Diving has evolved with the onset of technology. Its now common to have a Dive computer. As divers we use them daily, above and below the surface. Now that dive computers are affordable to the point of being used instead of a wrist watch. Do you really understand what they tell us?
Its fact that using a dive computer is far more effective then using tables. Using tables to work out your accumulated nitrogen levels gives you perdition of your nitrogen. Your computer gives the same information but with a greater accuracy. It is still only a prediction.
While your computer is recalculating your residual nitrogen levels continually during your dive, it is only operating on the information it is given.
It has depth and time which it uses to calculate your current nitrogen levels. While being conservative it cannot calculate the information it cannot access.
Here are some of the things it does not use in its calculations. The amount of effort being used for the dive. Computers operate on an average dive. If you use a lot of effort in a strong current your computer only knows what your dive time was. It cannot calculate the extra nitrogen that you have absorbed during the dive. It also cannot grade your dive fitness. If you are not dive fit the results will in actuality be different from the computers prediction.
These variables are not being used in working out dive times and depths. Your computer is using a calculation that is conservative. Using this when your computer says NO it should be acknowledged that it is using the best information it has to work with. In doing this the results should be considered with the knowledge that they are variable in the results. Having been told by divers that they had DCS or DCI after following their dive computer shows the variations that happen. There are always other circumstances that add to DCS.
Minimum surface intervals are developed on ideal situations and conditions. The diver and the ocean conditions are perfect. If you are doing 1 dive in a day then your computer is not going to make big judgements. When you are doing multiple dives then you have other things to consider.
Did you over exerted yourself on the dive or on part of the dive. Add a little more surface time. Dive fitness will affect the amount of nitrogen you absorb. You may need to add time to your surface interval to allow for your fitness. In using your computer to guide you consider that its guidance has limits.
When you dive do so in a conservative manner. The extra safety that dive computers give us allow a greater access to safety with better information. When you are using a dive computer do so with the knowledge that it has limits on its information. Safety is diving conservatively.
PADI IDC Staff Instructor 331032
AUS DIVING ACADEMY