Benefits of redundant continuous pO2 monitoring?

[NAND]

True. I am not doubting it can happen- if you would only rely on a single computer with no further po2 monitors and ignore best practise concerning sensor swaps. Bit still- having limited cells showing same value is rare if not very unlikely.

http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf

 

[rjack321]

According to what I have read elsewhere here on SB, it HAS happened that someone died because they had 2 cells that both became current-limited (to the same limit) at the same time. Their computer voted out the one good cell and then kept pumping in O2, trying to get the ppO2 up, until they toxed.

This has happened more than once.
Ron Akeson was one. There was another in Aus or OZ on an AP unit. Probably more but I haven't been counting.

Two cells can both fail similarly because cell decline is not necessarily linear. It can be more like cliff when two fall off at the same time. And as long as the two failed cells are within 10% ppO2, most 3 cell voting will consider the 3rd high cell as the erroneous one. Net if you both fall off a cliff at the same time, its not hard for you land within 10% of each other at the bottom.

 

[rjack321]

True. I am not doubting it can happen- if you would only rely on a single computer with no further po2 monitors and ignore best practise concerning sensor swaps. Bit still- having limited cells showing same value is rare if not very unlikely.

http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf

This is good to get you thinking. But there's actually no actual failure data behind the percentages in a good batch or average batch etc. One key dubious statistic is that 200 out of 1000 sensors fail out of the box. I've been diving CCR for 5 years and been through a little over 20 sensors in that timeframe. I had one fail in the first month and the remainder were retired after 12 months or I had a non-sensor issue that cause me to retired them early (I flooded two different times). Paul admits the percentages are arbitrary but then uses them to support his conclusions which is pretty shaky, especially the "early failure" mode.

 

[Wolfgang Jeschke]

I add a 3. Cell holder in the loop of my Poseidon 7 and connect via Sensorboard a Ratio IX3M.
If something goes wrong with the electronic I control po2 over manual add and 3. cell