How Do Shearwater Work Out SAC Rates?

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  • Опубліковано 15 гру 2024

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  • @reyneva
    @reyneva 5 місяців тому +2

    Hi Mark, lovely episode. My favorite so far. Keep up the good work!

  • @KitoriSin
    @KitoriSin 5 місяців тому +1

    Awesome episode! May i know what is the blue bracelet that you are wearing called? and where can i purchase it from?

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  5 місяців тому +1

      That is from a company called Bracenet. They make a range of items from collected ghost gear.
      All of their bracelets are named for different seas and oceans, the blue one is named Arctic Ocean.

    • @KitoriSin
      @KitoriSin 5 місяців тому

      @@ScubaDiverMagazine Thank you! 😊

  • @JulieVenhaus
    @JulieVenhaus 5 місяців тому +1

    #askmark Hi! Not Shearwater or dive computer related (although my husband and I have both ordered the Peregrine TX!). Would love to know your thoughts on XS Scuba’s Highland Backplate and wing products. Our local dive center carries them (and their regulators) and we cannot find any videos, good or bad. Thanks!

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  5 місяців тому +1

      I've used a few of their bits and they're decent quality. It's hard to go far-wrong with BP/W hardware...
      They're not a particularly _flashy_ brand so you won't find a lot online about them but, the quality and materials are fine.
      Have fun with the Peregrines, they're a top tier computer

    • @JulieVenhaus
      @JulieVenhaus 5 місяців тому

      @@ScubaDiverMagazinethanks!

  • @charlemagne8764
    @charlemagne8764 5 місяців тому

    My Garmin (MK2i) gives me a SAC rate in L/min as well as RMV in L/min. I understand the SAC rate is the consumption adjusted for depth, ie at the surface and RMV is the actual consumption. Do you know if my understanding is correct?

    • @Teampegleg
      @Teampegleg 5 місяців тому +1

      Yes but that isn't how anyone else would use RMV. Traditionally SAC was a volume measurement, it was something you calculated after the dive taking pressure used, average depth, and calculating that against your tank capacity. Then SRI came along and had real time SAC in pressure per minute. And then because people were giving pressure based SAC, instead of insisting on people diving units, they repurposed the term RMV form medicine. RMV is used by some for what SAC used to be volume per min at surface.
      I use SAC for volume with units and never use a pressure based SAC.

  • @stevenwood1468
    @stevenwood1468 5 місяців тому +1

    #ASKMARK My predix ai does a calculation for GTR (gas time remaining) , do you know how that calculation works ?

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  5 місяців тому +1

      Shearwater are clever with this one also: They take the known tank pressure and subtract enough gas to ascend to the surface at a safe rate and also subtract enough gas for a reserve.
      This remaining gas is then divided by the ambient pressure and your SAC rate to work out how many minutes it would take for you to breath down that gas and still be able to ascend to the surface with some reserve.
      But. It won't take deco or safety stops into the calculations so, don't go right up to the limit or you may need to go into your reserve

  • @douglasljdunn
    @douglasljdunn 5 місяців тому

    Useful preso. I track my RMV manually, simple calc to do.

  • @linyasen5
    @linyasen5 5 місяців тому +1

    Hi Mark. What kind of watch you are wearing? Is it a dive watch? If it is, what brand is that? I'm in the market for a dive watch/computer right now. Thank you!!! :)

    • @comebackdk
      @comebackdk 5 місяців тому +1

      it look like a TERIC

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  5 місяців тому

      Yeah, that's my Shearwater Teric. It felt right to wear it when Shearwater were sponsoring the video. It comes in a few colours now and there's also the Shearwater Tern if you're interested.

  • @leborde
    @leborde 5 місяців тому +1

    Isn't the internal volume of a 12l cylinder something like 11.1l?

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  5 місяців тому

      An Ali 80 has an internal volume of 11.1L. Steel 12L is the most common size cylinder here in the UK

  • @EnergiZeScuba
    @EnergiZeScuba 5 місяців тому

    Hi Mark, (Hi Shearwater, if any of you are reading this), I use the Perdix 2ti and every now and then (in 22 dives 2x) I have the problem that the SAC rate was very high (45bar/min or higher). I can't explain why this error occurred. Do you have any idea? My normaly SAC Rate is about 1,6bar/min

    • @Yggdrasil42
      @Yggdrasil42 5 місяців тому

      I would send that dive log to Shearwater support. Definitely interesting.

    • @a.karley4672
      @a.karley4672 5 місяців тому

      Hmmm. How *smooth* is the value from your *electronic* cylinder pressure gauge? If this is (erroneously) dropping to zero (or a low value), then you'd see that effect.
      I've seen this in (in house) lab equipment from loose wires in the analytical machinery. But we could go to manual calculation and get round the problem. Next break in operations, out with the soldering iron and solder the pressure cell's connections. Bug report filed to the technician who built it.
      The last time I calculated "SAC" rates was for cave diving, to work out if I'd be able to make a particular air bell before reaching 'thirds'. But always, the answer to such questions is "bigger tanks". Skip-breathing isn't really an option. I'm trying to remember what 1cu.ft/minute is in L/min. (28.4 L/cu.ft - I had to work it out.

    • @ozDomaNET
      @ozDomaNET 5 місяців тому

      3 suggestions:
      flooded/damaged transmitter
      or
      make sure your octo. is not free-flowing during your dive
      or
      if it is not happening during DSMB deployment.
      Shearwater is probably not as good and reliable as it used to be. My Perdix2Ti pressure sensor failed just after 6months/280 dives (soaked in fresh water every day)
      Another guys Teric pressure sensor also failed (within Waranty period).

  • @sparksi2519
    @sparksi2519 5 місяців тому

    Wait.... Shouldn't sac rate be in liters/min, rather?
    Surely the size of your tank doesn't affect your sac rate 😅

  • @Billys-Adventures
    @Billys-Adventures 5 місяців тому

    #askmark Please reduce the sensitivity on the mic. 😂 It picks up everytime you swallow

    • @ScubaDiverMagazine
      @ScubaDiverMagazine  4 місяці тому

      My bad, I usually wear polos to move it away from my neck, I'll do better next time