Sensors slightly erratic

XtremeJAH

My O2 sensors are less than half of a year old, and they have been giving me some erratic readings. Mostly, when i calibrate them, at least one, if not 2 sensors take a long time to reach their stable mv reading.

They got wet once, just from condensation, but never submerged or anything. What is the deal? should i replace them all? Is this normal? How long should it take the sensors to calibrate to their max mv reading?

One site that i read, said it should take 6 seconds or so to reach max mv readings, but i dont think i have ever seen one on my sensors EVER reach their max in 6 seconds. and this unit is 5 months old!

Sutty

I don't dive a meg so can't comment specifically.
However if I recall right the 6 seconds sounds like the response time of the cells (R22BUD - is the meg the same?), ie around 6 seconds from the cells being exposed to 100%O2 to them generating a mV reading of 95% of the final reading. The response in a Rebreather will be longer as it takes time for an effective flush to expose the cell faces to 100%O2.

Neil

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divingabe

Hi, I am a new Meg owner (since last August), and I have never gotten the sensors to reach max mv. in 6 seconds. I have been using the calibrating kit from INS, from the time I turn on the o2 it takes appx 30 seconds to flush the head and get the sensors to max. As far as checking the validity of your sensors, use the formula to check whether or not the voltage is appropiate for the sensor. Take the mv reading in air and multiply it by 4.78 and the sensor mv reading in o2 should not vary more than 1.25 mv or 2%. This checks its linearity, if ok keep the sensor if not change it.
I picked up the Andi Meg Manual when it was released and it does offer a wealth of info. It is a welcome addition to my library.
From my limited experience so far, some moisture on the sensor face will not damage it, once dried the effectiveness of the sensor is fully returned. It will only give erratic readings when wet, the water acts as a barrier to the oxygen and keeps the oxygen from reacting with the cell (as far as I understand the functioning of the cell).

Gabe

Stef Mylonas

I would have to agree with Gabe on that one. I use an Oxycheq analyser
but it works the same.

The O2 cells will go to max in 6 sec but it simply takes longer to flush the head to max O2 concentration.

The question is, what kind of calibration method you use?

More specificly how do you ensure that the concentration of O2 in the head at the point when you calibrate at maximum O2 is the same as what you have in your 02 cylinder. And does your method take more time?

Hope that was helpful,

Stef