Matching Dive Computer Algorithms

[KenGordon]

2. A backup to pick up where the other one left off, which ideally would use the same algorithm

With this combo, I can definitely satisfy 1. However, since the algorithms don't match, I'm not picking up exactly where I left off for 2

If you are usually diving to the conservative and only moving to the agressive one when the first fails it doesn’t really matter that they don’t match, you will just be following a slightly more aggressive profile if you have the gas and carry on all the way to the longer NDL. Doing that is a choice.

Deco is about probabilities, an occasional aggressive dive is not the same as every dive being aggressive. You would only be diving aggressively if you have a failure, that is unlikely, so overall your risk is increased a very very small amount vs two identical conservative algorithms.

 

[tursiops]

Deco is about probabilities, an occasional aggressive dive is not the same as every dive being aggressive. You would only be diving aggressively if you have a failure, that is unlikely, so overall your risk is increased a very very small amount vs two identical conservative algorithms.

I'm not sure this use of probabilities is appropriate. By this argument, if I only jump out an airplane without a parachute once in 10,000 jumps, my overall risk is very small.

 

[scubadada]

I'm not sure this use of probabilities is appropriate. By this argument, if I only jump out an airplane without a parachute once in 10,000 jumps, my overall risk is very small.

@KenGordon is talking about the very small difference between diving two deco algorithms within the available spectrum of conservative to liberal, not playing Russian roulette.

 

[tursiops]

@KenGordon is talking about the very small difference between diving two deco algorithms within the available spectrum of conservative to liberal, not playing Russian roulette.

I agree, I think that is what he meant, but it wasn't really what he said.

 

[dmaziuk]

I'm not sure this use of probabilities is appropriate. By this argument, if I only jump out an airplane without a parachute once in 10,000 jumps, my overall risk is very small.

You know there is a study, yes? -- Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial

 

[tursiops]

You know there is a study, yes? -- Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial

You mean, don't dive and all computers will be equally useful?

 

[dmaziuk]

On a NDL dive GFLo is completely ignored and doesn't affect NDL ... at least for SW it doesn't.

:sigh: from the horse's mouth: Buhlmann equation + GF:
P amb. tol. = (P i.g. - GF * a) / (GF/b - GF + 1)
GF = GF slope * Current Stop Depth + GF Hi
GF slope = (GF Hi - GF Lo) / (Final Stop Depth - First Stop Depth)

If this is implemented as defined above, on a no-stop dive First Stop Depth = Final Stop Depth = surface, the last bit results in division by zero, and the whole thing evaluates to GAMOVER.

 

[dmaziuk]

You mean, don't dive and all computers will be equally useful?

More like if you don't dive right up to NDL and don't cut your SI's right down to pressure group in the black square... they did jump out of aircraft, your "not diving at all" does not quite apply.

 

[dmaziuk]

Just to confirm, the Cressi's go to SF2 and there is no SF3?

No idea about Cressis, my Leonardo does not have SF3.

It does have user-settable altitude levels that will add conservatism. There are computers that add conservatism by simply adding altitude. I have no idea if Leo does that and if so, how altitude and safety factor play together. Or, for that matter, what those other computers do when you add both conservatism and altitude.

 

[dmaziuk]

So I found the cable, uninstalled and then reinstalled the Cressi interface program and now it works. And it does show NDL times throughout the dive.

Huh. You're right, the image of the computer up on the right shows the NDL as you move through the dive... I never noticed before.

I learned something today, thank you.