So you want to buy a new computer?

[Water Boy76]

I've heard from other divers that if you Deco with DSAT your the stops are long. Based on what you've said, does not sound like you intend to dive that way.
I also appreciate a computer that gives you more bottom time assuming you are responsible with your profile.

 

[stuartv]

I've heard from other divers that if you Deco with DSAT your the stops are long. Based on what you've said, does not sound like you intend to dive that way.
I also appreciate a computer that gives you more bottom time assuming you are responsible with your profile.

Assuming you are talking to me, you are correct. I do not intend to ever dive where my (current) computer goes into deco. To me, the deco ability that my current computer has is there purely for emergency use. I do and will dive it up to, but not exceeding (at least, not on purpose), the NDLs it gives.

I am about to start Tech training for deco. I will get another computer at some point, that is intended for use in deco diving, to use on deco dives. In the meantime, I will plan deco dives on a desktop computer and dive the plan using my current computer in gauge mode.

One of the DMs at my LDS got deco certified last year. We were talking about computers this past weekend. He has the same (Atom) computer that I have. And he bought a Petrel for his Tech training and deco diving. When we were talking on Saturday, he said "well, you could use the Atom for your deco diving. It's just not as nice or convenient as the Petrel for gas switches." I disagreed with him and pointed out that, as far as I can tell, the Petrel (and other computers intended for Tech diving) will give you deco plans that are calculated based on knowing what deco gases you are carrying (which you program in before you start your dive). The Atom can be programmed for up to 3 gases and you can switch between them on the fly. But, I think (and I certainly could be wrong) that if you dive it and go into deco, it does not calculate you a deco plan based on all the gases you have programmed. I think it just calculates based on the gas you are currently using. That is a big negative for trying to use something like an Atom for deco diving. When I pointed that out to my DM friend, he said "wow. You're right. I never even thought about that."

I assume the Atom would recalculate your stops and times if you told it you were switching from, say, EAN28 to EAN50. But, if you have it set to indicate that you are breathing Gas 1, which is EAN28, and you have it programmed for Gas 2 of EAN50, I'm pretty sure it will not calculate your stops and times factoring in a switch from Gas 1 to Gas 2. The Atom does not have a way to turn Gas 2 and Gas 3 "off", so it has no way to know whether you are actually carrying Gas 2 and Gas 3 or not. I mean, you have wireless AI transmitters on Gas 2 and Gas 3, then it could know that you DO have them. But, it has no way to know the difference between "I have Gas 2, I just don't have a transmitter on it" versus "I don't actually have Gas 2."

 

[ZzzKing]

Totally fair question. But, my point is that, among recreational dive computers, the reports I have looked at show a wide disparity in NDLs - especially on repetitive dives. People have to make their own decisions. But, when you're talking about a computer that gives you 8 minutes of NDL, where another computer would give you 50 minutes of NDL, I think it's totally legit to think you may have "outgrown" the computer that only gives you 8 minutes.

A dive computer has no idea what is going on in with the actual gas bubbles in your blood stream. Additional conservatism in a dive computer is not necessarily,a bad thing. If you have a liberal computer and know you will be into deco, then plan accordingly. Carry more gas if you need to. Know that you will have additional stops for longer on the way up. You don't have to end the dive just because your computer tells you to. You just need to handle your off-gassing in the proposer way. Look at it this way, what if you wore two computers, one giving you 8 minutes and one giving you 58 minutes of NDL. Should you take the conservative one off and put it in your pocket? Does that have any impact whatsoever on how your body is going to react to decompressing as you come up?

 

[chadmeister]

You are right !!!

So far we have coded 94 dive computers in our Dive Computer Research Tool :depressed:

And we aren't done yet (couple of vendors haven't responded yet ... and we know of few new models coming to the market in the next couple of months) .... I expect to easily surpass 100 once the tool is completed.

Alberto (aka eDiver)

This is a kickass link here! Thank you! It just showed me that my current computer was exactly what I'm looking into... Maybe no need to change...

Maybe add one more criterium: display (colored or not). I'm quite the visual person and I find colored displays can be easier to read (maybe not always in direct sunlight though).

 

[fnfalman]

There are old divers and there are bold divers. There are no old, bold divers.

The more I dive, the more conservative I become because I want to be around longer to do more dives. I stay well away from the NDL line regardless of whatever algorithm being used by the computer.

You roll your dice and you take your chances when you go into the water. You can take a greater chance and hug the NDL just to squeeze out a few more minutes in one dive, or you can take a lesser chance and surface well before the NDL.

