What Does Atm Mean Insofar As Waterproof Testers

[TJGladeRaider]

I must say that it has been interesting to see all the statements regarding my assertion that a pressure test to 4ATM is the equivalent of 132 feet. It's pretty clear that there are few divers/pilots among us.

I especially liked the one about the jello pudding . . . LOL

If you're interested, I'll explain it - if you disagree with my explanation, please go here:

Advice or, if that doesn't work:

http://www.oracleinternational.com/advice/

One ATM is defined as a unit of pressure equal to the air pressure at sea level. It equals the amount of pressure that will support a column of mercury 760 millimeters high at 0 degrees Celsius under standard gravity, or 14.7 pounds per square inch (1.01325 × 105 pascals).

As you go deeper under water (salt water), pressure increases at a rate of 14.7 pounds per sq inch (or 1 ATM) every 33 feet. It is different in fresh water (34 ft) and it would be a hell of a lot different in Jello Pudding.

I must acknowledge that the guy who said that pressure testing to 4ATM should have been 99 feet. That is in error only because I was not clear and he would not have been misled had I explained things a little better - specifically, pressure testers are set up such that the scale begins at zero, as opposed to one, so when you add 4ATM, you are subjecting the watch to the equivalent of a 5ATM depth.

Here is the relevant table.

http://www.online.uillinois.edu/oakley/nitrox.html

I hope that clears up any confusion.

Bill

[Miss Understood]

My dear William

That is a lovely explanation. I venture the opinion that most people nowadays would think "automated teller machine" when faced with the acronym "ATM".

Well said.

Edited May 27, 2006 by Miss Understood

[TJGladeRaider]

My dear, that is a lovely explanation. Well said.

Thank you Miss Understood, but the word "lovely" t'would be better applied to your countenace and classic coiffure.

Bill

[Focker]

Great explanation! Many people also get off on tangents about dynamic pressures vs. static... pressure rises resulting from the swimming motion.

Certainly there is a *tiny* difference but it's negligible.

A friend of mine is a commercial diver. His deepest dives were to 1800' in chambers, wearing a genuine Sea-dweller. The SD is rated to 2000' and he wasn't the least bit worried about it flooding due to dynamic pressure differentials.

Considering the 1/33 pressure difference between fresh and salt water, that should equate to 1,854 feet "fresh" ... even closer to 2000' limit, and no problems.

PS: Bill said it! How'd we wind up with such a classy gal among this crowd of malcontents?

If he was in a chamber, how the hell would his watch get wet?

[offshore]

Bell!