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View Full Version : Tables VS Computer Diving.



jlwest63
07-15-2007, 19:53
Here is the problem. Me and the wife dive with a computer. Our dive profiles are well withen the limits acording to the computer. She comes home and logs her dives and figures her PG and starts saying how we should dive the tables and if we don't bad things could happen.
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<DIV>How do I explain that you either dive one or the other and that one won't translate toeach other?</DIV>
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<DIV>I do the tables so I won't lose that skill in case it is ever needed in the future but I want her to quit freaking out about it. </DIV>
<DIV>Thanks</DIV>

cummings66
07-15-2007, 21:09
Tell her the computer is calculating for every change in depth where the tables assume a max depth for the dive. The wheel would be closer and you could explain why the wheel would give more dive time as well. So, instead of the tables saying you did a dive to 100 feet for 10 minutes when in reality you hit 100 feet for 1 minute and came up, the computer will say you did 100 feet for 1 minute. That's one reason the computer gives you longer dive times. It is an on the fly instant computing type device.
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<DIV>The Wheel would be the next closest thing IMO to a computer. Tell her not to freak over the tables not agreeing with the computer times, they rarely will unless you dive square profiles which most don't.</DIV>

TxHockeyGuy
07-16-2007, 14:29
Tell her the computer is calculating for every change in depth where the tables assume a max depth for the dive. The wheel would be closer and you could explain why the wheel would give more dive time as well. So, instead of the tables saying you did a dive to 100 feet for 10 minutes when in reality you hit 100 feet for 1 minute and came up, the computer will say you did 100 feet for 1 minute. That's one reason the computer gives you longer dive times. It is an on the fly instant computing type device.
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<div>The Wheel would be the next closest thing IMO to a computer. Tell her not to freak over the tables not agreeing with the computer times, they rarely will unless you dive square profiles which most don't.</div>

If the above doesn't work, take a multilevel diver class with her.

jacewindu
07-16-2007, 15:25
there's no comparison between table and computer diving. if she doesn't understand the difference, you can explain by showing that the computer essentially calculates the tables many times per second, saving you bottom time.

jlwest63
07-16-2007, 20:00
I told her the same thing that you all said but she would question it. Now that you have said it she understands. Woman.... :)

kevinj1
07-16-2007, 20:08
I told her the same thing that you all said but she would question it. Now that you have said it she understands. Woman.... :)
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<DIV>LOLhttp://www.scubatoys.com/forum/smileys/smiley36.gif</DIV>

frankc420
07-16-2007, 20:24
In essence a dive computer is a human with a dive table in hand, calculating multiple dives and combining them as 1 dive based on your dive profile. I know that sounds wacky but that's how I look at it.

I'm sure someone on here will post that the above is completely ridiculous but we'll see! smileys/smiley4.gif

TommyB
07-16-2007, 21:41
<div>.. unless you dive square profiles ....

</div>

Can you explain this Square Profile thing.. I asked someone about it the other day, and they pretty much said "all dive a square".
I guess they did not understand what I was asking / what I meant..

Ie, you go down to 50 feet for 30 mins, next dive is to say 30 feet for 20 mins etc etc... He said that would graph out as a square profile on the log..
I guess he was thinking straight lines ????


Thanks

frankc420
07-16-2007, 21:53
<div>.. unless you dive square profiles ....

</div>

Can you explain this Square Profile thing.. I asked someone about it the other day, and they pretty much said "all dive a square".
I guess they did not understand what I was asking / what I meant..

Ie, you go down to 50 feet for 30 mins, next dive is to say 30 feet for 20 mins etc etc... He said that would graph out as a square profile on the log..
I guess he was thinking straight lines ????


Thanks




A square profile is what you get off of a standard dive table. You have a max depth and an NDL. Regardless of how long you stay at the max depth. If you were to plan a dive to 100' and the NDL was 10 minutes, even if you were at 100' for 1 minute, you could only stay under another 9 minutes.

cummings66
07-16-2007, 22:32
What I meant by diving a square profile is you go to the depth on the dive table and stay there for the time indicated (including the descent). The dive time basically starts from when you start down to when you start up. So if you get in, start down and take 3 minutes to get to 100 feet, stay there 7 minutes and come straight up to the safety stop that's a square profile to 100 feet for 10 minutes. Ascent time doesn't count.

TxHockeyGuy
07-17-2007, 10:34
<div>.. unless you dive square profiles ....

