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Thread: Calibrating sensors, how long before diving...

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    Captain Meivi is an unknown quantity at this point Meivi's Avatar
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    Calibrating sensors, how long before diving...

    I always get up extra early on a day before diving to do all the pre-dive checks and all on my ccr.
    But now I'm thinking about instead of doing it the same morning would it be okey to do it the night before. All the assembly, checklist calibrating and pre-breathe and that (and I always do just a short pre-breathe before I enter the water aswell)

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    Supporting Member Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36's Avatar
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    Re: Calibrating sensors, how long before diving...

    I prefer to do it the night before. That way I have time to sort out any issues that might pop up without feeling rushed. I sleep better knowing that my gear is all sorted and ready too.
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    Re: Calibrating sensors, how long before diving...

    Quote Originally Posted by Dsix36  View Original Post
    I prefer to do it the night before. That way I have time to sort out any issues that might pop up without feeling rushed. I sleep better knowing that my gear is all sorted and ready too.
    Ditto. It sucks to deal with changing a cell out on a boat, usually with people waiting on you, when you could have done it the night before.

    AP's CO2 sensor usually forces me to recalibrate the next morning, but I'd rather lose that bit of O2 for the peace of mind knowing that they WILL calibrate.

    Jim

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    Re: Calibrating sensors, how long before diving...

    As a dive boat skipper, I've seen the SMS of sadness from guys prepping on the morning of a dive way too many times. Leaving it that late is leaving yourself zero wiggle room to sort out any issues.

    I generally build and test on the Thursday before a weekend dive, so I have all of Friday to hassle mates for loan gear or get to shops etc if there's a problem.

    Calibration? I check calibration on that Thursday build and again when I power up the unit before the dive, but since getting rid of the AP electronics I haven't needed to do a calibration outside of switching a cell in a long, long time :)

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    Re: Calibrating sensors, how long before diving...

    Quote Originally Posted by Captain Starfish  View Original Post
    Calibration? I check calibration on that Thursday build and again when I power up the unit before the dive, but since getting rid of the AP electronics I haven't needed to do a calibration outside of switching a cell in a long, long time :)
    Same here.

    I've just returned from 10 weeks of diving in Scapa Flow and during that time I calibrated once - after swapping out my cells.

    Calibrating every day can just mask issues with your cells. When I change my lime, I dry my head and look for the cells to read 0.21 in air. If they do that, what the hell is calibrating going to do for you?

    Periodically, I will run my cells through my cell checker to confirm linearity up to 2 bar.

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    rEvo FT / Hollis P-2/ rEvo lll

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    Re: Calibrating sensors, how long before diving...

    I had the same concern as you. The night before is the way to roll.

    Best regards,
    Chett. L

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    Re: Calibrating sensors, how long before diving...

    Quote Originally Posted by NickB  View Original Post
    Same here.

    I've just returned from 10 weeks of diving in Scapa Flow and during that time I calibrated once - after swapping out my cells.

    Calibrating every day can just mask issues with your cells. When I change my lime, I dry my head and look for the cells to read 0.21 in air. If they do that, what the hell is calibrating going to do for you?

    Periodically, I will run my cells through my cell checker to confirm linearity up to 2 bar.

    Yes. This. Exactly.
    Last time I calibrated, was when the cells went in. I check them before all dives that they read 0.21 in air and that the mv are where they should be, and that there has been no divergence from the mv the last time. On dive check that they will read >1.3. Put them in the pot periodically up to 2 bar.

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    Cognitive surrender TopLeft is an unknown quantity at this point TopLeft's Avatar
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    Re: Calibrating sensors, how long before diving...

    I've learned to do the check the night before. Same reasons as stated by those above as I have been "that guy" who delays several dives.

    My biggest stabilizing effort was switching to N@90 cells.

  9. #9
    Captain Meivi is an unknown quantity at this point Meivi's Avatar
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    Re: Calibrating sensors, how long before diving...

    Quote Originally Posted by NickB  View Original Post
    Same here.

    I've just returned from 10 weeks of diving in Scapa Flow and during that time I calibrated once - after swapping out my cells.

    Calibrating every day can just mask issues with your cells. When I change my lime, I dry my head and look for the cells to read 0.21 in air. If they do that, what the hell is calibrating going to do for you?

    Periodically, I will run my cells through my cell checker to confirm linearity up to 2 bar.

    So you, and others of u guys, doesnt calibrate it every day? Thats what im doing syn xD

  10. #10
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    Re: Calibrating sensors, how long before diving...

    Gods no.

    CHECK the calibration - at the very least, when the system is doing battery checks and opening the solenoid, make sure that all three cells run up to the same PPO2 at about the same pace. Make sure all are tracking the same as you breathe the loop. Switch the O2 cylinder off and flush the loop, then either breathe it back down to air or use your lungs/mouth/nose to flush it with air and continue checking the cells track together.

    If everything's working, you don't need to calibrate and doing so just wastes O2 and battery. If a cell or connection is starting to deteriorate, a calibration will get you diving but if you do it every time you won't notice it getting worse until it's too late.

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