Computer dies, why can’t I continue to dive on tables?

[UCFKnightDiver]

I don’t recall this being discussed in previous threads. I have had my dive computer die (or more commonly I forget to set the oxygen level and it reverts to 50% during a dive past 70 feet and locks me out for 24 hours).

I do NOT carry a redundant computer and I am not going to forgo diving for the next day. What I normally do is remove the battery and reboot the computer and start “fresh” and continue to dive for the remainder of the day. I make accommodations for the repetitive dive(s) by punching in a much lower nitrox mix and taking long surface intervals, longer safety stops and not going into deco on the computer, plus I use common sense on what I know are reasonable dive times. I know this is a dangerous practice and IS NOT RECOMMENDED by any agency, I’m sure.

I have been wondering if the following would be a safer and more reasonable approach to the situation:

Lets say you get down on a dive and find that your computer is going wacko. You know you are not in deco and you immediately ascend and do a normal (and maybe an extra) safety stop(s).

Now you break out the dive tables and assume that this dive was to the maximum no-deco limit for the maximum depth that you attained. (If you were not doing a square profile, maybe you should choose a more representative depth to represent your last dive). Then you use the dive tables and figure that the dive you just completed was to the no-deco limit for that depth. Now you plan the remainder of the day’s dives under this assumption and simply follow the tables. I would also take a peak at what my buddy’s computer says about subsequent dives and also not push the no-deco limits on the tables.

I know that this is not going to ever be a recommended practice, but it seems like a reasonable procedure to follow, Is it better than re-booting the computer and totally winging it, like I do now?

Diving with a buddy solves many issues that you have come up with. You can get dive info from your buddys computer, and use it to plan the next dive for yourself.

 

[goonsquad]

So, i don't have a computer and just use tables so my question is, do you guys who use computers primarily, not plan a dive and know your times? Why can't you just review your times and depths do the math on a table board and then plan accordingly?

Aren't the computer times based mainly off the same hard data, its just doing the math for you, right?
I'm a full on newbie so I'm just asking the stupid questions. Mainly because I don't understand why if the automated system goes down, the manual system no longer works.

 

[dumpsterDiver]

So, i don't have a computer and just use tables so my question is, do you guys who use computers primarily, not plan a dive and know your times? Why can't you just review your times and depths do the math on a table board and then plan accordingly?

Aren't the computer times based mainly off the same hard data, its just doing the math for you, right?
I'm a full on newbie so I'm just asking the stupid questions. Mainly because I don't understand why if the automated system goes down, the manual system no longer works.

Some of us who have done so many dives by following a computer, don't normally check with dive tables and very few people are using a computer and following along and logging dives and concurrently reviewing comparing the tables versus computers. I myself have a decent idea of what the no-deco limits are for various depths and even for repetative dives, so i am not blindly trusting the computer.

One of the problems is that if you do multilevel dives the computer will give you much more time than a sqaure profile table schedule, so the utility of comparing the tables versus computer is sometimes no better than a gut feeling for an experienced diver.

 

[gcbryan]

To respond to the OP I would say that's a reasonable approach depending on circumstances (using tables not resetting the computer).

For someone who dives a lot and under similar circumstances it works better than some other scenario. You dive a lot I believe and you spearfish and probably do similar dives/profiles frequently.

Even without a computer (just using a depth gauge and time) you would probably be OK if you just do what you always do. If you always do several dives with a similar depth/time profile then you can still do them without a computer and the results will be the same.

Just be more conservative until 24 hours is up and you have your computer back.

If it was a newer diver we were talking about then this isn't a very good idea because they don't have a common profile or the experience to know what the underlying factors are (don't know what risks they are taking).

 

[RTee]

I found very interesting the info gathered throughout the posts as I agree with a lot of them. One of the first thing I did when I got my computer was to use the average depth it provides me at the end of the dive and see if it is being used by the computer to calculate my next BDL based on the contemplated dive profile...and it does. Therefore, this, as a minimum, should provide me, with the necessary info, with the help of my logbook) to revert to the tables and keep diving.

Diving buddy...another great source...for most people, i.e. if you stick to same buddy and dive same profiles, then numbers should be the same as long as mixture and recent history are also coinciding.

Using the dive as if you have planned it with tables could either work great or fail miserably as your dive could have been a multi level one which, when using the table with all the time spent at the max depth no longer within NDL...hence perhaps reverting to the worst group...Z and starting the table planning sequence from there could be very safe indeed and prevent sitting a full day out and overindulging in margueritas...

As for 02 toxicity...your dive plan for the previous day (logbook) to properly track where you were so you could still enjoy diving.

