If all of that is true, then something is very wrong. You should have had plenty of gas.
OOA at very end of safety stop
- Thread starter Chavodel8en
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Scubagolf
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Stoo
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Don't be so hard on yourself... You could look at this as getting "best value" out of your fill... ;-)
Seriously though, these SPGs are like any other sort of guage... not necessarily 100% accurate... A friend I dive with uses one that seems to "plummet" from 700 psi down. Now that we're all aware of that. we turn the dive sooner with her...
Seriously though, these SPGs are like any other sort of guage... not necessarily 100% accurate... A friend I dive with uses one that seems to "plummet" from 700 psi down. Now that we're all aware of that. we turn the dive sooner with her...
Bubblesong
Contributor
Would not hurt to check over your equipment for slow leaks behind your head where you can't see them, and buddies might not notice. that has wasted my air on one trip, I didn't catch it until five dives in.
Wow thanks for sharing. Certainly reminds us how easy it can be to become too blase! I admit the amount of reserve gas I plan for has a lot to do with the site and dive conditions on shore dives.
mnjhuz76
Contributor
Wouldn't make me wonder too much if this tube/snail construction most SPGs incorporate wears out over time and becomes more and more inaccurate. I tend to trust the piezo sensor in my wireless transmitter a little more
There is a previous thread on this
The accuracy of the SPG
Bottom line is that some are more accurate than others and how they are off varies by the speciifc spg you have. Digital seem more accurate than analog.
On my last pair of dives, fellow sitting next to me went through his air noticably faster than usual. Turns out he had a leak in an air hose that neither he nor his buddy had noticed during the dive. Was at the crimp. I have had two hoses leak there. At the end of a days diving I put my hose back on my tank and rinse in a large storage bin full of fresh water. While laying there I watch for leaks. Catch small ones there, although I had one that was only active when tank above 1000 psi. That one found by a buddy during a dive.
The accuracy of the SPG
Bottom line is that some are more accurate than others and how they are off varies by the speciifc spg you have. Digital seem more accurate than analog.
On my last pair of dives, fellow sitting next to me went through his air noticably faster than usual. Turns out he had a leak in an air hose that neither he nor his buddy had noticed during the dive. Was at the crimp. I have had two hoses leak there. At the end of a days diving I put my hose back on my tank and rinse in a large storage bin full of fresh water. While laying there I watch for leaks. Catch small ones there, although I had one that was only active when tank above 1000 psi. That one found by a buddy during a dive.
Dan
Contributor
It's good to check your SAC after every dive. If it jumps from 0.4 to 0.6 CFM. Then you know something is wrong with your gear.
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That's one of the reasons I like my Air integrated Computer and using an electronic dive log system. Much easier to track quite a number of stats.
I play a little game with myself. I set certain numbers in my head and try to time it to be looking at the computer when that number comes up. It helps me think about what is going on in the dive and how it is likely to effect my air consumption. It's kinda fun too.
I play a little game with myself. I set certain numbers in my head and try to time it to be looking at the computer when that number comes up. It helps me think about what is going on in the dive and how it is likely to effect my air consumption. It's kinda fun too.
At 700 PSI, you had roughly 20 cubic feet of gas.
Let's assume you had a SAC rate of 0.66 on your safety stop. You would have gone through 2 cubic feet in the two minutes you were doing the stop.
Let's assume you took a full minute of elevated effort and breathing to reach your buddy ahead of you, get his attention, and start the ascent, and let's say that was at 50 feet. We'll give you a SAC of 1.0 for that effort. That's another 2.5 cubic feet.
Your gauge may have read 0, but you probably had at least a cubic foot or two left in it.
Put all of that together, and rounding up on the estimates, that means you used at least 13 cubic feet on a 1.5 minute, 40 foot ascent to the safety stop. Your average depth on ascent was almost exactly 2 ATA, so for that to be done through breathing alone, you would have had to have a SAC rate greater than 4.0 during that ascent, and that is pretty much unheard of. Assuming your tank was full at the start of the dive, your SAC rate was well below 1.0 for most of the dive, and it should have been even less during a leisurely ascent.
That is why I am suggesting that something is not right.
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