Nowadays, dive computers have replaced the use of dive tables. Dive tables would work only if precise monitoring is practised. A dive computer reduces risk while allowing you to maximize your bottom time.
A dive computer is an electronic instrument with a pressure sensor, electronic circuitry, a battery and a display. A programmed computer inside the instrument uses pressure and time information to continuously calculate the uptake of nitrogen by various compartments that have different half-times.
Names such as the Cressi Leonardo scuba dive computer, Aeris dive computer, Oceanic dive computers and Suunto dive computers will come to mind. Additional well-known brands will include NiTek Duo and NiTek Triodive computer, Mares Nemo Sport dive computer as well as Mares Nemo air dive computer.
With a proliferation of dive computers on the market, you’ll hear about the modified Haldane ratio, half-times, tissue compartments, Workman M-values, Buhlmann M-values, and algorithms in most of the computer literature. To make some sense of these terms, it pays to understand some basic decompression theory. You may wish to pick up “The Certified Diver’s Handbook: The Complete Guide to Your Own Underwater Adventures
” by Clay Coleman for more details.
As mentioned earlier, a dive computer continuously calculates the uptake of nitrogen by various compartments that have different half-times. A half-time is the length of time required for a mathematical model (compartment) to increase or decrease its gas absorption or elimination by one-half.
A compartment, which resembles, but does not duplicate body tissues, is completely saturated or desaturated in six half-times. When the absorption by any one of a computers compartments reaches a predetermined level, the device indicates that you are approaching the time limit after which a direct ascent to the surface will no longer be possible.
On reaching the time limit, the computer indicates a minimum depth – a ceiling – that you cannot exceed during ascent. You risk decompression sickness unless you wait till your dive computer indicates that sufficient outgassing has occurred to allow you to continue your descent.
A dive computer provides extremely accurate time and depth information. Other common features are a low-battery warning, a rapid-ascent warning, a dive log mode, a dive-planning mode, and information about flying after diving.