Question about air integrated computers and backup

[bureau13]

A lot of good points everyone, thanks for all the replies. One thing that for some strange reason never occurred to me was that you really DON'T need a pressure gauge to safely end a recreational dive, assuming you're not being stupid with your air. This makes perfect sense...but then again the point that if you're on a trip somewhere fantastic, it also makes sense to take some precautions so you don't have to end early.

jds

 

[paulwlee]

but then again the point that if you're on a trip somewhere fantastic, it also makes sense to take some precautions so you don't have to end early.

This is a very valid point and partly why I keep the SPG when I dive with a hoseless AI computer. (But partly because I now usually don't use AI and I don't bother to take the SPG off. An SPG is barely noticeable on a short hose.)

But keep in mind that most people who chimed in about having the SPG is talking about a hoseless computer, where there is an additional battery to fail and a less reliable link than a pressure transducer directly attached to the computer at the end of a hose.

Having both a hose AI computer (Cobra, etc.) and an SPG is a lot more bulky, and non-hoseless AI rarely fails except when the whole computer fails.

 

[haha49]

i dont like the air intergrated computers some of them will only go down to 500 psi and then beep and flash at you telling you low air.. when in fact you might only have 200 psi now thats scary when you think about it.. you might think you have a little left when in fact you dont but thats just 1 air intergrated computer..

 

[paulwlee]

when in fact you might only have 200 psi now thats scary when you think about it.. you might think you have a little left when in fact you dont but thats just 1 air intergrated computer..

Same thing can happen to a mechanical SPG. Over the years I've seen a few showing several hundred psi higher that it really should read.

 

[Arizona]

For what its worth, I've used my Mares Airlab for about 60 dives and it has been very reliable. The case is getting a little beat up, but I guess that is to be expected. The batteries are easy to change and it does Nitrox. As stated, if it malfunctioned the dive should come to an end. An SMB should be carried just in case.

If I had to do it over, I like my friends set up which is a D6 Sunnto and a simple pressure gauge less the depth gauge attached by a standard hose to the 1st stage. It looks real compact and does everything you most likely need.

 

[bureau13]

Really! The D6 is non-AI right? So you actually prefer non-AI computers? Or you just really like the Sunnto?

jds

For what its worth, I've used my Mares Airlab for about 60 dives and it has been very reliable. The case is getting a little beat up, but I guess that is to be expected. The batteries are easy to change and it does Nitrox. As stated, if it malfunctioned the dive should come to an end. An SMB should be carried just in case.

If I had to do it over, I like my friends set up which is a D6 Sunnto and a simple pressure gauge less the depth gauge attached by a standard hose to the 1st stage. It looks real compact and does everything you most likely need.

 

[charlesml3]

With the wrist unit also I can tell my ascent speed so ill still be able to make a safe accent..

Tim,

You don't need a computer to tell you about your ascent rate. If you're heading up faster than your bubbles, you're going too fast.

I'm quite sure that one day I'll have to abort a dive due to my computer failing but I have a spare reg on the boat anyway. It's old but it still works. I'll just switch them out. Until then, I'm diving with only the gear I absolutely need.

-Charles

 

[CompuDude]

Tim,

You don't need a computer to tell you about your ascent rate. If you're heading up faster than your bubbles, you're going too fast.

I'm quite sure that one day I'll have to abort a dive due to my computer failing but I have a spare reg on the boat anyway. It's old but it still works. I'll just switch them out. Until then, I'm diving with only the gear I absolutely need.

-Charles

That's an old rule of thumb (this old dog learned it too!), and it's better than nothing, but it was generated in the days of a 60 fps ascent rate. With today's more cautious 30 fps rate, the bubble trick is less useful.

 

[charlesml3]

Hey Compudude,

Yea, I was certified in 1981. Anyway, I've asked repeatedly why it has to be a 30fps ascent rate when "never rise faster than your bubbles" worked for me for nearly 15 years. I'm still waiting for a decent answer. I keep getting "it's safer." Well, not diving at all is SAFER. What I can't get an answer to is : "Why is the old bubble rule riskier?"

I think there's this tendency in Scuba diving to adopt most any rule or change that makes things safer. I look at dive tables now and compare them to the ones I had in 1981 and it's unreal how conservative they are now. I still wonder if that's because we really do understand the physiology better or if it's just fear of lawsuits in our fantastically litigious society.

-Charles

 

[Web Monkey]

What I can't get an answer to is : "Why is the old bubble rule riskier?"

Because bubbles can move in any direction at any speed depending on the current, and accelerate as they rise and expand.

They're better than nothing, but not better than a working depth gauge.

Terry