ECN Forum Forums General Topics of the Trade General Discussion Area thermocuople test

I'm wondering how i can test a thermocouple and a uv flame sensor with a DMM. I've got both on a seed dryer that i'm trying to troubleshoot. I'm meeting the gas man down there tomorrow to look at it together. Any help?
Thanks in advance.

[This message has been edited by zero76 (edited 05-09-2005).]

I know nothing about the flame sensor...but, for the TC...

A TC works by generating a small voltage, in proportion to it's temperature. This voltage can only be generated if there is a sharp change from one materiel to another. Over time, this 'seam' degrades.
First check the TC fo continuity. If good, than check for a steady voltage between the leads. If the voltage fluctuates, or the meter cannot seem to settle on a value, then the TC is probably bad. Ditto if the read-out on a TC meter bounces all over the place.

thanks for the reply, So if i understand correctly: if i remove it from the ckt. it generates it's own voltage? what approximate value would it read? It's a type J tc.

BTW i can spel thermocouple but i couldn't figure out how to change the topic in edit mode. z.

[This message has been edited by zero76 (edited 05-09-2005).]

I believe it's called Constantin or something like that and a typical furnace thermocouple used to generate 15mv and drop the gas valve coil out around 5mv.This was ten years ago on older furnaces,now LEDs flash a code.The tip should be cleaned of soot with steal wool when testing/suspecting or even seeing one IMHO.

[This message has been edited by frank (edited 05-09-2005).]