Fresh and salty deco

[tursiops]

It makes a tiny difference if you are diving tables, because the 3% (max) depth error can throw you over into the next row on the table. So, for example, your depth gauge (which is a pressure gauge) says you are at 99 ft but you are really at 102 ft. This could happen if you are diving fresh water, but your gauge is for salt water. Do you use the 100 ft line on the table or the 110 ft line? Well, for N2 adsorbtion you should use 100 ft, because the tables are for salt water! Remember, it is the pressure that counts, not the calculated depth.

 

[Johanan]

Thank you, friends, for contributions. If I may focus on my original question - it was about dive planning software for my iPhone, not so much about dive computers. There is one (Baltic Deco Planner) which I like in every way, but it doesn't have settings for fresh/salt water dives. I wanted to know, whether it is a real disadvantage. From your posts I figure out that it is not. There were many other interesting things in your posts. Thanks!

 

[rossh]

While we are talking about dive computers, probably the most annoying part, is when you have two computers on the same arm, and they do not align for depth. A 3% difference at 100ft is a 3ft between two readings. That's too much for most people - they allow a foot difference, but not 3.

Hence the EN13319 standard to bring all computers to the same mid point salinity setting.

 

[JohnN]

The beauty of the depth sensors only measuring pressure and using the computers to calculate your actual deco is that they are constantly adapting to any changes in the water pressure whether caused by temperature or salinity differences. If you're in a blue hole and drop through the halocline, your depth won't be 100% accurate, but all of your decompression will be.

Measure with a micrometer, mark with chalk, cut with an axe, hammer to fit, paint to cover

 

[Neilwood]

Measure with a micrometer, mark with chalk, cut with an axe, hammer to fit, paint to cover

Can I get a new monitor as mine has a substantial amount of coffee dripping down the screen???

 

[tbone1004]

Can I get a new monitor as mine has a substantial amount of coffee dripping down the screen???

you haven't heard that before? We went two steps farther than normal, but the first three bits are the common analogy for calculating decompression. People stress so much about it, but it is such a volatile process that divers that should have been bent on a profile aren't, divers that never should have gotten bent, get bent. Being concerned about 3% is negligible in the grand scheme of things and while the annoyance of having computers with different depth readings on their arms is valid, if you're concerned leave them on the EN standard which splits the difference, or just leave them on fresh water because it will always say you're slightly deeper than you actually are, which is rounding to safety.