Dive Computers
By Vlad Pambucol


  • Who am I
  • Diving experience
  • You ain't from around here boy!
  • Stop me if you can't understand
  • Ask questions any time


What is this all about

  • Dive Computers
  • Decompression theory


Decompression theory

  • How nitrogen dissolves in your tissues
    • Henry's law
  • What is saturation
    • Why saturation depends on depth and dive time
    • What happens when you go deeper - suprasaturation
    • What happens when you ascend.
  • Tissues and tissues compartments
  • Why bubbles form - microbubbles
  • Why do bubbles cause pain or paralysis


How tissues compartments may connect

  • Haldane model - parallel model
  • Series model - DCIEM tables (Canada)
  • Exponential linear - ongass exponential (fast), ofgass linear (slow)
  • Slab - only one compartment (British Sub Aqua Club tables)
  • Buhlmann model - parallel series


Haldane's model

  • J.S Haldane created his theory in the early 1900
  • Tissues half-live theory – how tissues accumulate and release nitrogen
  • Tissue half-live – the time necessary to allow the amount of gas to change by 50%
  • Haldane chose 5, 10, 20, 40 and 75 minutes as tissue times (limited by the technology)


Buhlmann's model

  • Developed by Albert Buhlmann over 30 years and published in 1983
  • More tissue compartments that Haldane
  • Tissues are parallel series tissues
  • The most used in the current computers
  • Full specifications of the decompression algorithm published


History of dive computers

  • First serious attempt to make a decompression meter done by the US Navy in the mid fifties
  • First decompression meter available to the public – Italy 1959
  • First commercially available (electronic) dive computer – Orca Edge 1983 based on the Haldanian decompression theory


Dive computers explained

  • Electronic devices that compute in real time your theoretical nitrogen level
  • Component parts:
    • The case
    • The pressure sensor
    • The O-rings
    • The PCB


PCB - component blocks


Features of dive computers

  • User replaceable batteries
  • Sturdy housing
  • Large displays
  • Color coded readings
  • Decompression algorithm range appropriate to your dive profile
  • PC downloadable
  • Auto-activation
  • Backlighting
  • Audible warnings
  • Altitude algorithms
  • Multiple tissue compartment models
  • Individual coded transmitters for hoseless air integrated computers


The new Uwatec computers

  • Maximum displayed depth 120 m
  • Resolution between 0.8 m and 99.9 m: 0.1 m, >99.9 m: 1m. The resolution in feet is always 1 foot
  • Calibration in fresh water.
  • Adaptive Buhlmann decompression algorithm with 8 tissues (ZH-L8 ADT)
  • Microbubbles compensation (6 microbubble levels)
  • Algorithm adjust for the workload, altitude (automatic) and temperature
  • Display water temperature and ambient temperature
  • User adjustable tank reserve setting
  • Factory replaceable battery. Life 5 years (500 - 1000 dives).
  • Nitrox capable. Oxygen mix adjustable in 1% increments.
  • Dives stored in the dive log: 99 logged dives.
  • Dive profile: 100 hours (smart pro), 50 hours (smart com).
  • Variable ascent rate.
  • Wet fingers contacts user interface
  • Auto switch on.
  • IrDA PC communication


Dacor Darwin Computer

  • Maximum displayed depth: 150 m.
  • Measurement resolution: 10 cm in the 0-100 m range / 1 m in the 100-150 m range.
  • Temperature compensation of the measurement.
  • Calibration in fresh water.
  • Algorithm: Deterministic-exponential algorithm, with M values (low bubble) derived from the Rogers methods (modified Haldanean).
  • 11 tissues.
  • Power supply: 2 alkaline 1.5 V batteries (type AAA) user replaceable. Life: 12 months with 50 dives
  • Nitrox capable. Oxygen mix adjustable in 1% increments
  • Manual adjustment for altitude.
  • Manual selection of fresh/sea water.
  • Manual clear of residual nitrogen.
  • Dive history: deepest dive, total number of dives, coldest temperature, total dive time.
  • Dives stored in logbook: 50 with profile for a maximum of approximately 38 hours.
  • Dive profile sampling interval 20s.
  • Buttons user interface
  • Button switch on before dive recommended but not required.
  • PC interface


Dacor Transcend Computer

  • Maximum displayed depth 99 m.
  • Modified Buhlmann algorithm, with EAN calculation for enriched air Nitrox dives and J correction factors for personalized algorithm.
  • Display user configurable.
  • Backlight changes color.
  • Nitrox capable
  • Manual clear of residual nitrogen.
  • Battery replaceable by user 2 years operation.
  • Dive profile intervals configurable by the user (20s/30s/60s)
  • Memory capacity for 100 one-hour dives with 20 sec profile intervals.
  • Wet fingers contacts user interface
  • 5 manual altitude programs.
  • Manual water salinity correction factor (0%, 1%, 5%).
  • PC interface.



  • Things to remember:
    • Diving with a computer makes your dive safer although DCS can still occur
    • Remember that the decompression model is a theoretical one
    • Read your computer manual and KNOW your computer
    • Follow what your computer is telling you to do
    • Check your batteries and don’t ignore the low battery warning




Updated November 6, 2003 11:50 PM by Vlad Pambucol