On Wednesday, December 31, 2014 8:14:03 PM UTC-5, dpb wrote:
On 12/31/2014 5:48 PM, Danny D. wrote:
dpb wrote, on Wed, 31 Dec 2014 09:00:35 -0600:

the flame detector is quite a bit more than
just a chunk of SS...
http://www.gayesco.com/Prod_Flame_Rods.htm

PHYSICAL CONFIGURATION
1. The flame rod consists of a center electrode and an outer metallic sheath.
2. The electrode is isolated from the outer sheath by an insulating material.
3. The end of the flame rod, in the flame path, has a special high temperature
hermetic seal with a threaded adaptor which is connected to the center
electrode.
4. A high temperature sensing rod is attached to the threaded adaptor.

I'm confused.
Is the "outer sheath" the ceramic?
Or, is the outer sheath the stainless steel rod exterior?

As it says, the center electrode is isolated from the outer metallic
sheath by the ceramic. IOW, it's a center rod in the center of a
ceramic insulator all surrounded by the outer case that you see. It's
not a "rod" at all but a composite assembly that looks solid from the
outside.

--

IDK what flame sensor you have there, but from the dimensions it looks
like it's a foot or more long, 1/2" in diameter and certainly not for a typical
home furnace. The one Danny has pics of does look like a small rod,
mounted on an insulator, connected to a wire. The descriptions I've
read about rod to flame conductivity also don't say anything special
about the reqts for the rod. They just say that a metal rod inserted
into a flame will conduct a current when voltage is applied. That would
seem to coincide with what he has, ie a metal rod on an insulator mount.