why analog?

[Hoyden]

Let me preface this by saying I have no tech experience, but I am now acquiring my gear and diving with it before getting into technical diving.

My question is this: I just bought a Suunto vyper, and already have a cobra. Would the cobra be a good substitute for an analog SPG?

I know that it is as prone to failure as any electronic device, but it is far more accurate than a traditional SPG, and it is a redundant depth gauge and timing device without adding another piece of equipment.

Is this configuration appropriate for tech (i.e. extended range and mixed gas)?
Also is it DIR? why or why not?

here is info on the comps.
http://www.aqualung.com/products/cobra.html
http://www.aqualung.com/products/vyper.html

thanks

My tech instructor is happy for you to use a AI computer in beginning tech classes as long as you have a mechanical spg hooked up too. Once you get to trimix this discussion is moot since afaik there are no trimix capable AIs.

If you want DIR answers, you may want to repost this in the DIR forum.

 

[texdiveguy]

I have not and never been a fan of AI computers for multi reasons.....an analog SPG is a sure thing.

 

[Cheekymonkey]

Well at trimix point you can still use the computer in gauge mode. right?

 

[limeyx]

Other issues that may not have been touched on:

1) You dont *need* 1-2 or even 10-20 psi accuracy.
If you really care about that much psi, your plan does not have enough safety margins in.

I always round to the next conservative 100 psi regardless.

2) Analog SPG is a proven technology, doesnt have batteries in it, wont get "confused" and start reading PSI from your buddies tank etc.

3) when you tech dive, you will start to carry more and more tanks (stages, deco bottles). The simplest solution is an analog SPG on each tank. Are you really going to have 3-4 different wireless/AI SPG's for all your tanks?

The benefit of having the SPG *ON* the tank is you can see which tank the reading is for

4) you dont need a trimix computer, AI or not.

5) I have definitely seen failures on the AI computers (surfaced from a nice wreck dive only to hear the groans of "Oh man, zero PSI, zero damn PSI" as some guy had got down to 40 feet and his AI had crapped out on him)


The analog gauge is simple, robust, sturdy and doesnt need much servicing. Easy.

 

[scuberd]

Thanks for the input, but I want to clarify one thing. The Cobra is not wireless. It is attached to the HP hose, so there is no danger of it getting a signal from anywhere else. (except maybe the CIA)

Maybe the best thing to do is to put an analog spg on my tech rig and save the cobra for a rec setup...

 

[texdiveguy]

Well at trimix point you can still use the computer in gauge mode. right?

Yes by all means,,,,this is the most popular method still in tec.

 

[limeyx]

Thanks for the input, but I want to clarify one thing. The Cobra is not wireless. It is attached to the HP hose, so there is no danger of it getting a signal from anywhere else. (except maybe the CIA)

Maybe the best thing to do is to put an analog spg on my tech rig and save the cobra for a rec setup...

Sorry -- my mistake on the wireless bit.

I would concur with saving it for recreational diving if you already have it.

So if it connects to the HP hose, that means you have a cable/cord that goes from the first stage to the computer? That (for me) would definitely pose a problem as computer/gauge is always on right wrist, and SPG on left post. I dont want to have such a cord running across my rig.

 

[Atticus]

The Cobra computer that he's referring to attaches to the HP hose just like an SPG. Perhaps this picture will help:

This isn't terrible, but it's not ideal in my opinion.

The disadvantages that I see are that it's slightly more of a failure point and that it's roughly twice the size of a small analog gauge. This won't be an issue until you start juggling sling bottles and need to fish it out from behind (or between) the clips. I haven't taken one of these out of the boot, but that might be one way to reduce its size.

YMMV, but I choose a small mechanical SPG.

 

[limeyx]

The Cobra computer that he's referring to attaches to the HP hose just like an SPG. Perhaps this picture will help:

This isn't terrible, but it's not ideal in my opinion.

The disadvantages that I see are that it's slightly more of a failure point and that it's roughly twice the size of a small analog gauge. This won't be an issue until you start juggling sling bottles and need to fish it out from behind (or between) the clips. I haven't taken one of these out of the boot, but that might be one way to reduce its size.

YMMV, but I choose a small mechanical SPG.

Interesting. So it sits in the same place as a regular SPG ? Then it's not *so* bad except I still dont see the advantage to get one.

if you already have one, then sure use it for rec diving if you want.

 

[Cheekymonkey]

Well you can always use it as a 2nd spg for doubles if you want that kind of redundancy if you have to isolate them for some reason.