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The personal decompression computer, or dive computer, is a small computer designed to be worn by a diver during a dive, with a pressure sensor and an electronic timer mounted in a waterproof and pressure resistant housing and which has been programmed to model the inert gas loading of the diver's tissues in real time during a dive. [31]
A dive computer, personal decompression computer or decompression meter is a device used by an underwater diver to measure the elapsed time and depth during a dive and use this data to calculate and display an ascent profile which, according to the programmed decompression algorithm, will give a low risk of decompression sickness.
The Shearwater NERD was released at Dive 2013 in Birmingham, UK. [19] Shearwater Perdix in compass mode. In 2015, the Perdix wrist mounted dive computer was released. The Perdix is similar to the Petrel but has a 30% longer battery life and a thinner and lower profile. [20] The computer was named after the grey partridge Perdix perdix. [21]
The US Navy has used several decompression models from which their published decompression tables and authorized diving computer algorithms have been derived. The original C&R tables used a classic multiple independent parallel compartment model based on the work of J.S.Haldane in England in the early 20th century, using a critical ratio exponential ingassing and outgassing model.
The DIR philosophy is opposed to the use of dive computers. Most other technical diver training agencies recommend using two — a primary and a backup. Doing it Right: The Fundamentals of Better Diving page 119 lists 13 reasons why DIR consider dive computers to be bad.
Dive computers have become more reliable and more affordable, so it is fairly common for tech divers to have a backup computer. This reduces the risk of a computer failure during the dive necessitating an ascent controlled by depth gauge, timer and dive tables, and all the extra functionality and flexibility remains available to the diver.
A lack of standardised dive computer user-interfaces can cause confusion under stress. [90] Computer lock-out at times of great need is a potentially fatal design flaw. The meaning of alarms and warnings should be immediately obvious. The diver should be dealing with the problem, not trying to work out what it is.
The Orca Edge was an early example of a dive computer that ran a real time algorithm. [2] Designed by Craig Barshinger , Karl E. Huggins and Paul Heinmiller, the Edge did not display a decompression plan, but instead showed the ceiling or the so-called "safe-ascent-depth" and a graphic display of calculated tissue gas loadings.