backup computers: several questions-need opinions

[yaml]

background: my wife and i have and love our atomic cobalt computers; we want a backup computer (e.g.oceanic BUD): small, effective, etc.
Question #1: compatibility, comparability,algorithm similarity: for additional safety's sake, would it be better if each computer were on different algorithms for a broader coverage of NDL's? or similar algorithms to serve as comparable backups for the other device?

Question #2: i assume it is possible to find out the algorithm any particular device uses?

Question #3: better or more confusing to set one device for moderate and the other for more conservative NDL's?

Question #4: i am also a freediver - need opinions on whether to get a hybrd computer (e.g. oceanic geo 2) which can be used for both freediving and scuba or better to get 2 different dedicated computers to be used separately : e.g an Aeris F-10 for freediving and a oceanic BUD?

appreciate any and all comments - thanks

 

[TSandM]

Well, the first thing is to ask yourself WHY you are carrying a backup computer. I believe the answer is that you would like to retain access to depth, time and decompression information in the event of the first computer malfunctioning. In that case, and since you have apparently decided that the algorithm used by the Atomic computer is acceptable to you, why would you want your backup computer to tell you anything different? In addition, if you are concerned about a mode of malfunction where the computer gives nonsensical information (which is something I personally have never seen), if you have two computers which always give you different information, you've lost the ability to notice if one is no longer tracking the other.

Except in the case of some technical computers, where you purchase the decompression software separately or where a specific program is loaded into the computer, the algorithms used are proprietary. In other words, an Oceanic computer will calculate differently from a Suunto which will be different from an Atomic.

 

[KeithG]

Having 2 computers that tell you different things is not much use. Which one do you rely on? If your primary says you are okay, but your backup locked out due to a fast ascent or a missed "safety" stop What should you do?

You do need to consider more than just the "algorithm". The computers reaction to various diving behaviors is also a concern. We have a computer that completely clears 12 hours after its last dive. We also have one that will clear sooner or later than 12 hours, based upon its calculated nitrogen loading.

So it makes most sense to use 2 identical computers with the same settings.

 

[SeaSoulSelf]

Hello Yaml,

My opinions/comments below. We have Oceanic PP2s and I have the Geo 2.0 backup. We set them conservatively.

"Question #1: compatibility, comparability,algorithm similarity: for additional safety's sake, would it be better if each computer were on different algorithms for a broader coverage of NDL's? or similar algorithms to serve as comparable backups for the other device?"

Similar algorithms would be best, in my opinion. There are comparison charts on the web and here on the board. This was a very helpful thread: http://www.scubaboard.com/forums/co...zers/305374-so-you-want-buy-new-computer.html

"Question #2: i assume it is possible to find out the algorithm any particular device uses?"

Yes. The BUD and Geo 2.0 have both the Pelagic DSAT and Pelagic Z+Buhlmann.

"Question #3: better or more confusing to set one device for moderate and the other for more conservative NDL's?"

I think this would be confusing. I would imagine this conversation in my head at depth: "Now...did I turn on the conservative factor? Should I push this one, or switch to this one to stay down 5 more minutes?" Temptation..not good. The purpose is to have a backup in case of failure.

"Question #4: i am also a freediver - need opinions on whether to get a hybrd computer (e.g. oceanic geo 2) which can be used for both freediving and scuba or better to get 2 different dedicated computers to be used separately : e.g an Aeris F-10 for freediving and a oceanic BUD?"

If you can find a backup that uses the same/similar algorithm as your Cobalt and meets your free diver needs...otherwise, Geo 2.0.

Good luck!

 

[t-mac]

Get a backup that has the same or a similar algorithm. Same is best. I believe you seek a backup for the reasons suggested by Lynn. I'm not sure what the Atomic runs, but the BUD runs two algorithms that can be made to mimic most others, so it is a good and economical choice. I don't recall if it has a free dining mode. Look at the oceanic website.

 

[mala]

i go for different algorithems on the back up as 1 its interesting to see and 2 you can decide yourself which one you would rather follow.

as for conservatism i tend to set them to the most agressive setting in case i need to get out as quick as possible.
you can always pad out your stops for conseratism.

 

[yaml]

appreciate all the input; any particular opinions re: D4 suunto vs oceanic geo 2? friends are recommending both but i would like to hear what the scubaboard "masses" have to say; again - much thanks for the input on the original questions

 

[NCadiver]

D4 you will be better off in the long run. If you are diving with your wife you have a backup computer already or get a full computer if you need a backup so you can use it as your main computer if need be.

 

[Peter69_56]

I dive with my wife and we both use ProPlus 2. When I was at Truk I used a VEO-2 as a backup, and guess what, it gave a different deco time (same algorithm though). Found that the VEO-2 had a fault and so sent it away and it came back and now they all read the same deco when diving. It sure helps if you and your buddy both have the same computer and same algorithm, thus if there is a fault, as I had, we used the longest deco time (which happened to be wrong but it was the safest to use). If you want a backup make it the same as what you and your buddy have, it makes things simpler and uses the KISS principle (Keep It Simple Stupid) which I like. Murphy can be very nasty when he wants things to go pear shaped.

 

[fred3798]

Seriously? Until a few years ago, charts that just look at your max depth range were sufficient. The rule that if your computer malfunctions, you must end your dive and cannot use your buddy's is just an ad for computers. A back-up computer is a very expensive redundancy. How about ensuring that computers work? My Suunto Vyper died after 60 dives but out of warranty. Suunto offered me 5% off a new one. I bought a Cobalt. If it dies amid dive, I will go no deeper and surface with my buddy when my air gets to 700 as I normally do unless her NDL gets short - which rarely happens on our Nitrox, touristy dives.