Manual Glow Plug update

[laserjock]

Okay. Interesting. What's the junction? Thermocouples use a junction of different metals to cause the voltage. Where do you measure? Plug to ground?

Not doubting you just trying to understand.

I would think a resistance measurement would be more sensitive and you probably could calibrate it if you know the alloy of the wire in the plug. There are tables of resistance of nichrome which is most likely what it is. Hmm. Interesting. It's sorta like the idea of using the vacuum gauge to improve driving efficiency that started in the 70's.

 

[bbjordan]

Apparently, measuring resistance works too, as the resistance changes with temperature.

 

[fsmyth]

There IS a junction - from the heating element to the body and to the center electrode.
That said, there cannot possibly be any way to depend on accuracy. Or similarity
between plugs. The voltage developed is minute, since the junction is not of the type
of metals used for that sort of probe. But it IS there, and measurable.
Same for the resistance. The element is not optimized for measurement, nor is it
anywhere close to an ideal curve. Same thing. It IS there, and measurable.
I doubt that it would be feasible to try to get a matched set of plugs, so the
measurements would vary from one to the next. Fine for monitoring changes
in the particular cylinder, useless for cylinder to cylinder comparison.