So got to, or just past the anniversary of of my first cells (insertion date, not manufacture) and exchanged them for new. On the last dive before the exchange 1 cell had started to behave erratically, never far enough to drop out on voting logic (SW GF) but certainly not stable.
Changed them out after leaving them out of packs for 72 hours min and calibrated. At that point though they were reading slightly high in air 0.22-0.23 with around 11.3-11.8 mv before calibration in o2.
Calibrated them in o2 on SW and HUD.
I didn't then check them again against dil or air in fairness.
Dived them yesterday and were fine at 6m on 2 separate 02 flushes on 2 dives despite moisture content on second dive.
I did perform a dil flush and got an average of 0.3 against a target of 0.3 so this was fine.
Last night though the cells at rest in air were still reading 0.22-0.23 n air, so let the head dry out and same again today.
I have checked the SW against the old cells (2 that were still OK) and they also read 0.23/0.23.
Before I break out the venerable KISS triples and check whether the SW is at fault is there an obvious, logical explanation I am missing.
At the practical level at the high side a 0.02 discrepancy doesn't worry me so long as it is still only 0.02 at higher ppo2's/pressures.
At the other end of the spectrum though which is more scary IMHO is that 0.18 would actually be 0.16, and although I don't allow the unit to drop this low its still a concern.
The inconsistency is common across all 3 so less likely to be wiring but always keep the M/F sections of the Fischer lubed with Fischer oil and was replaced around January anyway.
Could be the SW and can check against the Triples if necessary.
We are at circa 175m above SL but thought this would impact in the opposite direction, we are at circa 993 hpa atmosheric according to my altimeter.