Editing Dive computer (section)

== History ==
{{see also|Timeline of diving technology}} 
[[Image:Dive computer logbook.jpg|right|thumb|[[Uwatec]] Aladin Pro dive computer showing the log of a previous dive]]
In 1951 the [[Office of Naval Research]] funded a project with the [[Scripps Institution of Oceanography]] for the theoretical design of a prototype decompression computer. Two years later, two Scripps researchers, Groves and Monk, published a paper specifying the required functionalities for a decompression device to be carried by the diver: It must calculate decompression during a multilevel dive; it must take into account residual nitrogen loading from previous dives; and, based on this information, specify a safe ascent profile with better resolution than decompression tables. They suggested using an electrical [[analog computer]] to measure decompression and air consumption.<ref name="Kutter" />
{{expand section|From: The Future of Dive Computers
Michael A. Lang and Sergio Angelini <ref name="Lang and Angelini 2009" />|date=December 2024}}

=== Pneumatic analogues ===
The prototype mechanical analogue Foxboro Decomputer Mark I, was produced by the Foxboro Company in 1955, and evaluated by the [[United States Navy Experimental Diving Unit|US Navy Experimental Diving Unit]] in 1957.<ref name="Searle 1957" /> The Mark 1 simulated two tissues using five calibrated porous ceramic flow resistors and five bellows actuators to drive a needle which indicated decompression risk during an ascent by moving towards a red zone on the display dial. The US Navy found the device to be too inconsistent.<ref name="Kutter" />

The first [[recreational diving|recreational]] mechanical [[analog computer|analogue dive computer]], the "decompression meter" was designed by the Italians De Sanctis and Alinari in 1959 and built by their company named SOS, which also made depth gauges. The decompression meter was distributed directly by SOS and also by scuba diving equipment firms such as Scubapro and Cressi. It was very simple in principle: a waterproof bladder filled with gas inside the casing bled into a smaller chamber through a semi-porous ceramic flow resistor to simulate a single tissue in- and out-gassing. The chamber pressure was measured by a [[Pressure measurement#Bourdon gauge|bourdon tube]] gauge, calibrated to indicate decompression status. The device functioned so poorly that it was eventually nicknamed "bendomatic".<ref name=RRR10177 />

In 1965, [[R. A. Stubbs]] and [[D. J. Kidd]] applied their decompression model to a pneumatic analogue decompression computer,<ref name="Stubbs and Kidd 1965" /><ref name="Stubbs and Kidd 1965b" /> and in 1967 [[Brian Andrew Hills|Brian Hills]] reported development of a pneumatic analogue decompression computer modelling the [[thermodynamic decompression model]]. It modelled phase equilibration instead of the more commonly used limited supersaturation criteria and was intended as an instrument for on-site control of decompression of a diver based on real-time output from the device. Hills considered the model to be conservative.<ref name="Hills 1967" />

Several mechanical analogue decompression meters were subsequently made, some with several bladders for simulating the effect on various body tissues, but they were sidelined with the arrival of electronic computers.

The Canadian [[DCIEM]] pneumatic analogue computer of 1962 simulated four tissues, approximating the DCIEM tables of the time.<ref name="Seveke" />

The 1973 GE Decometer by General Electric used semi-permeable silicone membranes instead of ceramic flow resistors, which allowed deeper dives.<ref name="Seveke" />

The Farallon Decomputer of 1975 by Farallon Industries, California simulated two tissues, but produced results very different from the US Navy tables of the time, and was withdrawn a year later.<ref name="Seveke" />

=== Electrical analogues ===
At the same time as the mechanical simulators, electrical analog simulators were being developed, in which tissues were simulated by a network of resistors and capacitors, but these were found to be unstable with temperature fluctuations, and required calibration before use. They were also bulky and heavy because of the size of the batteries needed. The first analogue electronic decompression meter was the Tracor, completed in 1963 by Texas Research Associates.<ref name="Kutter" /><ref name="Seveke" />

