Originally posted by joewr
Folks,
Look at how all this started: Iguana Dawn wanted to get himself a new computer and, now, I am the one who will be poorer. I knew that there was something sinister about that reptilian reporter.
At any rate, I really like my N2 sat dial on my Matrix and refer to it rather regularly. Actually, it is what I use when I make my safety stops. I like to hang around at 20' or so until it ticks into the green. That might take more than 3 mins...
I also like to keep an eye on it whilst deep diving so I know when I am on the verge of going into deco. I have to look in my Suunto lit. to see how one does that on the Cobra--or I can wait a few hours for Warhammer the Informative to clue me in. That sounds like a good idea. WH, you are on cue.
Joewr
It works great at depth Joe. You'll have 2 indicators of NDL at all times while on the dive. The first one will be a numerical reading in right-center of the screen. The CTB graph will also tell you the same info on the left with 8 green notches, 2 yellows and 1 red. When you get to within 5 minutes of your NDL the last yellow notch on the graph will fill, if you stay to the NDL reaches 0, then the red one will fill and you'll now be in a deco dive. The confusion comes in when you ascend a little. Say you do a dive to 120ft and you stay at that depth till you get within 5 minutes of your NDL, then you ascend to 70ft. The Cobra/Vyper will recalculate your NDLs for 70ft while at the same time taking your time at 120ft into account. As a result, the CBT graph will go back into the green until you get within 10 minutes of your NDL at your present depth. The process will repeat itself as you ascend/descend shallower/deeper. The trouble is that as long as you have more than 10 minutes of NDL at any given depth, the graph will be in the green, no matter how long you have been down nor how close you came to your NDL previously on the dive or how much nitrogen you have absorbed. As long as you have 10 minutes or more of NDL at any given depth, the graph will be in the green. If you ascend to somewhere in the 30ft range or shallower it will be way into the green cause you have alot of NDL at shallower depths. You'll have no reference as to how much nitrogen you have taken on, you'll only know how long you can stay at your current depth without going into deco. The only time you'll see the loading is when you download the dive into Dive Manager.
I can't, for the life of me, decide why Suunto thought it was better to provide the NDLs in 2 forms rather than use the graph to show the calculated nitrogen loading. But I'm sure there was a reason. Theoretically, the computer provides you with ampel info and as long as you dive within it's limits and do the reccommended stops, your
suppose to be in the clear.
I'm going to load some of my profiles into some other software and see how it compares to Suunto's when I get a chance. I'm also going to try and get my hands on another computer to dive allong side my Cobra next time I do some deep dives and compare them. Interestingly, I took the average depth and used it to work the dives on the RDP. On the dive where Dive Manager showed the most loading, I ended that dive in the U pressure group with only 2 minutes of NDL to spare, according to the tables.
Also take into account that even though the Cobra/Vyper provides deco information it was never intended to be a deco computer nor does Suunto reccommend that it be used as such. In fact, Suunto recommends that you start your ascent towards the surface as you approach the yellow (or less than 10 minutes NDL) on the CTB graph. But that's sort of a double standard in my opinion cause if you follow that recommendation, you can't dive deeper than 120ft. And at 120ft the Cobra only gives you 10 minutes of NDL, so it would be blow and go dive. Of course that's on air and it would be different for nitrox.
I don't mean to turn anyone away from the Suunto computers. I like mine very much and would recommend it. I just wanted to provide a little feedback in some of the areas I feel they are lacking.