Oceanic Data 100
I can't get excited
Mar 17 '03
Author's Product Rating
Pros
Adequate, easy to use, backlight, 12 compartments
Cons
Too timid an algorithm, annoying log review. Not nitrox.
The Bottom Line
Fairly inexpensive, intuitive and adequate. Has a number of typical dive computer drawbacks.
The primary read-out is a somewhat intuitive (for some people) bar chart of nitrogen build-up. The measuring bar is curved and increases clockwise from green (within no-decompression limits), up the dial to a yellow area (probably wise to do a deco-stop) and on to the red zones (decompression stop(s) required). The red area is sectioned into quadrants with each increasing level adding another decompression stop. Then end result is that you only have to check to see if you're near the red to understand when you'll need to end the dive.
The only interface is a single button which turns on the computer as well as acts as a paging widget for pre-dive, settings and log review.
The algorithm used in the Oceanic computers as a whole is fairly timid, especially compared to Cochran units which are practically Navy Seal aggressive. The Oceanic algorithm seems to get to the NDC limit faster than comparable computers experiencing the same conditions. This timidity might be nice if your diving air as it would give you a forced safety margin. If, however, you've already built in a significant safety margin, diving Nitrox with an air computer for example, this added safety margin just results in less down-time.
Another negative is that the time-to-fly appears to be fairly arbitrary. For example, once when washing our gear, the regulator holding the computer sat for a bit at the bottom of the wash tank. The computer registered that as a dive and recalculated a ridiculously long time-to-fly from sitting in 3 feet of wash water.
Yet another negative, but one shared throughout most dive computers is the log interface. But since that's pretty universally bad, I won't go into it.
One last negative, really more an annoynace, is that the diver must remember to turn the thing on. While that's typical for most dive computers, one thing about the Data 100 is that it takes a number of seconds to self-test and set to 1 ATM. I've have to resurface a number of times to allow it to finish this booting after I dove in too soon.
One positive is that it's a cheap way to model 12 tissue compartments.
What does 12 tissue compartments mean? well, this seems like a good excuse to elaborate...
In basic scuba, everyone (should have) learned that the deeper one goes, the more nitrogen the body absorbs. Depth, or rather pressure, is only one factor of the equation. Other factors include solubility, the amount of gas that solid can absorb, permeability, the readiness of a gas to enter a solid, and contact area that, along with permeability determines how much gas is absorbed in a given time for a given pressure.
Solubility: A piece of bread can soak up a lot more water than a piece of cheese. Each part of your body, or tissue, has a different solubility to a given gas. For example, teeth aren't capable of absorbing anywhere near as much nitrogen as fat cells.
Permeability: The tissue in your lungs is designed to be permeable, whereas your teeth are designed to be impermeable. Each tissue in your body, from your muscles to your bones, has different permeability.
Contact Area: Blood does not flow to all parts equally. Teeth and fat cells have just a trickle compared to muscles and lungs. The amount of blood contact to a tissue, along with that tissues permeability, determine how quickly that tissue absorbs gas.
Your lungs are in constant and considerable contact with your breathing gas. Therefore your lungs are instantly permeated to the point of saturation. A tissue that has absorbed all the gas it can carry is called saturated. Your blood is in significant contact with your lungs, so, in general, your blood is very quickly saturated. Your bones and muscles are in somewhat major contact with your blood, but it takes the gas a little while longer saturate these tissues because they are less permeable. Every tissue has a different rates of saturation from the instantaneous lungs to slow-going fat cells; which have fairly minimal blood contact.
Because nitrogen is very soluble in fat, it can soak up a whole heap of nitrogen. However, fat cells have minimal blood contact and poor permeability. Therefore fat is usually the last bits of you to become saturated. For these same reasons, fat is also the slowest to release gas.
The solubility, permeability, and blood contact for a given tissue, say a kidney, is called a "tissue compartment." Dive computers use these "tissue compartments" to simulate the effect of a gas on your body at depth. The more "tissue compartments" a computer measures, the more accurate (theoretically) the computer can gauge the effect of a dive on your body. 9 to 12 compartments is fairly standard, but a few consumer models have 16 or more.
The Data 100 has 12 tissue compartments. So now you know...
Recommended
Yes