Quote: (Originally Posted by
Divejunkie)
Can someone help me with this please.
My question is to do with how the sensors are calibrated-
All calibration is, is the conversion of a mV reading to a PO2. As cell mV are expected to respond linearly, their should be a proportional change in mV with PO2.
The 2-point cal system of the Meg is unnecessarily complex. IMV, ISC has done a poor job explaining how this works, and it seems so many perform a procedure without understanding what is going on.
Quote:
... But what if the cells wont reach .21?
...?
It doesn't matter what PO2 the uncalibrated cells read in air or O2. What matters is the relative difference in mV between air and O2.
In pure O2, the mV should read 1/.21 = ~4.8x more than the air reading (assuming the altitude remains constant). If the above factor is 4.8x or a little bit more, than your cells are behaving as they should, and you can calibrate as instructed. Make sure you set the correct altitude as Joe says.
This 2-point system is a design flaw of the Meg. They should change to a more simple 1-point high FO2 system, thus reducing the liklihood of people getting it wrong.
I attach a customized checklist for the Meg, that contains a mV table to facilitate the process.