As I wrote in an earlier post on another subject, I got my OW cert back in 78 when technology was not what it is today. While I do my utmost to further my knowledge of diving and appropriately use all the tools that are out there, the fact remain there are still tools and should not prevent me from doing what I want when alternate methods or tools are available.

 

[kanonfodr]

Interesting topic as I found myself in a similar situation this week: left the computer at the house. It wasn't much of an issue since we were single tank diving on shallow reefs but it makes a strong argument for depth averaging and table knowledge within the team.

While I highly advise getting training that emphasizes depth averaging for your own safety, the concept of it is not difficult. I had my computer with me yesterday and my own average I did in my head differed from my computer's by two feet on the deeper side. Not bad for keeping track of a 93 minute dive. It does require vigilance on the part of the diver, which I am unsure if every diver is truly willing to commit to.

Peace,
Greg

 

[halocline]

I usually carry the PADI wheel specifically for this purpose. It does decent multi level calculations.

How safe any of this is depends on how aggressive the profiles are. I'd gladly dive without a computer in many situations where I'm familiar with the profiles and know that they are nowhere near NDLs. Using a buddy's computer for information is just as safe with regards to DCS as using your own IF you're diving the same profile and it is far from pushing limits. It's when you start getting closer to NDLs and/or O2 limits that guesstimating becomes a lot more dangerous.

Another option on the dive where your computer fails (and subsequent ones if you're guesstimating) is to do a longer shallow stop. No matter what the source or accuracy of your dive data is, doing an extended stop on an aggressive recreational profile is probably a good way to provide some additional cushion.

The computer only provides data; it's the profile management that determines the safety of the dive.

 

[The Chairman]

Please. Never, ever, ever reset your PDC to continue diving. Don't introduce a new computer in the mix either. Without your recent dive history to determine residual nitrogen, you are asking for problems.

If you had enough situational awareness to know your max depth and times, then going on tables makes sense. Garnering the info from your buddy(ies) also makes sense. If you don't have tables, then the rule of 120/140 works for me.

If you stuck with your buddy during the previous dives, then following their PDC on subsequent dives also makes sense. Just be sure to really stick with them and their profile.

Experience can make a huge difference in your comfort level diving without a PDC. You, and only you can make the final decision about what YOU are comfortable doing. I can tell you what I am comfortable doing, but you can't blindly rely on my experiences. Dive within your training and experience level and don't take chances, and please, please don't reset your PDC to continue diving.

 

[East West]

Goonsquad you got it right , but who can do the math when you have V Planner . Take away are computers and most of us are grounded . I lost my computer and did not own a bottom timer or depth Gage which now is on the top of my list to purchase .

 

[EzeeDiver]

I don’t recall this being discussed in previous threads. I have had my dive computer die (or more commonly I forget to set the oxygen level and it reverts to 50% during a dive past 70 feet and locks me out for 24 hours).

I do NOT carry a redundant computer and I am not going to forgo diving for the next day. What I normally do is remove the battery and reboot the computer and start “fresh” and continue to dive for the remainder of the day. I make accommodations for the repetitive dive(s) by punching in a much lower nitrox mix and taking long surface intervals, longer safety stops and not going into deco on the computer, plus I use common sense on what I know are reasonable dive times. I know this is a dangerous practice and IS NOT RECOMMENDED by any agency, I’m sure.

I have been wondering if the following would be a safer and more reasonable approach to the situation:

Lets say you get down on a dive and find that your computer is going wacko. You know you are not in deco and you immediately ascend and do a normal (and maybe an extra) safety stop(s).

Now you break out the dive tables and assume that this dive was to the maximum no-deco limit for the maximum depth that you attained. (If you were not doing a square profile, maybe you should choose a more representative depth to represent your last dive). Then you use the dive tables and figure that the dive you just completed was to the no-deco limit for that depth. Now you plan the remainder of the day’s dives under this assumption and simply follow the tables. I would also take a peak at what my buddy’s computer says about subsequent dives and also not push the no-deco limits on the tables.

I know that this is not going to ever be a recommended practice, but it seems like a reasonable procedure to follow, Is it better than re-booting the computer and totally winging it, like I do now?

Definitely and interesting question. I had something similar happen on a trip to Belize last year. I did the quick battery replacement and looong surface interval, followed by 18+ hours out of water. Now, this was based on the following information from my Wisdom 2 manual (see attached photo). No ill effects, hasn't happened again and definitely a lesson learned.

Anyone else's computer function this way?

Also, if this happens say, in the middle of the trip, could you not go back to dive 1 of the trip in your log book (hard copy) and calculate repetitive N2 loading with tables? This should give you a good idea of where you are. Should be more conservative than the real time capability of the dive computer...(flame suit on if I'm off here...)