Do you still calculate pressure groups if you use a computer?

[Squishy]

Hello all!
Just wondering if you still calculate the pressure groups in your dive logs if you dive with a computer? I understand that it is still good to know how to do it in case your computer fails, but as a general rule do you still do the calculations and note them in your log book?

Since getting my computer, I have not been calculating them. I log the depths, times, etc, though. Is that OK?

Thanks!
-Mike-

 

[Doc]

My wife does this. She works her tables and notes the number of pixels in her computer.

There is a very wide correlation, but not very predictable or usable. She notes her Pressure Group and pixels in her log book.

She insists on working the tables (even at dive #250), although by Tuesday of any given dive week, in theory- she is quite dead (as she doesn't sit out the 24 hour penalty for going into Group XZ or whatever that is way over in the corner on the other side of the plastic sheet thingie.) This makes the computation of the Pressure Group rather irrelevant as she breaks the penalty rule.

 

[wve]

It's your log book, so I imagine you can calculate them if you want to.

When I have time, I try to do so. Diving at altitude, as I often do, there are some extra maneuvers one has to go through when using tables.

The interesting thing is that I often find that because there is so much rounding when using the tables at altitude, my dives tend to go off the end of the tables, and I would not be able to make the dives that my computer allowed me to make.

Makes you appreciate the computer!

 

[yyidus]

I compute the pressure groups mostly out of habit and to fill out the log pages. It's a habit I picked up from my AOW instructor. It also keeps me in practice, and gives me an idea of the limits should I have computer issues.

One thing I've noticed is that on almost all my dives, I am beyond the limits of the tables (and have entered into 'must rush into decompression chamber'). I still fill it out and comment that I used a computer.

(no I'm not an insane diver.. it's just that usually my max depth is only used for a short part of the dive.... but according to the RDP, I have to use max depth for the entire dive -- I don't use 'the wheel').

 

[underwasser bolt]

I do the tables, but get ready for a lesson. You will be Z'd out on the tables even though the computer says you are fine. This becomes more pronounced if you do multiple dives over multiple days. The wheel is a bit better. I think it is good to know "how" to use tables, but there is little practical sense to do so if a computer is available.

 

[scubadiver888]

Hello all!
Just wondering if you still calculate the pressure groups in your dive logs if you dive with a computer? I understand that it is still good to know how to do it in case your computer fails, but as a general rule do you still do the calculations and note them in your log book?

Since getting my computer, I have not been calculating them. I log the depths, times, etc, though. Is that OK?

Thanks!
-Mike-

I only recently started using a dive computer so I still calculated my pressure groups. I also still bring along a dive watch and my tables. I've noticed on a few dives the computer said I was fine but the dive tables said I went outside the recommended time/depth. Mind you, the last dive I had like that, we started deep and slowly went shallow. For more than half the dive we were at 12 feet but we started at 60 feet.

I do it more out of interest. I think in the last 14 dives I violated the tables twice.

I'll keep using the tables. This way if my computer dies I can easily switch back to tables until I get it repaired or replaced.

 

[Thalassamania]

If I'm in a position where having my computer go down would screw up the work, I record the time of day and the scrolling no-D limits. That'll let me shift safety to tables with a minimum of fuss and lost time.

 

[emttim]

Hello all!
Just wondering if you still calculate the pressure groups in your dive logs if you dive with a computer? I understand that it is still good to know how to do it in case your computer fails, but as a general rule do you still do the calculations and note them in your log book?

Since getting my computer, I have not been calculating them. I log the depths, times, etc, though. Is that OK?

Thanks!
-Mike-

Good question, and one I've wondered about myself. I still calculate the pressure groups, but due to the fact that the tables involve lots of rounding, I have a feeling that on liveaboards and/or situations where I dive enough that the tables state I've violated NDLs even though my computer says I'm fine, I'll probably not calculate PGs and just leave that part blank on my log because as everyone else has said, tables aren't as accurate as dive computers when you change depths a lot during a dive.

 

[maged_mmh]

do it, just in case your computer quits

 

[Thalassamania]

Calculating the pressure groups will be a problem, recording the no-D limits is actually a much more accurate and useful approach. See Mike Emmerman's article and Phil Sharkey's comments in the AAUS Decompression Computer Workshop Proceedings.