makolber wrote, on Tue, 23 Dec 2014 16:08:42 -0800:

The flowing hot gas from the burner tothe probe creates a small current.

I'm trying to make sense out of these four descriptions of
how the typical gas furnace flame sensor works (because if I knew how it
works, I could devise a test that might not require measuring from 1 to
5 microamperes, which I can't adequately measure with my Fluke 75).

How a flame sensor works:
http://thehvacguy.wordpress.com/2012...ensor-problem/

How does a flame sensor work and how do you test it:
http://heatingandaircooling.com/2012...-flame-sensor/

How does a furnace flame sensor work:
http://www.ehow.com/how-does_4924695...nsor-work.html

How does the gas furnace flame rod work:
https://www.youtube.com/watch?v=uJU3806j2CE