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

[O-ring]

...I ran the same test on my Vyper. I set the computer for Nitrox mode, then set the mix at 32%, and descended to 107'.

10 minutes into the dive, my OLF was halfway up the scale on the left side of the computer display.

17 minutes in I hit the yellow bar on OLF and it started beeping at me and flashing CNS o2 warnings.

20 minutes in I got the second yellow bar and more flashing..

22 minutes in I hit the red bar, got beeped and flashed at a ton, went past my NDL, and got an ascent time of 7 with a ceiling of 10'.

 

[Genesis]

Now reference the NOAA tables that show that the allowed single dive exposure for a PO2 of 1.4 is 150 minutes.

BTW, you decended slowly Decend at the maximum computer's "sim" rate and you'll find that it toxes you at 15 minutes with a warning, and 17 with the "red alarm".

At no time does the PO2 alarm sound.

That is exactly what I saw, O-ring, and its wrong. My Vytec, on the same mix, same PO2 setting, same depth DOES NOT tox you in 17 minutes. It, in fact, gives you the full 150.

I've seen the beginning of this on actual dives where I've come up with a half-graph of CNS exposure - but according to the max depth display I NEVER EXCEEDED the 107' mark, and further, there's no way in HELL I was down there for 75 minutes on a single AL 80! In fact, my TOTAL runtimes on those dives was typically in the 25-30 minute range, including ascent and stops.

I thought that was strange, and now I know WHY what I was seeing was strange.

Its a bug.

As for "not pushing the PO2s", I don't. As for how do I know that Suunto adds 1% to the FO2 setpoint I specify, I can do algebra. 107 / 33 = 3.2424. Multiply by .33 and you get 1.0699; add in the .33 for ambient and you get 1.3999 - or a setpoint of 1.4.

That's all I have to be able to do in order to know that the MOD is being computed for a 33% FO2 when I have set a 32% one. If the math is too difficult then that's a valid reason not to be diving Nitrox!

If I dive to 107' on a 32% mix, I am actually at 1.3575 for the PO2. Significantly under 1.4; in fact, about halfway between 1.3 and 1.4. That is very conservative, and that the Vyper will tox you out while following that very conservative profile is insane.

As for "you'll tox at any time at 1.6", no you won't. The single exposure limit for 1.6 is 45 minutes, and the 24 hour exposure limit is 150 minutes at that PO2. Decompression is often done at a PO2 of 1.6, and tox incidents are EXTREMELY rare while following that regime.

1.6 during a WORKING dive (under significant exertion) is unwise, but even there it won't produce a hit "at any time." In fact, according to NOAA, 45 minutes is just fine - under working conditions (which is what NOAA computed the tables for in the first place!)

Backing off to 1.4 is VERY conservative - backing off even FURTHER is even MORE so.

To have a computer yell "TOX!" at you at one tenth of the NOAA single-dive exposure limit is quite a bit north of insane - and broken.

 

[Arnaud]

Genesis, I would assume this happens with every mix if the algorithm is bugged. Have you tried this with a mix other than 32%? Does it consistently give you 1/10 of the NOAA?

 

[Genesis]

Run right up to (but not beyond!) the setpoint for any FO2 in Nitrox mode and it screams at you in a VERY short amount of time.

The effect is very similar to having the computer "magically" and without warning decide you violated a deco stop and going into "error lockout" mode, in that once this happens its CNS/OTU computations are invalid from that point forward until the unit desaturates.

For "weak" Nitrox mixes (e.g. 28%, 30%) the linger times at those depths are short, so you're not likely to run into this without also incurring a decompression obligation.

However, the paradox is that as you enrich the mixture and go shallower, your bottom times become longer - yet the risk of getting into this pickle with a false tox hit goes up, as it is now very possible to exceed the "accelerated tox claim" time with the gas and bottom time you have at those depths.

 

[Arnaud]

Let's see what Suunto has to say...

 

[6Gill]

I wonder if this would effect the Suunto Mosquito computer?

 

[Genesis]

enough to test 6gill - just perform the simdive that I laid out.

Arnaud, so far no response from Suunto. I emailed them just before posting the thread here.

 

[jamiei]

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[Arnaud]

Jamei, I don't understand why you started this crusade against Genesis.

It looks like the Vyper is confusing NDLs and O2PP exposure (25 min. @ 110 ft vs. 150 min. of O2PP at 1.4). Again, these are 2 different concepts that have nothing to do with conservatism, especially if other Suunto computers don't have the same problem.

 

[jamiei]

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