Wireless

[Hollywoodivers]

I don't understand...Is the question use a tranmitter as well as a brass spg? If so, and the spg fails ...meaning the gauge pops or the hose splits...the transmitter is just going to confirm a dropping tank pressure much like the brass spg will. Upon isolation, then you dive would still be over...I hope I got that close..if that was the question...

If you are going DIR then a transmitter in lieu of would not be DIR...

 

[Rainer]

I don't understand...Is the question use a tranmitter as well as a brass spg? If so, and the spg fails ...meaning the gauge pops or the hose splits...the transmitter is just going to confirm a dropping tank pressure much like the brass spg will. Upon isolation, then you dive would still be over...I hope I got that close..if that was the question...

I had originally been thinking of a different failure (e.g. cracked SPG, where it wouldn't read right, but wasn't leaking).

If you are going DIR then a transmitter in lieu of would not be DIR...

Um, yeah, I wanted to understand WHY, so I posted. Got great responses (from most).

 

[Kevrumbo]

. . . .
It is just not needed. Give it a try... IRL figureing out your gas consumption in your head with a cross check with your SPG isn't that hard....

An Example: For my Steel 95 Doubles, my rule-of-thumb nominal consumption is 100psi/10min per 1ATA assuming a RMV of .75cf/min. So, if I'm at 100fsw, my Suunto D3 says 30meters which easily translates to 4ATA in your head. Multiply 4ATA by 100psi/10min per 1ATA equals a Depth Consumption rate of 400psi/10min --therefore I'd expect after 10 minutes at 100fsw, my SPG to have a delta of 400psi down from the previous reading . . .or if I want to check more frequently, say after 5 minutes, I would expect my SPG to be down by 200psi.

 

[cool_hardware52]

I don't understand...Is the question use a tranmitter as well as a brass spg? If so, and the spg fails ...meaning the gauge pops or the hose splits...the transmitter is just going to confirm a dropping tank pressure much like the brass spg will. Upon isolation, then you dive would still be over...I hope I got that close..if that was the question...

Why do you isolate? If the SPG fails shut down the left post. Turn the dive.

If you are going DIR then a transmitter in lieu of would not be DIR...

Transmitter period, with or without the analog SPG would not be DIR, at least as I understand it. Other than Bottom Timers what electronics are DIR?

Anybody have any stats on the failure rate of mechanical SPG's vs wireless? I'll bet the mechanical is several orders of magnitude more reliable.


Tobin

 

[roakey]

I guess I don't understand all the discussion about your buddy's SPG. Though it may give you a warm and fuzzy, it doesn't tell you what's in YOUR cylinders.

The point is, if you've done your gas planning correctly (another concept key to DIR, and why all this stuff all ties together and answering questions like “How about a second SPG?” are difficult to answer without widening the considerations), the worst case scenario is that you have an SPG failure right at the point of turning the dive. At that point, since gas consumption entered into your dive planning (among other things), you know you have enough gas to complete the dive (in fact at that point you have enough gas for TWO divers to complete the dive on just your gas) – don’t sweat it, just call the dive.

If you think there might be some factors that would make sharing gas difficult at the end of the dive (high waves, deco on backgas in a tight restriction, etc.) get some gas from your buddy at an earlier time so you know you have enough at the end.

But really, your gas planning should assure that you have plenty, since you saved enough gas for TWO divers to complete the dive on just your back gas, right? (Rock bottom, thirds, etc.).

And if your SPG fails before the moment of turn, you have even MORE gas to complete the dive, since you call the dive instantly upon failure. Without an SPG how do you know what's in your cylinders? Answer -- because of proper gas planning: More than enough.

Roak

 

[darkpup]

I guess I don't understand all the discussion about your buddy's SPG. Though it may give you a warm and fuzzy, it doesn't tell you what's in YOUR cylinders.

The point is, if you've done your gas planning correctly (another concept key to DIR, and why all this stuff all ties together and answering questions like “How about a second SPG?” are difficult to answer without widening the considerations), the worst case scenario is that you have an SPG failure right at the point of turning the dive. At that point, since gas consumption entered into your dive planning (among other things), you know you have enough gas to complete the dive (in fact at that point you have enough gas for TWO divers to complete the dive on just your gas) – don’t sweat it, just call the dive.

If you think there might be some factors that would make sharing gas difficult at the end of the dive (high waves, deco on backgas in a tight restriction, etc.) get some gas from your buddy at an earlier time so you know you have enough at the end.

But really, your gas planning should assure that you have plenty, since you saved enough gas for TWO divers to complete the dive on just your back gas, right? (Rock bottom, thirds, etc.).

And if your SPG fails before the moment of turn, you have even MORE gas to complete the dive, since you call the dive instantly upon failure. Without an SPG how do you know what's in your cylinders? Answer -- because of proper gas planning: More than enough.

Roak

How is this any different from what I stated?

You're basically saying that in the event you don't know how much gas you have left (i.e. your SPG fails, valve failures, reg failures, loss of gas, etc), you have a number of options based on the type of dive, depth, experience, training, situation, and team confidence. You're also saying that if the environment dictates that you switch to a known gas supply, then you switch to your buddies gas and use their SPG to monitor your consumption rate.

How is this not using your buddies SPG as a back up (i.e. breathing off of their tanks) when the situation requires it?

~ Jason

 

[Derek S]

Rainer -

Read this book (first one):

https://secure.gue.com/catalog/order

Look at these standards:

http://www.gue.com/Training/Standards/GUE_Standards_2006_ver4.pdf

Contact either one of these instructors for a class:

http://www.gue.com/Training/Instructors/ehayes.html

http://www.gue.com/Training/Instructors/rsherwood.html

All shall be revealed.

 

[rjack321]

If each gauge has an independent probability of failure of say 1 in 100 dives (way higher than reality for illustrative purposes, although I bet the wireless isn't a whole lot lower)

Then the potential failure of either gauge on a dive is 2 in 100 dives. This presumes the events are independent. This is higher.

The failure of both gauges has a lower probability since these are dependent events (you have to fail once in order to fail twice).
0.01 x 0.01 = 0.0001 or 1 in 10,000 dives

Really the o-ring on the wireless transmitter isn't any more or less of a failure point than the o-ring on the plug which would be in its place. Maybe its a bit easier to loosen with the knobby part sticking out. The real failure mode IMO is the actual breaking off of the transmitter.

For regular SPGs, they generally still read even with a cracked glass. They flood, but the needle still works for awhile until the the guts corodes. The Bourdon tube rarely breaks itself.

2 SPGs doesn't solve any problems. Between your gas planning and your buddies gauge you have a good idea of how much gas you have at any time. They are expensive do-dads and the money's better invested somewhere else.

 

[Scared Silly]

Wouldn't the more genernal DIR answer to the question be - the only redundant equipment needed is the minimum equipment for life support that will insure a safe and independent ascent to the surface?

 

[KMD]

1. I'm on a 30' to 60' reef dive with my buddy with al80 single tanks. The o-ring on my transmitter blows, and there's a leak of gas from my first stage. With the surface in site, no required deco, and plenty of gas, I would keep diving until my gas supply was close to my Rock Bottom number.

My reason for this decision is that I could surface at any time, my buddy has enough gas for both of us to reach the surface if the problem gets worse, and it's probably a great day for diving.

Not to jump over you on this, but waiting until close to rock bottom to surface is really not a great solution as your rock bottom number has changed due to the increased gas loss. In an emergency where your buddy needs to rely upon your gas supply there may not be enough to make a safe ascent.

On the other hand, I wont be hypocritical and say that I have never dove with a slow leak at the yolk vavle before.