</div>

Can you explain this Square Profile thing.. I asked someone about it the other day, and they pretty much said "all dive a square".
I guess they did not understand what I was asking / what I meant..

Ie, you go down to 50 feet for 30 mins, next dive is to say 30 feet for 20 mins etc etc... He said that would graph out as a square profile on the log..
I guess he was thinking straight lines ????


Thanks




Others have answered this but I thought I'd throw my own version of the answer.

There are basically 2 different types of profiles. A square profile means you descend down to a depth, stay at that depth for the entire dive, and ascend at the end. A multilevel dive profile is where you descend down to say 100 ft and stay a while, ascend up to say 60 ft and stay a while, and then ascend again at the end. It is called multilevel because you are diving at multiple depths.

Standard dive tables only account for square profiles and do not give you any "credit" for being at a shallower depth for any part of your dive. So if you were diving tables to 100 ft you could only stay down as long as whatever number your table tells you for 100 ft even if you didn't spend the entire dive there. Computers on the other hand (there are also special tables to handle this too) will see that you have ascended, are no longer on gassing as much nitrogen, and will give you "credit" for being shallower. This is what allows you to extend your NDL (No Decompression Limit) and if you have enough air will allow you to stay down longer.

Does this or any of the other answers make sense?

CompuDude
07-18-2007, 23:17
Yes, TxHockeyGuy nailed it.

Standard tables treat all dives as square profiles, so even if you dive down to 80' for two minutes, you treat the entire dive as an 80' dive, even if you were there for two minutes and then ascended to 30' and spent the rest of your dive there.

Many tech dives are true square profile dives, such as a deep wreck where most of the action is at a given depth. That's when cutting special tables comes into play.

The majority of recreational dives, however, are multi-level dives, where you spend significant amounts of time at depths much different than the max depth. This is where computers really make a huge difference. Using the PADI wheel, it is also possible to calculate multi-level dives of a limited sort (much better than the standard square profile tables), but even that can't really handle a true multi-level dive such as one over a sloping reef where your depth changes considerably throughout the entire dive, and you need to know your planned (multiple) depths ahead of time, which isn't always practical.

These are the reasons why computers are so much more popular for recreational diving, and yet tables (special ones, however) are still used for technical diving.

przeor
07-19-2007, 00:49
Use the wheel! if nothing else, you can use it to hypnotize her to listening to what you say!

Joew
07-19-2007, 01:54
Use the wheel! if nothing else, you can use it to hypnotize her to listening to what you say!

I hate the wheel! I don't know why PADi and other organizations haven't ditched it yet now that computers are so popular. The dang thing costs $50. Thats a pretty good start on a computer, if you ask me.

CompuDude
07-19-2007, 02:25
Use the wheel! if nothing else, you can use it to hypnotize her to listening to what you say!

I hate the wheel! I don't know why PADi and other organizations haven't ditched it yet now that computers are so popular. The dang thing costs $50. Thats a pretty good start on a computer, if you ask me.
You can find used ones for $10 on ebay. :) Just the thing to get through your DM test, then turn around and share the love with the next DM Candidate in line...

przeor
07-19-2007, 05:21
Anyone need one.... I've got one laying aroundhttp://www.scubatoys.com/forum/smileys/smiley20.gif

JahJahwarrior
07-20-2007, 18:22
Heck, I got a used computer for $50!!

I use a table to figure pressure group just for my logbook....I dive with a Suunto computer and Im told they use a very conservative way of measuring your nitrogen load. I do often refer to tables to get an idea of how long I can stay at what depth, but my computer will also tell me if I push a few buttons, and it will tellme based on my current nitrogen load too, so I can recalculate in between dives.

The other thing about a computer is, a doc could use it to figure out your dive profile if you had a problem. Unless you wrote out your profile on your table.....so computers are useful in emergency situations too. :)

thesmoothdome
07-20-2007, 18:30
Anyone need one.... I've got one laying aroundhttp://www.scubatoys.com/forum/smileys/smiley20.gif
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<DIV>Hehe..I've got on in feet and one in meters. Don't ask me why. I really have no idea where either one came from.</DIV>
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<DIV>Back to the OP. Can you download your dive info into your pc? The information you can show her might alleviate her concerns. Not only does mine show depth and time every 20 seconds, it has graphs on tissue saturation as well, plus a bunch of other info that might help her understand how a computer works. </DIV>