ATA vs ATM which is right? Need to know for magazine.

Discussion in 'Basic Scuba Discussions' started by paperdesk, Aug 12, 2008.

  1. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    Hello! I'm proofreading for a magazine and we have a series of articles about SCUBA diving. The author abbreviated atmospheres as ATM, but I learned it as ATA. I'm wondering if ATM is also correct, or possibly even more correct? Any ideas?

    Thanks!

    Ted
     
  2. Walter

    Walter Scuba Instructor

    18,583
    310
    0
    ATM or atm is atmosphere or atmospheres. ATA, ata or ATMA is atmospheres absolute. Both are correct, depending on what you want to say.
     
  3. Sideband

    Sideband Surface Interval Member

    # of Dives: 200 - 499
    Location: Carol Stream, IL
    1,514
    3
    0
    ATM is atmospheres, but ATA is atmospheres Absolute. In other words, 33' of water is 1 ATM of water but it is 2 ATA because of the 1 atmosphere of air above it.
     
  4. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    Hi Walter, thanks for the info. Here is what the article says: "At sea level, the pressure is 1 atmosphere (ATM). at 33 feet below the surface, the pressure is 2 ATM. at 66 feet, it is 3 ATM, and 99 feet it is 4 ATM."

    Is that right, or should it say ATA?
     
    Last edited by a moderator: Aug 12, 2008
  5. roakey

    roakey Old, not bold diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Colorado Springs, CO
    3,545
    9
    0
    As Walter says, depends. If you're talking about relative pressure, it's ATM:

    "For every 33 feet you decend, you increase the pressure by 1 ATM"

    If you're talking about the total pressure, it's ATA:

    "At 66 feet, you're subjected to 3 ATA of pressure".

    Roak

    [added on edit]

    Race, you responded while I was posting. Though both are technically correct, I feel that "ATA" would be more correct in your case.

    Roak
     
  6. Walter

    Walter Scuba Instructor

    18,583
    310
    0
    Either is correct, has the concept of atmospheres absolute been introduced? If it has, use ATA, if it hasn't, use ATM. I would replace that w with an s.
     
  7. nwhitney2003

    nwhitney2003 Nassau Grouper

    # of Dives: 25 - 49
    Location: Portland, Oregon
    141
    0
    0
    I'm wrong so I deleted my post
     
    Last edited: Aug 12, 2008
  8. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    So, IF I understand correctly, the article should list ATA not ATM? It doesn't really explain a lot more about the topic, it's not a technical article.
     
  9. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    Good catch, do you need a job? You can work for us :)
     
  10. Charlie99

    Charlie99 Orca

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
    7,966
    145
    0
    ATA is unambigous. It is atmospheres absolute.

    ATM has some possiblity of confusion. Personally, when I use ATM I mean gauge pressure, with sea level atmosphere as the reference. In other words, at 33feet you have a pressure of 1ATM and 2ATA.

    Not everybody uses that convention as the meaning of ATM, but everyone agrees that ATA is an absolute pressure, referenced to vacuum. If you use ATA you eliminate the confusion.
     
  11. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18

    We are talking about total pressure, though it doesn't go into great depth (lol) on the topic.

    Ted
     
  12. TwoBitTxn

    TwoBitTxn Scuba Instructor

    # of Dives: 200 - 499
    Location: North Texas
    3,984
    62
    0
    If it's a non-technical article geared towards non divers most of your readers will not understand the difference between ATA and ATM. I think ATM shold be used. If the majority of the readers are divers, there is the possibility that ATA will be understood.

    Naturally, any abbreviation should be defined before being used...
     
  13. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    Ok! That does make perfect sense. I'll change it to ATA.

    Thank you all for your help! I'm sure I studies this when I got my c-card, but since then it's slipped into a dark place in my mind that I couldn't access . . . .
     
  14. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    Ohhhhh. Just when I thought I had an answer . . .
     
  15. 300bar

    300bar ScubaBoard Supporter ScubaBoard Supporter

    7,432
    104
    0
    Just change the whole thing to BAR.Add 1 for atmosphere and your ready.:D
     
  16. Walter

    Walter Scuba Instructor

    18,583
    310
    0
    If you're not explaining, I would spell it out - atmospheres absolute.
     
  17. scubajcf

    scubajcf Scuba Instructor

    # of Dives: I'm a Fish!
    Location: Arizona
    1,092
    12
    0
  18. Doc Intrepid

    Doc Intrepid Scuba Instructor

    4,632
    6
    0
    Just FWIW, I agree that if the article is intended to be read by divers, I would use ATA.

    Since you must define either, ATA is a more frequently used variable when calculating mixed gas diving requirements and consumption in general.

    JMHO,

    Doc
     
  19. paperdesk

    paperdesk Barracuda

    # of Dives: 100 - 199
    Location: Inchelium, WA
    226
    3
    18
    300Bar, I had the same temptation . . .

    SCUBAjcf, I'm checking out the link.

    How's this? Trying to keep it simple:

    "At sea level, the pressure is 1 ATA (atmospheres absolute). At 33 feet below the surface, the pressure is 2 ATA." etc.
     
  20. Doc Intrepid

    Doc Intrepid Scuba Instructor

    4,632
    6
    0

Share This Page