Is a computer actually necessary?

[James connell]

most of what's been posted is on the "hairy" side of information.

while a computer is far from a nessesity for safe diveing, in some ways a computer can be more safe. you don't have to calculate your residual N2 between dives - the computer will take care of that. if you blow your profile - the computer is still tracking your real dive and has the data to get you up. But it can also increase the danger, it's NDL is often a rather 'hard line'. most tables have a safety factor ( not built in but it's there) - very few dives are truely square profiles if you push the computer to it's NDL you have done the same thing as if you went down and sat on the bottom at the max depth and for the max time the table gave you. in reality most dives only spend a small percentage of time at the max depth.

there is also the convience factor - a computer means you don't have to play with the tables, it'll help you plan a dive, do the surface time stuff for you and let you do repeat dives more easily.

i'd suggest you get one - y'll enjoy diving that much more.

pug - a trout will too it has an IQ of ~2

 

[g8trdiver]

I had this same argument with a divemaster on a liveaboard last year. Long story leading up to it - but let's just say it occurred to me at some point that my hubby was not really paying attention to his computer, but rather following my lead (not good esp once I started using Nitrox and he was on air - even though we were both using air computers at the time).

So, I insisted that A: He get Nitrox certified and B: even though using an air computer on Nitrox is acceptable, I insisted that for the first day of diving he use the tables when we were planning our dives on the liveaboard. Mostly because I just wanted him to take planning, surface intervals, and bottom time seriously. I didn't want to have to be the only one who did. He'd been diving for years, but I guess he'd gotten used to following the crowd. Luckily, he's a reasonable man, and let me bully him into doing this.

Anyway, one of the divemasters overheard us going over the tables, and started trying to convince us that using tables was "dangerous" because you could make a mistake. (don't you use a table when you calculate your max depth and sign the form when you use Nitrox, by the way....?)

The net result is that now he knows the tables in his sleep, and we both had a refresher on NDL and RNT - and we compared the table-planned profiles to what our computers told us our profiles should be, and had some nice geeky conversations over it all..... And now I'm more comfortable knowing that he's paying attention too. And that divemaster can kiss my patooty.

I'd rather dive with someone who knows the tables and uses a computer as well, than with someone who relies only on the computer.

Which leads to the next bit of advice: have a depth gauge separate from your computer's (in case your computer dies - which has happened to both of us at the same time), and have a timing device (watch) separate from the computer also. This way, assuming you've planned your dive BEFORE you dive, if your computer craps out, you don't have to abort the dive. You can continue with your plan.

Computers are a convenient tool - not a replacement for knowing the tables.

Maybe a little more than 2 cents.... but there it is.

 

[divemed06]

Necessity implies that you can't do without...

a) Air.....necessity
b)Brain....necessity
c)Computer...not if you have a and b

Diving has been around a lot longer than dive computers...

 

[Uncle Pug]

James connell once bubbled...
a trout will too it has an IQ of ~2

 

[bwerb]

pasley once bubbled...
If you leave the computer in the water to finish a deco while you sip a margarita on deck, then computers aren't any good due to operator error.

If the computer algorithm is "bend and treat"...you very well may find yourself quite safe, happy and content, sipping your drink of choice on the deck far before your computer has cleared and it will have nada to do with operator error...it will have to do with the fact that you used a very different decompression model which your computer was unable to follow.

I've found my computer is a very very expensive depth gauge and dive timer...oh...it tells the temperature too

 

[cwinston]

SDI/TDI does not require a thorough understanding of the dive tables, just their theory, at least not as far as I can tell from my class. They push computers heavily and leave tables up to the discretion of the instructor, so I found another instructor to show me the ins and outs of the tables. To make a long story short, I think it would be foolish to rely solely on dive computers, but just as foolish to completely discount their use by new divers, especially since only a computer can monitor ascent rate acurately enough to prevent over expansion injuries.

 

[GeekDiver]

Computers are great tools and cool gadgets.


If mine fails it won't end my diving cuz I know how to plan and use an RDP or Wheel for multilevel diving and I always have my watch as a backup. So no there not needed to be safe.

Ask your instr what she does in case hers fails. Did you take a SSI class. I heard that they don't teach tables anymore and require computers. Someone can correct me if I'm wrong but if true I think is a sad mistake. (You heard wrong - SSI does teach tables, and computers (using a computer is optional) - Rick Murchison)

 

[DA Aquamaster]

This is interesting.

I agree that computers are not required. I dove for years before they were available and me and my buddies never killed ourselves - on US Navy tables no less.

The thing about computers being the only thing accurate enough to measure ascent rates and prevent lung expansion injuries is the scariest statement I have heard on scuba board bar none. No offense but there is a real skills deficit floating around in that statement somewhere. You need get your eyeballs off the console and start looking at the water column and the stuff and/or bubbles floating in it.

