Nitrox is a great gas, but [...]]]> Now that enriched air diving is pretty standard and nitrox can be bought from most dive shops and dive stations around the world, dive computers have all developed so that they can plan and execute any dive – sometimes including when more than one mix of nitox is being used.

Nitrox is a great gas, but has its limited when deeper diving is being carried out. The deeper you go the less oxygen you can add to your mix as a result of the poisonous effects of oxygen on the bodies nervous system at increasing depth. The less oxygen you breath at depth, the more nitrogen tou must have in the mixture. Unfortunately nitrogen causes more than decompression sickness (which can be avoided by suitable dive profiles and decompression stops etc) – it causes nitrogen narcosis. Apart from being very dangerous, even mild narcosis means that a divers awareness is reduced with an unexpected consequence – there is often very limited recall of the experiences of the dive!

So more and more divers are beginning to see the advantage of diving with helium added to their breathing gas mix – not only to allow reduced oxygen partial pressures as the diving gets deeper, but also on relaatively shallow dives of 30 metres or so to increase the perception and this enjoyment during and importantly – after the dive.

The Suunto HelO2 dive computer is the first simple to use, intuitive and straight forward mixed gas diving computer allowing several gas switches during a dive (3 gases can be programmed into the start of each dive).

The Suunto HelO2 menu is similar to its stablemates the D6 and D9 watch versions. With four buttons it is easy to use and there is not the having to start over again if you make a mistake as often happens when only one or two buttons utilised.

Oxygen content from 8 to 100 can be accommodated in air, nitrox and trimix programmed as one of 8 gas mixes into the HelO2. It can dive to 120 metres which is deep enough for any recreational deep diver who is likley only to qualify up to a maximum of 80 or so meters depth. It uses the Suunto Reduced Gradient Bubble Model algorithm.

The Suunto HelO2 Diving Computer can be used in conjunction with wireless gas integration.

The Suunto trimix computer is priced at around £700 but you can pick one up for under £600 from the large scuba gear outlets – for example Divers Warehouse will send one post free for £591 within the UK.

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The computer provides real time decompression information during the dive  based on gas mixtures that the diver [...]]]> The Dive Rite Nitek X Diving Computer is not cheap retailing at £1,265 in the UK. New in 2009 it is a trimix decompression dive computer that uses a modified Buhlmann ZH-L16 algorithm with gradient factors set as follows:

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The computer provides real time decompression information during the dive  based on gas mixtures that the diver sets before the dive. They can however be also changed underwater if this becomes necessary. Dive Rite says that the computer is simple to use and the menus are intuitive which means that a complex user manual is not needed. As with all such promises, the reality is that it does pay to familiarise yourself with this unit fully before diving – it is pretty straight forward though.

The Dive Rite Nitek X Dive Computer is supplied as an open circuit dive computer as standard, but can be upgraded at a cost to closed circuit rebreather use – it includes a PO2 set-point and external oxygen sensor via an optional fourt cell.

Dive Rite diving computers and scuba gear are supplied by Sea & Sea in the UK.

The new Vyper Air has an integrated electronic diving compass that continues to work within a massive 45 degrees tilt range. The [...]]]> The Vyper by Suunto has been a well known dive computer model for several years. Now an upgraded version has been released that has provision for adding a wireless receiver to manage gas consumption.

The new Vyper Air has an integrated electronic diving compass that continues to work within a massive 45 degrees tilt range. The wireless transmitter allows the user to monitor tank contents (one gas mix only) and gas consumption rate.

This is an easy to use computer that will suit most divers taking their diving up to a semi-technical standard. The next step would be a Suunto Vytec which would give you three gases for a few pounds more or a Helo2 which would allow trimix within the different gases on a complex dive.

As a step up to your Gekko, the Vyper Air is a good value diving computer that is more advanced than it brother the Vytec, which has been around for a while now. The Helo2 does everything the Vytec does with the addition of multi gas and helium for £250 more. I would leave the Vytec out of the equation and choose between the Vyper Air and the Helo2 depending on what your short term plans are! Personally I have decided on the Vyper – and if I do have a go with Trimix in the next year or two I will use it in gauge mode while I am learning to cut my own decompression tables!

