Diving with multiple computers?

[jlevine]

Hello,

I currently own a Suunto Cobra and love it. I have not had any problems with it. I am wondering, however, what some of you do regarding the potential for computer/gauge failure. Since the Cobra is an air-integrated all-in-one device, I would lose a lot of functionality if it failed. One of the instructors at my LDS dives with two computers for this reason. Do any of you do this?

Regards,

jsl

 

[Charlie99]

Just think through what happens if your computer fails. Can you safely abort the dive?

In the type of diving I do, I always know what my decompression status is, I can do a rough judge of depth (or use buddy's depth gauge or computer), and don't have any required deco stops deeper than 10'.

I don't have air integrated, but even if I did, the loss of pressure info should also not be a problem. You always have enough gas for both you and your buddy to safely abort the dive. Right?

I would only go to redundant devices if my decompression stops were significant enough that I needed some help on the time and depth measurements, or if I were diving in such poor visibility that I needed to rely upon the depth gauge to control my ascent.

--------

Now that you have safely surfaced, you need to figure out what to do for your next dive. I suggest keeping an SPG in your save-a-dive kit. As far as decompression planning, most computer manuals advise the very conservative "no more diving for 24 hours". My plan, which I have never had to implement, is to simply assume that I am a Z pressure group diver on the PADI table and go from there.

 

[pdoege]

I dive two computers.

I deco out on the most conservative one, they are normally within 1 minute of each other anyway.

If they both fail I fall back to tables.

If I am diving tables then I use one as a bottom timer and the other as a bail out for the tables.

However, this is a lot less important in recreational diving. If the computer fails you just go on up and plan your next dives via tables.

Regards,
Peter Doege

 

[jakubson]

Hello,

I currently own a Suunto Cobra and love it. I have not had any problems with it. I am wondering, however, what some of you do regarding the potential for computer/gauge failure. Since the Cobra is an air-integrated all-in-one device, I would lose a lot of functionality if it failed. One of the instructors at my LDS dives with two computers for this reason. Do any of you do this?

Regards,

jsl

I dive two computers. I started for liveaboard diving. 5 dives per day for 5 days in a row on Nitrox, I wanted to be sure i kept track of N2 and O2 in case of a computer failure. Compared to the cost of a liveaboard vacation, a second computer amortized over many vacations is minor.

For local diving, I do not need it, but since I have it, I use it.

 

[pants!]

Keep a spare SPG and bottom timer in the bag you leave on the boat or on shore. If your Cobra dies during a dive, switch out the components on your surface interval. Just do the rest of your dives using tables.

Alternately, keep just a spare SPG in the bag and wear a wrist-mounted computer, so if you do more diving that day it knows your current NDL status.

 

[pickens_46929]

However, this is a lot less important in recreational diving. If the computer fails you just go on up and plan your next dives via tables.

Whoa here... if you're recreational diving and your computer fails, you plan your next dive via tables?

How do you know what Pressure Group (PG) you were at on the tables since you no longer can access your computer?

I think you would need to stay out of the water a minimum of 6 hours to become a FRESH diver so you could start to use the tables.

Am I missing something?

Dave

 

[pants!]

If your computer fails, you should already know what your max depth was, and you should know within 5 minutes what your bottom time was. Use that data, plug into your tables, and bam.

 

[Charlie99]

If your computer fails, you should already know what your max depth was, and you should know within 5 minutes what your bottom time was. Use that data, plug into your tables, and bam.

Except that I'm almost always waaaaaay off the tables because of multilevel profiles. even with a single AL80 it's not uncommon for my max depth to be greater than 100' and runtime (which is used for bottom time with most tables) more than 60 minutes.

OTOH, if I assume that all compartments are within DSAT/Spencer/PADI limits (good assumption since that's what my Pelagic/Oceanic computer is based upon), then just assuming pressure group Z and going from there is reasonable. I do review my dives to see if it's probable that any of the special rules of the PADI RDP that invoke 1hr or 3 hour miniminum SI's are likely to be applicable.

Play around with any deco program a bit, and you will see that a few extra minutes hang at 15' will increase your safety margin signficantly, as will planning a dive as a square profile, but diving it multilevel.

 

[Bill51]

I always carry a backup computer if I’m doing multiple dives. If you’re on a dive vacation it’s one of the cheapest insurance policies you can have that you’ll get to maximize your dive time. I used to carry my Orca Pilot in my BC pocket as a backup until my wife discovered the neat 3 minute at 15’ timer on it and now she has me wear it where she can see it hanging on my BC during safety stops.

In 10 years I’ve only needed my backup once when I messed up an O Ring on my primary computer and flooded it, but without that backup I would have needed to have skipped at least 2 great dives in Grand Turk.

For new divers I highly recommend that they buy a relatively inexpensive computer as one of their first purchases even if they know it won’t be the computer they ultimately want. If the computer is small enough it will be perfect for their backup computer when they buy the one the really want after they’ve been diving long enough to know what they want. If it turns out they don’t go on with their diving, they’re not out a ton of money.

 

[stacktester91]

I always carry a bottom timer (citizen watch) as my back up. It profiles the dive (max depth, ave. depth, start, end time, total time and temp, but does not calculate NDLs. I use my computer as my primary, double checking with tables, but always wear the watch as a back up.