The dive computer is a very useful tool used by divers all over the world. It is one of the first pieces of equipment we buy as it allows us to dive safely.
What does a dive computer serve for?
You have to know that the computer is a tool that can save your life.
The primary function of a computer is to measure your dive time and depth and using this data to calculate the level of nitrogen absorbed by the body throughout the dive in order to tell you how long you can swim at certain depth staying within the limit of no decompression. Dive tables also let us calculate it, but unlike the computers they do not adapt to the actual data of the dive. It means that a dive table does the calculation considering only one given depth throughout the dive, though in reality you do not stay on the same depth all the time of the dive, the bottom can bring you up and down. The tables can not foresee it. When you do the calculation with a table you take the maximum depth of the dive and get the data as if you were at that depth all dive time. Dive computers however do take into consideration the real-time depths and minutes of the dive, so they provide us continuously with the refreshed data about the no-decompression limit. That´s why with the computer collecting the actual data of the dive you can stay rather longer underwater.
Another advantage of the computer is that it also indicates the moment to do a safety stop and counts the minutes of it. In case you have gone beyond the limit, it shows you how long and at what depth you need to perform the decompression stop. After the dive it calculates the desaturation time and the hours before you can take the plane or go to altitude. It also contains a plan mode that measures the maximum dive time or depth for your next dive.
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As you understood, this is the essential tool that helps you avoid decompression sickness. However, it only lowers the risk, not eliminates it, because the chance to suffer from decompression sickness also depends on many factors like physiology, age, health condition, alcohol or drug consumption, fatigue, stress, cold and much more. All this has to be taken into consideration on your own as your computer doesn´t include it in the calculations. This is your responsibility to do the right assessment of the state of your body and stay within the limits of the computer without getting too close to it.
Moreover, computers can give you details about the air and water temperature, the bottom time, the hour, but also about the ascent rate. Each computer has its own limit: some tell you that you should not ascend at more than 10 meters per minute, others, less conservative, will allow you to go to 14 meters per minute. It is the same for the no decompression limit, computers from different brands have different algorithms that can give you more or less time underwater. Normally dive computers have several algorithms integrated in their system so that you could choose the one you prefer. It´s recommended to choose the conservative mode that calculates the decompression limit as if you were at a slightly bigger depth. That provides you with more safety.
Some computers display more options and can be used with different kinds of gases. For example, when you dive with enriched air (mixture of gases that contains more oxygen than the air) such a computer indicates you the maximum depth you can reach to avoid oxygen toxicity. Some computers have modes for technical diving with varied mixtures of gases. You can also find computers with integrated compass or connected to a transmitter to show your air consumption.
The design and colours also vary a lot. Some people prefer a big screen that shows you the information clearly whereas others like to have it size of a watch so that they can wear it out of the water too.
The price of a computer can go from 150€ to more than 1000€ depending on its functions.
Why is it important to have your own dive computer?
As soon as you become an independent certified diver, it is recommended that you use your own dive computer, even if you dive with a group lead by a professional guide.
Firstly, the dive computer takes into consideration the data of your own dives, e.g. previous dives, your depth and timing of the actual dive (not other divers, but yours!). Remember that when diving in a group you are not always at the exactly same depth having the exactly same duration of the dive as the others. You need to have your own data to get the right no decompression limit. This makes the computer the essential part of equipment of each diver.
Secondly, the computer keeps your previous dives in memory, so you can easily fill in your log books with your personal information. All computers can be connected to a laptop so that you can save the dive history on it rather than on paper. Having your own gives you a chance to keep a memory of all the time you have spent underwater.
If you doubt you can choose a good computer for yourself, do not hesitate to ask for advice in your dive center. The professionals will help you choose a proper computer that would fit you the best, according to your preferences and dives you are planning to do.