Can you monitor your tank pressure mentally?

[Ber Rabbit]

I get my students started on this the first scuba session. I tell them they need to monitor their buddy regularly and communicate air pressure. A staff member can come up to them at any time and ask how much air their buddy has. Our gauges show the numbers in 250psi intervals so that's how accurate I expect them to be. It doesn't take them long to get the hang of how often they need to monitor their buddy's gauge to be dead-on with their answer. That's when we look at the relationship between our own gauge and our buddy's. While that's not exactly "mentally monitoring" your air it can lead there with experience.
Ber :lilbunny:

 

[loosebits]

It takes time and familiarity with the tanks you are diving. In my 104's, I know my pressure to well within 100 psi quite consistantly (of course a 100 psi in 104's gives quite a large margin for error). When diving anything else (e.g. singles or double 80's), I'm not nearly as accurate.

 

[cadiver67]

Well...
Since you said I can't judge your buddy skills or air consumption because I've never seen you dive, that would imply that I can grade you on your words since I've seen them.

No Fair - it's your fault I started this poll in the first place.

I wanted to see if I was the only one, but it looks like me and 12 others are PSI challenged.

 

[ClayJar]

If it makes you feel better, my significant buddy (8 dives), her little sister (6 dives), and her parents (not many, and one post-checkout vacation, respectively) all fall in the pressure-challenged category. Her older sister, on the other hand, has been diving quite a bit more than they have (on par with you, probably, and many of those dives with me), and she has acquired the capability.

Of course, she only became proficient at gauging her air consumption once she fixed her weighting, arrived at the nirvana of horizontal trim, and thereby pegged her buoyancy. It seems, perhaps, it may be a lot easier to tell how much air you're using when you've got a proper baseline (i.e. "relaxed and cruising"). Or maybe it's just purely experience-based without any relation to form, save coincidence.

 

[cadiver67]

Of course, she only became proficient at gauging her air consumption once she fixed her weighting, arrived at the nirvana of horizontal trim, and thereby pegged her buoyancy. It seems, perhaps, it may be a lot easier to tell how much air you're using when you've got a proper baseline (i.e. "relaxed and cruising"). Or maybe it's just purely experience-based without any relation to form, save coincidence.

Yes I can't wait to get to nirvana.

I was pretty close in my wetsuit, now I am in a drysuit, was hating life for the first few dives, but things are feeling good again.

 

[ClayJar]

I didn't actually get the trim problems and related SAC spike when I went dry (who knows why), but when I went to a backplate and wing, my trim went p'tooie and my SAC shot up 25%. The second dive with the BP/W, I got half that back, however, once I figured out how the infernal thing worked (hehe). By the last dive that day, I grokked the BP/W and found it absolutely *delightful* to dive with... and my SAC was back where I'd started or even a couple percent better.

For the "what on earth am I doing diving this?!?" dive, it took a few minutes to get my estimating in line with the higher consumption, but I suppose the many, many dives of estimation practice helped.

Obviously, there have been times when I've been in an unusual situation of some sort or other. When I feel as if I'm in a situation for which I don't have a firm grip on my likely air consumption, I'll shift into check-early-check-often mode. The same goes for any time I see I'm using more (or less) air than I expect. If it's outside my expectations, or if I have no expectations for those conditions, I'll drop back into "safe mode" and not be disappointed at all. (I'll just do a lot of thinking to analyze the estimation failure -- if it's just a new situation, I add it to my mental library, but if it's a deviation from an existing expectation, I want to know why.)

 

[Charlie99]

Of course, she only became proficient at gauging her air consumption once she fixed her weighting, arrived at the nirvana of horizontal trim, and thereby pegged her buoyancy. It seems, perhaps, it may be a lot easier to tell how much air you're using when you've got a proper baseline (i.e. "relaxed and cruising"). Or maybe it's just purely experience-based without any relation to form, save coincidence.

My guess is that if you are going around negatively buoyant, finning to maintain depth, you are working so hard on the mechanics of diving that you don't have a lot of excess brain power left over for good situational awareness and estimating air consumption. For me at least, it was when buoyancy control became an autonomic function that the brain cells freed up got put to use paying attention to the rest of the world.

 

[SparticleBrane]

now I am in a drysuit, was hating life for the first few dives

I'll agree with you on that one.

 

[Rick Inman]

I still have less than 100 dives below 150', so I'm not as confident in "knowing" my gas supply at all times that deep. But on recreational dives, I am confident within 200psi.

Last Saturday four of us made a dive to a max depth of 120' (guys I've dived with plenty of times) and I'd put money on knowing their gas within 200psi. I worked pretty hard on this for about a years worth of dives, though. It's really a pretty easy trick once you get in the habit of just thinking about it.

I'll admit, I usually just check my gage a couple of mins into the dive to make sure everything is working right, and then sometimes don't look again. I'm following a plan, which means a gas plan based on time and depth. As long as I'm following the plan and nothing unusual comes up, and I know in my head how much gas I have, why should I check?

 

[TSandM]

This is where knowing your SAC rate and knowing the tank factor for your tank come in useful. I know my SAC rate tends to run about .4, and if I'm using a tank with a tank factor (cu ft/100 psi) of 3, then at 66 ft (3 ATA), I'm using 1.2 cu ft/min, or 6 per 5 minutes, which is 200 psi per 5 minutes.

I can do mine pretty well, and with well-known buddies it's pretty easy (I know Kirk's SAC rate, and Bob's is the same as mine, and Peter's is about .5). I haven't gone through the "ask at 10 minutes and figure out their SAC rate from the data" exercise yet, but it would have been fun to play with while we were down here.