Back in the dark ages whe divers shared the oceans with Megaladon (the shark, not the rebreather), a company marketed something called "Dive Bubbles". They were little ping pong sized balls that rose at 60 fpm. The ad copy promoted the theory that you could take one of them out of their little 3 pack holder on your SPG hose and follow them up. They died a swift and mericful death as just about every diver on the planet understood in the pre-dive computer era that you could follow your real bubbles up for free and not have to worry about losing them. Your very smallest exhaust bubbles will rise about 30 fpm and make a great reference. Plant one in front of your mask and follow it up until it starts to get big, then find a smaller one. Nobody had dive computers 20 years ago and the vast majority of us survived just fine without lung expansion injuries. (not sure what happened to Megalodon, I suspect he choked on someone's lost Dive Bubble)

Ummm...sorry for the rant.

A dive computer, while not needed, is very nice to have in some situations. I dive at high altitude and tables tend to be very restrictive in terms of bottom time at altitude with all the rounding, starting as a group C diver etc. Multi-level tables like the PADI Wheel help, but a computer gives you much more bottom time and saves a lot of work.

Someone mentioned that a computer dive is essentially a square profile dive and that diving to the NDL is like maxing a table with a square profile. This is true to a point, but computers, like multi-level tables have shorter NDL's as the designers in both cases recognize the square profile problem and add a saftey margin. If you take two divers, one with a table and one with a computer and send them to a constant 50 ft depth, the computer diver will reach his NDL first.

The trend in dive training is definitely toward computers and they are becoming the norm. This is not a bad thing, The bad thing is the dumbing down of certification courses where dive table use and theory is taught in increasingly less depth or detail. What an OW student gets today in any course, is far less than I got in OW class in 1985, ie. how to use tables in all situations up to and including unintentional deco. (teaching planned deco was reserved for the deep diving portion of AOW class) This went right along with teaching a thorough knowledge of the major gas laws including the formulas and the math - something else that is barely touched on in the idiot proofed modern OW classes.

Hmmm...I'm back to ranting again...Sorry.

In short unless you are hard core tech bound, get a computer as it will be useful and it will quickly help you develop an intuitive idea of where you stand in terms of deco in most situations. BUT at the same time know your tables, use them on a regular basis to stay current, plan on having your computer fail on every dive and have a contingency plan ready for that special day when it does. I routinely do deco with my computer, but I also figure the contigency plan and take the deco schedules for possible depths and times with me (either written on my old AOW deep diving contingency planning slate or written on a piece of vinyl tape stuck to the top of my fin blade) in case the computer dies.

A backup depth gauge (even a small, inexpensive, low profile capillary depth gauge is fine) and a dive watch or dive timer is a very good idea as well in the event of computer failure.

You can also carry a backup computer in a BC pocket or in a wrist mount. The small Pelagic hockey pucks by any name work well for this and you can get them for relatively little money. Just be sure you don't violate it on a dive if it is more conservative than your primary computer.

 

[BigJetDriver]

DA Aquamaster once bubbled...
In short unless you are hard core tech bound, get a computer as it will be useful and it will quickly help you develop an intuitive idea of where you stand in terms of deco in most situations. BUT at the same time know your tables, use them on a regular basis to stay current, plan on having your computer fail on every dive and have a contingency plan ready for that special day when it does.

DA has made an excellent point here and one that deserves re-stating in other words!

Mr. Murphy is always with us, and a computer, while it is a most excellent tool, can on occasion fail. The question is then: "Whatcha gonna do now, G.I?" (...And no, I don't mean HIM...)

If you do as DA suggests, you will be current and comfortable with the tables and will revert to your back-up plan with depth gauge, bottom timer, and tables from your pocket.

You should have these items with with you even if you are "hard core tech bound", as DA puts it. As reliable as they are, even a VR3 or HS Explorer can occasionally fail.

I would also most respectfully disagree with the ancient and honorable Uncle Pug. While it is a cute and funny little slogan, computers, in and of themselves, do NOT rot your brain! If this were so, astronauts would be vegetables, and jet pilots would be zombies.

If I may be so bold as to interpret here, the correct meaning of the statement is that OVER-DEPENDENCE on the computer will make your mental skills rusty.

If you do as DA suggested, you will have the best of both worlds!

 

[scubajoe]

GeekDiver once bubbled...

Ask your instr what she does in case hers fails. Did you take a SSI class. I heard that they don't teach tables anymore and require computers. Someone can correct me if I'm wrong but if true I think is a sad mistake.

SSI teaches tables, well an SSI instructor does if he/she wants to meet SSI standards. We also teach proper computer use.

Joe