New computer advice needed!

[Squalo305]

Hi everyone! I know there are always discussions on this matter, I just dont seem to find my answers on other threads. I currently use a suunto cobra 3, been using it for the past 10 years or so. I think it is time to make a change into something less conservative and I am also looking into a backup computer (diving with both of them) and I would really appreciate your help.
so I would like your opinion on this ideas.
1) getting an Oceanic pp4 (I think this one might be close to the shearwater algorithm when using the less conservative one) in a hose and a shearwater perdix AI on my wrist/strobe arm
2) using 2 AI computers one on my wrist another on my camera strobe arm, although I don't know if the transmitters can interfere

I chose those computers also because I think its better to use user changeable batteries than rechargeable ones, in my experience they start to lose battery power over time and changinG one battery is faster Than charging one.
what are your recommendation? I think is a good idea to get the to computers with the same algorithm but sometimes you dont find the exact same one unless is the same brand.
is going hoseless a good idea? Or is it playing it safe to keep one in there?
or in your experience what would be the best combination of two computers? I normally dive with my camera and use a wrist computer with no AI on the strobe arm, but now I am getting into liveaboards and I think is a good idea to dive with two computers with AI just in case one fails on the trip.

sorry for my english sometimes I don't know if I write things correctly, thank you for your help!!

 

[d^2b]

If you have an SPG (which I think most will recommend) I don't really see a problem with a non-AI computer as a backup.

 

[Squalo305]

Like Brass and Glass SPG?

 

[vovanx]

why you want to mount a computer on the strobe arm instead of your other wrist?

 

[kelemvor]

2) using 2 AI computers one on my wrist another on my camera strobe arm, although I don't know if the transmitters can interfere

Not much of an issue, but check with the manufacturer(s) before making a purchase just in case.

Most computer manufacturers support multiple transmitters for either buddy monitoring or multiple tanks or both. Some (shearwater) do it by having two models of the transmitter. Others (Scubapro) do it by just allowing you to pair multiple transmitters with a single computer or multiple computers with a transmitter. Personally, I think scubapro's method is a little better but that's beside the point.

If you're going to use multiple computers, the ideal situation is having two identical units. Second best is to ensure you have two computers that use the same algorithm (shearwater uses Bühlmann ZHL-16C or VPM-B). It's not the end of the world if they don't match, but if your backup computer isn't the same and it happens to get locked out on dive 8 of your trip, then you don't have a backup anymore so what was the point. If your backup is less conservative than your primary then I guess that's a non-issue.

 

[Squalo305]

why you want to mount a computer on the strobe arm instead of your other wrist?

I keep it on the strobe arm of my camera, because if you dive with a camera it’s much easier just to look away from it to the computer.

 

[d^2b]

Like Brass and Glass SPG?

Sure. I guess if you already replaced your SPG with a hose-integrated computer that's a different discussion. It's maybe less clear that an analogue backup is needed in that case for recreational diving.

 

[dmaziuk]

I normally dive with my camera and use a wrist computer with no AI on the strobe arm, but now I am getting into liveaboards and I think is a good idea to dive with two computers with AI just in case one fails on the trip.

Keep in mind that transmitter range is typically limited to 1..1.5 m so the further away you have the wrtst unit, the greater chance of it losing the signal (intermittently as there's also a pattern to signal propagation, cardioid IIRC).

OCi and a ProPlus might be the way to go if you don't mind the OCI's size and the combined price tag.

 

[Squalo305]

How about a brass and glass spg, and one shearwater transmitter with two computers? Is this a good idea? Or is it better to stick with another plan and use a computer in the hose?

 

[lowwall]

Assuming you want the Perdix AI, here's three backup options in ascending order by price:

1) Get a Perdix, keep your Suunto as backup. It's not a perfect solution, but a backup is really meant to be a backup. Mute all alarms on the Suunto and ignore it unless you have trouble with the Perdix. If you find that you are going into deco on the Suunto while you are OK on the Perdix, you can set it to gauge mode and treat it as a backup pressure gauge (losing the tank pressure reading is the most likely Perdix failure mode). If you do have it in gauge mode and completely lose the Perdix, then you would begin a normal ascent unless you know your remaining NDL time.

2) Get a Perdix, use a non-AI computer with similar algorithm and an SPG as a backup. I'd suggest the Deep 6 Excursion Dive Computer (or very similar Crest CR4 if it's more readily available to you). There's a long thread here with examples of how closely the algorithms match. For example see the photos on Thoughts on Deep 6's new DC .

3) 2 Perdix or a Perdix and a Teric. You only need one transmitter to get pressure info on both computers. I'd still get a backup SPG in case the transmitter fails.