 A wrist watch sized dive computer incorporating an electronic compass A dive computer or decompression meter is a device used by a scuba diver to measure the time and depth of a dive so that a safe ascent rate can be calculated and displayed so that the diver can avoid decompression sickness. Image File history File links Suunto_D9_Dive_Computer. ...
Image File history File links Suunto_D9_Dive_Computer. ...
Scuba divers exploring fish and coral. ...
Decompression sickness (DCS), divers disease, the bends, or caisson disease is the name given to a variety of symptoms suffered by a person exposed to a reduction in the pressure surrounding their body. ...
Purpose Dive computers address the same problem as decompression tables, but are able perform a continuous calculation of the partial pressure of inert gases in the body based on the actual depth and time profile of the diver. As the dive computer automatically measures depth and time, it reduces the need for the diver to carry a separate watch and depth gauge and is able to warn of excessive ascent rates and missed decompression stops. Many dive computers also provide additional information to the diver, for example, the water temperature, information on the diver's oxygen toxicity or the pressure of the remaining breathing gas in the diving cylinder. Dive Tables, Decompression Tables or Tables are printed cards or booklets that allow divers to determine for a particular dive profile and breathing gas, the Decompression stops required for that dive in order to avoid decompression sickness. ...
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ...
A wrist watch A watch is a small portable timepiece or clock that displays the time and sometimes the day, date, month and year. ...
A Depth Gauge is a device used to measure pressure and display the equivalent depth in water. ...
A Decompression Stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive in order safely to eliminate inert gases from the divers body to avoid decompression sickness. ...
Oxygen toxicity or oxygen toxicity syndrome is severe hyperoxia caused by breathing oxygen at elevated partial pressures. ...
The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ...
Air is the most common and only natural breathing gas. ...
12 litre and 3 litre steel diving cylinders A diving cylinder or SCUBA tank is used to store and transport high pressure breathing gas as a component of an Aqua-Lung. ...
 A dive computer showing the log of a previous dive Image File history File linksMetadata Download high-resolution version (1944x2592, 932 KB) An Aladin Pro dive computer in logbook mode I, the creator of this work, hereby release it into the public domain. ...
Image File history File linksMetadata Download high-resolution version (1944x2592, 932 KB) An Aladin Pro dive computer in logbook mode I, the creator of this work, hereby release it into the public domain. ...
History The first mechanical analogue dive computer, the decompression meter was marketed by Scubapro in 1972. It was very simple in principle: a waterproof bladder filled with gas inside a big casing bled into a smaller chamber through a calibrated porous ceramic cartridge (to simulate tissue in/out gassing), whose pressure was measured by a manometer whose graduation indicated decompression stops. The device was eventually nicknamed bend-O-meter. A page from the Bombardiers Information File (BIF) that describes the components and controls of the Norden bombsight. ...
A manometer is a pressure measuring instrument, often also called pressure gauge. ...
Several analogue decompression meters were subsequently, some with several bladders for illustrating the effect on various body tissues, but they were sidelined with the arrival on the scene of electronic computers.
Early examples of recreational diving digital, electronic computers, from 1979, are the Hans Hass DecoBrain and Orca Edge. Recreational diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. ...
A digital system is one that uses discrete numbers, especially binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (an analog system). ...
This page refers to the year 1979. ...
Display information Dive computers provide a variety of visual dive information to the diver.
Modern dive computers display the following information on a LCD: Reflective twisted nematic liquid crystal display. ...
- Current depth.
- Maximum depth reached on this dive.
- No stop time, the time remaining at the current depth without the need for decompression stops.
- Dive time, often measured from the end of the last longer surface interval.
Many dive computers also display additional information: A Decompression Stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive in order safely to eliminate inert gases from the divers body to avoid decompression sickness. ...
- Required decompression stop depth and time.
- Water temperature.
- Ascent rate.
- Dive profile (often not displayed during the dive, but transmitted to a personal computer).
Some computers are designed to display information from a diving cylinder pressure sensor, such as: 12 litre and 3 litre steel diving cylinders A diving cylinder or SCUBA tank is used to store and transport high pressure breathing gas as a component of an Aqua-Lung. ...
- Gas pressure.
- Estimated remaining time based on available gas and rate of gas consumption.
Some information is only shown at the surface to avoid an information overload of the diver during the dive: - "Time to Fly" display showing when the diver can safely board an airplane.
- A log of key information about previous dives.
- Maximum non-decompression bottom times for subsequent dives based on the partial pressure of the gases in the tissue.
Audible information Many dive computers have warning buzzers that warn the diver of events such as: - Excessive ascent rates.
- Missed decompression stops.
- Maximum operation depth exceeded.
