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D4i Novo - Nitrox Bottom Time

Discussion in 'Suunto' started by IslandAdventurer, Oct 15, 2018.

  1. IslandAdventurer

    IslandAdventurer Registered

    # of Dives: 100 - 199
    Location: Ireland
    Hi All,

    Looking for some advice with my D4i novo. Yesterday was using it on a Nitrox dive (30% Mix).
    It was a non-repetitive dive and the first in a week so there should have been no residual nitrogen.

    Anyway the dive started at 28m and proceeded to 24m in the first 10mins. My computer was giving me just minutes of deco left. At 15 mins into the dive, still at 24m I only had around 3 mins of NDL displaying. I swallowed up a few meters, still 3 mins... At 28mins @ 20m I exceeded the NDL and was given a ceiling alert and deco stop + mandatory safety. I proceeded up, did the stops and finished the dive.. (48mins 28m Max)

    It was really strange to get such a short NDL for the depths and times so I plugged the D4i in and downloaded the graph (attached image). Suunto's DM5 gives a completely different NDL throughout the dive. It also shows the when the computer went into deco but gives an NDL of 33 mins a minute before.

    What could have caused this? The computer was definitely set to 30% (Check a bunch of times after the dive and confirmed in the image). My NDL should have read 33 mins and should not have entered deco. Any ideas?

    PS. I know this profile is not ideal but there was serious atlantic surges along a wall and we were getting tossed around toward the end of the dive (hence the accent warnings) Winter is coming to Ireland!

  2. scubadada

    scubadada Diver Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Philadelphia and Boynton Beach
  3. BigJeff

    BigJeff Contributor

    # of Dives: 2,500 - 4,999
    Location: Wales
    NDL does seem short on the computer, and about right on the downloaded profile.

    Have you double checked the Altitude and Personal settings on the computer?
    These can have a big influence on NDL times if not set to the defaults of 0 and 0.

    Not sure what else to suggest unless you step through the dive on the D4i in the logbook mode and check to see that there are no strange depth spikes or fast drops in NDL.
    DM5 uses the sample rate (20sec?) data to calculate NDL while the computer in use underwater will calculate from the real time (1sec) sample rate.
  4. IslandAdventurer

    IslandAdventurer Registered

    # of Dives: 100 - 199
    Location: Ireland
    Personal / altitude set to 0. ppO2 1.4. No weird depth spikes on the graph in logbook mode, the downloaded graph also shows that, if there was it would have affected the max depth record.. anyway it's a weird one. Contacted Suunto to see. Also don't think this is related to the faulty pressure sensor issue as there's over 200 dives on this computer and it's never had an issue before, plus a faulty sensor wouldn't really affect the algorithm for calculating NDL without showing inaccurate depths on the downloaded graph.. my buddy on the dive was also using a suunto and had a widely different NDL for the same nitrox settings.
  5. Efka76

    Efka76 Contributor

    # of Dives: 100 - 199
    Location: Edinburgh, Scotland
    We have the following facts:

    1) Your computer personal / altitude factors were set on 0, ppO2 1.4
    2) Your buddy who was diving on Suunto computer (was it the same model using the same algorithm?) had different NDL on the same Nitrox settings (I assume that your buddy's dive profile was the same).
    3) DM5 shows you correct NDL on that specific time when your computer went into deco mode.

    In this case I think that it was your computer fault and I would send it to authorized dealer for checkup.

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