Suunto Cobra vs. Vytec profile inconsistent

[SeahorseDeb]

Have a question maybe a user might be able to answer. I dive with a Suunto Cobra, one of my buddies uses a Vytec. I noticed on one recent dive mine threw me into a 10 minute deco stop 17 minutes into the dive, yet my buddy's did not. I looked at our computer printouts side by side. They're identical. My buddies computer threw him into a deco stop at 27 minutes into the dive. What gives? We are using the manufacturer default and are not using a personal preference setting. And if you're wondering, I'm not questioning the safety, I'm questioning the inconsistency. The dive was well within the navy no-decompression limits, our computer simply was telling us that the users need to do a short deco based on the fact that both models are RGBM units. Neither of us willfully ignored the warnings nor attempted to throw either buddy into danger.

 

[NCadiver]

Was he using the 50% or 100% RGBM setting and was the Personal or altitude settings on?
Page 42 in the Vytec and the Vytec DS manual.

 

[Scared Silly]

If the altitude and personal settings were the same then as said above check the RGBM setting on the Vytec.

BTW It may sound odd, but I dive my Vytec at 100% unless doing planned deco dives. Then it is 50%, which then matches my other deco software.

 

[ajduplessis]

Was this the first dive of the day, or a repetitive dive? You will have to keep surface interval times also into consideration, however the big difference in data you provided does sound fishy. Check RGBM settings as mentioned.

 

[bleeb]

How aggressive a profile was this? Was there any significant sawtoothing? 10 minutes of deco at t+17 minutes sounds like a bit. Is there any possibility it was indicating a 10' ceiling, rather than a deco stop? Was your buddy's deco stop at t+27 minutes on the same dive, and how much deco was it recommending for him? Do you know what your's was saying at that time?

Another issue with Suuntos that no one has mentioned yet is their sensitivity to rapid vertical motion. I've gotten warnings and I think there are reports here on SB of people getting mandatory stops just from raising their computers too fast to look at them, and these don't necessarily show up on downloaded profiles except sometimes as an alert. From the discussions, wrist mounts seem to be more vulnerable to this misreading than consoles, although even two identical units wouldn't be subject to the same environment. However, I wouldn't have thought this was significant enough to generate the stop times you're finding.

 

[SeahorseDeb]

I'll answer each of you in this reply. Thanks for your feedback. It will be interesting to see what the outcome of this is once we work through this with your help. NCadiver and ScaredSilly I've asked my buddy to check the manual per your suggestions. Ajduplessis It was our first dive of the day, and first in a 24 hour or longer period. Bleeb the profile was to drop down to 100ft and then ascend back up to about 48 feet. There was no sawtoothing on the descent as the site provides an instant dropoff to 100 ft. We took 7 minutes to hit 104 feet, most of which was adjusting our ears and trim. We only spent about 1-2 minutes at that depth. We had a slow ascent from 104 feet up to 80 feet of 20 minutes. From 80 feet then we ascended to the safety stop which took 4 minutes. The only sawtoothing was at 33 minutes into the dive when we were performing our safety stop. The water in the lake was extremely choppy so holding a 15 foot stop (with no ascent line or anchor line) was pretty difficult. That was maintained for 4 minutes. My deco warning came at 17 minutes into the dive at 90 feet, my buddy's deco warning came at 27 minutes into the dive at abut 82 feet. Our average depth was 64 feet. Mine is a console my buddy's is a wrist mount. Your comment "However, I wouldn't have thought this was significant enough to generate the stop times you're finding" validates my feelings as well. Thankyou!!!

 

[Hatul]

I'll answer each of you in this reply. Thanks for your feedback. It will be interesting to see what the outcome of this is once we work through this with your help. NCadiver and ScaredSilly I've asked my buddy to check the manual per your suggestions. Ajduplessis It was our first dive of the day, and first in a 24 hour or longer period. Bleeb the profile was to drop down to 100ft and then ascend back up to about 48 feet. There was no sawtoothing on the descent as the site provides an instant dropoff to 100 ft. We took 7 minutes to hit 104 feet, most of which was adjusting our ears and trim. We only spent about 1-2 minutes at that depth. We had a slow ascent from 104 feet up to 80 feet of 20 minutes. From 80 feet then we ascended to the safety stop which took 4 minutes. The only sawtoothing was at 33 minutes into the dive when we were performing our safety stop. The water in the lake was extremely choppy so holding a 15 foot stop (with no ascent line or anchor line) was pretty difficult. That was maintained for 4 minutes. My deco warning came at 17 minutes into the dive at 90 feet, my buddy's deco warning came at 27 minutes into the dive at abut 82 feet. Our average depth was 64 feet. Mine is a console my buddy's is a wrist mount. Your comment "However, I wouldn't have thought this was significant enough to generate the stop times you're finding" validates my feelings as well. Thankyou!!!

It's a mystery. Why don't you borrow your buddy's computer and make a test dive so you're now wearing both computers. If they give different advice then you know the algorithms are different.

Another idea is to use Suunto's dive simulator. Make a simultaneous simulated dive on both computers. It may be hard to get the same profile on both but you may get close and it may give you a clue to what's going on.

Adam

 

[bleeb]

Another idea is to use Suunto's dive simulator. Make a simultaneous simulated dive on both computers. It may be hard to get the same profile on both but you may get close and it may give you a clue to what's going on.

Another (related) idea: If you're using the Suunto Dive Manager program, you should be able to pull up what each computer thought it's N2 loading was for each compartment at the times of the two deco warnings. That might give some additional insight as to why each of the computers reported what it did, at the time of the two alerts.

 

[SeahorseDeb]

Bleeb & Hatul My buddy emailed the dive profile to me and I imported it to my dive manager. I printed out both profiles and if you hold them up to the light they're identical. As for tissue loading, at the end of the dive my numbers were 31, 60, 95, 124, 118, 94, 83, 47, 24. My buddy's were 29, 55,80,94,90,71,64,37,19. My buddy viewed the thread and in relation to the settings the reply was "I was using P0, A0, and RGBM100 - 100%." Thanks to everyone for their follow-up in solving this mystery. Debbie

 

[Scared Silly]

One other thought, the Cobra is air integrated so is the Vytec if using the transmitter. IIRC Suunto model will take into the amount of gas being used. Is it possible that you were breathing more than your buddy?