measure O2 in tea

[humble1]

What do you use to measure Dissolved O2 in the brewer?

[Kiril]

A DO meter, and they can get mighty expensive in a hurry, especially the multi-purpose units.

http://www.aquaticeco.com/index.cfm/fuseaction/listings.categories/ssid/17

I might add, there are other ways to measure DO, but the meters are by far the easiest.