Summer Worsley, Dive Instructor
The Suunto Eon Steel
Suunto is a Finnish company that has built up a solid reputation over more than three decades designing and building dive computers. They started making mixed gas computers over ten years ago and are now on their second dedicated technical algorithm the ‘Fused™ RGBM’ (more about that later).
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Suunto Eon Steel on the go!
Photograph from letao.com.tw
Suunto Eon Steel Dive Computer: Key Specifications
- Rechargeable lithium-ion battery
- 20 hours dive time on a fully charged battery
- Tilt-compensated digital compass
- Ten different dive modes with four custom views each
- High contrast, color display
- Air/Nitrox, Trimix, gauge and CCR modes
- Up to 10 gases
- Deep stop function
- Wireless air integration supports up to 10 PODs
- No decompression dive planner
- Dedicated DM5 software for decompression dive planning and configuring dive modes
- Gas time remaining
- Graphical dive log
- Movescount App for dive logging
- Isobaric Counter Diffusion warning
- CNS and OTU tracking
Which is Better, the Suunto Eon Steel or the Mares Genius?
The Suunto Eon Steel and Mares Genius dive computers are similar in many ways. They both do full Trimix, they both have color screens, and they both have the ability for wireless air integration. They also have in-built compasses, color screens, rechargeable batteries, and are rated to 150m/492ft.
That’s about where the similarities end. The Mares uses a very different algorithm (Buhmann’s HL-16C with gradient factors) meaning diving with a buddy on this computer would give you very different ascent times and stop depths. It can only account for five gases and doesn’t have a CCR mode. The Mares is cheaper than the Suunto, possibly reflecting the fact that this is one of Mares’ first Trimix computers compared to Suunto’s ten years of experience.
While Mares will undoubtedly be a name to watch in technical computers in the future, for now, we’d prefer to stick with the tried and tested Suunto.
What You Need to Know About the Suunto Eon Steel
After spending some time in the water with the Eon Steel, these are the features we noticed:
You can set alarms for four different warnings on the Eon Steel: depth, dive time, tank pressure, and gas time remaining. These show up as both visual and audible alarms. The good news is that you can disable the audible alarms in settings prior to the dive if, like this reviewer, you hate any kind of beeping during your dive.
The color-coded indicator shows you if the battery is charging (green icon), contains enough charge (between full and three hours, white icon) or has three hours or less power remaining (red icon). If you have less than two hours of battery time remaining, a pop-up message saying “recharge needed” will appear and you cannot start a dive, a safety feature that should stop you from running out of battery mid-dive.
Custom Dive Modes
You can set up to ten different dive modes for different situations making it easy to switch between different setups according to what kind of diving you’re doing.
This is very handy for people who switch from single gas recreational to mixed gas technical diving or instructors who like to have a different set up when they’re teaching compared to when they’re doing their own personal diving.
The Eon Steel allows you to change which information is visible such as multi-gases, temperature, maximum depth, and so on. You can also set up four custom views for each mode, allowing you to switch between screens when you’re underwater to see even more information. You can choose between three views: prominent (big), graphical (dial type indicators), and classical (text only). A scrollable bottom line can be configured to show the most relevant information for you.
Personal and Altitude Settings
One of the best changes in the new Fused™ algorithm is the ability to not only make the model more conservative but also more aggressive. You can change between +2 or +1 (more conservative), 0 (default) and -1 or -2 (less conservative).
Suunto warns that 0, -1 or -2 carries a higher risk of DCS however, so make sure you read their recommendations before changing it.
You can also change the setting for diving at different altitudes with choices of 0-300m/0-980ft, 300-1500m/980-4900ft, and 1500-300m/4900-9800ft.
This computer supports more air integration units than we’ve ever seen with the ability to use a huge TEN transmitters (or ‘PODs’ as Suunto have called their new version of the transmitter) at once. Great news for techies who want to monitor all of their gases, instructors who want to see how much their students are breathing, or mums and dads who want to keep an eye on how long the kids have left underwater.
It’s possible to program up to ten different gases into the Eon Steel. These are used to calculate an accurate deco time with the computer assuming all gases will be used, rather than some previous algorithms that worked out a deco time based only on the gas that was currently being used.
That does, however, mean it’s best to program all gases in before the dive and remember to remove any that you won’t be carrying. In case of emergency (or if you’ve forgotten to add or remove a gas before the dive), it’s also possible to add or remove gases in dive mode.
SAC and Gas Time Remaining
When paired with a POD, the display can be configured to show your surface air consumption (SAC) rate and your gas time remaining (GTR). SAC is a calculation of how many liters or cubic feet per minute you are breathing.
GTR uses this figure to work out how long you can stay at the depth you’re at before you run out of gas. As you remember from your open water course, the deeper you go, the faster your gas runs out, so this is a very useful tool to extend your dive time.
Closed Circuit Mode
The Fused™ RGBM algorithm allows you to use the Eon Steel as a backup for closed circuit rebreather (CCR) diving.
A constant ppO2 can be used, with two set points. These are 0.7 and 1.3 as default, but both can be adjusted on the computer or via Suunto’s DM5 software. It’s also possible to customize a set point. This is useful if, for example, you use pure oxygen at the end of your dive to help speed up your deco.
Graphical Dive Log
The dive log is displayed in graph form, showing your dive profile in detail, great for those of you who like to make sure your profiles are nice curves without any sawtooth sections. It’s also another handy tool for instructors who can show their students what a good profile should look like.
