Dive computer

A dive computer helps the divers in planning and conducting dives to avoid decompression sickness ( the bends ). During the dive, the dive computer continuously measures depth and dive time and calculates a profile of the dive. The dive computer can be seen as a successor, or to complement decompression table and the ( historical ) mechanically constructed Dekometer.

• 5.1 Air Integrated Dive Computer
• 5.2 dive computer for technical diving

History

Dekompressiometer

When the U.S. Navy, the first decompression tables published in the 1930s - a reduced risk of decompression sickness - the need for a device was quickly realized that automatically controls the dive and the diver warns against exceeding of limits. Therefore 1951, the Scripps Institution of Oceanography in San Diego was commissioned to develop the foundations for such a device. Two years later, the Institute published a report that identified four requirements for such a device:

The authors recommended an analogue electronic implementation in 1953.

Because the electronics in those days was not sufficiently developed to such complex tasks to solve in a small space, the Navy hereby authorize the company to build Foxboro (now Invensys ) a mechanical- pneumatic Dekompressiometer. The 1955 appliance, introduced was called Mark I and was criticized by the Navy, as it is too vague and not very stable. Mark I simulated two tissue types with a total of five flow resistance of porous ceramics and had five bellows for data acquisition.

1959 a commercial Dekompressiometer by Carlo Alinari was introduced, called SOS. It works similar to the Mark I, but was limited to a simulated tissue and replace the bellows by a bubble. A large spread found this device only after Scubapro in 1963 acquired the import rights to do so. Although the correctness of the simulation of repetitive dives was very controversial, it was loved by divers around the world because of its high reliability.

From the late 1960s until the early 1980s, many different Dekompressiometer by different companies were developed and sold. All built on the mechanical-pneumatic concept, although some of the word "computer " contributed in their name. Other well-known Dekompressiometer:

• DCIEM Mark: If 1962 brought by the Canadian Institute DCIEM on the market and simulated four different tissue types.
• GE Deco meters: General Electric imagine a 1973 device from which to normal in Dekompressiometer ceramic membranes based instead on semi-permeable silicone membranes, which allowed deeper dives.
• Farallon Decomputer: The company Farallon Industries Calafornia offered from 1975 to a device that simulated two tissue types and was particularly easy to read. Since, however, in practice, strongly deviated from the then distended Navy decompression table, it has already been put back a year later from the market.

Analog Electronic Dekompressiometer

Parallel to the development of the mechanical-pneumatic Dekompressiometer also concepts have been developed, consisting of an analog electronic computer. The simulation of the tissue was carried out in a network of ohmic resistors and capacitors. This analog -electronic devices proved to be too little thermal stability and required a large Kalibrationsaufwand before each dive. In weight and size of the analog electronic devices exceeded, as a powerful battery for their operation was mechanical-pneumatic needed by far. The first analog electronic Dekompressiometer was the Tracor, which was completed in 1963 by the Texas Research Associates.

First digital dive computer

With the increasing performance and miniaturization of the digital computer, the 1970s was also the interpretation of measured values ​​and calculating the zero time in real time possible middle. However, a great challenge agency still represents the power of these mobile computers, as the processors and memory modules that time not very energy -efficient and more powerful working NiCd batteries were still very expensive and rare. The first digital dive computer was a device that looked externally to a cash register and remained above the water. This desktop computer was able to simulate four types of tissue and to calculate the decompression time remaining correctly. He has only been used with surface supplied diving, in addition to the hoses for the Lufversorung and heating, an additional empty tube brought with them, which enabled the computer diving pressure measurements. This was built for the laboratory digital device with the relationship XDC -1 presented the DCIEM Institute completed in 1975 and use it for research. His successor, the XDC - 2 was prepared by the Fimra CTF Systems Inc. and worked on the same principle as its predecessor. It was sold in large numbers mainly to institutions that dealt with hyperbaric medicine. Approximately 700 copies of the successor model XDC -3 were sold between 1979 and 1982. It was so compact that it could be carried under water, so the XDC - 3, the first true digital dive computer was. There were four 9V batteries for the power supply needed, yet the term is limited to only about four hours. The XDC -3 was also marketed under the name Cyber ​​Diver.

From 1976, the dipping equipment Dacor built (now Head ) a digital dive computer, but executed no tissue simulations, but only a saved Navy decompression table omit. The Canadian company brought KyberTec 1980 Cyber ​​Diver II on the market, which also had only a decompression table omit, but also has an air integration. His successor, Cyber ​​Diver III, which appeared a year later, calculated as the XDC -3, by tissue simulations, the decompression time remaining. In 1980, the U.S. Navy with the development of a dive computer with the name UDC. He simulated nine tissue after a decompression of Edwards Thalmanns and got along with mixed gases. In 1983, the Orca Industries Inc. before her model Edge (Electronic Dive Guide ) to the public, which had a graphical display as the first dive computer and capable of the zero time for multilevel dives had to be calculated. The Edge twelve simulated tissue types and could be operated for about 12 hours with only a single 9V battery. In the U.S., the Edge was commercially very successful and has been sold in large numbers. In a collaboration between the U.S. Divers Company (now Aqua Lung International) and Oceanic in 1983 started the development of a dive computer. Ready became the Data Scan 2 respectively DataMaster II only in the year 1987, when a decompression were already available on the market.

