Flame rectification - how does it actually work?

[bennygas]

I don't know about anyone else, but this has puzzled me for some time.

I understand roughly how i think it works in principle - i.e. applying a potential difference across a gap full of ions (i.e a flame) will allow a current to pass, and i follow how this may be employed to rectify AC into DC (so as to be distinct from flame conductance), and I follow as to how this could be measured to confirm the presence or not of a flame at a burner.

That said, that's just in theory, and there's no saying the theory i have in mind is right - and the more I think about it the more confused i get. Does anyone on here know how it works. what's the process? where are voltages/currents measured? any good threads or websites to explain it?

 

[CES]

Have a read here.
http://www.google.co.uk/url?sa=t&rc..._-XwAQ&usg=AFQjCNE1oV8mUjjxyLoo7edXrpV2pAnceg

Its a pdf file

 

[tamz]

This video explains the principle quite well

[video=youtube;JE3MzApSN7E]http://www.youtube.com/watch?v=JE3MzApSN7E[/video]

 

[bennygas]

nice little video that, cheers tamz and CES (pdf's good too). cleared up the point that was throwing me - the earth from the burner is monitored for a returned, rectified signal. When I was seeing the earth from the electrode on boilers I was thinking it just leaked straight to earth - apparently not. nice to see the yanks are using the cold main as an earth still! if i've misunderstood that, cut me some slack - i got 3 kids under 4 charging about round me - no wonder daycare costs so much.

 

[bennygas]

is this why checking ionisation current seems to figure in some boiler servicing routines these days (e.g. on the greenstar he, via inbuilt dianostics).. i guess dirty probe increases resistance, ergo lower current and need for clean up/inspection of electrodes). if so, is there a technique for measuring ionisation current that doesn't involve integral diagnostic systems? or is this a complete dumbass question?

 

[bennygas]

just read your article properly CES - answer to my last post was in there. sorry. my question was "dumbass". thanks for the pdf. smashin'.