=== Digital ===
The first digital dive computer was a laboratory model, the XDC-1, based on a desktop electronic calculator, converted to run a DCIEM four-tissue algorithm by Kidd and Stubbs in 1975. It used [[pneumofathometer]] depth input from [[surface-supplied diver]]s.<ref name="Seveke" />

From 1976 the diving equipment company Dacor developed and marketed a digital dive computer which used a table lookup based on stored US Navy tables rather than a real-time tissue gas saturation model. The Dacor Dive Computer (DDC), displayed output on light-emitting diodes for: current depth; elapsed dive time; surface interval; maximum depth of the dive; repetitive dive data; ascent rate, with a warning for exceeding 20 metres per minute; warning when no-decompression limit is reached; battery low warning light; and required decompression.<ref name="Seveke" />

The Canadian company CTF Systems Inc. then developed the XDC-2 or CyberDiver II (1980), which also used table lookup, and the XDC-3, also known as CyberDiverIII, which used microprocessors, measured cylinder pressure using a high-pressure hose, calculated tissue loadings using the Kidd-Stubbs model, and remaining no-stop time. It had an LED matrix display, but was limited by the power supply, as the four 9&nbsp;V batteries only lasted for four hours and it weighed 1.2&nbsp;kg. About 700 of the XDC models were sold from 1979 to 1982.<ref name="Seveke" />

In 1979 the XDC-4 could already be used with mixed gases and different decompression models using a multiprocessor system, but was too expensive to make an impact on the market.<ref name="Seveke" />

In 1982/1983,<ref name="Seveke" /> the [[Hans Hass]]-''DecoBrain I'', designed by ''Divetronic AG'', a Swiss start-up, became the first decompression diving computer, capable of displaying the information that today's diving computers do. It worked with a stored decompression table. The DecoBrain II was based on [[Albert A. Bühlmann]]'s 16 compartment (ZH-L12) tissue model,<ref name=RRR9434 /> which Jürg Hermann, an electronic engineer, implemented in 1981 on one of Intel's first single-chip microcontrollers as part of his thesis at the [[ETH Zurich|Swiss Federal Institute of Technology]].

The 1984<!-- 1983?<ref name="Kutter" /><ref name="Deep Blue" /> --> Orca Edge was an early example of a dive computer.<ref name=RRR9434/> Designed by [[List of United States Virgin Islands Senators|Craig Barshinger]], [[Karl Huggins]] and Paul Heinmiller, the EDGE did not display a decompression plan, but instead showed the ceiling or the so-called "safe-ascent-depth". A drawback was that if the diver was faced by a ceiling, he did not know how long he would have to decompress. The Edge's large, unique display, however, featuring 12 tissue bars permitted an experienced user to make a reasonable estimate of his or her decompression obligation.

In the 1980s the technology quickly improved. In 1983 the Orca Edge became available as the first commercially viable dive computer. The model was based on the US Navy dive tables but did not calculate a decompression plan. However, production capacity was only one unit a day.<ref name="Deep Blue" />

In 1984 the US Navy diving computer (UDC) which was based on a 9 tissue model of [[Edward D. Thalmann]] of the Naval Experimental Diving Unit (NEDU), Panama City, who developed the US Navy tables. ''Divetronic AG'' completed the UDC development – as it had been started by the chief engineer Kirk Jennings of the Naval Ocean System Center, Hawaii, and Thalmann of the NEDU – by adapting the Deco Brain for US Navy warfare use and for their 9-tissue MK-15 mixed gas model under an R&D contract of the US Navy.{{citation needed|date=January 2023}}

Orca Industries continued to refine their technology with the release of the Skinny-dipper in 1987 to do calculations for repetitive diving.<ref name=RRR10185 /> They later released the Delphi computer in 1989 that included calculations for diving at altitude as well as profile recording.<ref name=RRR10185/>

In 1986 the Finnish company, Suunto, released the SME-ML.<ref name="Deep Blue" /> This computer had a simple design, with all the information on display. It was easy to use and was able to store 10 hours of dives, which could be accessed any time.<ref name="Kutter" /> The SME-ML used a 9 compartment algorithm used for the US Navy tables, with tissues half times from 2.5 to 480 minutes. Battery life was up to 1500 hours, maximum depth 60&nbsp;m.<ref name="Deep Blue" />

