Question What loop pO2 for overnight storage

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LFMarm

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Hello,

I was told not to store sensors in a high pO2 environment because it accelerates their depletion. Does this apply to long duration or also to 12-18h? The reason I am asking is because I sometimes do the calibration the night before diving and do a positive with O2. Should I leave the loop at 1.0 for the night or bring it down to 0.21?

I assume that it doesn’t really matter for such short duration but wanted to hear what others are doing. Thanks@
 
No experience (nor science) on my side, but I’ll guess it will ever so slightly eat away at the cells; so cells that should survive 18mo in air for example (no diving), would maybe do.. 15mo with occasional diving.. 12mo with daily diving..
adding on top of that the overnight +ve test, maybe lose a month 🤷🏽‍♀️

Long term users are far better to comment on the arbitrary numbers I just made up

Sounds like a good project for some under/grad chem students to publish a paper about — “micro depletion in galvanic cells” or something like that

But a safe guess.. do the o2 calibration and then do the overnight +ve test with air, might save you an extra dive or 2
 
Yeah, you can do a dil flush to bring the PPO2 down to 0.21, assuming air dil. I was never a big fan of leaving the loop at a high PPO2 or pulling negatives overnight.
 
I've had similar thoughts and just do a couple cycles of breathing ambient air into the loop, then venting it down thru nose, until sensors read ~0.21 again before closing and storing.

I am too much of a miser to use what is indeed an insignificant amount of precious diluent to do this--especially if it contains helium--and instead treat this like a 'vent the loop properly and completely' drill.
 
I always turn off everything, dump the pressure, then fill the loop with air by sucking a vacuum, releasing my lips to let the air back in, and repeating a dozen times or so.

Theory being that oxygen sensors are batteries that are depleted in oxygen. More oxygen means less battery life.
 
I was told not to store sensors in a high pO2 environment because it accelerates their depletion. Does this apply to long duration or also to 12-18h? The reason I am asking is because I sometimes do the calibration the night before diving and do a positive with O2. Should I leave the loop at 1.0 for the night or bring it down to 0.21?
Sensor lifespan was rated at ambient air, PPO2=0,21. So, leaving sensors at high PPO2 loop
accelerate its depletion - chemistry of converting lead to its oxide is dependent
only from fraction of O2. So, more hours you dive, higher PPO2 you use - cells die earlier.
If we assume linear progression, leaving sensors at PPO2=0,8 for 12-18h is same as 48-72 hours in ambient air.

I've had similar thoughts and just do a couple cycles of breathing ambient air into the loop, then venting it down thru nose, until sensors read ~0.21 again before closing and storing.
Same for me.
 
SOP for solid state cells is less than 0.3 (so's they'll turn off). Elevated pO2 is elevated current for galvanics, so in theory they'd wear out faster if you made a habit of it?
 
SOP for solid state cells is less than 0.3 (so's they'll turn off). Elevated pO2 is elevated current for galvanics, so in theory they'd wear out faster if you made a habit of it?
Actually the general advice for “run overnight +ve checks at 0.2 ppo2” seems to extend well for SScells not to drain the battery
 
High PPO2's will deplete galvanic cells faster and will keep Solid State cells ON using the battery. I do my positive with o2 just to see if it maintains above 1.02 for a few min, but then I will flush it back down to .21 and run a longer positive check on air so the cells are not under high PPO2 during storage.
 

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