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Gaz usage and tank pressure correlation

Lotram
2 months ago

Hi,

I recently did my first dives with the mk3i and T2 Transceiver, and I’m puzzled about the air usage graph: the mean usage (1.4 bar/ minute in my case) does not add up at all to the tank pressure graph (going from 195 to 51 bars in 48 minutes, i.e. approx 3 bar/minute). I was using a single air tank.

Do I need to consider another parameter, such as the depth / PO2 to explain this ?

I’m new to the dive computer world, so maybe that’s common knowledge, but I can’t find any explanation about this

  • 0 2 months ago

    well, this is either average or maximum. the 1.4 is which one? you realize gas consumption changes in depth and according to outside factors. it is not constant, hence the graph shows the detailed consumption at depth and time. hold over the graph to access those.

  • 0 2 months ago

    The discrepancy likely comes from the fact that the air usage graph shows mean consumption, not accounting for depth changes or other factors like the PO2. Air consumption increases with depth, and your dive computer adjusts accordingly. It’s common for air usage rates to vary based on depth and breathing patterns, so those factors might explain the difference.

  • 0 2 months ago in reply to SAB

    Hi, thanks for your answer.

    i do understand that air consumption increases with depth, because of increasing pressure, but I’m simply using the definition of a mean : 1.4 bar / minutes * 48 minutes = 67 bars, which is very different from the 144 bars drop. 

    So this means the air consumption graph is not the direct derivative of the tank pressure one. I’m wondering if this is because it’s implictly using depth factor, to show what would be my surface consumption.

    sorry if my question is not clear, english is obviously not my first language, and I haven’t done math in english in a long time.

    so to clear, my question is purely about numbers and math, because I should be able to get 1 graph from the other, not about the reasons of why my air consumption changes

  • 0 2 months ago in reply to Lotram

    i am not sure i follow, the 1.4 is the average probably, but it is not constant so you can use it for the whole tank consumption...and the gas consumption graph has 3 options - bars. liters per minute and rmv,  all those are calculated by the depth factor, if you check the rmv spikes are mostly at the depths. so definitely you have to take into account the depth factor, you can't do the math only with the average