Computers and Tables

[Steve_Dives]

I fill out the log complete with the group designation just to practice with the tables, and to show myself how much bottom time the computer gives me. I also write in the log that it was a computer dive because running the tables on some of the dives looks like there was a problem.

For example, my deep dive was 90 feet and 45 minutes.

On the SSI tables (which show only no deco times) I would have been well into the required decompression zone. I guess I would have to call DAN if I only had those tables.

On the NOAA tables I would have spent over a third of the dive hanging at ten feet.

On the Navy tables I would have had two level stops with a total of about 10 minutes.

Can't find my NAUI tables...

And the computer suggested a level stop for less time than our planned safety stop. The suggested stop cleared before we moved above 50 feet.​

 

[String]

Tables assume square profile (unless you compute average depth in head or use some evil abomination like the wheel) whereas computers track the actual dive profile. Therefore unless you stay at maximum depth and dive a full square profile dive a computers decompression/loading data will differ from tables.

Secondly, tables use different models to the tables so the designations aren't compatible anyway.

 

[J.R.]

My logbook has a shaded section exclusively for computer dives, you need only fill in those portions as you have mentioned in your OP

Cool... I haven't seen one of those... could you put up who makes em' or where I could find them. Sounds like something of interest to me... thanks.

 

[Minipinny]

yeah ... i usually do this by using the 120 rule:

dive time + max depth = 120

for example, if my next dive is going to be to 70 feet, i expect my bottom time to be around 50 minutes for the first dive

for the second dive, i have to take into account residual nitrogen, so after a minimum of one hour surface interval, i half my bottom time available (in the above case, to 25 minutes)

Thanks for this tip I will try it out this weekend.

 

[H2Andy]

keep in mind that the above is worst case scenario, in case

1. my computer fritzes out between dives; and

2. i don't have the exact information needed to calculate the actual profile for the prior dive

it's worst-case scenario, as it assumes an I group after one hour surface interval

 

[ClayJar]

For example, my deep dive was 90 feet and 45 minutes.

Can't find my NAUI tables...​

45 minutes with a maximum depth of 90 feet would give you an 18 minute stop at 15'/5m on the NAUI tables. (50 minutes is in the very last column on the 90' row on Table 1.)