER GUIDE