Oceanic NDL Algorithm Change?

redacted · Sep 8, 2006

I am diving a Data Plus and my buddy is diving a VEO 180. Over a couple days of diving on EAN32 at FGB with most dives in the 80 to 90 ft range, we noticed his NDL just before we started ascent was quite a bit lower than mine. Typically, after about 30 minutes of dive time I was looking at an NDL around 30 minutes and he was looking at 20 minutes or a little less. We tend to stay fairly close with him typically a couple feet shallower than me so it is not a difference in our profiles. Are the newer computers a bit more conservative than the older models?

Charlie99 · Sep 8, 2006

awap:
Are the newer computers a bit more conservative than the older models?

Not according to the manuals. The Veo 180 manual has the same NDL table as my Data Plus 2 computer.

It also has the same reciprocal ongass/offgas while submerged, but 1 hour surface credit control upon surfacing (all compartments offgas at 60 minute halftime on the surface).

Tamas · Sep 8, 2006

Actually I have noticed something very similar comparing a VT3 and a ProPlus2 -- same dive and same profile, the VT3 had more 'bubbles' and entered DECO sooner then the ProPlus2

cerich · Sep 9, 2006

Safety stop recommendations and a slowere assent rate (30 fpm vs. the old 60) are changes over the years, NDL's I'll have to look into closer, I'm not aware of a change.

redacted · Sep 9, 2006

cerich:
Safety stop recommendations and a slowere assent rate (30 fpm vs. the old 60) are changes over the years, NDL's I'll have to look into closer, I'm not aware of a change.

Thanks Chris

My buddy and I will also try to record some controlled data on this when we get a chance.

rakkis · Sep 9, 2006

The most obvious difference is breathing flow rates. More volume/time will make the computer account for higher N2 accumulation. And this assumes perfectly matching profiles, which you'll never get

ianr33 · Sep 9, 2006

rakkis:
The most obvious difference is breathing flow rates. More volume/time will make the computer account for higher N2 accumulation. And this assumes perfectly matching profiles, which you'll never get

Huh ??? I think you have a basic misconception about dive computers.

cerich · Sep 9, 2006

our air integrated computers do not increase tissue loading with increased respiration

Tamas · Sep 9, 2006

cerich:
Safety stop recommendations and a slowere assent rate (30 fpm vs. the old 60) are changes over the years

and those would not affect the tissue loading/DECO obligation calculations at depth

redacted · Sep 27, 2006

L:ittle more info. We fionally got together for another dive. Plan was he would dive both computers and then we would compare dive plan outputs for subsequent dive. Just to be sure, we went thru the dive plan mode with both computers clean. Surprise - his was showing shorter NDLs even with zero N2 loading. For example, my Data plus showed 50 ft for 1:20 - his showed 50 ft for 1:07. I suspect he might be stuck in an altitude mode (We were in central TX diving at an elevation of 620 ft). I think he is going to try running the reset procedure before he sends it in for service just in case it has not forgotten our trip to west TX.

Oceanic NDL Algorithm Change?

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