Buying gear and need advice

[Stu S.]

Last summer I had a regulator problem; a hose got damaged on the boat just prior to the dive. The mate on the boat pulled out a "loaner" reg. That loaner had an SPG on it only.

Lucky I use a wrist computer.

If I had a console or AI computer, it would have meant fast handiwork changing hoses around in rough seas, or no computer for that dive. As my computer has no connection to the regulator set, I proceeded to dive as usual.

 

[MauiScubaSteve]

Other than with physical monitors, (like on the new Galileo Sol) how is the computer supposed to know when you're breathing? It's connected to the HP port.

How large is your normal breath? Do you breath with a natural rhythm? I teach that my mantra is inhale for 2 seconds, exhale for 4 seconds.

When the computer sees a sizable decrease in pressure, that might be the start and size of the inhalation. Shortly after that the pressure changes very, very little for a while, that could be the exhalation. Now another similar inhalation / exhalation confirms the computers assumption and predicting time remaining is based on breath size (in psi) and breaths per minute. Or it may not know when your breathing, but it definitely knows how many psi were used in the last minute (2, 3...).

If your entire dive is a peacefully tranquil drift at the same depth through-out, the time remaining might be a number of interest. If your dive ends with some exertion at that same depth, the time remaining for the whole dive up to there is meaningless and you all the sudden have a way smaller number (perhaps smaller than necessary to finish the dive underwater).

Here's another example; shallow reef dive, moving out 250 yards and down to max 45'. Just after checking 'puter (30 fsw, 1:00 tr, 2300 psi, :24 dt) there's a shark or ray moving down and out to the end of the reef. With a small burst you follow and snap a couple pics. After the excitement you check your puck (44', :23, 1700, :30) which shows less time remaining than it took to get here!

An inexperienced diver might worry about the short time remaining, and anxiously rushing back before running out of air might be the cause of the excessive air consumption that the computer seemed to correctly predict. It might take a few minutes of breathing the way you will for the remainder of the dive before the computer will give you valid time remaining values, verifying your hunch that you can calmly check out the reef some on the way back, rather than rush. I've seen AI's where the biggest display number is this wildly fluctuating number (time remaining).

 

[halocline]

When the computer sees a sizable decrease in pressure, that might be the start and size of the inhalation. Shortly after that the pressure changes very, very little for a while, that could be the exhalation. Now another similar inhalation / exhalation confirms the computers assumption and predicting time remaining is based on breath size (in psi) and breaths per minute. Or it may not know when your breathing, but it definitely knows how many psi were used in the last minute (2, 3...).

Again, the computer is connected to the HP port and does not read the change in IP that accompanies a breath. What you're talking about could only happen if the computer were attached to a LP port where the pressure fluctuates on demand.

Other than that, I think we're on the same page, sort of. I would not trust a AI "gas time remaining" figure for dive planning. I wouldn't even pay attention to it. Maybe it works great for some people, and more power to them (and it).

 

[MauiScubaSteve]

What you're talking about could only happen if the computer were attached to a LP port where the pressure fluctuates on demand.

If the Air Integrated Computer knows the tank pressure at a given time, it can take the difference in tank pressure between two give times and know the tank pressure used for that period of time. If the computer tracks the size/timing of the significant drops in tank pressure it can estimate/predict future similar drops in tank pressure. What does the LP port have to do with that?

 

[Eric Sedletzky]

In the beginning I dove tables and guages for several years then got a suunto vyper with nitrox wrist computer. I dove that for several years then lost it during a kayak dive gone bad. I went back to guages and will remain with guages and tables from here on out. I dive singles and rarely reach my NDL with the type of diving I do. If I dive doubles it is generally doing a teck dive and that is all tables anyway. With all my diving I do several deep stops and stop every 10 feet till I hit 10 feet and will hang for several minutes. I pretty much religiously do this every dive combined with depth averaging and glancing at the tables between dives for residuals.

