Diving without a computer

[turbinetech2]

When you dive, if your computer stops working for whatever reason, do you stop diving? If you are conversant with the dive tables and can calculate bottom times with a bottom timer/dive watch, would you continue to dive? This has not happened to me, but I have experienced water in my PDC before getting it to seal. This did not appear to affect the operation of my computer, but when it had water in the battery compartment I was "working" at about 10-12 feet drilling some holes. Hopefully I can ask the next question without starting a flame war of one agency vs another. The dive center I received my cert from teaches with SDI as the certifying agency. They do teach the tables (lightly) but IMO teach the use of dive computers as a primary dive tool in regards to dive/bottom times. I am only certified as OW at this point, so please keep that in mind. I am not talking about technical diving or going below 60 feet.

 

[Ed Marshall]

My computer has never failed but, if it did, I would end the dive simply because it is air-integrated and I do not dive with a back-up pressure gauge.

Ed

 

[Thalassamania]

If, at end of each dive, you record the time and the scrolling adjusted no-decompression limits you can use that data to get you back onto printed tables. IF not, well the AAUS recommendation is that you're out of the water for 18 hours.

 

[H2Andy]

When you dive, if your computer stops working for whatever reason, do you stop diving?

if it's my last dive of the day, no. using my backup watch, i'll know how much time i've been at depth. since i check my depth often, i will know what my max depth has been.

using the rule of 120 (time + depth = 120), i will then calculate how much time i have left at this depth, and, providing there is structure that will allow me to maintain my depth without a pressure gauge, i will continue the dive, substracting perhaps 5 minutes for safety, then head up slowly and do as long a safety stop as i can.

if it's not my last dive of the day, yes. i'll do a slow ascent, and do my regular safety stop (about 10 minutes between 30 and 5 feet in stages).

why? so i can take a long surface interval and calculate my next dive using the tables.

i know this is not SOP, but i feel comfortable using the max values for my last dive and planning accordingly for the next dive by using the tables.

 

[lamont]

When you dive, if your computer stops working for whatever reason, do you stop diving? If you are conversant with the dive tables and can calculate bottom times with a bottom timer/dive watch, would you continue to dive? This has not happened to me, but I have experienced water in my PDC before getting it to seal. This did not appear to affect the operation of my computer, but when it had water in the battery compartment I was "working" at about 10-12 feet drilling some holes. Hopefully I can ask the next question without starting a flame war of one agency vs another. The dive center I received my cert from teaches with SDI as the certifying agency. They do teach the tables (lightly) but IMO teach the use of dive computers as a primary dive tool in regards to dive/bottom times. I am only certified as OW at this point, so please keep that in mind. I am not talking about technical diving or going below 60 feet.

At 60 feet, your NDL time on air is 55 minutes. On nitrox, or shallower on air, you will have even more time. Unless your dive times are longer than that, you're unlikely to actually hit your NDLs. Even assuming total failure of your dive computer so that you don't know depth or time, you can still continue a dive given your dive buddies working gauge -- provided that the discrepancy in your depths is not too great, and your dive buddies computer (assuming the same deco model) should be within a few minutes of where yours would be if it were working. Moving up to 30-40 fsw and continuing on the dive will give you an extremely long amount of NDL time. The bigger question in my mind, assuming total failure of the computer so you didn't know your depth, would be reserving enough gas to get back to the upline so that you had some kind of visual reference to ascend and do your stop on.

 

[NadMat]

I currently dive without a computer at all for most of my simple local dives. When I rent a computer I have my pressure and depth gauge in my console and still have watch on wrist in addition to the rented computer. And I always figure my dive plan with tables beforehand anyway, just sheer force of habit. So I would finish my dive within my planned table dive limits. It may shorten my dive, but usually won't end it unless it happens near planned end of dive.
just my 2psi

 

[jeckyll]

That's the exact reason that I carry an analog dive watch as well as an analog, burdon-tube based, depth gauge as backups for my computer.

Pre-dive 2 I do a check on the computer in plan mode to see what NDL I have at the max depth for dive 2 and will simply exit the water before that time is up should I experience a computer failure.

Obviously with that method there would be no dive #3 but I've never done 3 dives in one day so that's not really a concern.

YMMV

Bjorn

 

[Mantasscareme]

I've had a computer fail at the very start of the dive. Solution: I did my best to stay level with my dive buddy and went by what his computer said, since mine isn't air itegrated, I still had full use of my guages. Now I realize how potentially dangerous that situation was (bad diver! bad diver!). Now whenever I dive, I always carry a spare between myself and my buddy. If one of the two computers fails to activate when we hit the water, the diver with faulty computer gets the spare.

 

[jeckyll]

How is carrying a spare between 2 divers in case of a failure different than diving your buddies computer if yours fails? I'm just curious as I don't really see the big difference unless you both carry a spare...

 

[Mantasscareme]

Well, every time a computer's failed me, (twice so far), it was on the initial descent. The spare just changes hands before there is any difference in depth between myself and my buddy (assuming that its the first dive of the day so there is no difference in residual nitrogen). If the computer fails later in the dive, or it's the second dive of day, then the spare would not help and the dive is aborted. I definately don't recommend trying to transfer a spare if there's already been a difference in depth between the buddy pair. I never push my no-deco limits anyway, that adds another margin of safety