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RonMicjan · 9th October 2006, 01:31

well first an oxygauge is not a dive computer, just a one cell po2 monitor. I believe you may be asking about an Oxy2 with an AirZ O2 wireless dive computer made by Uwatec for the dolphin.

The system uses 2 cells and averages the output and will tell you when a cell is out of range, but not give you the data for each cell, so in effect its like diving a single cell readout, no redundancy, fine for SCR dolphin, but not for CCR where you may need to verify one cell against another.

the primary reason why the unit sucks for CCR diving is the way the deco algorithm works. the system is expecting you to be on a SCR and that you will have a minimum PO2 near the surface and a maximum PO2 at depth, and a constant Fo2, exactly the reverse of how a constant PO2 CCR works, where you have a maximum Fo2 of oxygen at the surface and minimum at depth. where this becomes the problem is when the dive computer sees your Fo2 fall at depth, it assumes that you are working very hard using up all the O2 in the loop (on an scr, this is what happens when you work hard, the bag Fo2 falls) so it increases your deco obligation thinking your metabolic rate is very high, then it wont give you much credit when you come shallow and your fo2 is back up, cause now you are resting and off gassing slowly.

I did several dives on this computer when I first converted my dolphin to CCR and wondered why the alarms kept going off and why I was so far off my constant PO2 CCR dive tables. I soon went to a tied in explorer dive computer and my bottom times extended significantly. Later I did some diving with Dave from BC and he was using the same uwatec stuff I had abandoned, we were finding 30+ minutes of deco difference between his computer and mine.

the VR3 dive computer has an SCR mode, that does the look ahead based on a constant FO2, if you use this mode while on CCR your real deco will run out much faster than the projection. But you will find the inverse true if you dive SCR while in CCR mode, the look ahead will be expecting a constant PO2 and your SCR will be delivering a constant Fo2. There is some discussion of the difference between constant PO2 diving and constant Fo2 in my article rebreather math, here

hope this helps and my assumtion on which item you have is correct too

9th October 2006, 01:31	#4 (permalink)
RonMicjan Would rather be diving... Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Astoria, Oregon USA Posts: 1,164	Re: Oxyguage and MCCR Dolphin well first an oxygauge is not a dive computer, just a one cell po2 monitor. I believe you may be asking about an Oxy2 with an AirZ O2 wireless dive computer made by Uwatec for the dolphin. The system uses 2 cells and averages the output and will tell you when a cell is out of range, but not give you the data for each cell, so in effect its like diving a single cell readout, no redundancy, fine for SCR dolphin, but not for CCR where you may need to verify one cell against another. the primary reason why the unit sucks for CCR diving is the way the deco algorithm works. the system is expecting you to be on a SCR and that you will have a minimum PO2 near the surface and a maximum PO2 at depth, and a constant Fo2, exactly the reverse of how a constant PO2 CCR works, where you have a maximum Fo2 of oxygen at the surface and minimum at depth. where this becomes the problem is when the dive computer sees your Fo2 fall at depth, it assumes that you are working very hard using up all the O2 in the loop (on an scr, this is what happens when you work hard, the bag Fo2 falls) so it increases your deco obligation thinking your metabolic rate is very high, then it wont give you much credit when you come shallow and your fo2 is back up, cause now you are resting and off gassing slowly. I did several dives on this computer when I first converted my dolphin to CCR and wondered why the alarms kept going off and why I was so far off my constant PO2 CCR dive tables. I soon went to a tied in explorer dive computer and my bottom times extended significantly. Later I did some diving with Dave from BC and he was using the same uwatec stuff I had abandoned, we were finding 30+ minutes of deco difference between his computer and mine. the VR3 dive computer has an SCR mode, that does the look ahead based on a constant FO2, if you use this mode while on CCR your real deco will run out much faster than the projection. But you will find the inverse true if you dive SCR while in CCR mode, the look ahead will be expecting a constant PO2 and your SCR will be delivering a constant Fo2. There is some discussion of the difference between constant PO2 diving and constant Fo2 in my article rebreather math, here hope this helps and my assumtion on which item you have is correct too __________________ http://www.tmishop.com CCR Training, sales and diving bits Dealer for Megalodon CCR's, Oxycheq, Aerospace Lubricants Tribolube, H2Odyssey, Haskel Sport Booster, Gas Fill Whips and more... Last edited by RonMicjan : 9th October 2006 at 01:34.
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