Deep first computer dive

[CrawfishDiver]

Ok I am sure this has at some point been talked about at length but I watch the board daily and haven't seen it recently. My SSI Dive con book says that you must dive a computer deepest dive first or it will not read correctly. I have heard that this has been ammended. anyone have more information on this?rofile:

 

[fire_diver]

I believe this depends entirely on the computer's algorithm. Some may punish you for doing a reverse profile, others probably wouldn't. Sorry, but I don't have any specific info.

Comrade Stroke - FD

 

[CrawfishDiver]

I have both suunto cobra and veo 100

 

[MXGratefulDiver]

Suunto computers use an RGBM algorithm, which penalizes you pretty heavily for doing reverse profiles.

... Bob (Grateful Diver)

 

[rjchandler]

I have never heard of this. Are you sure it says "correctly"?

 

[CrawfishDiver]

I think they term used was properly but the Idea of the section was that you should not dive a reverse profile. However I was told by a guy at the shop that research had been done stating that it would harm the calculation.

 

[MXGratefulDiver]

It does not harm the calculation ... nor does the computer give you inaccurate information if you do reverse profiles. That's not what they mean.

What they are referring to is how the computer calculates your no-decompression limit, based on its method for calculating residual nitrogen and off-gassing rates.

If you do a shallow dive first, then do a deep dive, the computer calculates your NDLs to provide you with less overall bottom time than it would if you were to do the exact same dives in the reverse order.

All dive computers will ... to some degree ... some more than others, depending on the algorithm they use for calculating NDL.

That's all it really means ...

... Bob (Grateful Diver)

 

[DoItRite]

Prior to recent studies, reverse (shallow profiles before deep) were strongly discouraged. Without being too technical, each successive dive (if shallower) would allow for better offgassing. There are theories that now refute this. However most algorithms will give you better bottom times if diving deeper first.

 

[rjchandler]

I have both suunto cobra and veo 100

By the way, if you take both your computers on a series of dives you will see how much of a difference the algorithm can make.

 

[MXGratefulDiver]

By the way, if you take both your computers on a series of dives you will see how much of a difference the algorithm can make.

Indeed ... I've dived my Suunto Vytec and Oceanic Versa Pro side by side on the same wrist and noticed as much as 28 minutes difference in the NDL, depending on the dive profile ...

... Bob (Grateful Diver)