Out of air incident.

[archer1960]

I think the key here is "beginning" versus "open water". One can be "open water certified" and still be a "beginner". One can be "advanced open water" certified, and still be a beginner.
...

Divegoose

Or, on can be Open Water (or Advanced Open Water), and be a very experienced diver too (I.E. NOT a beginner) .

 

[billt4sf]

OK, let me do a simple math that you can prove me wrong. Let's say I'm in 60' deep, ~ 30 psig or 2 barg or 3 bar absolute (bara) ambient pressure. The SPG is showing 150 psig or 10 barg or 13 bara pressure. I have 30" long hose of each low pressure hoses for the 2nd stage primary regulator + octopus + BCD inflator (total 90" long) with 1/4" (6.5mm) ID hoses, which sum of the volume comes up to 76mL x 13 bara hose pressure / 3 bara ambient pressure = 328 mL ambient air volume. My lung has about 6000mL volume. 328/6000 x 100% = 5% of my lung volume. I call that OOA.

Dan,

One time I got caught in a washing machine current and it deposited me at 50 feet, I looked at my SPG and it said ZERO. I looked again -- really zero? YES. But I was breathing - HARD. I took maybe 30 seconds to get to the surface, breathing hard all the way, inflated my BCD and kept breathing from the reg because I was freaked out. (My first experience in a washing machine current).

My point is that those SPGs are not accurate. Thank God for that on that dive!

- Bill

 

[Dan]

Dan,

One time I got caught in a washing machine current and it deposited me at 50 feet, I looked at my SPG and it said ZERO. I looked again -- really zero? YES. But I was breathing - HARD. I took maybe 30 seconds to get to the surface, breathing hard all the way, inflated my BCD and kept breathing from the reg because I was freaked out. (My first experience in a washing machine current).

My point is that those SPGs are not accurate. Thank God for that on that dive!

- Bill

Wow! That's good to know Bill. I am glad that you made it out alright.

For critical instrument such as this, I have redundancy. I have 2 SPGs on my gear. One is a gauge, as shown in the picture, below. The other one is on my Dive computer console (SUUNTO Cobra2). I was told by LDS regulator technician that my gauge reads lower that the actual pressure. My Cobra2 shows a more correct reading & calibrated every time the battery is changed.

The 2nd critical instrument is the dive computer itself. I have the 2nd one on my wrist, SUUNTO D4. If one of the 2 dive computers runs out of battery during the trip, I can continue diving with the 2nd one. It happened a couple of times. I now even carry extra batteries, o-rings & right screwdrivers to replace the batteries on the road. Thank goodness that D4 & Cobra 2 use the same battery, CR2450, which I can order a pack of 5, online from Walmart for $5.49 ($1.10 each): https://www.walmart.com/ip/Insten-I...-Button-Cell-Watch-Battery-Pack-Of-5/45000350. They are now sitting in my travel tool box.

 

[KDAD]

I was told by dive technician that my gauge reads lower that the actual pressure. My Cobra2 shows a more correct reading & calibrated every time the battery is changed.

What are you calibrating the Cobra against every time the battery gets changed out?

 

[Dan]

What are you calibrating the Cobra against every time the battery gets changed out?

I should correct my statement & describe it better. Re actual recalibration is not every time the battery gets changed out, it's more like every other times. It doesn't get off calibration that often. I compare it with the SPG. If it is consistently slightly higher than the SPG, especially at the low end, below 500 psig, say about 10% higher, I'll skip the recalibration.

The SPG seems to indicate more accurate pressure at the higher end. Hence it's not a linear error, as if the pressure reading vs. actual pressure has steeper slope than that of the Cobra2.

I have the Cobra2 recalibrated when it's not in emergency, i.e., if it's just showing low battery during the dive trip. I'd send it out to nearest SUUNTO service center to change the battery & have it calibrated after the dive trip.

 

[Dan]

OK, let me do a simple math that you can prove me wrong. Let's say I'm in 60' deep, ~ 30 psig or 2 barg or 3 bar absolute (bara) ambient pressure. The SPG is showing 150 psig or 10 barg or 13 bara pressure. I have 30" long hose of each low pressure hoses for the 2nd stage primary regulator + octopus + BCD inflator (total 90" long) with 1/4" (6.5mm) ID hoses, which sum of the volume comes up to 76mL x 13 bara hose pressure / 3 bara ambient pressure = 328 mL ambient air volume. My lung has about 6000mL volume. 328/6000 x 100% = 5% of my lung volume. I call that OOA.

Let me correct my own poor math. I forgot to include the tank volume at 150psig (13 bara). At 60' deep (3bara), the tank (assuming the AL80 has 11.2L volume) should have = 11.2L x 13 bara / 3 bara / 6L lung volume / deep breath = 8 deep breaths. The tank should have more air volume available as I slowly ascend. Is that right?

 

[archer1960]

Let me correct my own poor math. I forgot to include the tank volume at 150psig (13 bara). At 60' deep (3bara), the tank (assuming the AL80 has 11.2L volume) should have = 11.2L x 13 bara / 3 bara / 6L lung volume / deep breath = 8 deep breaths. The tank should have more air volume available as I slowly ascend. Is that right?

Yes, you will be able to get more air out of the tank as you ascend.