A dive computer or Personal Dive Computer (PDC) is a digital device that makes real-time calculations on diving information for divers. The dive computer is worn on the wrist, similar to a watch.
Though dive computers 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.
Dive Computer vs. Dive Tables
Have you learned how long you are able to stay underwater at specific depths using dive tables before? Dive tables are used to calculate how long it is safe to dive at specific depths and whether a decompression stop is required. Dive tables are also known as dive charts, decompression tables, and recreational dive planners.
Reading dive 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 dive tables 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 PDC takes away the possibility of human error in calculating safe diving depths, diving periods and decompression stops. The dive computer precisely measures the depth and time spent underwater in real-time. A dive computer also calculates more accurately. With the continuous information, it can re-calculate as you are diving while a dive 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 dive table which often leads divers to take longer decompression stops and spend less time at certain depths.
Another advantage of dive computers is the added features that give more details about the dive. Read more about these extras next.
Extra Features of a Dive Computer
Depending on the dive computer 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 when diving to avoid decompression sickness. However, how fast or slow to actually go is difficult to calculate with a dive table.
Without a PDC, ascending at the safest rate is guesswork. A dive computer, can accurately tell you whether you are swimming up too fast, many models even have a warning system installed.
Dive computers that have air integration or Air Time Remaining (ATR) offer an added safety precaution. Air integration monitors how much air is still available for the dive and so 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 dive 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 the diver how much air is still left in the tank. However, the gauge does only that; it doesn’t provide time-related information.
Many dive computers 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 on your dive computer. Note that this is separate from the no-decompression limit.
This feature is specifically for Nitrox divers. Nitrox divers use a different composition in the air tank which has added risks for central nervous system (CNS) oxygen toxicity.
For these divers monitoring the exposure to oxygen is very important. A dive computer shows how much time is left for oxygen exposure to still be safe.
Dive computers show this information in either minute left within the safe time limit. Another way a PDC shows this information is through percentages of exposure.
Dive computers also track all the dive information that you would fill into a dive log. And much more accurately than you could manually. The Mares Smart Wrist dive computer, for example, can log 25 hours of dives, and also has a dive plan mode.
The information collected on the PDC is easily transferable to a computer where you can log the information into a digital dive log. A PDC comes with a cable that links to a PC.
Why You Should Use a Dive Computer
So why should you own a dive computer? Dive computers are great pieces of diving gear. They make your dive safer thanks to its 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 during your dive are never completely accurate.
Wearing a PDC during a dive 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 during dives whether it is by using dive tables or a dive computer. The main reason to use the dive computer is the extra control over the many variables that divers need to deal with.
However, familiarizing oneself with the dive computer first is essential. If you are still taking a diving course then ask the instructor to also teach you how to use a dive computer, as well. It’s important to always follow your dive training, even when using a PDC.
Once you fill comfortable, it’s a good idea to invest in your own dive computer, and there are so many options of dive computers to choose from. Knowing how to take care of your dive computer is essential too, to make sure your new piece of kit stays in good shape.