What is a dive computer? A scuba computer or Personal Dive Computer (PDC) is a digital device that makes real-time calculations on diving information. The device is worn on the wrist, similar to a watch.
Do I need a dive computer? Though they are not mandatory, they have become a standard piece of equipment for frequent divers. This is because a PDC is a more accurate and detailed alternative for dive tables.
Never used a dive computer before? Here is all you need to know about scuba computers and how they work. This is a very popular piece of scuba equipment and here we will inform you of what to look out for when picking the best dive computer for your next experience.
Table of Contents
Computer vs. Tables
Have you learned how long you are able to stay underwater at specific depths using dive tables before? These are used to calculate how long it is safe to stay at specific depths and whether a decompression stop is required. The tables are also known as dive charts, decompression tables, and recreational dive planners.
Reading the tables is an essential skill for frequent divers and an important part of any diving course. However, these tables can appear confusing to the untrained eye.
Learning to read them takes a bit of practice but comes naturally when done often enough. Still, even professional divers can sometimes make a mistake in the calculations.
Using a diving computer takes away the possibility of human error in calculating safe diving depths, diving periods and decompression stops. Scuba diving computers precisely measure the depth and time spent underwater in real-time. A scuba computer also calculates more accurately. With the continuous information, it can re-calculate as you are diving while a table is a static method that you cannot adjust while diving.
For example, a PDC adjusts the calculations to how much time you spend at different depths and whether you spend more or less time at that specific depth. This is more difficult to plan with a table that often leads divers to take longer decompression stops and spend less time at certain depths.
Another advantage when diving with a computer is the added features that give more details. Read more about these extras next.
Extra Features
Depending on the model, there are many extra features that enhance your diving experience. For example, the Suunto Eon Steel dive computer features a pressure sensor which transmits information wirelessly to the device when it is held close to the tank, and the reading is pretty much instant.
Here are a few examples of common specs for PDCs.
Ascent Rate Monitors and Warnings
Ascension must be done slowly to avoid decompression sickness. However, how fast or slow to actually go is difficult to calculate with a table.
Without a PDC, ascending at the safest rate is guesswork. These devices can accurately tell you whether you are swimming up too fast, many models even have a warning system installed.
Air Integration
Scuba computers that have air integration or Air Time Remaining (ATR) offer an added safety precaution. Air integration 
monitors how much air is still available and therefore how much time can still be spent underwater safely.
Air integration calculates this using information about both the diver’s air consumption rate and the capacity of the air tank. These calculations are also adjusted in real-time.
Since the information is constantly updated, the PDC can factor in how the time changes when there are rough water conditions or at different depths. For example, the air consumption rate might increase when there is a strong current.
A submersible pressure gauge or SPG does show how much air is still left in the tank. However, the gauge does only that; it doesn’t provide time-related information.
Nitrogen Monitoring
Many also monitor the level of nitrogen in your system. This is also called a Tissue Loading Meter.
The nitrogen monitor is another safety precaution to avoid decompression sickness. By checking how much nitrogen is still in your system, you will know whether you have spent enough time at your decompression stop.
Just like the ascent rate monitor, the tissue loading meter can be set as an alarm device. Note that this is separate from the no-decompression limit.
Dive Nitrox
This feature is specifically for Nitrox divers. As they use a different composition in the air tank which has added risks for central nervous system (CNS) oxygen toxicity.
Therefore monitoring the exposure to oxygen is very important. And these devices show how much time is left for oxygen exposure to still be safe.
They show this information in minutes left within the safe time limit. But another way a PDC shows this information is through percentages of exposure.
Dive Log
They also track all the information that you would fill into a log. And much more accurately than you could manually. The Mares Smart Wrist model, for example, can log 25 hours, and also has a dive plan mode.
The information collected is easily transferable to a computer where you can log the information into a digital log. A PDC comes with a cable that links to a PC.
Why You Should Use a Scuba Computer
So why should you own a dive computer? They are great pieces of diving gear. They make your experience safer thanks to their accuracy and constant monitoring.
How do you measure your exact depth underwater? It is quite difficult to know how deep you are which is why all the other calculations are never completely accurate.
Wearing a PDC keeps track of a ton of information that you could never precisely monitor yourself, let alone all at the same time. It offers exact information on decompression stop times, nitrogen and oxygen levels and how much air is still inside the tank.
Safety should always come first whether it is by using tables or when diving with a computer. The main reason to use the scuba computer is the extra control over the many variables that you need to deal with.
However, familiarizing oneself with the device first is essential. If you are still taking a diving course then ask the instructor if they do dive computer training to also teach you how to read a dive computer. It’s important to always follow your training, even when using one of the devices.
Once you fill comfortable, it’s a good idea to invest in your own computer, and there are so many options for them to choose from so think about your requirements to find the best scuba diving computer for you. Knowing how to take care of your dive computer is essential too, to ensure your new piece of kit stays in good shape and maintains its longevity.
We hope that we have answered the most common questions about what is a dive computer, scuba diving computers and a little of the computers and how they work. But remember safety first and always ensure that you have divecomputer training where possible, but that you are fully aware of their uses.