 

[rjack321]

And, of course, that's all based on an assumption that the computers in question have an established record of not getting people bent and/or using known algorithms that have been shown to be reliable at not getting people bent.

If one computer had a record of bending 1 in 1,000 dives, another 1 in 3,000 dives and the third one in 1 in 5,000 dives which one would you chose? Bent is not a binary state - more like a set of odds.

You roll your dice and you take your chances when you go into the water. You can take a greater chance and hug the NDL just to squeeze out a few more minutes in one dive, or you can take a lesser chance and surface well before the NDL.

Or you can got right to the NDL but add time shallow as semi-required stop time.

 

[Rhone Man]

A dive computer has no idea what is going on in with the actual gas bubbles in your blood stream. Additional conservatism in a dive computer is not necessarily,a bad thing. If you have a liberal computer and know you will be into deco, then plan accordingly. Carry more gas if you need to. Know that you will have additional stops for longer on the way up. You don't have to end the dive just because your computer tells you to. You just need to handle your off-gassing in the proposer way. Look at it this way, what if you wore two computers, one giving you 8 minutes and one giving you 58 minutes of NDL. Should you take the conservative one off and put it in your pocket? Does that have any impact whatsoever on how your body is going to react to decompressing as you come up?

I have never agreed with that approach. I think the dive computer should always make its most accurate prediction as to where "the line" is as possible, and it should be up to the diver to build in as much or as little conservatism as they choose armed with the best knowledge possible. Excess conservatism just means deliberately asking for less accuracy. In an emergency I really want to know where the line (probably) is, and I'll adjust my dive plan based on that knowledge. Artificially making me think I have absorbed more nitrogen than I really have does not assist me in these determinations.

 

[ZzzKing]

To each his own I guess. You want to ride right on the line, I want to back away from there a little.

Neither your computer nor mine are telling us what is really going on inside us anyway and buying one just because it gives us more bottom time is ridiculous. Just because the computer says you are at the end of your NDL doesn't mean you have to end your dive. It just means that if you don't come up slowly and hit the stops that make it happy, it will shut you out for a day. If you don't care about being conservative, just slap another computer on and jump in. You are in control, not the computer.

I'm not saying that this is your attitude but the algorithms that a dive computer uses are not based on the compartments in YOUR body and they aren't forcing you to end your dive early. My initial comment was in response to a guy who just wanted the computer with the most bottom time so he could dive closer to the edge for a longer period of time. He just seemed to want a computer that would agree with what he already wanted to do.

 

[Stoo]

Nice read. As a new diver, all the choices and advice from my shop have my head spinning. This is a very well thought out post.

Most of what your LDS is likely BS anyway, and based on the brand that they prefer to sell. Any of the computers listed will do a decent job of getting you back to the surface intact. Look at the features, and see if you can understand and read the display easily, and buy it. Honestly, the only complaint that I have ever had with recreational computers is that they die far too soon... or at least the ones I had did. Perhaps SB can help with information about that.

Much of what you pay for in a more expensive computer are just the frills, so you would want to assess those and decide if they're worth the extra cost. The $700 computer won't keep you un-bent any better than the $250 computer. So you need to decide which of these "frills" (aka "features") are worth having.

It's important to understand that decompression theory is exactly that... a theory. Each of the algorithms behind these computers are interpreting this theory in a slightly different way, and if you conservatively follow it's instructions, you'll be fine.

One thing to consider: if you have regular dive buddies, find out what they use and if they like them. If so, consider getting the same model so that your profiles match.

 

[DevonDiver]

You can take a greater chance and hug the NDL just to squeeze out a few more minutes in one dive, or you can take a lesser chance and surface well before the NDL.

Or your can increase your training, so as to make NDL irrelevant and do the bottom times that you desire... knowing how to safely mitigate the risks associated with doing that. i.e. technical diving.

Technical diving isn't just about going deep and dark... it's about doing the dives that you want to do...very safely.

I do a lot of technical diving in the 100-130ft (30-40m) range... enjoying bottom times 2-4x longer than even the most 'aggressive' recreational divers. On surfacing after a well-planned, conservative, ascent profile, I am also fresher and more vital than they are (indicative of much less decompression stress). I sidemount whether it is rec or tec, so the only additional cost to me for doing these as technical dives is a 40cuft of 50% or 100%...cost <$10 for gas.. small change, given the vastly longer bottom times I enjoy.

It's not simply a choice between avoiding NDLs like the plague or diving super-aggressively to get a little more bottom time. You can be very conservative AND enjoy exceptionally long dives.

People tend to overlook that option; disregarding technical diving as the preserve of 'hardcore' divers doing 'extreme' dives. The truth is... technical diving is very liberating.