Suunto Experts

[Warhammer]

I had an interesting experience with my wife's Vyper and my Cobra this past weekend. I wore the Vyper on my wrist and the Cobra was cliped off on one of my Ranger's hip D-rings. I must admit that I pushed the limits of both computers, but what was interesting was that the Cobra went into deco once on the second dive of a 3 dive day, and Vyper did not. Granted the Vyper got within a minute of deco, so I assume it was all about postion, the Cobra was probably a little deeper than the Vyper resulting in the deco. The Cobra went out of deco before I ever reached my first planned stop at 30ft, so no big deal. But what was interesting was that while I was doing an extended safety stop at 15ft, I checked the Consumed Bottom Time on the Vyper and I wasn't even registering on the scale. Not a single notch. Anyone care to explain why? I know I had to have been loaded pretty good with nitrogen, since I had just came out of deco. I also checked the Cobra, with the same results. I checked it several other times on other dives, and always got the same result. Granted I usually didn't think about it until the later part of the dive (since I was diving nitrox and you have to switch screens to see the CBT), and on most of the dives, I spent at least 10 minutes at 15ft. Is it possible that I had completely decompressed with only a 10 minute stop at 15ft?

 

[Warhammer]

I think I know what it is with the CBT deal. Suunto computers, at least the RGBM ones, don't measure nitrogen loading. They instead measure bottom time and hense Consumed Bottom Time. The first notch in the CBT isn't filled in till your NDL is below 100 minutes. I'm sure I probably had way more than 100 minutes at 15ft, so that's why it didn't register on the safety stop. I think I understand it, but I'm not sure I like it. No way to tell if you are coming up in the red, yellow, or green.

 

[Rick Murchison]

Another (very irritating, by the way) possibility is if you were diving in Nitrox mode (and if you dive Nitrox at all you probably keep the computers in nitrox mode since you can't change modes between nitrox and air once you're in a dive sequence - yet another extreme irritant) then the CBT graph shows your O2 loading unless you press the "Time" button, where it'll show CBT for a few seconds.
Rick

 

[Warhammer]

Yeah, I know. I did push the time button in order to display the CBT. I was just shocked that it wasn't even registering, espeacially since it had just put me into deco a few minutes earlier. But if you think about the way Suunto computers work, it makes sence since the graph doesn't show nitrogen loading. Like I said above, it shows consumed bottom time instead of nitrogen loading. And since I was at 15ft, I probably had eons of bottom time left at that depth. I guess that's fine, but I had rather see the nitrogen loading instead.

And yeah, I learned the hard way about not being able to switch from air to nitrox mode during a series of dives, so they now stay in nitrox mode 24/7.