Suunto Vyper **SERIOUS BUG** in CNS O2 computation

[Genesis]

I did not say the Cobra does - or does not - have the problem.

The Vyper I have, and one that Rich owns, does.

My Vytec DOES NOT. I have personally verified the Vytec against the same test. It behaves normally.

If "1.4 is the recommended exposure" how come the Vyper allows you to SET THE EXPOSURE from 1.3 to 1.6? Is that a bug too? No, its a feature - you choose the exposure you are willing to tolerate, and the computer should compute the CNS loading appropriately for the setpoint you have chosen.

In the specific case under test, it does not do so. In fact, it racks up CNS exposure at a rate ten times the proper rate for that PPO2.

 

[jamiei]

.

 

[Genesis]

The one the Vyper reports is the OLF.

Its wrong.

The computation is in error. It really is that simple.

Suunto has a responsibility to fix this. Not all of their computers have this flaw (as I noted the Vytec does not) but if you run close to the setpoint on PPO2 you will get an unwelcome and completely unexpected surprise, and in a big hurry, with the Vyper.

I personally use a 30% mix most of the time, since I mix my own gas. But if I BUY gas, I usually am limited to what someone banks or pumps through their membrane system, which is typically 32% - and many of our dive sites around here are in the 100-110' range.

It is reasonably easy to run afoul of this alarm while diving a reasonable and somewhat conservative profile, and well within gas supply limits. The true MOD for a 32% mix is 111', niot 107', so bumping up against the 107' limit is not particularly "aggressive" for a tank that is full of 32% gas.

I can and often do have bottom times of 20+ minutes in the 100-110' range; not all of it is at the full depth, of course, but I can trip this bug on a real dive using a real profile and without running out of gas. The worse news is that one you trip the alarm you've lost all computation of CNS loading from that point forward until the unit desats, since CNS loading continues until your PPO2 drops below 0.5 - which, for 32% Nitrox, doesn't happen until you ascend above about 25 feet. As such it will continue to show you as in the "tox risk" zone even though you are in fact nowhere near it. Further, even if you don't go into "alarm" mode, you're still showing a falsely-high CNS loading from that point forward which does not comport with reality.

Having blown the computation, the computer will from that point onward that day tell me that I am out of CNS time (or have very little CNS time left) when I have, in fact, consumed approximately 10% of my total CNS clock!

That kind of error is NOT minor or inconsequential.

It could easily lead a diver to conclude that they had done something seriously wrong in their profile while at depth, and to make a rapid ascent to where the alarm quits *****ing (which will not happen until you ascend over 25' or so!)

The consequence of THAT could be ugly.

 

[norcaldiver]

I have a couple questions.

First and most importantly, why would you go to the MOD? It was pounded into my head that these are not set in stone. If you go over, you will surely get hurt, but you could still get hurt by not going over and being close, the MOD is a 90% rule. 90% of the people are ok at the MOD, 10% showed signed of tox, so just don't EVER push it in the open water. Maybe I'm wrong, but that's what I was tought.

The second is this is in SIMDIVE. Everyone that uses SIMDIVE raise their hands.......yeah, that's what I thought. It's like tetris on your phone, it's neat, it's there, but noone every plays with it after the 1st hour of owning the computer. It's more of a display toy for the LDS to sell the computer than anything. Is someone willing to actually dive this profile to see if the bug is really there? I'm not.

 

[Genesis]

First and most importantly, why would you go to the MOD? It was pounded into my head that these are not set in stone. If you go over, you will surely get hurt, but you could still get hurt by not going over and being close, the MOD is a 90% rule. 90% of the people are ok at the MOD, 10% showed signed of tox, so just don't EVER push it in the open water. Maybe I'm wrong, but that's what I was tought.

But you're not going there - that's the point.

The Suuntos already give you the "10% margin", more or less, in that they overestimate O2 percentage (by a full percent) from what you set. They also overestimate N2 loading (by that same full percent) from what you set.

Also realize that people have dove 1.6 PPO2s for years without (many) hits. 1.4 is quite conservative to begin with. When you add in the ADDITIONAL conservatism that Suunto provides by default, you're quite a ways away from "the margin" to begin with.

If you were really running "to the wall" then I'd agree with you - but you're not, and that's by the design of their computers.

