Now it's time to choose a wrist computer.

[SaltyCracker]

Something to keep in mind about computers. Every time you open the battery case you risk a cross thread or misaligned o-ring. If the battery floods, they are toast. if you have the shop replace it and do a pressure test to assure the seal, you are spending $40 a year. Plus as others have mentioned, the data cables are another $100.

A sealed rechargeable battery and blue tooth will pay for themselves over time. A computer is a marriage. My Aeris 300ai lasted seven years and it was old when I got it. Neither of the subsequent two computers made it beyond two seasons. one flooded and one had a battery contact issue. I spent the money on a peregrine. Bang for the buck it was a solid investmen.

The computer I just got did recommend that I have a service tech do the battery change but I'd never have to have it changed every year. And the data cable came included though I do realize many don't and are expensive. In general, I stay away from electronics that utilize an integrated non serviceable rechargeable battery. I do see the attraction though and understand why it would be convenient.

 

[Belzelbub]

This past August I had a brand new SPG fail on me. I was trying out a friends Perdix AI and backup SPG. When I turned the tank on both went to the same PSI or close enough around 2911psi. As the dive progressed the SPG never changed from 2911psi. After the dive I turned the tank off and the SPG went to zero....tried it out on another tank to see what it would do,,,It went to full pressure when turned on but would never go down while being used...the Perdix AI performed as expected

This is a good example. Not only that mechanical devices can fail, but also how they fail.

So with that said, what would be the hierarchy of redundant gear? For me I guess it would first be anything electronic then next would be my regulator/octo/SPG kit. Then what? Mask/fins/snorkel? Would anything beyond that even be practical?

Really depends on the type of diving you do. Multi-day trips in remote locations where repair or replacement isn’t an option suggests one level of redundancy. Local trips suggest another. I normally do local dive trips off of private boats, so don’t generally carry a bunch. I do bring Along batteries, tools, and o-rings. If my kids are diving, their regs are on board as well, but I usually don’t bring a spare regulator.

I always feel that mechanical devices are less error prone than finicky electronics. Especially when saltwater is introduced into the environment.

Perhaps. However, the example posted by @gqllc007 also illustrates how a failure presents. In that case, the mechanical SPG just stuck at the reading before the failure. Generally, electronic sensors fail such that there is no question that it’s dead. They tend to report something that is so far off, there is no question.

Had the SPG failed later in the dive, it might not be as obvious. If it were to fail around 1200 psi, but not be noticed until the psi in the tank was around 700, that would be worse.

 

[Belzelbub]

The computer I just got did recommend that I have a service tech do the battery change but I'd never have to have it changed every year.

Which one did you get? In most cases these days, the batteries are user replaceable, despite the tech recommendation. Some older computers were filled with oil and/or used soldered batteries. Those certainly raise the skill level, but most aren’t all that difficult. But, if you have any hesitation, it’s probably best to have a tech do it. At least the first time, then maybe watch and see if you are comfortable doing it yourself.

My most recent computers came with the tools necessary to change the battery myself. My Shearwater even came with spare o-rings for the battery compartment.

And the data cable came included though I do realize many don't and are expensive.

That’s good. I wish my first DC came with the cable. I never got around to getting one until it died. As such, there’s a big gap in my dive log, as some paper logbooks got lost and I didn’t start downloading until 2013.

 

[Gareth J]

At least the Shearwater wont lock you out.

Unfortunately, for 99% of those with some form of diving qualification, that is a very bad thing.
Very few people have even a rudimentary grasp of decompression theory. Having something they can abuse, then continue diving is not a good thing.

It is all well and good to say buy the best, and you only buy once. But not every one can afford that.
Most would do better to get a good set of basic equipment, and upgrade over time as their diving (and fashion) requirements change. And, perhaps more importantly, spend the extra money actually going diving!

First on the list is a good set of regulators, but most modern CE compliant regulators are excellent. A basic set of Apex reg's will do anything you need.
Good protective clothing to suit the environment you are diving is very high on the list. I dive temperate (cold) waters. We can lend kit, either personally, or from the club. But drysuits and base layers are personal, and very few want to lend drysuits (granted, most of us will lend an old - or back up suit, old suits tend to be the 'damp' suit we no longer use).

Modern displays are certainly better than the old backlit LCD, certainly, I have upgraded my CCR unit to the newer displays, partly because my old eyes had trouble with the small typeset, and cause I broke it .

