Dive Computer or Tables - which is safer for a newer diver?

[Tyger]

That is really interesting. If that chart is right, pretty much every computer is more conservative than PADI's table for recreational depths???

If that chart is correct, AND if you dive a square profile.

Once you get into ML, the computer can credit you where PADI's table can't.

If you're curious, when you log your computer dives, calculate your pressure group using the tables, and see how the computer's nitrogen loading calculation compares to the table's.

 

[Them]

That is really interesting. If that chart is right, pretty much every computer is more conservative than PADI's table for recreational depths???

One possible explanation:

Tables are based on setting time from start of descent to start of ascent. So a 60' table dive will include some 0' time. That can safely be factored into the table and any sensible table compiler would.

The computer times may be actual bottom time. So the 60' computer number may be what it would give if it started at 60'. It doesn't need to include the 0' to 60' range because it constantly recalculates based on current depth.

If that's the case (and it would be a reasonable case) the tables will appear to give more bottom time on paper, but the computer will give more bottom time in practice.

 

[nimoh]

I don't remember where I found this, so use or disregard as you see fit. I found it on the internet while trying to research which computer I wanted to buy. Note that the computers are more conservative for a particular depth than the USN dive tables.

View attachment 134641

I am not familiar with this chart, although it makes sense.

However, I think the discussion is that the tables are used in a square profile while the computers will give you credit for time spent at shallower depths, and this makes the tables more conservative.

 

[DevonDiver]

The issue of repetitive dives also needs to be considered. I'd like to see similar figures on the table for a second dive. An algorithm may credit you more NDL for a solitary dive, or a first dive, but then penalize you on subsequent dives. Or may not...

Back to the original point: It's worth remembering that the shorter NDL is 'safer' - in that it provides a greater buffer.

 

[BDSC]

Another thing to consider is this. Some dive resorts and liveaboards require you to have a computer to dive with them. Some will even lend you one if you don't have one. To me it just makes sense to get a computer to start with and learn how to use it so you won't have to "figure it out" when you get there.

I just don't see any downside to using a computer and I see diving with them being superior to having to remember tables. I guess a computer could fail and we know some have but I have been diving computers since 91 and have never had a failure of any kind. It's rare.

 

[Lopez116]

Thanks all for your guys' input. I appreciate the various takes on this.

 

[freewillie]

Technically there is a difference between more accurate and safe.

A dive computer is a tool to calculate bottom time just like the tables. It is a more accurate device and as the previous post point out you get calculations for actual levels in a multilevel dive. If you start your dive at 50 feet, then go to 60 ft, then 30 ft, back down to 50 ft, then end your dive and surface the computer takes into account the different levels and the actual time you spent at each depth. It allows for more bottom time with a greater degree of safety than the charts alone. The same previous dive the entire calculation would have been 60 ft only for the whole dive.

Certain brands of computers have a reputation being more conservative than others, while some allow you to choose more conservative profiles over more liberal profiles. If you wanted increased safety then choose a more conservative computer.

Personally I trust my computer to do the calculations for me since I'm not very good at math. There is also user error involved in using the tables, and I feel like I'm more likely to misread and miscalculate the dive. I know essentially how to use them and what they represent. It's just that I'm likely to mistake my pressure group and time calculations. In this case I find the use of a computer safer for me personally.

Technology is a wonderful thing. When I was buying new golf clubs recently the salesperson said, "why not take advantage of the new technology to hit the ball straighter and farther?" Same is true for diving. The computers make diving easier. Not necessarily safer than tables, just easier to use than tables. It is up to you to dive safer by using the computer appropriately and actually monitoring it routinely during a dive. It doesn't do you any good if you don't check it, and then realize that it put you in Deco because you weren't paying attention to your time and your depth.

 

[Lopez116]

Can anyone recommend entry-level computers that are reputed as more conservative and/or have the ability to select a more conservative configuration?

 

[Pane]

I learned to dive when computers were still an oddity mostly, and so obviously used tables all the time. Then when I got back into diving about 10 years later, computers were everywhere and it was assumed you used one on the trips I went on. I have to say that I love the extra dive time you get out of them, as well as extra dives later on the same day.

I think having one is just great. It gives you a lot of information about your dive, and it can let you know when you're straying too deep or going up too fast.

If you really want to be hyper-conservative (most computers are pretty darn conservative already), you could always use a table on the boat to plan your next dive, while assuming you dived a square profile. The computer would then be a tool for making sure you stay within your planned dept and ascent rate.

In the end, it's your decisions on how to deal with the information tables or the computer give you that determines your conservatism.

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Can anyone recommend entry-level computers that are reputed as more conservative and/or have the ability to select a more conservative configuration?

I can heartily recommend the Suunto Vyper. It's one of the cheapest, it's rugged, you can change the batteries yourself, it can be programmed for nitrox, and Suunto uses a pretty conservative algorithm. It can also be set to use solely as a dept gauge/timer.

 

[Tyger]

Can anyone recommend entry-level computers that are reputed as more conservative and/or have the ability to select a more conservative configuration?

I use a Suunto Zoop, which is fairly entry level, and according to that table Suunto uses one of the more conservative algorithms. Also, it has 2 additional levels of conservatism you can set (As well as two levels for altitude diving).