In 1987 Swiss company UWATEC entered the market with the Aladin, which was a bulky and fairly rugged grey device with quite a small screen, a maximum depth of 100 metres, and an ascent rate of 10 metres per minute. It stored data for 5 dives and had a user replaceable 3.6 V battery, which lasted for around 800 dives. For some time it was the most commonly seen dive computer, particularly in Europe. Later versions had a battery which had to be changed by the manufacturer and an inaccurate battery charge indicator, but the brand remained popular.<ref name="Seveke" /><ref name="Deep Blue" />

The c1989 Dacor Microbrain Pro Plus claimed to have the first integrated dive planning function, the first [[EEPROM]] storing full dive data  for the last three dives, basic data for 9999 dives, and recorded maximum depth achieved, cumulative total dive time, and total number of dives. The LCD provides a graphic indication of remaining no-decompression time.<ref name="Microbrain manual" />

=== General acceptance ===
Even by 1989, the advent of dive computers had not met with what might be considered widespread acceptance.<ref name="aaus" /> Combined with the general mistrust, at the time, of taking a piece of electronics that your life might depend upon underwater, there were also objections expressed ranging from dive resorts felt that the increased bottom time would upset their boat and meal schedules, to that experienced divers felt that the increased bottom time would, regardless of the claims, result in many more cases of [[decompression sickness]].{{citation needed|date=August 2016}} Understanding the need for clear communication and debate, [[Michael Lang (diving scientist)|Michael Lang]] of the California State University at San Diego and [[Robert William Hamilton, Jr.|Bill Hamilton]] of Hamilton Research Ltd. brought together, under the auspices of the [[American Academy of Underwater Sciences]] a diverse group that included most of the dive computer designers and manufacturers, some of the best known hyperbaric medicine theorists and practitioners, representatives from the recreational diving agencies, the cave diving community and the scientific diving community.<ref name="aaus" />

The basic issue was made clear by [[Andrew A. Pilmanis]] in his introductory remarks: "It is apparent that dive computers are here to stay, but are still in the early stages of development. From this perspective, this workshop can begin the process of establishing standard evaluation procedures for assuring safe and effective utilization of dive computers in scientific diving."<ref name=aaus/>

After meeting for two days the conferees were still in, "the early stages of development," and the "process of establishing standard evaluation procedures for assuring safe and effective utilization of dive computers in scientific diving," had not really begun. [[University of Rhode Island]] [[diving safety officer]] [[Aquanaut|Phillip Sharkey]] and Orca Edge's Director of Research and Development, Paul Heinmiller, prepared a 12-point proposal that they invited the diving safety officers in attendance to discuss at an evening closed meeting. Those attending included Jim Stewart ([[Scripps Institution of Oceanography]]), Lee Somers ([[University of Michigan]]), Mark Flahan ([[San Diego State University]]), Woody Southerland ([[Duke University]]), John Heine ([[Moss Landing Marine Laboratories]]), Glen Egstrom ([[University of California, Los Angeles]]), John Duffy ([[California Department of Fish and Game]]), and James Corry ([[United States Secret Service]]). Over the course of several hours the suggestion prepared by Sharkey and Heinmiller was edited and turned into the following 13 recommendations:

