How to measure O2 in a chamber?

[Si14]

Dear all:

I want to make a chamber as O2-free. The chamber is not perfectly sealed, so it has some small holes. I have used N2 gas (by pumping N2 from one input and escaping of O2 from holes in junctions). Now, I want to measure the amount of remaining O2 inside chamber. How can I do that? Is there any meter or other non-destructive! way?

Thank you very much,
Regards

[Mapes]

Yes, there are electrochemical sensors that measure the partial pressure of oxygen; they are easily found with an Internet search.