IANTD does or at least 20yrs ago.
DGX still sell them , check post #11.
Cool, but the OP said he's taking AN/DP (I think), which is a TDI course. I wouldn't think a TDI course would require you to use IANTD tables...
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IANTD does or at least 20yrs ago.
DGX still sell them , check post #11.
How did you get 0.7 and 32.35? What size tank are you assuming? When you say 1.48 ATM do you mean 1.48 PPO2? What computer is telling you 77 cuft?I'm not sure what I'm doing wrong here. I planned a dive at 32% @ 120 ft for 20 minutes. I know the max dept is 110 at 1.4 but at 1.6 its 132'. Just testing. ATA is 4.6 which I got by 120/33+1. RMV is .7. ATM is 1.48. PSI/min is 32.35. I took .7 x 4.64 x 20 and get 64.4 cubic feet. My computer says 77 cubic feet. if I take 32.35 x 4.64 I get 150 psi per minute at depth or 13.3 minutes. What did I mess up?
Sure, for example the NAUI EAN36 table covers dives with as much as 39 minutes of mandatory decompression stop. The other NAUI tables also all cover deco. They don't cover mixed gas diving or accelerated deco on oxygen or anything else but simple decompression with a single gas. I don't know about you, but given the size of my sac I'd have to bring a lot of gas to do 140 minutes at 80' and then do a 39 minute deco stop at 15'.Are there "deco tables"?
I know nothing about deco diving but fully understand non deco tables. My impression was that computer programs (at least fancy spreadsheets) were routinely used for deco dive planning. Is it normal to teach / use totally manual planning and calculation of deco dives?
My impression is that the added complexity of various gas mixes, depths and deco obligations would make manual calculation very error prone.
Thoughts / opinions? (I am just trying to learn a very little bit about stuff I will never use...)
This was done in the to get the RMV. I am using alum 80s. I am using a dive calc. I put in 3000 PSI, 20 minutes for depth at 120'. It games me 4.64 ATA and PSI/min or SCR of 32.35
Gotcha! That calculator is telling you that if you spent 20 minutes at 120 ft, and in the course of that dive used 3000 PSI in a single Aluminum 80, you were breathing the equivalent of 32.35 PSI/min on the surface. The formula is gas used (3000 psi) / (Time (20 min) * Depth in ATA (4.64)). It's common to talk about these numbers in terms of volume because PSI varies depending upon the types of tanks you're using. This 32.35 PSI/min can be converted back to volume using the 2.5 tank factor 32.35 PSI * 2.5 cf/100 PSI = 0.81 cf/min. It's important to understand how these things are calculated rather than blindly using the calculators. The other thing this doesn't account for is the fact that you have two tanks, so remember, if you use 1400 psi from one and 1600 psi from the other, the input numbers need to account for this.
The number you get from the calculator is probably not far from correct, but that's just a coincidence. To get that number for you, you'll need to go underwater, note your tank pressures, note your average depth, note your time, and use those real numbers to calculate how much gas you need at a given depth. Track those numbers across many dives in different environments. Understand your baseline. Most experienced divers will fall in the range between 0.5 and 0.75 cf/min. If you're learning a new configuration, it might be higher. If you're very relaxed and/or small/female, it might be lower. A decent guesstimate if you don't have real numbers is 0.75 cf/min (I was assuming that's where you got the 0.7 number).
It's also useful to have quick tricks to make calculations more idiot-proof underwater, because I'm an idiot doing math underwater. In sidemount, when I'm switching tanks every 200 psi, I like to know how many minutes it'll take me to breathe 200 psi at a planned depth. You'll learn these sorts of tricks from the class. They take underwater practice to get right. You'll learn to be a bit less dependent on your SPG. It becomes a sanity check of mental expectations.
Do ask your instructor for help if you don't understand this stuff. It's really important to know how the numbers fit together, but the math can make it a little daunting at the start.