I have a bottom timer now on my wrist and I figure if I ever go to an exotic location and they ask me if I have a computer and I'll say "Yeah, right here, see look". They wont know the difference.

 

[drrich2]

Hi:

A few basic thoughts.

1.) I use an Oceanic VT3. I like that I can download dive data to my computer, then study my dive profile (i.e.: did I go up & down a lot, ascend to fast, spend most of my time deep or just drop down for a moment, etc...).

2.) I've got the wireless transmitter but don't use it yet. I like the console guage fine for that, and a guy on a dive boat pointed out to me people who aren't paying attention may try to pick their tanks up, grab the thing like a handle, or knock the tank over (which you're supposed to be careful not to do, but it happens), and it can break off.

3.) If you're buying gear, take a long, hard look at how fast you go through air, & whether you'll be diving locally. I'm a big guy, and while I've gotten a bit better with practice, I still go through air a lot faster than my (smaller & much more physically fit) friend & my wife. Might be worth your while to get a larger cubic foot capacity steel tank. And then you've got high-pressure & low-pressure options; I've got a high-pressure but when I bought it I didn't even know there was a low-pressure option. It's a 3400 PSI steel (not aluminum) high-pressure tank (I think 130 cf, if memory serves; having been diving this winter!), and some local dive op compressors can't get it all the way that high (but I still get a lot more time in the water vs. an 80 cf tank).

4.) Since you'll need your regulator serviced annually if you follow standard guidelines, might be worth finding out what brands your favorite local dive shops will service.

5.) Getting back to the dive computer thing, if you're in a situation where you're going to be making 2 to 4 dives from a dive boat, for example, depending on circumstances it may be useful not to have to immediately on site write all the details in your log book (assuming the dive computer is keeping up with some of the info.).

6.) My dive computer records temp.s while I dive; interesting to see later (if you hit a thermocline at 20 feet while diving, you may later wonder how cold the water was, & what the temp. change above & below was).

7.) One thing I've found diving in the real world vs. training in my Open Water course is that while I generally have a rough plan for what I'm going to do, I don't usually rigidly drop down to an exact depth or just short of it (say, 40 feet), then dive no deeper than that indefinitely. In other words, if I dive a reef at Bonaire & spot a Tarpon a bit further down (deeper) the reef than I'd planned on going, with the computer on I can go a bit further down for a better look at it (without completely blowing a pre-dive plan made onshore with dive tables to keep within NDL's).

So while I like (& use) guages for some things, I like to have that dive computer on.

Richard.

 

[vladimir]

Actually this "thinking in advance" ie "Planning" has worked out pretty Good for me in the past so I think I'll continue, but thanks for your ...er expertise was it?

Plan to spend twice? no, actually the plan is to spend Once. As in buying a computer Once, Next year, where I'll get More computer for Less money AND have redundancy in gauges... your familiar with redundancy yes? would thought you would have appreciated it... fairly common in Diving really... maybe You should brush up.

Maybe you should update your profile to give us an idea where all this, er, expertise came from. Alternatively, you could dial back the attitude a little and take advice in the spirit it was offered.

 

[PvtStash]

Maybe you should update your profile to give us an idea where all this, er, expertise came from. Alternatively, you could dial back the attitude a little and take advice in the spirit it was offered.

Snarkiness offered in response to your "maybe get certified first before making decisions".

Turn back the dial under your Own hand sir... and perhaps I wouldnt have to touch mine.

 

[dkatchalov]

Snarkiness offered in response to your "maybe get certified first before making decisions".

Turn back the dial under your Own hand sir... and perhaps I wouldnt have to touch mine.

 

[vladimir]

Snarkiness offered in response to your "maybe get certified first before making decisions".

Turn back the dial under your Own hand sir... and perhaps I wouldnt have to touch mine.

Yeah, that wasn't me.

Maybe get certified first, and then start making decisions.

But I think Ron probably offered the advice in the spirit of helpfulness. Maybe not. When I get snarky, it's a lot more obvious than that. Subtlety has no place on the internet.