why analog?

[scuberd]

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

 

[Cheekymonkey]

I have no idea bout the DIR stuff man, but if your cobra was already considered appropriate, I would imagine that there is no reason a suunto vyper can't be additional backup.

 

[TSandM]

The digital gauges may give you a readout to more significant figures than you can interpret an analog gauge, but how important is that to a diver?

My husband and I did a little test a while back, comparing on all of our tanks the readouts of his Cobra with my ability to read my SPG. The results were interesting -- There was surprisingly little difference between the two.

The DIR setup is an analog SPG clipped to the left hip D-ring. Analog because you're not dependent on circuitry or batteries for one of your most critical pieces of information (although others will argue that SPGs have their failure modes as well, as any device does). The use of dive computers is not recommended.

 

[Peter Guy]

I'm NOT DIR but I do know that a Cobra is NOT DIR. Just about all (all?) tech diving types use an analog SPG because of its (supposed) superior reliability. There are several threads relating to the accuracy of SPG's vs. Air Integrated Computers and, quite frankly, there doesn't seem to be any distinct accuracy benefit either way.

I'm still trying to figure out why an AI Computer is more a "danger" while doing tech diving than the bottom timer on the wrist or the Cochran computer being used. Yes, it is an electronic device and thus subject to failure -- but the SPG is a mechanical device and subject to failure -- and the failure rates of either appear to be quite small as long as you take care of them properly.

All of the information, pressure, depth, time is necessary for safe diving. If your SPG fails, your bottom timer is your backup (you know your SAC rate, you know your depth and time you should be able to guestimate remaining gas). If your timer fails you should be able to guestimate your time using the SPG and your depth. However, if any of those devices fail, you thumb the dive.

The ONLY explanation I've heard as to why an SPG is preferable to an AI computer that has merit is that the SPG is easier for your teammate to read!

 

[Cheekymonkey]

Ah well being esier for the teamate to read is important, but in that case I don't see the problem although not DIR fo using an analog gauge as well as a wireless spg for backup.

 

[jonnythan]

The Cobra is more likely to fail or break than an analog SPG. Moreover, it's much larger and will probably get in the way when trying to carry stage or deco bottles.

It's not DIR.

 

[scuberd]

Jonny, can you substantiate the claim that it is more likely to fail? is there data to support that? I would be interested in reading about it.
Also, I was comparing the cobra to an analog SPG and without the boot, the cobra is actually just slightly smaller.

 

[TSandM]

Oh, my Cobra is substantially larger than either of my SPGs!

I don't think anybody has data on failure rates for either AI dive computers or SPGs. I suspect both are fairly low, but the dive computer has more MODES of failure -- battery running out, seals failing, or software corruption. Whether this actually translates to a higher failure rate is something I don't think anybody really knows.

 

[Cheekymonkey]

Tends to be a common assumption, although I have only ever had computer problems once, and spg problems never.

 

[amascuba]

For me one of the big things is why would you want to combine two critical functions? If you lose one function you would lose them both. One of my favorite lines of George Irvine that makes so much sense for many things is "It tries to fix a problem that doesn't exist".

What do you gain from combining the two functions?