# Only those makes and models of dive computers specifically approved by the Diving Control Board may be used. 
# Any diver desiring the approval to use a dive computer as a means of determining decompression status must apply to the Diving Control Board, complete an appropriate practical training session and pass a written examination. 
# Each diver relying on a dive computer to plan dives and indicate or determine decompression status must have his own unit. 
# On any given dive, both divers in the buddy pair must follow the most conservative dive computer. 
# If the dive computer fails at any time during the dive, the dive must be terminated and appropriate surfacing procedures should be initiated immediately. 
# A diver should not dive for 18 hours before activating a dive computer to use it to control his diving. 
# Once the dive computer is in use, it must not be switched off until it indicates complete outgassing has occurred or 18 hours have elapsed, whichever comes first. 
# When using a dive computer, non-emergency ascents are to be at the rate specified for the make and model of dive computer being used. 
# Ascent rates shall not exceed 40 fsw/min in the last 60 fsw. 
# Whenever practical, divers using a dive computer should make a stop between 10 and 30 feet for 5 minutes, especially for dives below 60 fsw. 
# Only 1 dive on the dive computer in which the NDL of the tables or dive computer has been exceeded may be made in any 18-hour period. 
# Repetitive and multi-level diving procedures should start the dive, or series of dives, at the maximum planned depth, followed by subsequent dives of shallower exposures. 
# Multiple deep dives require special consideration.
 
As recorded in "Session 9: General discussion and concluding remarks:" 
<blockquote>Mike Lang next lead the group discussion to reach consensus on the guidelines for use of dive computers. These 13 points had been thoroughly discussed and compiled the night before, so that most of the additional comments were for clarification and precision. The following items are the guidelines for use of dive computers for the scientific diving community. It was again reinforced that almost all of these guidelines were also applicable to the diving community at large.<ref name=aaus/></blockquote>

After the AAUS workshop most opposition to dive computers dissipated, numerous new models were introduced, the technology dramatically improved and dive computers soon became standard scuba diving equipment. Over time, some of the 13 recommendations became irrelevant, as more recent dive computers continue running while they have battery power, and switching them off mainly turns off the display.

=== Further development ===
c1996, Mares marketed a dive computer with spoken audio output, produced by Benemec Oy of Finland,<ref name="Raivio 1996" /> and the Thamann VVAL 18 decompression model was tested in the Cochran dive computer.<ref name="Lang and Angelini 2009" />

c2000, HydroSpace Engineering developed the HS Explorer, a Trimix computer with optional P<sub>O<sub>2</sub></sub> monitoring and twin decompression algorithms, Bühlmann, and the first full RGBM implementation.<ref name="HSE Manual" />

In 2001, the US Navy approved the use of Cochran NAVY decompression computer with the VVAL 18 [[Thalmann algorithm]] for Special Warfare operations.<ref name="Butler and Southerland 2001" /><ref name="Butler" />

In 2008, the [[Underwater Digital Interface]] (UDI) was released to the market. This dive computer, based on the RGBM model, includes a digital compass, an underwater communication system that enables divers to transmit preset text messages, and a distress signal with homing capabilities.<ref name="utc" />

By 2010 the use of dive computers for decompression status tracking was virtually ubiquitous among recreational divers and widespread in scientific diving. 50 models by 14 manufacturers were available in the UK.<ref name="Azzopardi and Sayer 2010" />

The variety and number of additional functions available has increased over the years.<ref name="Perdix manual" /><ref name="iX3M AI" />

Wristwatch format housings have become common. They are compact and can also serve as daily wear wristwatches, but the display area is limited by the size of the unit and may be difficult to read for divers with poorer vision, and control buttons are necessarily small and may be awkward to use with thick gloves. Battery life may also be limited by the available volume.<ref name="wristwatch" />

====Smartphone housings====
Waterproof housings are marketed which use a smartphone, depth and temperature sensors and a decompression app to provide dive computer capabilities. Depth ratings vary, but 80msw is claimed for some. Bluetooth wireless communications have been used for communication between the smartphone and external sensors. Specifications may not mention any validation tests or compliance with standards relevant to diving equipment. A variety of features are offered based on the smartphone platform. Android and iOS operating systems are supported.<ref name="DivePhone" /><ref name="substack" /><ref name="dpreview" /><ref name="Ozygit et al 2019" />

{{expand section|VPM algorithms, Gradient factors, open source DC (Heinrichs Weikamp), 2012? - generic smartphone housings. Added gimmicks, some actually useful during a dive, added complexity of operation, multiple gas integration, gas endurance forecast, digital divesite map storage and display (Mares?) |date=May 2021}}