How to log comp dives?

[LI Diver]

On my recent trip to Bonaire I noticed on attempting to log my dives I could not rely on my computer to give me info to plot the pressure groups because of the multi-level nature of the dives. On the dives I planned it was fine but on the dives that were guided my plans based on the max depth from the briefing were useless because of the guide obviously using his computer to weave back up from our max depth. Of course I referred to my (air) computer on my wrist and not doing a trust me dive.BTW I was diving 32% nitrox and well aware of my max depth and total 02 exposure and using the aforementioned air only computer for an added safety level. My comp does not have a downloadable feature and when using max depth and time (square dive profile) was off the air charts.Do I just leave the pressure groups blank and note comp dives or do I need to invest and in and learn how to use a wheel which was not taught in my ow class. What do most people do. ???:huh:

 

[Walter]

Pressure groups are only used when diving tables, not when diving computers.

 

[TSandM]

I gave up logging pressure groups.

This problem really bothered me as I kept doing more and more shore dives -- all terrain-based, none of them the square profiles that tables assume, and many of them off the charts. I asked a bunch of questions about how you plan and how you evaluate such dives. What I came up with is that the interative procedures of a dive computer are probably the best way to do it. There are other strategies -- Diving the tables is ridiculously conservative; the wheel is cumbersome and becomes essentially unusable if the dive doesn't have more or less definable "levels"; mental depth averaging techniques require the diver to have developed meticulous dive monitoring procedures AND an understanding of decompression curves so that they know where depth averaging can be applied and where it cannot, and how to weight the averages, etc.

In other words, there's no perfect way. But you can't shove a wandering, terrain-based multi-level dive into a square table. Doesn't work.

 

[spectrum]

Ignore the pressure group entry in the log. Since you probably always dive with the computer you can make a note that covers dives going forward. You might think about logging the lowest NDL value as a reference. You can observe this as you leave the bottom or it may be retrievable.

If your computer has a dive planning mode use that to scroll through the allowable bottom times for subsequent dives. On the subsequent dives you can expect the similar extended dive times (over planning mode) if you are making a multi level dive.

Pete

 

[LI Diver]

Thanks everyone!

 

[mred]

What I do is use the rdp and log pressure groups based upon the deepest depth I achieved during the dive ... I do this more for practice using the rdp than any other reason ... at times it is actually fun to see the advantage the computer gives you when using it during a multiple level dive... WHAT have I found out however? is that 90 percent of the time I did not actually go over the table EVEN when doing four dives in a single day, and EVEN using ONLY the max depth achieved ...

I also dive nitrox, and enjoy doing the calculations ... When on nitrox I have NEVER gone over my tables ...

 

[Charlie99]

I have an Oceanic computer with a "tissue loading bargraph" where the bars show the loading relative to the M-value limit for the compartment closest to the limit.

Rather than pressure groups I routinely log how many bars showed on the bargraph.

On some dives I'll also note either the maximum number of bars reached during the dive; or or dives where I went slightly into deco, how many minutes of required 10' stop time were required before I started my slow ascent and deep stops.

On dives that significantly outside the normal profile --- i.e. a lot more time spent either deep or shallow than is normal, I'll note that fact and/or approximate average depth. This is to help me plan future dives if I return to that divesite.

 

[LI Diver]

What I do is use the rdp and log pressure groups based upon the deepest depth I achieved during the dive ... I do this more for practice using the rdp than any other reason ... at times it is actually fun to see the advantage the computer gives you when using it during a multiple level dive... WHAT have I found out however? is that 90 percent of the time I did not actually go over the table EVEN when doing four dives in a single day, and EVEN using ONLY the max depth achieved ...

I also dive nitrox, and enjoy doing the calculations ... When on nitrox I have NEVER gone over my tables ...

You must be diving a square profile like from a boat or surface swimming to an area where you can descend to your max depth fairly quickly and ascend in a slow but vertical line. In Bonaire we did a lot of shore diving where there was much to see while swimming to the drop off in 20-30fsw and then a fringing reef dropping down to about 100' with goodies all the way down but some specific to a certain depth. Then a sloping ascent back to 20' for off gassing and adding mucho time to our dives.

Ed

PS I also enjoy doing the calculations, just not during the actual dive.

 

[LI Diver]

I have an Oceanic computer with a "tissue loading bargraph" where the bars show the loading relative to the M-value limit for the compartment closest to the limit.

Rather than pressure groups I routinely log how many bars showed on the bargraph.

On some dives I'll also note either the maximum number of bars reached during the dive; or or dives where I went slightly into deco, how many minutes of required 10' stop time were required before I started my slow ascent and deep stops.

On dives that significantly outside the normal profile --- i.e. a lot more time spent either deep or shallow than is normal, I'll note that fact and/or approximate average depth. This is to help me plan future dives if I return to that divesite.

Thanks Charlie I was thinking of doing something similar. I have an Oceanic veo 100 and it shows bubbles I guess I could record how many bubbles and note at what depth I spent most time as well as how long at max.

 

[BabyDuck]

yeah, i log max and average from the computer. i used to figure out pressure group, mainly for tables practice, until i was off the ndl per the tables more than i was on them. that's the reality of using computers! hooray, we don't have to pretend we did a square profile!