Quote: (Originally Posted by
Genesis)
All oxygen cells are sensitive to humidity in the gas being sampled. There is no humidity compensation circuit in these devices (nor could there easily be on a self-powered fuel cell due to power requirements).
Is this a big deal? Only if you push your PO2s (reading low by a consistent amount presents you with a hedge against DCS, but at the cost of increased CNS O2 risk.)
Maybe not such a big deal, but it makes me feel a lot more comfortable when cells are reading what they are supposed to. In the last 6 months or so, I don't do any pre-dive calibration. I like to check on the way down @4.5m, and again on the way out. If any discrepancy, I'll calibrate right after the dive while cells are wet.
Result is .23-.25 and 1.05-1.1 in ambient air/O2 respectively, and about 1.6 @4.5m when cells are dry. Re-Cal isn't needed until a good 6-10 hours operation have passed. I take a marginal DCS risk to protect against under-estimating cells. Is that wise?