Liberal vs Conservative

[rlowe]

No, this is not a thread of political nature

I have been researching computers, because I am in the market for one, and have some observations. I have narrowed down my choices to Uwatec, Aeris and Suunto. I am leaning on cutting Uwatec because of some recent threads I have read that promote FUD (Fear, Uncertainty and Doubt) in the algorithm. So down to the Aeris and Suunto offerings. For reference, I am looking at the Vyper and Atmos 2.

The primary difference between these two lines seems to be the algorithm philosophy. From recent studies, it seems the Suunto is very conservative, particularly on multi level dives with a reverse profile. This concerns me because I want as MUCH safe bottom time as possible. Aeris seems to compensate more the way I would expect, by adding time back as you ascend to shallower water. This concerns me because I want as much SAFE bottom time as possible.

Can you all with first hand experience help clear the smoke and help me make a more informed decision.

Randy

 

[Mark Vlahos]

No, this is not a thread of political nature

I have been researching computers, because I am in the market for one, and have some observations. I have narrowed down my choices to Uwatec, Aeris and Suunto. I am leaning on cutting Uwatec because of some recent threads I have read that promote FUD (Fear, Uncertainty and Doubt) in the algorithm. So down to the Aeris and Suunto offerings. For reference, I am looking at the Vyper and Atmos 2.

The primary difference between these two lines seems to be the algorithm philosophy. From recent studies, it seems the Suunto is very conservative, particularly on multi level dives with a reverse profile. This concerns me because I want as MUCH safe bottom time as possible. Aeris seems to compensate more the way I would expect, by adding time back as you ascend to shallower water. This concerns me because I want as much SAFE bottom time as possible.

Can you all with first hand experience help clear the smoke and help me make a more informed decision.

Randy

Hi,

This may or may not help you.

I dive a Cochran, and while it is not on your list of considered computers I will use it as an example. The Cochran computers at shallow depths (above 90 feet or so) are liberal computers, as you get shallower they get even more liberal. If you as a diver are uncomfortable with the liberal nature of these computers you can add conservatism. This is a setting on the computer that will make it compute your nitrogen loading as if you were diving at a deeper depth than you actually are. By adding conservatism the bottom time remaining number will decrease, allowing you less time on a dive before your should head for shallower water or the surface.

I used to own an Aeris computer and the one that I had did not have the ability to add conservatism, but you can do this yourself, either by never letting the little dots get out of the green and in to the yellow. Or just head for shallower water or surface when the computer tells you that you have 3 minutes remaining, assuming that the dive is fairly deep, or 10 minutes if you are more on the shallow side. These numbers are up to you, you can follow your own adjusted number or choose to stay longer.

I have no experience with Suunto Computers so I am not able to provide you with any information.

I have no experience with Uwatec Computers so I am not able to provide you with any information.

If any manufacturer is knowingly making an inherently dangerous computer based on crazy algorythms they will not be able to stay in business very long. The heirs of the divers they have killed would shut them down. Plus, I don't think that any of the major computer manufacturers care so little about their customers that they don't take safety seriously, or at least the threat of lawsuits will force them to take it seriously.

Just keep your bottom times away from the limits and ascend slowly and you should be fine with any computer out there, just pick the features you like and stick with a company that has a good track record for reliability. Remember that computers do fail, it is folly to think that whatever you get will never fail, so a warranty is a consideration. But even a warranty won't help if the failure happens during your week long liveaboard! Keep working the tables and remember a watch and depth guage.

Good Luck,

Mark Vlahos

 

[scubabamatxn]

Just my 2 cents-- i have owned a Vyper for three years. Yes, it is conservative, but I usually make 4-5 dives a day for 6 days in a row when I go on vacation. In my opinion, the 'conservative' computer gives me peace of mind, since the true effects of muti-day/multi-dive activities are not well understood. Finally, you add the unpredictable elements of cold water , exertion, etc.--- well, you get the picture. Good luck, and safe diving!

