Computer vs tables

[TSandM]

To be absolutely honest with you, I use gauge mode a) because I feel I can do so safely, and b) because it gives me the information I really WANT (depth and dive time) in the biggest numbers in the center of my screen. In computer mode, my computers put the dive time in tiny numbers in the bottom right-hand corner, because it's not really important, is it? What's important is your NDL time remaining, which has the big number/center screen position. That annoys me, so I use the display that gives me the information I want and use where it's easiest to see.

On our trip to Cozumel this spring, I did put the computer back in computer mode because of the amount of diving we were going to be doing, and the depths involved. The second day, I forgot to set it for 32% and bent it (and my backup, which was in my pocket, which I also forgot to set). That was the end of computer mode for me.

 

[RS]

Hey TS&M,

Shouldn't your avatar have confetti and a big glass of champagne??

 

[Pumpkin King]

Theoretical Dive: Wreck in 100'. Planned visits are the hull at 80', the deck at 60', and the bridge at 30'. For ease of calculations, plan for 10 minutes at each site. We also are assuming this is the first dive with no nitrogen buildup to begin with. Dive 1 is using a completely square profile, Dive 2 is using my 0:00 SI method. These use the RDP.

Dive 1: 80' for 30 min. = PG R (which is actually the NDL for 80'.)

Dive 2A: 80' for 10 min. = PG C
0:00 SI leaves 14 min. RNT at 60'
Dive 2B: 60' for 24 min. (14+10) = PG I
0:00 SI leaves 48 min. RNT at 35'
Dive 2C: 35' for 58 min. (48+10) = PG L

Credit is obviously being given for something, as at the end of the dives, there is a PG difference of 6. My question is whether this credit comes from somewhere we don't want it to or not. Can anybody with software/computer run this and see if it cries?

 

[TSandM]

I don't have a deco program to run it through, but your ten minutes at 35 feet is going to be offgassing most of your faster compartments that picked up nitrogen during the deeper phases of the dive. In effect, it's a decompression stop. I'm sure this is why you end up in a lower pressure group, compared with considering that the whole dive was spent at 80 feet, where you would be ongassing continuously until you began your ascent.

I would do that dive by depth averaging the 80 and 60 foot segments for a 70 foot average. They're close enough depths that I wouldn't weight it for the deeper segment. I have 35 minutes by tables at 70 feet on AIR, but I'd be on 32%, so my EAD is actually about 56 fsw, which I would consider 60. At 60 feet, I have 50 minutes. Twenty is well within my boundaries. I'd consider the 35 foot segment as the beginning of my minimum deco. I'll spend as much time as I want above 30 feet if I have enough gas, because the NDLs at that depth are functionally infinite and you are offgassing almost all compartments by the time you get up there. The longer you sit in the shallows (at least within the limits of my cold tolerance) the cleaner you are when you surface.

 

[Blackwood]

If the GUE/DIR method of tracking NDL is more conservative than the computer,
(which is what I think you said in an earlier post) why put the computer in gauge mode?
Especially when doing NoDECO diving on unfamiliar sites?

Why not keep it enabled and simply ignore the NDL stuff and use it as a backup
to your mental calculations in case you make a mistake?

--- bill

In addition to TS&M's answer regarding how information is displayed on her computer, I'll note that, as far as I know, that computer (Uwatec TEC2G) will NOT display real-time average depth when in the default (computer) mode.

So in order to use it as you suggest (backup to her mental average depth calcs), it MUST be in gauge mode.

The longer you sit in the shallows (at least within the limits of my cold tolerance) the cleaner you are when you surface.

To a point.

 

[TSandM]

To any point where my thermal tolerance will permit me to stay in the water, anyway!

I hadn't noticed that about the Tec 2g. I haven't had a chance to dive it yet, because I've been fighting a miserable cold since Christmas Day. The computer I have been using is a Vytec.

 

[gcbryan]

Gray, you're so right. The vast majority of my diving locally is done at only a few sites, and the profiles are so familiar to me that I could do them without a depth gauge if I had to

The place where it gets more important is with repetitive dive, repetitive day trips. Then you really have to start thinking about what you're doing. Travelling and doing dives outside of your accustomed profiles requires some careful thought, too.

What you say is true however wrecks that aren't too destroyed are similar to walls in a multi-level way and if your personal limit at home is 100 fsw for example then it will be your limit regardless of where you go. It does take some thinking of course especially repetitive dives but if one doesn't make them too repetitive (being conservative) then that's not much different than home. You dive every day at home as well don't you.

 

[amascuba]

In addition to TS&M's answer regarding how information is displayed on her computer, I'll note that, as far as I know, that computer (Uwatec TEC2G) will NOT display real-time average depth when in the default (computer) mode.

So in order to use it as you suggest (backup to her mental average depth calcs), it MUST be in gauge mode.



To a point.

Yup. The Uwatec Tec and Tec 2G both only do depth averaging in gauge mode.

I accidentally left my tec 2g in computer mode on 21% for my dives yesterday.. oops. I had been playing with the different features on it the week before... I just watched the depth and run time.. I ignored everything else that it was showing.

 

[PCBCaptChris]

A dive computer is just like any other piece of technology. If it works, it can make your experience easier, and in some cases safer. Back in the day dive computers were on the razor edge of safety. Now-a-days they have been "stepped off" a considerable amount and are much more conservative. Add to that the non-mandatory decompression stop for 3-5 minutes that most computers count down for their novice users it is even more conservative. Yet, a computer may still allow an inexperienced person to be less attentive during a dive and have a dive the is not as safe as it would otherwise be. Again, a dive computer is just like any other piece of technology. If you learn how to use it and understand the principles behind it, it can increase your awareness of what is going on around you. Depth averaging is a technique that has it's merits. It does allow on, on a piece of paper, to illustrate in a concrete fashion what is going on. I would go so far as to say that it would be a good idea for everyone that uses a dive computer to understand depth averaging. I just don't believe it is essential to do every dive.

I dive constantly. If I were to do depth averaging every dive it would just take a couple of seconds each time. However, I don't believe, given my education, training, and experience, that it is going to make me more attentive to the situation at hand. So, here is my dangerous statement: I'll trust in my computer. Knowing that I understand and am aware of what is going on enough that I can bail myself out when(not if) it dies.

 

[gcbryan]

I'll be dangerous as well...I wear a computer and ignore all but the depth/time for the most part but when I happen to see the NDL information it doesn't make my eyes fall out

I dive the same way regardless of what the computer is displaying. I do wear a backup computer in gauge mode for several reasons one of which is if I incur a small deco obligation on my computer it stops displaying runtime without pushing buttons so I just refer to the gauge mode computer for that info.