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Question about GTR in Perdix AI

Discussion in 'Shearwater Research' started by Hatul, Nov 15, 2016.

  1. Mike1967

    Mike1967 Contributor

    # of Dives: 100 - 199
    Location: Victoria, Australia
  2. AJ

    AJ Solo Diver

    # of Dives: 500 - 999
    Location: Netherlands
    Ok, thanks. Thought so but was confused.
  3. Jay

    Jay Need to dive more!

    # of Dives: 100 - 199
    Location: Melbourne, OZ.
    FYI from SW:

    "The GTR calculations on the Perdix AI are only for single-tank diving that does not require decompression stops.

    GTR is a tool for no-stop (i.e. no decompression) diving. We do not recommend GTR as a tool for decompression diving. Decompressing diving involves significant pre-planning of gas reserves and typically requires multiple tanks and gas mixtures. The complexities due to managing multiple tanks and differing styles of gas management would make setup of GTR too complex for reliable use. We tried this during development, and experienced testers frequently made setup mistakes that resulted in incorrect GTR. Shearwater feels that GTR is a great tool for single-tank, no-stop diving, but unfortunately does not work well for more complex diving."

    from How is GTR calculated for multi-tank dives or decompression dives? - Shearwater Research

    and a fair bit of anti-GTRness from Tech divers in general. The main point is being that it might allow divers to be lazy with gas management rather than using it as a verification tool. More info here: Do any Tec-Rec (or light deco) divers use GTR?
  4. Father

    Father Instructor, Scuba

    # of Dives: 500 - 999
    Location: Kwajalein Atoll, Marshall Islands
    So, does the Perdix not calculate SAC rate?

    I'm a little confused on the difference between SAC rate and GTR.
  5. NAM001

    NAM001 Contributor

    # of Dives: 500 - 999
    Location: the moon
    sac is consumption rate. gtr is how much time you have to reach your designated onboard pressure. IE you are set to be on board with 500 psi ad you have 750# YOU ARE AT 100 FT AND THE COMPUTER SAYS AT 50 psi a min you have 5 minutes. if you went up to 30 ft the time would change to 10 minutes because the consumption rate would be less. TTS is different in that it is (either) the time it will take to go to the surface at designated ascent rates or the time till you have to start your ascent. I dont remember which for sure. Its been a long time since i have used an AI computer.
  6. NAM001

    NAM001 Contributor

    # of Dives: 500 - 999
    Location: the moon
    perhaps it should be reworded a bit to say single air source. a set of doubles is a single tank when the crossover is open.

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