Incident due to battery change on dive computer

[AfterDark]

I really don't get this at all; many like myself dove years maybe decades without computers. I for one have never been bent, as least not so bad that I noticed. I bought a computer about 4 years ago, I just bought a second of the same kind this year for a backup, something you the OP should consider if you are going to stake your safety on a less than reliable device and power supply, you should at least have two! I never dive without tables they are a part of my dive gear, the computers may stay home, the tables never do.

Think about giving yourself an advantage, learn and use the tables. Safe diving.

 

[Hawkwood]

...

Think about giving yourself an advantage, learn and use the tables. Safe diving.

If I may add..."learn and use the tables properly".

 

[AfterDark]

If I may add..."learn and use the tables properly".

You may, but if one learns them then proper execution is understood as part of use.

 

[underH2Oman]

I think your experience reminds me the most of the 5-P's. (Prior Planning Prevents Poor Performance)
IMO you should enter the water with the plan and exit according to the plan. Feel free to use a computer but remember the computer you wear is only calculating for the person wearing it. Switching to a different computer or not understanding what it is telling you can cause problems. Read the manual.

I am glad you did not become a statistic but also think you may have been nearly one. If your computer was violated you should have never entered the water for the second dive.

Knowing that your computer does multi level calculations and tables do square profiling switching between them is like making your own dive tables.
I reviewed the PADI dive table based on the information you provided and numbers show;

your 1st dive to 93ft for 46 minutes- PADI tables have the max time before required deco at 20 minutes your dive over doubled that.I do not know if PADI produces tables for your profile.

According to the US navy air tables your dive required 47 minutes of deco at 20ft for that dive. after your surface interval 1.75hrs and conducting the 2nd dive to 80ft for 39min you would require 1min at 30ft and 147 at 20 ft.

If you started your ascending at the 20 minute mark the required deco could have been reduced to 77min at 20 ft.

 

[boulderjohn]

Your 1st dive to 93ft for 46 minutes- PADI tables have the max time before required deco at 20 minutes your dive over doubled that.I do not know if PADI produces tables for your profile.

It doesn't. If he was following the PADI tables for that dive, he should have done a very long safety stop and then been out of the water for 24 hours.

If one takes the OW course based on computers, one is taught that all computers have certain features and perform certain tasks. One is taught to find how to use those features and perform those tasks for their specific computerlbefore diving it. One of the things you are taught is to take a glance at the computer regularly during the dive. The amount of deco that the computer required for that dive is SIGNIFICANT. That computer should have been making it very clear that this significant requirement was being earned while the diver was in the dive, and the diver should have seen it and started up before it came to that. Another thing that would be taught in the course and made clear in the manual is that ignoring the computer's deco obligation will result in it going into gauge mode for a period of time--locking you out for the second dive. If you decide that you know more than the computer (and that can be a valid decision), you should be aware of the consequences and be ready to live with them.

Another feature all computers have relates to something stated in one of the responses--they can plan a square profile dive, just as a table can. They all have a dive planning feature that allows you to enter a planned depth and get a maximum amount of time at that depth. If it is your second or third dive of the day, it will include those dives and the surface intervals in that calculation.

If you are going to use a computer as a guide for your dives, you really need to know how to use it, and you can't be ignoring it unless you are very much positive you know what you are doing and are willing to accept the consequences, both with your body and with future computer functioning.

 

[Asteve]

After changing the battery on my dive computer I had to reset the date/time and units of measure but forgot to change the Personal Safety Factor to "Medium" (the default is Personal Safety Factor 2). Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) that was identical to one done in December without issue. The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes (did that) and another at 10 feet for 31 minutes. I realized at that point what happened and only did three minutes at 15 feet. This was the first time ever that the computer told me I was in deco so had no prior experience. With Personal Safety Factor 2 the bottom time is roughly cut in half. A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes.

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer. 20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco.

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet. The dive tables said that we probably went into deco on the second dive and should not have spend more than 10-15 minutes there. I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same. Lost quite a bit of sleep that night and decided that was never going to happen again.

My first thinking is this is a troll or April fool joke, or I have got off my Med's again.

1. Read the manual of your dive computer.
2. If you are going to dive off someone else computer read the Manual.
3. Read the manual.
4.You have 1,000 to 2,499 dives and you are still alive?
5. The computer calls for 31 minutes stop at 10 feet so you only do the minimum safety stop, Did you have air to do more.
6. Following the leader is a sure way to get hurt.
7. You did not know the computer would lock you out, read the the manual.
8. Did any one pull out dive tables for the second dives or look at the first dive and plan the second dive.
9. Would the computer even let you set it to the correct safety factor after the first dive.
10. I do not even know where to start on the second dive, but I would find different people to dive with.

 

[Peter Guy]

A couple of comments:

a. Where did you get the 70 Ft average depth -- calculated or from the computer at the end of the dive. If that, then your "dive" would have had a deeper average depth as the "dive" does not include the final ascent. My guess is that you had gone over anyone's NDLs by the time you started your ascent.

b. Learning Dive Tables vs. Computers -- way too many threads on this and all the comments are the same. As for me, go ahead and dive your computer but: 1. Don't "ride" the NDL on your computer; and 2. Learn a simple method for guesstimating your NDL -- even if it is the "rule of 120 (or 130 on 32%)" -- that is, your NDL time and depth = 120 -- which for 70 feet means 50 minutes -- MAX. This simple rule of thumb allows you to do some basic dive planning and watch to see if the information you are getting from your computer makes sense. (And yes, there are many other, perhaps more accurate and/or sophisticated ways of mentally doing NDL planning/diving -- Minimum Deco being one of them.)

 

[jcaplins]

Is it possible for you to download the data from the computer and then upload it here or display a picture of the profile? For both dives?
I would guess that the dive was not 46 minutes at 93 or 70 feet. But rather average was 70 feet, and it was 46 minutes total ( from splash to ladder).

Decent/ascent rate, decent/ascent profile, max bottom time, time at stops... are all important to get a true picture of the risks for the dives.

 

[Wookie]

Not necessarily. SDI OW doesn't teach tables (unless the instructor chooses to go above and beyond the standards) and PADI OW also has that option as well now.

And what does this say about the dive industry and dive training? Only another reason I don't teach introductory classes.

 

[DiveNav]

.... Did a wreck dive to a maximum of 93 feet (70 feet average for 46 minutes) ...... A look at the PADI dive table said we were at the limit but not into deco with 70 feet/46 minutes. ...

If You use the PADI tables you should use the maximum depth (rounded up) and not the average depth. 100ft for 46 minutes .... way into deco for PADI.... No more diving for 24 hours.

..... Did a second dive 1-3/4 hours later ...... I called the dive and we ascended from 80 feet ....

See above.

Your dive computer told you the right thing.

I suggest you put in divePAL the dive profiles of those 2 dives so you can analyze them further and see how aggressive your were.
As I said multiple times, it is not a dive computer that makes a dive aggressive or conservative. It is the dive profile (and the gas mix being used).