Movescount is Suunto’s online community where you can keep and share your dive log with others. The Eon Steel has Bluetooth, making downloading your dives onto the Movescount app via your smartphone very quick and easy.
This point isn’t quite as positive as the ones above. The Eon Steel’s algorithm will lock divers out if they do not follow the computer’s exact instructions regarding decompression. When this happens, the computer displays only time and depth.
We spoke to Sameh Sokar, technical Instructor Trainer, GUE technical Instructor, and the owner of Scuba Seekers Dahab. While testing the Eon Steel, the algorithm locked at 75 meters (246 feet) as the prepared dive plan didn’t match the computer’s decompression model. Sameh noted that Suunto may have adjusted the model since then, but from what we can gather, the algorithm lock remains.
The Suunto Eon Steel’s Decompression Model
The Fused™ RGBM is Suunto’s newest* version of Wienke’s reduced gradient bubble model (RGBM). It uses the previous Technical RGBM combined with Wienke’s full RGBM to get the best out of both.
There are two types of algorithms in common usage, dissolved gas models and free gas models. Dissolved gas models take into account gas dissolved into the tissues, using theoretical values for compartments that represent the different types of tissues within our bodies. The most popular example in use at present is Buhlmann’s ZHL-16C.
Free gas models are based on us all having silent bubbles within our system at all times. These need to be controlled in both size and pressure to prevent DCS. The most popular example of a free gas model is VPM.
RGBM takes both of these into consideration by using 15 different compartments to account for dissolved gas but also having deeper stops to control bubbles.
There is an overlap when the computer will use the different algorithms, switching between 40m/131ft and 55m/180ft on air or Nitrox dives and between 30m/98ft and 45m/148ft on dives using gas mixes with higher amounts of helium.
The Fused™ algorithm also gives a different profile to most traditional models in that the stop ceiling is continuously rising (assuming you are at or near the ceiling and off-gassing). This allows you to have a more continuous ascent, which Suunto claims provide a smoother and more natural decompression profile.
The Eon Steel displays not only ceiling (minimum stop depth) but also floor (maximum stop depth); if you find yourself decompressing in rough water, you can be slightly deeper than your ceiling to reduce the risk of violating it while still being sure you’re off-gassing.
As is standard with most Suunto computers, the CNS calculation is worked out by rounding the percentage up 1% (in other words it treats Nitrox 32% as 33%). This is why the maximum depth shown for gases can be slightly shallower than expected if you calculated the MOD using Dalton's Law, something which some find frustrating when trying to use the best gas for a certain depth.
*Note: Suunto has just released the Fused™ RGBM 2 on its D5 dive computer. This is not yet available on any of their technical computers, an update that our reviewer suspects will happen soon.
What Does This Mean for the Diver?
Compared to the Technical RGBM, Suunto says the Fused™ RGBM will give you longer no-deco times and shorter ascent times on Trimix.
The combination of dissolved and free gas models is a middle ground for those who have read the arguments for both models and like having the ability to combine bits from each.
Being able to see your full deco window (with ceiling and floor) is a handy tool, although the big thing to be aware of is that if you violate the ceiling the deco time is paused until you descend back down. If you violate it for more than three minutes by 0.6m/2ft or more, the computer will lock you out.
This means that although it will still show you depth and time information, it will no longer tell you where the deco stops should be, or for how long.
There are three different types of stops displayed on the Suunto Eon Steel: deco stops (mandatory), deep stops (can be turned off) and safety stops (advised). It’s worth making sure you understand the difference between these before using this computer to ensure a safe profile.
Suunto’s After Sales and Servicing Support
Suunto has service centers all over the world. The company is generally quick to respond to customers and has a good reputation.
Any Ongoing Maintenance?
As with most dive computers, the Eon Steel needs very little maintenance. It should be rinsed with fresh water and dried after every dive. It shouldn’t be allowed to soak because water contact will keep the screen turned on, which will deplete the battery. Suunto recommends maintenance every 500 hours or two years, whichever comes first.
It comes with a scratch guard sticker, which should be installed by the user to protect the screen.
For more information about the Suunto Eon Steel and maintenance, check out the user manual.
The Eon Steel continues to build upon Suunto’s reputation as a progressive dive computer manufacturer. Suitable for recreational, mixed gas technical, and CCR divers this computer will grow with you, no matter what type of diving you do.
It’s large, easy to read, and customizable display means you have all the information you could want available at a glance.
Manufacturer’s Specs and Features:
- 150m/492 ft max depth
- Suunto FusedTM RGBM algorithm
- Digital compass
- Air integration up to 10 gases
- 10 gases programmable
- Air/Nitrox, Trimix, gauge and CCR diving modes
- Audible and Visual Alarms
- Color screen
- Backlit screen
- Rechargeable battery
- No-decompression dive planner
What We Like:
- Battery time remaining indicator
- Custom dive modes
- Comes with a strap or bungee
What We Don’t Like:
- Algorithm lock: If you spend more than 3 minutes above the decompression ceiling the algorithm will lock you out (and you will need to finish your deco based on tables). We want our computer to help us surface safely, not give up on us if there’s a problem!
- No option for a one button press bailout on CCR
- Can’t switch off deep stops when using trimix
- CNS calculations give very conservative maximum depths
- Heavy at 347g/12.2oz
Buy This Computer If:
You’re a Suunto fan who is wanting a computer that does more. This is a good computer for the recreational diver who is interested in moving into technical diving in the future. The ability to use the Eon Steel as a backup for CCR dives is a great bonus and all the customization possible means instructors will love it.
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