Texass once bubbled...
WHY? Just for fun mainly.
After filling out my log, I run a plan using a guesstimate of my SI on the computer. My brain doesn't internalize that number as well as if I can say "Hmm, I am now at this PG." I like to go through the mechanics of using a table for the same reason. Unfortunately if the table says I'm in the black I can't do that, at least I don't know how to.
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Your computer has a planning mode, right? You can use the planning mode to put yourself back on the tables. By starting with your adjusted NDL and reading the table backwards. Here's how:
Directly upon surfacing, enter the planning mode and look at the adjusted NDL for the next dive. Pick any depth, say 60 ft. Suppose your computer tells you that your adjusted NDL for 60ft is 20 min.
Now you take your table (I'll use the PADI table for this example) and look at the back of it where you see the adjusted NDL's. Read the table backwards by looking across the 60ft row until you find 20min and then up to find your pressure group. That's your current pressure group, in this case N.
If you wait for a period of time you need to adjust for your surface interval too.
Say in the previous example you discovered after 30 min (perhaps after getting back on the boat and de-kitting) that you were an N. What was your group when you surfaced? For that you need to go to the surface intervals on the front of the table. Start at the bottom of the table and find group N. Look up the N column until you find the 30min SI, in this case from :29-:33 min, and read to the left to find your group when you surfaced, in this case V.
Easy, eh?
There are a couple of "gotcha's" in this story, though. One has to do with surface intervals. Your PADI table uses a 60min compartment for off-gassing. That's most likely faster than your computer. If you wait long enough you'll find that you've totally cleared on the PADI table but your computer is still giving you an adjusted NDL that's less than a cleared value. The best way to avoid this is to check as soon as possible after surfacing. And obviously this difference makes it unwise to use this technique for planning subsequent dives.
The other gotcha has to do with your bottom time and maximum depth. After finding your group on the PADI table, you might notice that your bottom time and/or maximum depth are off the scale. This is logical given the differences between tables and the computer.
R..
