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Thread: Question re: PSR-11-39-MD cells for Prism2

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    RBW Member dr.rob is an unknown quantity at this point dr.rob's Avatar
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    Question re: PSR-11-39-MD cells for Prism2

    Hey gang, be easy on me as this is my first post!

    I was certified 2 months ago on the Prism2, and have already racked up 25 dives (about 30 hours) on the unit. So far I am loving the unit! I am thrilled with my decision to go CCR and would never go back to OC unless somehow it is not possible to dive CCR.

    I have a couple of questions regarding the cells. They are new PSR-11-39-MD type cells, all opened at the same time 2 months ago, and have "Use by November 2015" stamped on them.

    I notice that cells #1 and #3 are always very close to each other, whereas #2 always reads a bit higher mV.

    For example, at my last calibration, they read 12.2, 12.9 12.2 mV respectively in air, and 56, 60 and 57 mV in 100% O2.

    Is this something to be concerned about? Does this mean cell #2 is better/fresher/newer than #1 and #3? Does the Shearwater algorithm decide that #2 is more accurate, or does it get voted out?

    Also, I was reading another thread talking about calibration, and some people say you should try flushing with 100% at 6 meters, to see if your cells can get to a pO2 of 1.6.

    So on my last dive 2 days ago, I tried just that at the end of my dive, and I could only get to a pO2 of 1.5. The mV readings of the cells were: 83, 92 and 83 respectively. Is this something to worry about? Is it possible my cells are getting old already?

    cheers,

    Rob

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    Re: Question re: PSR-11-39-MD cells for Prism2

    Quote Originally Posted by dr.rob  View Original Post
    Hey gang, be easy on me as this is my first post!

    I was certified 2 months ago on the Prism2, and have already racked up 25 dives (about 30 hours) on the unit. So far I am loving the unit! I am thrilled with my decision to go CCR and would never go back to OC unless somehow it is not possible to dive CCR.

    I have a couple of questions regarding the cells. They are new PSR-11-39-MD type cells, all opened at the same time 2 months ago, and have "Use by November 2015" stamped on them.

    I notice that cells #1 and #3 are always very close to each other, whereas #2 always reads a bit higher mV.

    For example, at my last calibration, they read 12.2, 12.9 12.2 mV respectively in air, and 56, 60 and 57 mV in 100% O2.

    Is this something to be concerned about? Does this mean cell #2 is better/fresher/newer than #1 and #3? Does the Shearwater algorithm decide that #2 is more accurate, or does it get voted out?

    Also, I was reading another thread talking about calibration, and some people say you should try flushing with 100% at 6 meters, to see if your cells can get to a pO2 of 1.6.

    So on my last dive 2 days ago, I tried just that at the end of my dive, and I could only get to a pO2 of 1.5. The mV readings of the cells were: 83, 92 and 83 respectively. Is this something to worry about? Is it possible my cells are getting old already?

    cheers,

    Rob
    Hi Rob.
    It is not uncommon for the AII cells to vary in their mV outputs right out of the box. This is nothing to worry about and does not indicate anything about the cells health.
    As far as the O2 flush, try it at 7 meters which should make it a bit easier to hit 1.6 without blowing through a lot of O2.
    "However beautiful the strategy, you should occasionally look at the results." Winston Churchill
    A is A

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