Is this a gimmick or useful feature?

[oreocookie]

I've been looking into computers recently and might be getting one this summer, and I've noticed that some mention a salt/fresh water setting, not sure if you tell it what kind of water you're going to be in, it figures it out or what. The Nitek Duo and it's twins have it, but I haven't seen it on other computers (maybe I'm not looking hard enough, dunno). Can anybody tell me exactly what this feature does or how it works (user input or automatic)? I would assume since salt water is more dense than fresh, depth readings might be different (but normal depth gauges don't have salt/fresh settings, right?) So what is the point in this?

on another note, I'm considering getting a Suunto Gekko (I'm considering others as well) and wondering how conservative Suunto's actually are? I know they're one of the most (if not THE most) conservative computers, but how much more conservative are they?

 

[vixtor]

The depth error between salt and fresh is about 2%. This is ~0.8 meters at 40 meters depth, which I think you can safely ignore. Also, this error is only relevant to the "real" depth (if you care about the distance between surface and you), and it doesn't affect the nitrogen load calculation, because nitrogen load is pressure dependant (not depth dependant), and the computer measures the real pressure (but it is not converting it on the display to the real depth eventually). Most are salt water calibrated (at least most that I saw).

 

[BabyDuck]

the duo setting is something the user toggles. once it's set, it stays on 'salt' or 'fresh' until you change it, so you don't have to reset it every time unless you change types of water every time.

 

[vixtor]

so.. as I forgot exactly the conclusion, gimmick in my opinion.

 

[simcoediver]

so.. as I forgot exactly the conclusion, gimmick in my opinion.

It is not a gimmick. Nitrogen loading is different in salt water than fresh and in order for a good dive computer like the Nitek Duo to give you highly accurate readings it has this setting. When you take your Nitrox course you will see what I mean. Calculations are different.
Nitek duos are excellent computers. A gimmick is an air integrated computer.

 

[YourMama]

A gimmick is an air integrated computer.

Oh Jeez...here we go!

 

[djanni]

Oh Jeez...here we go!

My sentiments as well!

 

[simcoediver]

LOL ! Oops sorry, did not mean to start anything, its just my opinion and Ive been told often by my better half that my opinions are crap.

 

[vixtor]

smicoediver, nitrogen loading is different in salt water and fresh water if you estimate it by tables (where you have nitrogen load as a function of depth), because at the same depth in fresh water there is less pressure than in salt water (as salt water is more dense).

if your table would display nitrogen load not as a function of depth, but as a function of ambient pressure, the nature of the liquid environment arround you will not matter, and that's how the computer works (for example, while closed in a barometric chamber at 4atm, a computer will display a fake depth of 30 meters while you are on the first floor of the hospital, but it will still monitor correctly the nitrogen load, because the measured value of 4atm based on which nitrogen load is estimated is correct).

The computer is not estimating nitrogen load by depth, because it has access (using its internal sensor) to the more meaningful value of ambient pressure (which is always measured correctly, no matter what fluid you are in). Because of this, any computer will compute correctly the nitrogen load, in any kind of water, salt or fresh. But, even while it is computing the correct nitrogen load, it might display the wrong depth, because it estimates it based on an incorrect density factor.

Please explain me how is nitrogen load different in salt water than fresh water, when you express it as a function of pressure (like the computer), not as a function of depth (like the tables), and what calculations are different.

Have they missed this from your Nitrox course? I guess you observed the calculations are different because your tables were nitrogen load(depth), not nitrogen load(ambient pressure).

Niteks might be wonderful (never said they aren't). Still the salt/fresh water calibration is gimmick, it only changes the displayed depth, not the nitrogen load function.

It is not a gimmick. Nitrogen loading is different in salt water than fresh and in order for a good dive computer like the Nitek Duo to give you highly accurate readings it has this setting. When you take your Nitrox course you will see what I mean. Calculations are different.
Nitek duos are excellent computers. A gimmick is an air integrated computer.

 

[vixtor]

and btw, no dive computer is "highly accurate". as long as there's no sensor in your body to measure the nitrogen in your tissues (is this even possible?), there's nothing accurate about them. just an estimate, safely rounded enough to avoid most accidents.

sorry to disappoint.