 

[RichLockyer]

Ditto. DCS incidents are reported to have increased in recent years, and a lot of te blame is being put on people getting right up against NDL and then riding it all the way up. Of course, at 30-50ft, the computer "relaxes" and shows over an hour of available NDL, so the diver relaxes and it not as attentive to his safety stop and ascent rate.

Suunto appears to be conservative, but I've carefully gone over some of my profiles using it, and it's really NOT that bad. For instance, a recent dive had an average depth of 53ft, and my total dive time was 65 minutes.
On the tables, that would have been a 60ft dive. My max depth was 107ft.

 

[outlawaggie]

Pick up this month's ScubaDiving Magazine. They answer this exact question. They even review your selections. It includes the bottom time allowed on a variety of dive profiles. It is suprising how different some of them are.

 

[Charlie99]

Of course, at 30-50ft, the computer "relaxes" and shows over an hour of available NDL, so the diver relaxes and it not as attentive to his safety stop and ascent rate..

Some computers give a better feedback: comments of Tissue Loading Bargraph vs Bargraph of NDL

A couple of other good threads

 

[pasley]

...This concerns me because I want as much SAFE bottom time as possible. ...

The trouble is SAFE bottom time is a tough one to pin down. There are so many variables, age, hydration, fatigue etc. In my mind, diving with out getting bent is more important than pushing it to the edge and diving for 5 extra minutes. Remember DCS is not and exact science. 100 divers diving side by side, same dive profile, same age and general health, and one or more may get bent. It happens. But pushing the limits is just that, pushing your luck.

My first computer was the Oceanic Data Pro. A good computer, but liberal dive table (IMHO). At age 48 (then) not a good choice for me. After my Chamber ride in which I did not violate the computer and I switched to SUUNTO COBRA. I have changed it to P2 which is ultra conservative.

On a 100 foot dive, I lose maybe 5 minutes of bottom time over more liberal computers. But keep in mind that is on super chicken setting of P2. On shallower dives, I have not noticed any difference.

But honestly, my biggest limiting factor on diving is normally my dive buddies running low of air.

In the end, the choice is yours. But ask yourself, is a few more minutes of bottom time really worth the increase in risk of DCI which could result in paralysis or death? That is the real issue here being debated.

 

[rlowe]

I definately do not intend to play chicken with DCS. I just want to understand the pros and cons of the differences among these computers. All the responses have been great.

Do you all rely on the computer for NDL, or do you plan your dive, dive your plan and refer to your computer for reference?

I very rarely have a square profile so I would think general planning would be in order, but would use the computer for more guidance through out the dive.

Randy

 

[scubatoys]

I've been using the Aeris computers for years. Everything from multiple lake dives to several weeks in Truk Lagoon on 32 mix when every dive was a 100+ foot - 5 dives a day. I've used it when staying out of deco - and intentionally pushing into up to about 10 minutes of deco required... all without any problems.

A friend of mine was using a Suunto in Truk - and it affected his bottom time a lot... might have been the profiles there - no shallow reef there. You're either on the wreck at 100 feet, or you're hanging in mid water. After 2 days, he grabbed my backup Aeris for the rest of the trip.

If I want to back off the aggressiveness, I just set it to beep on the last dot of yellow, before it hits deco, then make a very slow ascent with lengthy safety stop. But that's me... I'm a rebel... I cut off my matress tags and run with scissors.

 

[DA Aquamaster]

I use a Shwerwood Wisdom which is more liberal than the pelagic hockey puck I used before that. I was initially concerned at the greater bottom time, but it has not been a problem. The Wisdom is more liberal in terms of bottom time but requires generally slower ascent rates and a 3 minute saftey stop at 20 ft.

With any computer it is also relatively easy to add conservatisim by either keeping the bend-o-meter in the green or by adding deep stops and slower ascent rates. With Nitrox computers you can also dive with the computer set to air or a lower percentage of nitrox to gain extra saftey (provided you track your CNS clock and PPO2 manually)