Specific wrist mounted computer questions

[forestfish]

I have been doing my research, but find I still have some questions that aren't addressed. Most discussions of dive computers (DCs) devolve into a discussion of the algorithms. I am not interested in that discussion (I read them, and I am satisfied with my interpretations). So please - NO ALGORITHM mentions for this thread.

I am more than a beginner, but will not be doing technical diving, so I want a fairly simple watch-style dive computer. I don't need air integration. I've thought of doing Nitrox, but no plans for it so far.

1. Are all dive computers water activated? or only some?
2. Do I need to worry about the surface interval before the next dive begins to be recorded? So far all of my dives are hit the water, go down, see stuff, ascend, and sit on boat or beach for a while before rinsing and repeating.
3. will all DCs offer fresh and saltwater options?
4. do I need to wear my DC when I'm out of the water? will it assume if I am not wearing it that I am not diving (which will be true)?

DCs on my short-list currently are:
Aqualung i200 or i300 (preferences? reasons for one over the other?)
Cressi Giotto
Mares Puck Pro Plus - but no depth alarm - should this concern me?
Oceanic Geo 2.0 - but only logs 24 dives before needs to be downloaded

Thanks.

 

[caruso]

Don't know if all dive computers are water activated, I know that Oceanic Dive computers have the menu option for it to turn on when exposed to water. Easy enough to check the specs and manuals for the specific computers you are considering.

Do you need to worry about the surface interval? No need to worry but you certainly need a surface interval after deeper dives or you'll have to shorten your subsequent dives and/or risk DSC because you haven't been out of the water long enough. As far as the dive computer goes, all dive computers have a specific depth at which they stop logging dive data, mine is at 5' or shallower. So if I'm in 5' of water or less, it turns into post dive or surface interval mode until I return to a depth greater than 5' at which point either the dive is continued or a new dive is logged depending on how much time has passed since the computer last measured dive data. With my computer, anything less than 10 minutes is considered a continuation of the earlier dive.

It's my understanding that all dive computers can be used in salt water, they can absolutely be used in fresh water. Edited to add- I misunderstood the question. There's no need to change the computer to account for a dive in fresh vs saltwater, worst thing that can happen is your actual depth can be displayed inaccurately up to a few feet- no big deal.

You need to wear your dive computer when out of the water if you're looking to impress nondivers as to your amazing scuba skills and maybe score some points if you know what I mean. <wink>. It's certainly a good conversation starter when an attractive woman in a bar says "Whats that thing on your wrist?" and you delve into your many deep diving ship wreck adventures. That's the only reason that comes to mind.

I turn off ALL alarms it's annoying to me and other dives. If you need your computer to warn you with flashing lights and beeps that you that you're about to hit your no deco limits or you're too deep than you really need to be above the water not under it.

 

[BertStevens]

I would not consider a DC without Nitrox capability. A few dollars more could make your computer somewhat future proof if you decide to take it in the future.

 

[runsongas]

1) pretty much all are these days, some of the older early ones were not. the PPS computers have an option to toggle on/off the water activation.
2) no, but some will either count it as a continued dive and some also penalize your NDL for short SI
3) no, some do not do salt vs freshwater depth compensation. some split the difference and use the EN13319 standard.

i200 is watch sized and smaller than the i300, you pay a premium for this. oceanic geo2 is an i200 with dsat dual algorithm. popular watch sized choice in that price range.
i300 can be found pretty cheap currently because it is discontinued. can call up LP and see if they can do 150ish.

puck pro plus only has one button it looks like, which annoys some. also runs rgbm vs dsat/z+

 

[RonR]

1. Most, but not all, dive computers can be automatically activated, some by pressure, others by detecting when they are wet.
2. Computers will keep track of your surface interval.
3. While fresh and salt water have slightly different densities, there is no difference between fresh and salt water as far as the computer is concerned, computers only look at pressure, which is what matters physiologically. Some computers offer settings for salinity- this only changes the depth display numbers to be slightly more accurate in a "tape measure" sense, and has nothing at all to do with decompression calculation.
4. No, so long as your computer is out of the water as well you are fine.
Nitrox capability is pretty basic in computers now. If you don't use nitrox, leave it on air. Down the road, it could prove good to have.

Ron

 

[caruso]

3) no, some do not do salt vs freshwater depth compensation. some split the difference and use the EN13319 standard.

As if this matters in any practical sense. It doesn't.

 

[gr8jab]

I can't comment about all, but I can say some things about the Geo 2.0

2. Surface interval: I don't know the exact time, but the Geo 2.0 automatically assumes you've started SI after a few minutes at the surface. Between descents, I've been floating on the surface chatting with my son long enough to trigger a SI (and a second dive upon descent). You need not be out of the water to begin SI. Wet Activation does not imply 'start of dive' or 'end of dive', just automatically goes into dive mode when wet. It uses water pressure to signal the beginning/end of a dive, with a few minutes grace period at the end. After a SI, it will automatically begin the next dive whenever you descend.

4. To the dive computer, surface is surface. You can wear it or not. Doesn't matter if it is on your night stand or in your backpack, same difference. There is no motion sensor or something needing skin contact. It gives you credit toward surface interval and time-to-fly either way. You can even go swimming with it, Wet Activation will not trigger another dive all by itself.

Geo 2.0 comments:

Menu is a little strange to get used to, but that's not uncommon. Every computer has a different idea about how the buttons should work. Generally, I set it and forget it. Sometimes I'm switching between air and nitrox, and have to fiddle with it, but generally not. It remembers your gas settings for repetitive dives (over several days). Once you're fully clear of all residual nitrogen (extra day?) it resets to 'air'. Soap box: The younger generation programmers never owned a Casio G-Shock, so they feel the need to makeup a new button/menu pattern, instead of copying the tried and true that every 40 year old learned in the 80s and 90s.

The USB cable/connection to my laptop is VERY EASY and has never been a problem. The cable is expensive, so consider that in your purchase price. I think it shares a cable with another computer (different branding), and can be purchased cheaper than the GEO branded one. I use SubSurface for Windows, and it works great.

I've never had a problem with the 24 dive storage limit, but your behavior might be different. I travel with my computer, so even at 4 dives/day, I won't go 6 days without downloading my data.

The contrast is good, but some of the icons are small (like all watch-size computers). If you're old and need bifocals, you might want to find something with a larger screen.

Cheers

 

[dmaziuk]

Aqualung i200 or i300 (preferences? reasons for one over the other?)
Oceanic Geo 2.0 - but only logs 24 dives before needs to be downloaded

These are the same family of Pelagic computers, AL versions are basically Oceanics in a fresh coat of paint. With Geo and i200 you pay extra for smaller form factor. I forget which Veo is the i300 equivalent, 2.0 probably.

Cressi Giotto
Mares Puck Pro Plus - but no depth alarm - should this concern me?

I don't know if depth alarm is going to be useful on your dives, and note that MOD alarm should still work. Pucks tend to be the cheapest option, with the cheapest uplink cable as well. Both Pro Plus and the Giotto are two-gas "light deco" computers with up to 100% O2. So is AL i100 I believe.

 

[Fires]

Definitely go for a computer with Nitrox. Most even have it by default nowadays. Even if you don't think you will use it anytime soon, I am sure of you continue diving, you will use it at some point!

 

[Magnus Lundstedt]

I would not consider a DC without Nitrox capability. A few dollars more could make your computer somewhat future proof if you decide to take it in the future.

I have not seen any divecomputer produced the last 5 years that do not handle nitrox, do they make them anymore?