They won't be exactly the same due to differences in sampling & recalculation intervals as well as precision and round-offs. E.g. if one recalculates every 20 seconds and another: every 15 seconds, they can only "exactly match" once a minute (assuming their clocks are perfectly synchronized). That would be more pronounced during depth changes and should start converging once you level off.
Dive Computer No Deco Computations Question
- Thread starter butterwm
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They won't be exactly the same due to differences in sampling & recalculation intervals as well as precision and round-offs. E.g. if one recalculates every 20 seconds and another: every 15 seconds, they can only "exactly match" once a minute (assuming their clocks are perfectly synchronized). That would be more pronounced during depth changes and should start converging once you level off.
That has not been my experience. About a decade ago, I got a Suunto DX for testing and also had a Oceanic Atom I was using.
I was on a deco dive and the Suunto had me doing a lot of deeper stops which I was obeying. At one of the stops, I could see my richer deco gas that I had stashed about 3 feet shallower and my Oceanic didn't have me requiring a stop at my current depth so I figured I would get to the gas and accelerate my deco.
The Suunto had about a minute left at the current stop I was at so I just went to the gas.
That was a mistake. The Suunto went into violation mode (under water on a dive no less) and no longer gave me any stop information. It was insane. I luckily had my Oceanic with me.
I personally only dive Shearwater at this point. For the diving I do, I really don't think any of the other mainstream dive computers are suitable for me.
I understand that a lot of computers go into a 24 or 48 hour lockdown after surfacing and after a violation. I won't argue if that is right or wrong (but I do dive Shearwater computers which don't do that).
However, to go into lockout mode while on a deco dive is absolutely unacceptable IMO. Go ahead and penalize me or alert me or whatever, but to lock me out during a dive is ludicrous.
I will never dive a Suunto again.
- brett
David Carron
Registered
I've given a fair bit of thought to the correct behaviour in this case in the context of a dive computer I designed.
The ascent profile calculated and displayed is supposed to be the one with an "acceptable chance of DCI" which, without the ceiling violation, is just the output of the ZHL decompression model I was using.
However in the case of a ceiling violation, the safest profile to display could be anything from "the violation is so trivial that it doesn't really matter", through "if you lower your GFs a little (how much?), and recalculate you'll be ok" to "given that ceiling violation, the damage is done and there's no way you're avoiding a hit so ascend directly to the surface and call for help immediately".
The problem here is that there is no relevant theory to guide us, so the computer is pretty much forced to assume the worst. So, what sense does it make to display ZHL's output since it is "strongly suspected" to be on the dangerously short side of the ascent profile with acceptable chance of DCI?
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