Dive computer and a Deco stop

[TexasMike]

One of the other threads regarding deep diving made me think of a question on how our dive computers function.

I know that the "nitrogen saturation" graphs will decrease after going deep when you spend time at a shallower depth. But if you were to go deep enough for long enough for your computer to recommend a deco stop, would it erase the deco stop if you were to come up shallower and spend enough time there?

For example, If you were to go to 100 feet and stay there for 10 minutes (I don't have my tables, but I think that's enough time to put you in deco), and you computer said you need to spend "x" time at say 20 feet for deco, would your computer erase the deco stop of you were to motor around at 40 feet for a signifcant period of time? Or would it still require the 20 foot stop?

I don't have my dive computer manual handy so I can't refer to it for my Genesis ReAct would handle the situation.

Oh, and I would say that doing an extended safety stop after such a profile would be a good idea anyhow, even if the deco stop was erased.

 

[Mverick]

If you went into deco it will give you credit for the sightseeing you do at a shallower depth. One of the reasons to do your deepest dive first and come up to the shallows for sightseeing. If you go shallow to deep you'd still have the deco.

 

[joewr]

Mike,

I have never actually seen the program the my computer uses (it is a Matrix--somewhat dated just like me), but I have gone into deco and come out of it by ascending slowly. A recent example was on Saba: we dove to 140 feet and I my N2 "meter" clicked into the red near the end of the dive (I had started down earlier than the other divers and my buddy had stayed about 10' above me so she did not go into deco at all.). As I remember my computer called for 1 or 2 minute stop at 60'. I started up about 30 secs. after going into to deco, but by the time I reached 60' I was out of deco. Just to be safe, I lingered at 60' for a minute and resumed my normal ascent.

The Matrix is not the most recent generation of computers and it "lets" you come up at 60'/min. without penalty. Newer models call for 30'/min--I do not know whether they use a different algorithm for deco, though. All this info should be in the manual you got with the computer. Mine gives a complete discussion of this topic.

Joewr

 

[Tavi]

Hi Mike,
On Suunto's website you can download their Dive Manager Software. It has a simulator you can "play with" to answer questions like this. I don't know, but I would Imagine that it would be similar to what a computer of a different make would do.

Tavi

P.S. Reading about all the things the Swamp Rats are doing almost makes me want to move to Texas.