Top reasons to buy a dive computer

Once you have qualified as a diver your attention may start to turn to which pieces of equipment you will need to buy for yourself. I know I did and as a typical bloke “bright and shiny” things where high on my agenda.

Oceanic OC1 Computer

Oceanic OC1 Computer

 All joking apart, a dive computer is an almost essential piece of dive equipment and one that most divers should use on every dive. As with much dive equipment, dive computers come in a range of styles, makes, and price range but all serve the same purpose – to supplement or replace the standard tables such as the RDP or Tables 88 or whatever your agency recommends. The main difference between a dive table and a dive computer is relatively simple. Tables only allow you to plan the dive as though it was all completed at one depth which for the most part is not how it is done.  You could also argue that it is not good dive practice.  Dive computers on the other hand constantly monitor the pressures and depths during a dive and continually track and calculate theoretical nitrogen uptake and its elimination based upon the actual dive profile. This is a big advantage because the computer takes into account the decrease in pressure as a diver ascends to shallower depths.

The main reasons to buy a dive computer are therefore:

    1.  Constant tracking of theoretical nitrogen loading The purpose of dive computers is to make divers aware theoretically of how much nitrogen they are absorbing, as well ascent rate and other key points to help them avoid decompression sickness. They are based on the same or similar theories as dive tables. Both tables and computers are systems for tracking the theoretical up-take and elimination of nitrogen within a diver’s body. Computers however, do this as a constant process and therefore more accurately reflect the profile the diver has completed.  This results in a more accurate analysis of nitrogen loadings.
    2.  More time underwater with multi-level diving techniquesComputers allow divers to have more time underwater on multi-level dives and still stay within safe limits. A dive computer allow a much longer dive when a multi-level approach is used because it takes into account the fact that much of any dive tends to be spent at a shallower depth than the maximum. It is important to note that this does not make the dive any more dangerous

      Oceanic Geo 2

      Oceanic Geo 2

    3. Accurate depth/time recordings One of the greatest challenges facing a diver is the accurate determination of maximum depth and bottom time. Whilst modern depth gauges are fairly accurate it is sometimes difficult to read them accurately.  It is not always easy to see, or remember to look at your watch to record time at the various depths etc.  Therefore the actual depth and time of a dive are often recorded inaccurately. These inaccuracies make any dive table calculations potentially flawed. Dive computers eliminate this concern because they maintain an accurate record of both depths and dive time. However you should always remember that all devices can fail and that you should always carry a second method of determining depth and time, eg analogue depth gauge and a watch.
    4. Decompression status made simple – no more dive table errors Many divers have difficulty remembering how to use dive tables. Dive computers perform all of the calculations automatically. During a dive, the computer constantly tracks depth, dive time and non-decompression time remaining. Most computers will even calculate decompression time and ceiling depth should a diver accidentally end up in a decompression situation. At the surface, the computer keeps track of the surface interval and automatically calculates a diver’s adjusted non-decompression limits. These calculations are all done automatically and are continuously based upon a diver’s actual profile.

      Oceanic Atom 2

      Oceanic Atom 2

    5. Ascent rate indicators Divers are taught to ascend slowly and never exceed the maximum ascent rate prescribed by their respective dive tables. These ascent rates vary, but the range tends to be around 18metres per minute. Exceeding the proper ascent rate may increase the likelihood of decompression sickness. Unfortunately, tables cannot assist a diver in calculating ascent rate.  The diver needs to assess this for himself.   All dive computers feature ascent rate monitors or warnings that allow a diver to monitor his or her ascent, and therefore help to avoid rapid ascents.
    6. Enriched air computers Many of the current dive computers offer the facility to change the depth/time calculations based on the mix of air the diver is using. Increasing the amount of oxygen in the mix – using enriched air or nitrox – can result in longer bottom times for a given depth by reducing the amount of nitrogen absorbed by the body.  Dive computers capable of being adjusted to cater for these changes in the gas used will automatically calculate the new decompression limits for the dive based on the percentage of oxygen entered. Some even more advanced computers, can cope with up to two different gas mixtures and even Tri-mix (a gas mix including helium as well as oxygen and nitrogen) for more technical diving.
    7. Air Integrated ComputersAir integrated computers (that is computers connected to your cylinder via a hose or radio transmitter link) offer divers an added dimension. They not only provide accurate information with respect to depth, time and decompression status, but they also display accurate cylinder pressure and air time remaining information. The air time remaining is based upon a diver’s air breathing rate, cylinder size or capacity and the diver’s depth.  Whilst a submersible pressure gauge (SPG) presents divers with a reading of how much air is left in the cylinder, it can’t provide the same level of information and accuracy as a dive computer connected to the cylinder  The modern generation of air integrated dive computers provides accurate information on  exactly how much time a diver has left underwater based upon depth, air supply remaining and diving conditions.  Nevertheless, on any dive you should ensure that you monitor your air consumption and ensure that you take every precaution to avoid out-of-air situations.
    8. Integrated compass  One more recent trend, particularly on the higher end computers, is for these devices to include an electronic compass. These devices offer similar functions to the compass that most divers already carry with them either on their wrist of mounted with the SPG and depth gauge. The big advantage is that by combining all the information into a single device a single glance can give you all the information you need during the dive.

One key point to note, and one that is often overlooked, is that you should make sure you know how to use the computer.  You need to know what all the displays mean and how to set alarms etc.  If you accidently go into decompression the computer will be able to calculate a safe stop time and depth for you, but you need to understand what it is telling you.  It is too late then to get the manual out !!!  If you are unsure go back to the dive centre you bought t from and they will be pleased to help

On a final note, whilst dive computers are getting ever smarter, and more reliable, they are still pieces of equipment which will have a rate of failure however small. All dive computers are also still based on variations on the theoretical decompression algorithms used in the standard tables. It is important to remember, that however impressive a dive computer may appear it must be used conservatively, wisely and properly.

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