This is something people forget – when choosing a computer get one that is ideal for your diving now, not what it might be in a year’s time. If I bought a helium computer now I would be tempted to use it and not get acquainted with the new deco regimes. In a similar way I believe my air diving was so much safer for spending years on BSAC 88 tables before I even owned a computer!

Technical specifications:

• Reduced Gradient Bubble Model
• Option of 1 or 2 minute deep stops
• 4 button ease of use
• Air, nitrox, gauge modes
• Option of secondary deco gas
• Personal safety adjustable
• Back light – soooo important!

There is [...]]]> This is quite a big dive computer and so the big screen should mean easy to view information. This turns out to be very much the case with an extremely user friendly display. It is only the more advanced features that send you searching for the manual but that is only to be expected.

There is a big digit mode for people like me who are suffering the beginnings of long sightedness! This is probably an overlooked feature for many manufacturers.

This is a sports diving computer which will also allow for up to three mixes of nitrox to be used during a single dive. Therefore it is a great step up from a basic diving computer for those who want to extend their diving range a little but are not contemplating closed circuit diving and also know that if they have a go at trimix mixed gas diving at some point they will only need a depth timer for the first dozen or two dives.

The performance of this computer is top rate, and certainly merits a 9 out of 1o. It is rather pricey at around £450 for the entry level model but a good buy all the same – 6 out of 10 for value because you have to upgrade for 3 diving gas algorithm.

Time will tell if this dive computer is to provide a few years complaint free diving, but if it is anything like my old Alladin Nitrox dive computer which gave 6 years of sterling service I am sure this will meet the challenge. Dive computers of most makes will serve the purpose, but the Uwatec Galileo is set to be one of the few diving computers that excels.

Technical details:

• Buhlmann ZH-8L algorithm
• Adjustment for increased safety
• Deeps stops
• 3 minute safety stop (adjustable)
• Nitrox 21-100%
• Max PO2 – 1.6 bar
• Altimeter
• Electronic Scuba Diving Compass
• PC Link
• Upgrade – heart monitor
• Upgrade – three NO2 mix algorithm

In conclusion a great computer with an on board electronic compass, but very pricey since the entry level model does not include the 3 gas algorithm.

Yes it was a very well engineered bomb proof and clever dive computer. You could [...]]]> I had always wanted a VR3 diving computer from makers VR Technology. When I finally bought one this year I was disappointed. Why? Because the pinnacle of diving computers turned out to be a heavy and impractical lump of confusing electronics!

Yes it was a very well engineered bomb proof and clever dive computer. You could easily change the batteries yourself and it was capable of adjusting to some very advanced scuba diving. At a cost you could upgrade to all sorts of things, so if your thing is diving to 1000 feet, with up to 8 different gas mixes, it was the bees knees of dive computers for the job.

The trouble is that I was moving into the slightly more technical arena – would be using air and various different nitrox mixes with stronger NO2 for decompression. I would also be instructing during easy sports dives, traveling to the Red Sea and other places to see new sights and perhaps try my hand at photography. The VR3 was more than I needed, ate through the batteries and was confusing to use.

Would the C be a better choice and should I trade in for one?

The makers claim that the NHeO is much more intuitive to use – however this turns out to be because they have simply removed many of the functions of the VR3. It is a cut down version of the VR3. One of the attractions to me of the VR3 was the great British engineering of the indestructible case – yet in use this computer was too clumsy. Fine on a dry suit but it would not seat well on a wet suit (forget a bare arm!) unless you tightened the strap enough to restrict your blood supply. The new NHeO is housed in a plastic case which promises to be a more comfortable item to wear.

The back lit display is smaller than many, but easy to read underwater so long as you opt for the colour option (at an extra £160). The VR Technology NHeO lags behind the Suunto HelO2 in terms of ease of use but is the choice (as was the VR3) if you are planning to upgrade to closed circuit diving.

I would rate it as a computer for the serious mixed gas diver who only needs up to 4 different gases on any one dive who also has an old Suunto Gekko for his or her holiday diving and instructing – and aspires to a Buddy Inspiration!

Marks: 6 out of 10 – Performance & 6 out of 10 for value