I have only just added a Shearwater Perdix to my kit. After years of diving CCR, it's nice to have a backup unit that is a CCR compatible computer. I used to use a Suunto Vytec as the backup, until I smashed it. Then an OSTC Sport, which I still carry when diving with OC buddies.
It's the first AI computer I've bought since the Suunto Eon back in the early 90's.

By the time you progress from OW to mixed gas or CCR, computer technology will have moved forward significantly. That includes what will be thought of as best decompression practice.

 

[Joris Vd]

I put my money where my mouth is and bought a Deep6 Excursion. $300 and more capable than the Peregrine

I like the deep6 and wanted to buy it during the sale (sadly they don't ship to Europe atm), but in no way shape or form is it more capable than a peregrine??

1 gas nitrox support up to 56% on the deep6

3 gas up to 100% on the peregrine, a proper backlit display, and you can actually fully customise GF.
edit: although I have to admit, if you have a need for multigas you'd probably better skip the peregrin and go straight perdix.

 

[Belzelbub]

Unfortunately, for 99% of those with some form of diving qualification, that is a very bad thing.
Very few people have even a rudimentary grasp of decompression theory. Having something they can abuse, then continue diving is not a good thing.

That makes sense to some extent, and in the event of a violation, sitting out is certainly prudent. However, in some cases, a relatively minor violation on a conservative computer can result in a 24 hour lockout that might be a tad extreme.

It’s not unreasonable to consider that a newer diver may listen to “more experienced buddies” and do that last shallow dive. If a computer locks you out, the diver can still take it along, but it’s not tracking tissue loading. In that case the diver would be better served with a computer that is fully functional.

Not saying that the subsequent dive should be done at all, but I like the approach of presenting the diver with all the information, and continuing to guide even if they make a bad choice.

 

[CT-Rich]

That makes sense to some extent, and in the event of a violation, sitting out is certainly prudent. However, in some cases, a relatively minor violation on a conservative computer can result in a 24 hour lockout that might be a tad extreme.

It’s not unreasonable to consider that a newer diver may listen to “more experienced buddies” and do that last shallow dive. If a computer locks you out, the diver can still take it along, but it’s not tracking tissue loading. In that case the diver would be better served with a computer that is fully functional.

Not saying that the subsequent dive should be done at all, but I like the approach of presenting the diver with all the information, and continuing to guide even if they make a bad choice.

At some point you have to accept a standard. If you wear a computer to track your NDL, you either accept its verdict or why even bother. DC have made diving a lot safer while extending the amount of time you can spend in the water. The idea of having your computer say you violated the NDL and then deciding it doesn’t apply to you is kind of like asking grandma to referee a game and then punching her because you don’t like the call.

Either respect the call or don’t ask her to referee.

 

[Gareth J]

At some point you have to accept a standard. If you wear a computer to track your NDL, you either accept its verdict or why even bother. DC have made diving a lot safer while extending the amount of time you can spend in the water. The idea of having your computer say you violated the NDL and then deciding it doesn’t apply to you is kind of like asking grandma to referee a game and then punching her because you don’t like the call.

Either respect the call or don’t ask her to referee.

Worse than that, the ignorant do not know what risk they are taking by ignoring the violation.

Lets be honest, American diving agencies, unless you step on to the 'technical rung', don't even teach decompression diving within the basic qualifications. The skippers throw there teddies out of the pram if divers over run the NDL time. You have divers racing to the surface to avoid this!
Be consistent, if you are not teaching basic decompression diving within the core training, don't advocate tools that allow you to ignore the violation of the decompression models.

 

[scubadada]

That makes sense to some extent, and in the event of a violation, sitting out is certainly prudent. However, in some cases, a relatively minor violation on a conservative computer can result in a 24 hour lockout that might be a tad extreme.

It’s not unreasonable to consider that a newer diver may listen to “more experienced buddies” and do that last shallow dive. If a computer locks you out, the diver can still take it along, but it’s not tracking tissue loading. In that case the diver would be better served with a computer that is fully functional.

Not saying that the subsequent dive should be done at all, but I like the approach of presenting the diver with all the information, and continuing to guide even if they make a bad choice.

In 2129 dives, about 5% light deco, I have not violated the deco requirements. I dive DSAT and GF high of 95. I dive my more conservative computer.

 

[dmaziuk]

In 2129 dives, about 5% light deco, I have not violated the deco requirements. I dive DSAT and GF high of 95. I dive my more conservative computer.

That ^^^. Despite what one may read on the Internet, they don't "lock you out", they lock you out if you violate the deco requirements. On a basic rec dive that's probably because you ran out of gas.

If you don't have the gas to overstay your NDL, then don't. How hard is that?