Diving two different computers - got "Suunto'd" - and a whale shark

[kcprofessor]

While I can't say it is true for all computers, my Suunto HelO2 can't be taken out of gauge mode for 48 hours after the dive. Pretty much makes it useless for the next dive. Even using two Suuntos can get you into trouble because of all the different varieties of the RGBM algorithm they use. The latest computers use a "fused" RGBM, while the HelO2 uses a "technical" RGBM and the Vyper Air uses a "recreational" RGBM. ARGHH! I am still looking for a reasonably priced backup for my Petrel. All it has to do is run ZHL-16C. Using tables is fine, but you pay a very large penalty in allowable bottom time because no one dives a square profile!

 

[beaverdivers]

I believe that you would be off the dive tables after your first dive of the day.

One question: What were your computers reading when you spotted & swam with the whale shark?

Was the Suunto putting you into deco?

Just a suggestion, next time get the diver in the shot with the whale shark. It makes for a better perspective especially if you are diving with a wounded warrior. It would only be topped if you had the Oriskany in the shot as well.

Incredible experience; the Oriskany & a whale shark! Nice .

 

[stuartv]

Other than having a stop, what are the communities thoughts on diving two computers that are a little out of whack, when the opportunity isn’t there to have them match? We’re doing Cozumel for the first time in October and I doubt those DM’s would be as forgiving if this happened there

Personally, I feel like the chances of a Perdix crapping out are so slim that I would just dive it and leave the Suunto on the boat. If the Perdix did crap out, I would probably just switch to the Suunto the next day. That's not "recommended" because the Suunto wouldn't know about any residual nitrogen or any oxygen clock that you might still be carrying from the previous day. But, the Perdix at Medium and the Suunto are both so conservative that I personally would do it that way and not worry about it.

I dive the GEO 2.0 in gauge mode. If my Perdix craps out, I will switch the GEO 2.0 into dive mode.

Not for at least 24 hours after you get out, I believe.

Not real sure, but I did haul ass off the line at 56' to head back out to the whale shark as it made its pass. I never varied more than +/- 2' the entire time, but I was moving pretty fast. With the camera rig, it's possible I moved it too fast.

You can download your dive data from the Perdix to Subsurface, which is free dive logging software. Once you do that, you can look at your dive profiles in Subsurface and see what your exact ascent rate was at any point of the dive.

 

[dmaziuk]

I’m not spending another $1,600 on backup computers right now.

Well, there's any number of computers that don't cost $800/pop and have a "free" mode: gauge with tracking, so you can switch it to dive mode without waiting 24/48 hours as is typically the case with gauge -> dive switch. Geo2 seems to be a popular option. No idea what happens if you switch and it thinks you're bent into one hundred nazi crosses, though.

 

[MXGratefulDiver]

If you're going to run two computers the best approach is to get two that run the same algorithm ... or something reasonably close. I currently have three, of which I will only dive two at a time. I have a Xeo, a Petrel, and a TDC-1 (new design that I'm field testing). They all use programs that can be set for similar levels of conservatism. And if you do decide to bend one, none of them will lock you out for two days, like most recreational computers will. While they will show some minor variances, depending on profile, they're relatively close enough that a slow ascent or an extra minute or two in safety stop range will typically take care of it.

... Bob (Grateful Diver)

 

[Scared Silly]

While I can't say it is true for all computers, my Suunto HelO2 can't be taken out of gauge mode for 48 hours after the dive. Pretty much makes it useless for the next dive.

I was going to post the same. With most all computers one can not go from gauge mode to air/nitrox mode without waiting 48 hours. Further, one can not go from air mode to nitrox mode without waiting 48 hours because O2 and CNS calculations have not been done.

Even computers like the Geo2 which have a free mode and can be switched to dive mode are probably not going to be helpful because here again according to that computer there could well be a deco violation.

 

[Dan]

I was going to post the same. With most all computers one can not go from gauge mode to air/nitrox mode without waiting 48 hours. Further, one can not go from air mode to nitrox mode without waiting 48 hours because O2 and CNS calculations have not been done.

Even computers like the Geo2 which have a free mode and can be switched to dive mode are probably not going to be helpful because here again according to that computer there could well be a deco violation.

I set both of my console & wrist dive computer to Nitrox & just change the oxygen concentration to whichever gas in the tank before using it. If dive 1 is using EAN32, then, I set the O2 concentration to 32. If the dive 2, 2 hours later will be with air, then I set O2 concentration to 21.

 

[kcprofessor]

I set both of my console & wrist dive computer to Nitrox & just change the oxygen concentration to whichever gas in the tank before using it. If dive 1 is using EAN32, then, I set the O2 concentration to 32. If the dive 2, 2 hours later will be with air, then I set O2 concentration to 21.

That is what I do, but there are some limitations to be aware of. Not big, but most computers require you to put in the whole number of the O2 concentration and ignore the decimal percent. Since the exact percentage of O2 cannot be input, the computer rounds it up to the next percentage point for O2 exposure calculations and rounds down for N2 calculations such as NDL. Probably doesn't make a difference over a few dives, but might over a multi-day dive trip ith 4 or 5 dives per day.

 

[Dan]

True. I try to avoid switching air to Nitrox, back & forth. But there were times when the boat had limited capacity (filling up time) in Nitrox & we planned to do shallow dives.

 

[RainPilot]

The Nitek Q is pretty reasonably priced now (around 400$) and you can set your GF the same on it and the Perdix, which is what Im doing. Obviously buying a new PDC when you have a "working" one is a PITA but for those who are looking for a reasonable backup for a SW that may be an option.