Decompression

The first full-fledged decompression, the decompression of the calculated not only the zero time, but in complex multilevel dives in real time, was brought in 1983 by the Swiss company Divetronic AG in cooperation with the diving pioneer Hans Hass on the market. Called this dive computer Deco Brain and he simulated 12 types of tissue after WZR -12- decompression model of Albert Bühlmann. The electronics engineer Jürgen Herman succeeded in 1981 at the ETH Zurich to implement the decompression model of Albert Bühlmann on a microcomputer by Intel. He could Deco design with a Brain energy-saving and easy dive computer Miniaturization of hardware. The produced from 1985 successor, the Deco Brain II was based on the WZR -16 model and was powered by a NiCad battery that is sufficient for an operating time of 80 hours. The Divetronic AG also developed the model for Dacor Micro Brain and was involved in the completion of the UDC in the U.S. Navy before it was taken over in 1989 by Scubapro.

The Finnish manufacturer Suunto Diving Instruments - spot with the SME -ML in 1986 a very compact and inexpensive decompression before. He was now in line of Navy tables and pointed, powered by a 1.5V button cell, a period of 1500 hours. His downfall was that he could count only up to 60m depth. Suunto is today the largest manufacturer of dive computers.

In 1987, the model of the Swiss company Uwatec Aladin, which built on the WZR -12- decompression model and particularly in Europe reached a very wide circulation. The French company Beuchat has been involved in the development of Aladin and sold it under its own brand. Uwatec is now a division of Scubapro.

Current development

Numerous manufacturers now offer decompression. Wireless air integration, the calculation with different breathing gas mixtures or an integrated electronic compass are self-evident today. Some of the additional breathing and heartbeat frequency of the diver is wirelessly collected and included in the calculation. Recent developments go towards large color display and apps, similar to that of smartphones is known. So the 2010 model presented Icon HD net ready Mares offers a 2.7 " color display and the ability to, for example, to supplement it with maps.

Construction

The dive computer consists of a flameproof enclosure, in which a sensor (usually silicon pressure sensor ) for the water pressure (and possibly also for other physical quantities ), a microprocessor and LCD screen, more recently, fully graphical OLED display on the top. located Due to the better seal come as often controls electrical contact sensors ( instead of mechanical buttons) are used. The dive computer can be used individually, worn with a bracelet or with other devices in a console.

Calculation methods

The saturation of the tissue with the / the inert gas ( s) (nitrogen, helium, etc.) and the tolerance to a surge of these gases are calculated dynamically during runtime. To this end, in a data field from a given number of variables (eg, 16 in the known calculation methods ZH -L16 ) simulates a corresponding number of model tissues, which are the respective inert gas pressure, which can be calculated from the breathing gas composition and the specific dive depth, applied. This model tissue respectively correspond to different tissue compartments of the human body.

The calculation of the saturation state of this tissue ( a few seconds in the field ) are repeated so that all variables reflect the dive profile depending on the particular inert gas partial pressure of the individual tissues in short time intervals. This provides a relatively accurate mathematical representation of the saturation level of the individual tissue.

At the same time, it is checked whether, starting in each case still be tolerated by the current state of saturation of the body tissues, the current ambient pressure of all tissues symptoms. It can be inferred then, to what pressure (water depth ) can still be surfaced.

Since people react differently to a supersaturation of their body tissues and subsequent depressurization, the computational method in dive computers can still cover only a certain part of the collective. In usual dive computers, it is assumed that one to three percent of users will have Einhaltens despite the predetermined by the computer Auftauchvorschriften Dekompressionsprobleme. This symptom may involve (DCS I or II) or be asymptomatic.

Unlike a dive table, the application requires a normalized dive profile, dive computer can calculate the Auftauchvorschrift for almost any Headed dive profile. However, there are also limits here, since identical dives in different individuals of a group lead to a different high residual saturation. For repetitive dives, this can lead to a not exactly determinable Inertgasvorsättigung the individual diver, when he begins the next dive. This is due to, inter alia, that the removal of the residual remaining in the body inert gas during the surface interval from person to person is very different. Nor can individual risk factors (obesity, alcohol or nicotine consumption, etc.) hardly include in the calculation.

Known models of computation and what manufacturer they use (2013 ) today:

Functions

• Lighting
• Dive time
• Current depth
• Average depth
• Maximum dive depth
• Water temperature
• Compass
• Warning against too rapid ascent (optical, acoustic )
• Decompression time remaining
• Display of safety stops
• Display of deep stops, decompression and decompression
• Into account the effects in a repetitive dive
• Warning when the depth or duration is not respected the decompression.
• Display the no-fly time: When a diver desaturated shortly after a dive and not yet fully in an airplane rises ( lower air pressure is exposed ), it can also have there a decompression illness.
• Manual or automatic adjustment of the height of the water table above sea level (important for altitude diving at a height above 700 m).
• Warning of falling below the set maximum diving depth
• Alarm clock function
• Log files: For subsequent evaluation of dives most dive computers have a logbook function, which allows to retrieve the data from one or more stored dives.
• PC interface: In order to transmit data by means of software for detailed analysis (eg, graphical representation of the dive profile ) to a computer. Depending on the model, there is also the possibility of updating the device software, firmware, and the setting of the dive computer (eg personalization feature ).

Models

Air Integrated Dive Computer

Air Integrated Dive Computer involve also the pressure in the compressed air bottle in the calculation and indicate for which immersion time, the supply of breathing gas is still. Some devices use the air consumption of the diver in the calculation of Stickstoffaufsättigung or decompression with a. Some computers can be connected directly to the Finimeterschlauch, thus replacing an additional pressure gauge. Other dive computers are wirelessly connected to a pressure sensor at the first stage of the regulator, which transmits the pressure values ​​at the dive computer.

Dive computer for technical diving

The currently most complicated models, but almost exclusively in technical diving to the application, in addition, can still offer the following options:

• The use of different breathing gas mixtures, also in the course of a single dive;
• The real-time monitoring of the oxygen content in the breathing gas (especially interesting when rebreather diving );