Incident due to battery change on dive computer

[stuartv]

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

Well, is it better to have a diver that does not know how to use tables and so they actually do what their computer tells them? Or a diver who thinks they know how to use tables (because they were trained on them at some point, however many years ago), ignores their computer, and then totally blows a deco obligation?

I'm very new, so I could have a totally skewed perception, but it doesn't seem like there are many people getting bent from doing what their computer says to do. It seems to me that if people follow their training, they'll be fine, whether they use a PDC or tables. If they don't follow their training, it also doesn't matter whether they use a PDC or tables. And, it's easier to use a computer correctly than it is to use tables correctly.

For someone who drives a car, it might be legit to make them learn how to ride a motorcycle, too, as a backup. But, if they're going to drive the car for the next 2 years and never ride a motorcycle, is it REALLY better to give them the idea that they COULD if they need to? I am quite confident in saying that EVERYONE is safer if nobody ever takes a class on how to ride a motorcycle, then doesn't ride for 2 years, then hops on one and hits the city streets.

 

[Lorenzoid]

Planning or lack thereof aside ...

... The dive computer decided that I went into deco and demanded a stop ....

Computers don't do that without warning. As far as I know, all computers compute and display "no-deco time remaining"--that's their main function. When you saw that number heading toward zero more rapidly than someone with your level of experience might expect, why didn't you start ascending? You can hardly blame the computer for you being unaware that the computer has a conservative default setting.

 

[AfterDark]

Well, is it better to have a diver that does not know how to use tables and so they actually do what their computer tells them? Or a diver who thinks they know how to use tables (because they were trained on them at some point, however many years ago), ignores their computer, and then totally blows a deco obligation?

I'm very new, so I could have a totally skewed perception, but it doesn't seem like there are many people getting bent from doing what their computer says to do. It seems to me that if people follow their training, they'll be fine, whether they use a PDC or tables. If they don't follow their training, it also doesn't matter whether they use a PDC or tables. And, it's easier to use a computer correctly than it is to use tables correctly.

For someone who drives a car, it might be legit to make them learn how to ride a motorcycle, too, as a backup. But, if they're going to drive the car for the next 2 years and never ride a motorcycle, is it REALLY better to give them the idea that they COULD if they need to? I am quite confident in saying that EVERYONE is safer if nobody ever takes a class on how to ride a motorcycle, then doesn't ride for 2 years, then hops on one and hits the city streets.

More like learning to drive a stick just in case, during an emergency, a car with a stick shift is the only car you have access to.

 

[kwinter]

I think the most telling part of this story is that the OP seems to think the problem came from not putting into the computer a more aggressive profile factor than the default. As if to say that the computer algorithm changes the physiology. I have a problem with the philosophy of altering conservativism just to meet the desire to not have required deco.


iPhone. iTypo. iApologize.

 

[BRT]

Except for shore diving I have never done a dive in Cozumel that the Padi tables would not have had me in decompression. I have never been in decompression by my computer. I have never known myself to have DCS. I suspect there are a lot like me. Kind of makes the tables look foolish in the computer age.

 

[Bert van den Berg]

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.

Hi jc,

The first dive profile is attached. The computer would not log the second dive since it was unwilling/unable to do the deco calcs.

From the profile I concluded that it would be equivalent of spending the entire 46 minutes at 70 feet which according to PADI is not a deco dive (on the edge but not over) and would have put me into dive group C after 1-3/4 hours.

I appreciate everyone's efforts in responding but some of the people responding have not read my original posting as carefully as they should have. The computer told me that the first dive put me into deco because it defaulted to ultra conservative mode after a battery change. I did read the user manual three years ago but the user manual does not tell you that the Personal Safety Factor defaults to ultra conservative mode when you change the battery. The same identical dive on the same computer set to "average" conservatism previously did not put me into deco.

Cheers,

Bert

 

[rhwestfall]

from pure tables (square profile) - that is a 95' dive for 40 minutes.... DECO! In reality, something different.....

0-3 minutes - descent to 95'
3-5 minutes @ 95'
5-6 minutes - ascent to 66'
6-40 minutes @ 66'
40-48 minutes ascent to SS & Surface....

Lets see if Alberto can quickly put it into DivePal or someone can input it into something else.....

 

[KenGordon]

30/70gf gives about 24 minutes of stops, vpm-b 3 8 minutes and -2 5 minutes.

 

[boulderjohn]

Hi jc,

The first dive profile is attached. The computer would not log the second dive since it was unwilling/unable to do the deco calcs.

From the profile I concluded that it would be equivalent of spending the entire 46 minutes at 70 feet which according to PADI is not a deco dive (on the edge but not over) and would have put me into dive group C after 1-3/4 hours.

I appreciate everyone's efforts in responding but some of the people responding have not read my original posting as carefully as they should have. The computer told me that the first dive put me into deco because it defaulted to ultra conservative mode after a battery change. I did read the user manual three years ago but the user manual does not tell you that the Personal Safety Factor defaults to ultra conservative mode when you change the battery. The same identical dive on the same computer set to "average" conservatism previously did not put me into deco.

Cheers,

Bert

View attachment 206247

That's not how the PADI table works. To use it appropriately, you go with the maximum depth. But I'll play the game for a minute. Here's another way to look at your graph from a PADI table point of view.

1. You did a 7 minute dive to 100 feet followed by no safety stop (required at that depth) and no surface interval. That puts you at least into dive group C at the time you reach 70 feet.
2. In dive group C, you have 28 minutes maximum at 70 feet. You did roughly 33 minutes until you began your ascent from 70 feet, putting you well into deco.
3. The PADI tables are based upon the assumption that the diver will make a 60 FPM ascent rate. If you go slower than that, you are actually adding to your bottom time. The ascent to your safety stop should have taken you less than a minute, but it took you about 6 minutes. That means you further overstayed your bottom time and added to your decompression obligation.

But then, you weren't using the tables--you were using the computer. Except you ignored it and decided on your own that you were OK.

 

[stuartv]

[/I]
More like learning to drive a stick just in case, during an emergency, a car with a stick shift is the only car you have access to.

You think computer versus tables is more analogous to car-with-auto versus car-with-stick? Auto vs stick seems like Rec PDC versus Tech PDC (in Tech mode).

Riding a motorcycle is a totally different skillset to accomplish the same end as driving a car (i.e. getting from A to B). Using tables is a totally different skillset to accomplish the same end as using a PDC (i.e. diving without exceeding NDLs).

I don't see any reason whatsoever to require people to demonstrate proficiency in operating a motorcycle in order to be licensed to drive a car.

I also don't see any reason to require people to demonstrate proficiency in diving using tables in order to be able to do Recreational diving using a PDC. If they follow their training, the worst thing that will happen is that they will miss out on some diving when their computer croaks and they don't have a backup. And if they don't follow their training, it doesn't really matter what tool they were using. If they aren't going to pay attention to their computer and ascend when it tells them, surely you don't think they will carry a note of (or remember) what their NDL time is and then pay attention to that and a bottom timer, do you?