Do you check your cells

Ken West

I had a bad sensor alarm on a dive last week. Pulled the cell and it read 8.9mV in air. Prior to the dive it had read 16.2mV. The interesting thing here is that when I took the cell out of the head and left it on the desk for a couple days the voltage climbed back up over 16mV. I thought perhaps I had some moisture or schmegma on the membrane and that it had just dried out and returned to normal function so I put it back in the head and took it diving. A few minutes into the dive it was voted out again and I got a low sensor warning. Cell was current limited and would not go over .8 at twenty feet after an O2 flush. Pulled the cell and it was dry as a bone. Obviously I am not diving with this cell any longer but it is interesting to note that it now reads 17mV in air. When it is loaded the cell voltage drops off rather quickly. If I ever doubted the value of an O2 flush to verify cell function, I certainly don't anymore !

dave t

current limiting is the cells in-capability to put out a voltage (current) high enough to match the surrounding ppo2. it may happily put out the correct reading in air at 1bar and also o2 at 1bar (surface) but its inability above that is the current limit. the more current limited it becomes, the more possibility of non-linearity there is. The output of a new cell is a curve which hopefully is a fairly straight line in the po2's we need to worry about only dropping off at the top end. As the cell dies that curved bit gets nearer to our working zone.

At least thats how I understand it

Dave

Divejunkie

Anyone got a design and instructions for a pressure pot?

Depth-junkie

I voted only when installing new cells, due to the question asking MV checks.

I only do this when checking and installing new cells, But i always when assembling my unit switch the head on in the open air and make sure the cells are reading ambient correctly, and i always at the start of a dive make sure the cells can reach above set point I.E running a SP of 1.3, i make sure the cells reach above to 1.4-1.45. And at the end of the dive i always flush the loop with O2 @ 6m to make sure the cells reach 1.5ish or above.

Dont really see the point in regular checking the MV output, as the vision gives me all the info i need during calibration, and along with my own dive practises is enough for me to know my cells are good for the dive in question.

ATB
Gareth

bletso

I just converted an old pressure cooker.

Dale

mountain diver

same,just habit.

Gobfish1

Have you got a some picks of the thing you can post
please Dale

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Steve G

Apparently not the only gay diver in the village

http://drinkingliberally.org/blogs/o...nzee-glock.gif

http://www.scubatunes.com/audio/vol01/mp3/HiTech.mp3

bendomatic

for one cell, it's only when i calibrate (air) cos the VR3 shows for that cell. don't need to calibrate that often. the other two cells never. always check at start of dive to reach 1.6 (6m). the only other time i checked voltage was when a new one out of the packet failed to calibrate in air. it was cactus.
rachel

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why deal with idiots on the net when you have to spend all day dealing with them at work.

teksimple

I stand corrected: SMI cells ARE made by AII. May I ask how long you have had that sensor in question?


ASIDE: I wish I had a separate non-Rebreather World-sponsor account now because everyone will assume there is a sales ploy behind my posts.

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

Andy Del

I check MV readings every now and then, and can now also check for linearity via Ron's nifty pressure pot and my thumb.

It was reassuring to find all 3 of my cells are in range in air, and will read up to 2.0 (1.99) in O2 at 2ata...

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Yellow - the colour of greatness!