Is there a Dive computer that gives you an ending pressure group?

[darry_99]

My wife has a Tusa IQ300 and I have a Oceanic Datamax. They are both ok to use. However, since we dont always stay at the max depth all the time, I am trying to figure out which computer to get next - something that actually calculates your ending pressure group based on your mutli-level dive profile.

Any recommendations are highly appreciated.

PS: I use the dive tables based on the info I get from my DC, but I dont think it is accurate / precise.

 

[PerroneFord]

Computers don't use pressure groups and if you want to reference the tables, then you really need to stick to diving the tables and just use the computers as backups. Trying to use both to plan your dives will be a lesson in frustration.

 

[wedivebc]

My wife has a Tusa IQ300 and I have a Oceanic Datamax. They are both ok to use. However, since we dont always stay at the max depth all the time, I am trying to figure out which computer to get next - something that actually calculates your ending pressure group based on your mutli-level dive profile.

Any recommendations are highly appreciated.

PS: I use the dive tables based on the info I get from my DC, but I dont think it is accurate / precise.

Ending pressure group is a method employed to allow you to calculate residual nitrogen loading for multiple dives when using tables. Pressure groups are not valid from one table to another and since a dive computer stores residual tissure loading from one dive to the next the pressure group value is meaningless.
I would suggest you look at a computer that uses similar algorithm to your wifes. I have looked at the Tusa DC Hunter as a decent dual mix nitrox computer. You will probably be able to share a data cable with her for computer downloads.

 

[darry_99]

Ending pressure group is a method employed to allow you to calculate residual nitrogen loading for multiple dives when using tables. Pressure groups are not valid from one table to another and since a dive computer stores residual tissure loading from one dive to the next the pressure group value is meaningless.
I would suggest you look at a computer that uses similar algorithm to your wifes. I have looked at the Tusa DC Hunter as a decent dual mix nitrox computer. You will probably be able to share a data cable with her for computer downloads.

wedivebc - Thank you for your explanation - although I am not sure I follow it completely. What I have been doing so far is looking at max depth, dive time, surface intervals from my computer and then using the tables to figure out the ending pressure group. How do you fill up the log book differently when using the computer?

Thanks!!

 

[SelkieDVM]

There's no reason you can't continue to do this. You can use either the table bottom time or the computer's. However since the computer calculates your nitrogen load based on your actually depths throughout the dive rather than max depth they will give you more bottom time which might put over the limit according to the tables. Not to say you actually are over the limit, it's just a matter of one method using a lot of rounding and the other being more exact. Also, as said previously, the computer will keep track of your previous dive info and limit the time for the next dive accordingly. Hope this helps?

 

[Dan Watkins]

Is there any reason why you want to log this pressure group?

Knowing your pressure group is neccessary when diving by tables, but one of the main reasons for using a computer is that it applies the appropriate amount of tissue loading for your actual various depths throughout your dive, and time spent there. For planning your next dive, your computer should have a function that shows you how long you can stay at various depths taking into account your current surface interval and your current tissue loading.

Computers and Tables essentially are doing the same thing, except the tables use a perfectly square profile, assuming all your dive time was at your max depth. Computers sample data throughout yoru entire dive so you don't have to use a table's square max depth pofile. Table pressure groups are not relevant when using a computer.

If for some reason your computer failed, then you want to simply use your max depth and use that pressure group to switch over to tables, but if you aren't switching to tables, why bother logging a table letter?

 

[darry_99]

Lilla & Dan,

Thanks for your replies - they help.

The reason I was calculating the ending pressure group was to fully fill up my log book. I guess that is not necessary when using a dive computer

 

[ReefHound]

Your logbook is to serve you, not vice versa. Don't feel compelled to fill out useless data because there is a blank for it and feel free to note important data even if there is not a blank for it.

 

[PCBCaptChris]

I wouldn't fill in the blank myself. However, if you really wanted to fill it in you could take the Max Depth and Time and Calculate from your computer up your Letter Group with the table of your choosing... IT wouldn't be particularly useful though... It might be good practice later for coming up with your residual nitrogen with a table...

 

[Bubbletrubble]

Darry_99,

Let me guess. Your dive logbook has an empty space for ending pressure group...and that's why you feel compelled to fill it out. If you have a dive computer, you should just leave that space empty...like the rest of us. I remember when I first switched from diving tables to using a dive computer. I felt the same way. Let it go. Enjoy the diving.

There really isn't a good way to get your ending pressure group from a dive computer. I guess that, immediately following a dive, you could enter the "Plan" mode of your dive computer which will display your NDLs for given depths...and then match this up with the adjusted NDLs listed on the Repetitive Dive Timetable. For instance, immediately after you finished your first dive, if your dive computer Plan mode said that your NDLs were 55 min at 40 fsw, 20 min at 50 fsw, 8 min at 60 fsw, and 2 min at 70 fsw...then the ending pressure group of your first dive was probably Group S.

Also, I would heed the advice of wedivebc regarding getting a dive computer that has an identical/similar algorithm as your wife's. It'll definitely make things easier for you when you dive together.

Edit: I just saw your last post, Darry_99. Glad that you figured things out.