I am diving a converted Dolphin, and I always remove my cells from the counterlung when calibrating them (ie. place them in a stream of pure oxygen).
I have never been able to calibrate the sensors when installed in the counterlung and doing O2 flushes, because I find it impossible to completely flush the whole loop with oxygen. That is, there is always some diluent present in the scrubber and other places, that dilutes the pure oxygen in the counterlung before i can complete the calibration.

This makes me curious to how f.ex. Inspiration divers can be sure that their sensors are in pure oxygen when calibrating.

Can someone enlighten me on this ?

Kind regards
Morten