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Welcome to Dive Gear Reviews, a comprehensive guide to scuba diving equipment. Scuba diving is an expensive pursuit, so looking up reviews for a particular article of equipment is a wise precaution before investing any hard-earned money in it. However, consumer reviews may or may not be written by an experienced diver, and magazine reviews could be suspect due to the advertising ties of the publication in question. Dive Gear Reviews provides cross-referenced reviews assembled by an expert, making it possible to see at a glance what multiple sources said about a particular piece of scuba equipment. If one magazine loved a scuba regulator or a dive computer, but the consumers hated it, that information will be found here.
18
April

Product Guide: Dive Computer Features and Formats

Written by Dive Gear Reviews Editor. Comments Off on Product Guide: Dive Computer Features and Formats Posted in: Dive Computers, Scuba Product Guides
wristwatch dive computer

A sporty Suunto D9 wristwatch dive computer.

For the new diver, investing in a dive computer can be intimidating. After all, a novice has not been diving long enough to establish their preferred style of gear arrangement or style of diving, let alone figure out what they want out of their gear or what their future scuba intentions are. Many of the features surrounding dive computers are in jargon to boot. Sorting these issues out is critical for so important and expensive a purchase as a dive computer.

Algorithms

The algorithm is at the heart of what at dive computer does, and represents a decompression model. The computer crunches numbers throughout the dive, revising its estimates based on what a diver does and the decompression model in question, providing the diver with information on no-decompression time remaining and possibly an estimate of the body’s nitrogen load. The result is a more accurate picture of the body’s nitrogen load following a dive than is the case using dive tables, since most dive table calculations assume the diver was at the maximum depth of the dive for the entire time.

The algorithm is usually described as either liberal or conservative, with some regarded as in between. The more conservative a dive computer, the more of a safety margin it assumes in making calculations. Most recreational divers follow a format of two dives per trip, with the deepest dive scheduled first. For a diver in good health and following safe diving techniques, the differences between a liberal or conservative algorithm are negligible under such circumstances. However, on a liveaboard cruise or a dive vacation, the number of dives often rises to three or four per day. Under those circumstances, a diver with a liberal dive computer might end the day with a mild case of the bends.

Another thing to remember is the numbers put out by a dive computer’s algorithm are a guide, not a hard and fast law. A diver can increase or decrease the level of conservatism on a dive computer simply by adding or subtracting minutes from the computer’s indicated no-decompression time.

The Display

The display is at least as important as the algorithm, perhaps even more so. No dive computer is worth very much if you can’t read the tiny little digital read-out in the gloom at 100 feet. At least some of the read-out needs to be big enough to read at half an arm’s length and in low light. If the display relies on color-coded indicators on the computer’s bezel to meter data, then those indicators must also be easy to read. Features like big characters on the dot matrix display or back lighting are very, very desirable in a dive computer.

Console vs. Wristwatch

Console dive computer

A typical console dive computer.

Each of these two dive computer formats has objective advantages. Wristwatch computers are compact, and therefore very travel-friendly. Even the biggest, clunkiest wristwatch dive computer is still small enough to store in any carry-on or checked bag without taking up much space or weight, making the wristwatch format a very travel-friendly one. Even a diver who wants to rent all of her gear at her destination can still afford to take along a wristwatch dive computer.

One objective advantages for consoles is the reduction of clutter during dives. Excepting those divers who can afford a pricey wireless, air-integrated dive computer (see below), every regulator set-up has a console with at least a depth gauge and tank pressure gauge. By consolidating the dive computer into that console, the diver has one less item of gear to fiddle with and one less object on her wrist. Plus, the console needs close monitoring anyway, so another advantage of a console computer is putting all the dive data displays into one object.

 

Air-Integration

The minimum for a dive computer to qualify as “air-integrated” is that it tracks air tank pressure, supplementing or replacing the tank pressure gauge on the console. However, most dive computers with air-integration also run calculations on how long the air in the tank will last based on consumption patterns during that dive. Always check the actual features to see what a dive computer manufacturer means by “air-integrated.” The latter is a handy feature for a predictable dive with a steady amount of moderate swimming, but huffing and puffing from fighting a strong current or kicking away from a triggerfish will throw those calculations for the remainder of the dive.

Air-integration is only possible because the dive computer can put a sensor in contact with a HP port on the regulator, so as to monitor tank pressure. That sensor contact might take the form of a console computer at the end of an HP hose. However, a number of computers come with wireless air-integration. This does away with the HP hose altogether by screwing a transmitter into the regulator’s HP port.

Air-integration is a useful dive computer feature, but the feature sometimes has one major drawback. Most console computers and all wireless computers with air-integration replace the analog tank pressure gauge. If the computer fails for some reason, the diver is left without a back-up, which usually means aborting the dive.

Battery Replacement

This is an often-overlooked feature for dive computers. Sooner or later, the battery will run out and must be replaced, ask two questions about the computer’s battery features before purchasing the computer. First, can the owner replace the battery or must the computer be shipped back to the factory for replacement? Second, is the replacement battery reasonably priced and readily available, or is it exotic and expensive? Sending the computer back to the factory and/or exotic, expensive batteries are big negatives and should be avoided.

Digital Compass

As a rule, digital compasses are much easier to use and more forgiving than their analog equivalent.

Nitrox and Mixed Gas

technical diver with dive computer

Note the dive computer on this tec diver's wrist.

For most divers, having at least a nitrox-capable dive computer is a sound investment in the future. This means the computer has growth potential, and won’t need to be replaced if the diver starts using nitrox. Even if a diver never uses nitrox for weekend dives, the enriched oxygen gas is a smart safety precaution for dive-intensive trips, such as those liveaboard cruises with three daytime dives and a night dive on the agenda. Without a dive computer that supports nitrox use, a nitrox-trained diver must either replace the old computer or go back to using tables for nitrox dives.

Mixed gas is a different story, since it is applicable only to technical diving, which isn’t as easily acquired as mere nitrox certification. Most divers know whether they are interested in eventually getting into technical diving before they buy their first computer, so this should be an easy call. Many high-end computers include mixed gas computations as part of the package, but only those who are interested in becoming tec divers should care about that.