- Oxygen toxicity limits exceeded.
Oxygen toxicity or oxygen toxicity syndrome is severe hyperoxia caused by breathing oxygen at elevated partial pressures. ...
Operation Modern dive computers are battery-powered computers within a watertight case. These computers track the dive profile by measuring time and pressure. All dive computers measure the surrounding pressure to estimate the partial pressure of gases in the human tissue. More advanced dive computers also include additional information into the calculations, for example, the water temperature or the diving cylinder pressure. This does not cite its references or sources. ...
The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ...
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ...
The computer then uses the profile and a decompression algorithm to estimate the partial pressure of inert gases that has been dissolved in the diver's tissues. Based on these calculations, the computer estimates when a direct ascent is no longer possible, and what decompression stops would be needed. In mathematics, computing, linguistics and related disciplines, an algorithm is a procedure (a finite set of well-defined instructions) for accomplishing some task which, given an initial state, will terminate in a defined end-state. ...
Examples of decompression algorithms are Buhlmann's algorithm, the Multi-Tissue Model, the Varying Permeability Model, and the Reduced Gradient Bubble Model. The Variable Permeability Model or VPM is a decompression algorithm that was developed by D.E. Yount and others for use in commercial and recreational diving. ...
The reduced gradient bubble model is a decompression algorithm used in several dive computers, particularly those made by Suunto and Mares. ...
Many dive computers are able to produce a safe decompression schedule for dives that take place at altitude, which requires a slower ascent than at sea level, because the computers measure the atmospheric pressure before the dive. When divers travel before or after diving and particularly when they fly, they should transport their dive computer with them in the same pressure regime so that the computer can measure the pressure profile that their body has undergone. Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ...
Special purpose dive computers Some dive computers are able to calculate decompression schedules for breathing gases other than air, such as nitrox, pure oxygen, trimix or heliox. The more basic nitrox dive computers only support one or two gas mixes for each dive. Others support many different mixes. Air is the most common and only natural breathing gas. ...
Nitrox refers to any gas mixture composed (excluding trace gases) of nitrogen and oxygen; this includes normal air which is approximately 78% nitrogen and 21% oxygen, with around 1% other gases. ...
General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ...
Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used during the deep phase of dives carried out using Technical diving techniques. ...
Heliox is a gas that is composed of a mixture of helium (He) and oxygen (O2). ...
Most dive computers calculate decompression for 'open circuit' SCUBA where the proportions of the breathing gases are constant: these are "constant fraction" dive computers. Other dive computers are designed to model the gases in some 'closed circuit' SCUBA (rebreathers), which maintain constant partial pressures of gases by varying the proportions of gases in the mixture: these are "constant partial pressure" dive computers. // SCUBA is an acronym for Self-Contained Underwater Breathing Apparatus. ...
Inspiration closed circuit diving rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ...
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ...
Cautions The ease of use of dive computers, however, also exposes the diver to other dangers. They allow divers to perform complex dives with little planning. This may lead divers to exceed their competence and experience by relying too much on the computer rather than proper planning, discipline and monitoring.
Many dive computers have menus, various selectable options and various display modes, which are controlled by a small number of buttons on the front of the computer. The diver should become familiar with the control of the computer on a series of shallow and undemanding dives before relying on it for more challenging dives.
For safety reasons it is recommended that a dive plan should be established before the dive and the followed throughout the dive unless the dive is aborted. This dive plan should be within the limits of the decompression tables. This increases the margin of safety, and also provides a backup decompression schedule based on the dive tables in case the computer fails underwater. Dive Tables, Decompression Tables or Tables are printed cards or booklets that allow divers to determine for a particular dive profile and breathing gas, the Decompression stops required for that dive in order to avoid decompression sickness. ...
Different brands and models of dive computers use different decompression algorithms and safety factors. Some produce conservative decompression schedules and others produce aggressive decompression schedules. The main problem in establishing dive computer algorithms is that the gas absorption and release under pressure in the human body is still not completely understood. Furthermore, the risk of decompression sickness also depends on the physiology, fitness, condition and health of the individual diver. Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ...
A diver wishing to reduce the risk of decompression sickness can take a number of precautionary measures such as:
- Use dive computers with a conservative decompression model
- Use safety factors with dive computers (e.g. using a high altitude dive mode for a dive at sea level)
- Add additional deep safety stops during a deep dive
- Make a slow ascent
- Add additional shallow safety stops
- Have a long surface interval between dives
Many computers go into a "lockout" mode for 24 hours if the diver violates the computer's safety limits, to discourage continued diving after an unsafe dive. While in lockout mode, these computers display warning signs telling the diver that the dive computer cannot be used.
External links
Dive Computer Manufacturers
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