Newbie dive computer question

[firerescue434]

all,
I am very new to all of this, have only had my cert. for a couple months, i was wondering if there were any dive computers that will give you the diving groups. (ie) you dive once, your a C diver, second dive you're an s diver. I thought that was the point of a dive computer, could someone please help me understand a little better, or was i just wrong on that assumption?
Thanks!

 

[Blackwood]

The above assumes there is one and only one dive table.

The repetitive groups between two tables aren't necessarily the same (or even close). Consider that PADI's no stop tables have 26 letter groups (I think), whereas IANTD's, for example, have 10.

It also assumes that computers run the same algorithm as tables. Generally speaking, they don't. They 'track' more compartments. Even if they worked off maximum depth (which they don't), the numbers wouldn't jive.


The main points common cited for computers are: ease and increase bottom time.

 

[DivingPrincessE]

I don't think any dive computers give you your pressure group ("diving group") but most (if not all) have an NDL indicator. Mine (Pro Plus 2) has a type of bar graph on the left. It is green for most, then a small orange section, then red. You monitor it and stay in the green, when you are close to or in the orange you end the dive. If you go into the orange you can do a deep stop (1/2 the depth of your deepest depth that dive) and extend your safety stop until you're in the green again. Easy peasy.

 

[Teamcasa]

I doubt any modern dive computers give you a table letter designation. Mine, like DPE, is a ProPlus 2 and tracks nitrogen loading by a series of dots on a colored scale. If I keep it in the green or sometimes even a touch in the yellow, I’m fine. If however, it goes into the red, the computer will force a decompression stop or it will go into a fault mode.

The bottom line is bottom time. Computers track your entire dive based on all of the time at depth averaging each, whereas the table assumes you were at max depth the entire dive.

In addition: Once you understand and get used to your computer, you will rarely look at a dive table again unless you have a computer failure. Once you chose a computer, spend time at the bottom of a pool and just play with it until you have a full understanding of its features and return to ScubaBoard for the inevitable questions.

 

[Mr Carcharodon]

all,
I am very new to all of this, have only had my cert. for a couple months, i was wondering if there were any dive computers that will give you the diving groups. (ie) you dive once, your a C diver, second dive you're an s diver. I thought that was the point of a dive computer, could someone please help me understand a little better, or was i just wrong on that assumption?
Thanks!

Generally speaking most dive computers will give remaining no decompression time. The dive tables assume a square profile, i.e. that you spent the entire dive at the max depth, but dive computers will calculate for a multi level dive. So for example if you spent 5 minutes at 90 feet and then spent an other 40 minutes at 40 feet the dive computer would give you a longer no decompression time than a table would. The letter groups are not very useful for many types of dives, but are simple and conservative so that is why they are the starting point for decompression management.

You can use the tables too to check the computer by reading out the max depth and dive time after the dive. But if the depth v. time profile was not square you the computer will think you have less residual nitrogen than the table does. And in fact you do have less residual nitrogen.

Also different computer manufactures use different no decompression limits, and to some degree the NDLs user adjustable by setting the "conservatism". That can lead to two divers on the same dive having significantly different NDLs..

 

[CoralSeaMan]

Most dive computers I am familiar with simply give the same general information as a table in a graphic form, for instance, yellow dots with a low nitrogen load or big red ones in a decompression mode. The computer replaces the table because it tracks information more precisely and takes less time. Even so, similar diving principles apply so you need to think about time at depth and surface intervals. Most importantly, you have to pay attention to the information they do provide and you have to remember these are theoretical models and not a guarantee that if you dive close to the margins you will not get hurt.

 

[JayJudge]

Most modern computers track actual depth, computing every few seconds/feet, to give a true time at depth and do computations off of that. On surface interval mode, they will allow you to see theoretically what your next profile can be, how long you have been out, etc. Some more advanced computers can be set conservative or liberal, some warn to do a safety stop while others do not. When purchasing a computer, get one that does the type of diving you are doing or will be doing in the near future. It is pointless, and can be dangerous, to get a muti gas computer if you are strictly doing non deco, air diving. I don't think there are very many that are strictly air, anymore, but, once you have decided on what computers have the features you want, post with questions about them- I'm sure someone has used that brand, etc.
-J

 

[fisheater]

In addition to tracking your theoretical nitrogen loading/off-gassing status with great precision (which the tables lump into a few letter-designated "pressure groups"), they will also allow you to plan your next dive with much greater precision than using a table.

Why not visit the website of some of the major dive computers and downloard their manuals? It's a great way to familiarize yourself with new gear and it costs nothing.

 

[Chernish]

A lot of dive computers have a "simulation dive" function that gives the NDL times for given depths, so you can plan your next dive.

As to "the point of dive computers", they are numerous. For example, they follow your profile more exactly than a table ever could, thus giving you extra bottom time. Depending on your actual profile, the gain can be very significant. Another example, since we are speaking about diving groups: they follow the nitrogen loads in all compartments, not only in one as in the diving groups of the tables.

Cheers!