The second is this is in SIMDIVE. Everyone that uses SIMDIVE raise their hands.......yeah, that's what I thought. It's like tetris on your phone, it's neat, it's there, but noone every plays with it after the 1st hour of owning the computer. It's more of a display toy for the LDS to sell the computer than anything. Is someone willing to actually dive this profile to see if the bug is really there? I'm not.

SIMDIVE is an exact replication of the "first dive of the day" .vs. reality.

I have seen suspiciously-high CNS loading on some of my dives on that computer - loadings that are simply not supportable by the actual profile that I was diving at the time. Interestingly enough, when I "recalc" the dive series in SDM (and new dives typically come up with "pressures invalid" when downloaded) suddenly the CNS loading looks "normal." Heh, what's that about?

My problem with this bug is that it could easily lead someone to make an unsafe ascent by leading them to believe they are at risk for a CNS hit when no such risk exists.

That's very bad; we are all taught that a bends hit is serious, but likely survivable - while a CNS hit is likely fatal. So if your CNS alarm goes off, are you going to believe it - and ascend until it stops - or will you ignore it? That depends on if you believe it, right?

A rapid ascent from 107' is quite dangerous. One prompted by an erroneous computation - rather than a real need - is even worse.

 

[O-ring]

After thinking about it and spending countless hours researching the problem, I have discovered a fix for the CNS o2 computation bug.

Turn on your computer and press Mode, Set, Pref, Model, Gauge.

CRYB!

 

[Genesis]

Ok, ok, that will indeed "fix" it

Just like turning off the switch "fixes" a burned out light bulb, right?

 

[O-ring]

Genesis once bubbled...
Ok, ok, that will indeed "fix" it

Just like turning off the switch "fixes" a burned out light bulb, right?

Sorry, I couldn't resist...I am surprised UP didn't beat me to it..

 

[jamiei]

1.4 is the recommended limit. I can't believe you said "not many hits" and act like thats ok. Glad I'll never die, I mean dive with you. At 1.6, you can get hit at any time, period. You talk about not messing around with O2 tox, but you seem to feel like hitting the MOD and pushing the NDL is ok. You're so backwards... Anyone that has any business at all diving to 107' and using Nitrox should know better than to shoot to the surface. You're crying for no reason. You should watch your guages closely, especially at that depth. The O2 graph doesn't just jump up on you and say, oh hell, surface, surface now... Computers are for idiots, right... What about those that can't even use a dive computer? This thread has pointed out all the basics of diving with nitrox and O2 toxicity and you still don't seem to have a clue.

WHY NOT DIVE AIR??? WHY DIVE TO THE MOD UNNECCESARILY??? IF YOU CAN'T FIND 28%, JUST USE AIR!!! STOP CRYING... MOST FOLKS USE AIR AFTER A DEEP NITROX DIVE TO AVOID CNS O2 TOX... THIS IS REDICULOUS... and you need to go over your Nitrox and OW material some more... You've forgotten a lot of the basics... HOW DO YOU KNOW THAT SUUNTO ADDS 1% to the FO2??? YOU ACT LIKE YOU KNOW IT ALL, BUT WHAT YOU SAY PROVES YOU WRONG!!

 

[Brules]

Damn jamiei, do you work for Suunto, or do you do your board warrior for them for free???

Sorry, but you obstinate refusal to admit that Genisis has a legitamate point makes you look like an jerk with your constant attacks and trying to make him look like an idiot, while all along ignoring that there IS a possible problem.

And ANY problem, no matter how slight, with a dive computers algorythm's should be taken VERY VERY VERY seriously no matter if any normal or reasonable diver would ever need to use that feature or gas %.

No matter WHAT you say jamiei, someone somewhere WILL use this feature, and possible be severly injured or die from it. The only thing you can safely assume is the contast ignorance of humans, and their tendancy to do STUPID STUFF.

Look at the current Uwatec lawsuit if you want an example of how some quirky flaw that no one expected to be used/found/experienced caused deaths/serious injuries.

By you relying on the premise that no one should use this set up, is exactly the same kind of thinking that gets people injured/killed.

So instead of attacking Genesis for pointing this out, can you not just say, hmmmm wow, that COULD be a problem. Lets see what Suunto has to say before I start making personal attacks on someone's intelligence level because I am a Suunto fanboi and can't see past that.

Sorry to be harsh, but I am just calling it like it is.

Brules