Then I'm even more proud of ya for remembering it!
BTW... that is why profiling works... it is operating within a realistic range of precision... just axe me.
"about" 10M or 33ft??
- Thread starter blackwater
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BTW... that is why profiling works... it is operating within a realistic range of precision... just axe me.
That's just like your post pesky...
pescador775
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Another stalker, I'm honored.
:mean:
:mean:
But if it makes you feel better... hey, glad to help.
The Iceni
Medical Moderator
In answer to blackwater's question, lets assume the salinity in the North Sea is 30 ppt. and fresh water it is zero.
Using Frank Tapson's programme;
..........................Sea water............Fresh water
Salinity.......................30....................0 PSU (ppt)
Density....................1023................1000 Kg/M2
Pressure at 10 M
...................................1.0033...........0.981 bar
.....................................0.99.............0.968 ats
..................................14.551...........14.223 psi
.................................100,327..........96,784 Pascals
So, an atmosphere is slightly greater than a bar but only by a percentage point or two!
I would reinforce the importance of the reduced surface pressure at altitide, though.
As we are now in the 21st century;-
Measure using a laser micrometer,
Mark using a felt-tip pen
But cut the tables using a chainsaw!
ut:
"Actually, pressure does increase linearly at diving depths."
No one ever said it doesn't. What was said is that 33 fsw is not necessarily 33 ft from the surface. 33 ft does not equal 10 m, but 33 fsw does equal 10 msw. 10 m equals 32.8 ft. 33 ft equals 10.05 m. A very minor difference.
fsw and msw are not measurements of depth (or distance from the surfasce) they are units of pressure. For practical purposes you can ignore the differences, since pressure is the important factor.
No one ever said it doesn't. What was said is that 33 fsw is not necessarily 33 ft from the surface. 33 ft does not equal 10 m, but 33 fsw does equal 10 msw. 10 m equals 32.8 ft. 33 ft equals 10.05 m. A very minor difference.
fsw and msw are not measurements of depth (or distance from the surfasce) they are units of pressure. For practical purposes you can ignore the differences, since pressure is the important factor.
pescador775
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Walter, that last post is circular double talk, complete nonsense. You are implying that the terms '33fsw' and '10msw' are the same, that they are also different, but also not different even though the height of the water columns are different. That they are linear but not linear, that they are based on salt water which varies in percentage all over the world. Thus, these differences are important but insignificant.
No. You simply misunderstood me.
33 fsw is the exact same pressure as 10 msw by defination. It is a measurement of pressure. They are not different.
ft is linear. fsw is not. m is linear. msw is not.
The confusing part is that 33 fsw is not the same as 33 feet deep.
"important but insignificant."
I have no idea how that wormed its way into your mind. 33 fsw is not the same as 33 feet deep, but it is close enough as to render the difference insignificant. I personally do not consider the difference between feet and fsw important. Even if you never grasp the difference, it will make no difference unless you convert from 33 fsw to 10.05 msw. That would not be correct, but the difference is still insignificant.
33 fsw is the exact same pressure as 10 msw by defination. It is a measurement of pressure. They are not different.
ft is linear. fsw is not. m is linear. msw is not.
The confusing part is that 33 fsw is not the same as 33 feet deep.
"important but insignificant."
I have no idea how that wormed its way into your mind. 33 fsw is not the same as 33 feet deep, but it is close enough as to render the difference insignificant. I personally do not consider the difference between feet and fsw important. Even if you never grasp the difference, it will make no difference unless you convert from 33 fsw to 10.05 msw. That would not be correct, but the difference is still insignificant.
OP
blackwater
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First off, I fully understand that they're "close enough" for measuring while I'm swiming around. esp. since
1) my depth guage's percision is in feet, not mm
2) The depth guage works by pressure, so if the salinity changes then the linear depth would be differnent than the equivelant pressure at the reference salinity, but since we're concerned with pressure anyway, the acutal linear distance is mute.
Being a programmer, I would like to write a program to show the various tissue loadings over time. (an educational tool, not a true dive planner), and this requires converting between: depth, fsw, and pressure
Using the "measure with a micrometer" mentallity, I want to get it right the first time.
published M-values vary in units from fsw, msw, ata, bar,..... If I'm going to code those to several places, then it seems that the conversions should also use several places.
It seems to be agreed that 1 bar is close to but not exactly equal to one atm.
And that fsw and msw are unit used by the dive community, and are close to but not exactly equal to the equivelent pressure at that linear depth for TBD salinity.
33 linear feet = 10.0584 meters,
10 linear Meters = 32.80839... feet
I did find one reference which stated:
1atm = 14.7 psi and
1atm = 33fsw and
1atm = 1.01325 bar and
1 bar = 10msw
1 bar = 1 Newton/Sq. meter = 1Pascal.
****
and yes, Dr. Powell when I took your class it became clear that their are many variables beyound just the easy to measure pressure (via "depth" guage) and time, but I would like to have my simplified model built on a basis I can belive in. In the end, my PC doesn't do well under water, and I don't have that long of an extention cord, but it is interesting to see how various changes affect the outcome.
****
I'm just suprized that there is no "official" definition of what fsw and msw are.
GT
1) my depth guage's percision is in feet, not mm
2) The depth guage works by pressure, so if the salinity changes then the linear depth would be differnent than the equivelant pressure at the reference salinity, but since we're concerned with pressure anyway, the acutal linear distance is mute.
Being a programmer, I would like to write a program to show the various tissue loadings over time. (an educational tool, not a true dive planner), and this requires converting between: depth, fsw, and pressure
Using the "measure with a micrometer" mentallity, I want to get it right the first time.
published M-values vary in units from fsw, msw, ata, bar,..... If I'm going to code those to several places, then it seems that the conversions should also use several places.
It seems to be agreed that 1 bar is close to but not exactly equal to one atm.
And that fsw and msw are unit used by the dive community, and are close to but not exactly equal to the equivelent pressure at that linear depth for TBD salinity.
33 linear feet = 10.0584 meters,
10 linear Meters = 32.80839... feet
I did find one reference which stated:
1atm = 14.7 psi and
1atm = 33fsw and
1atm = 1.01325 bar and
1 bar = 10msw
1 bar = 1 Newton/Sq. meter = 1Pascal.
****
and yes, Dr. Powell when I took your class it became clear that their are many variables beyound just the easy to measure pressure (via "depth" guage) and time, but I would like to have my simplified model built on a basis I can belive in. In the end, my PC doesn't do well under water, and I don't have that long of an extention cord, but it is interesting to see how various changes affect the outcome.
****
I'm just suprized that there is no "official" definition of what fsw and msw are.
GT
33 fsw = 10 msw = 2 atma In an "ideal" world were sea water actually weighs 64 lbs/cu ft and fresh water actually weighs 62.4 lbs/cu ft that would be at linear depths of 33.075 feet and 33.92308 ft. Since the weight of both sea and fresh water varies we never know at exactly what linear depth we'll hit exactly 1 atm or 2 atma.
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