Re: thermocouple ID


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Posted by joewizard on January 12, 19100 at 11:29:48:

In Reply to: Re: thermocouple ID posted by john Odom on January 12, 19100 at 10:25:56:

Colors.. hhmmm.. The insulation is mica, and one side must have a slight red dye in the mica, because its obviously redder than the other. I think the red(der) lead is always negative on thermocouples? In any case the two leads can be told apart by color. Other than the slightly redder wire covering, there is no difference between them. Both of the bare wires have a steel-color, if that is of any help.

The lead wires are continuous.. they are the thermocouple wires themselves. They are screw-connected directly to the bayonet plug. There are no leads soldered/welded to them.

No insulation or coloring on the wires except for mica. Mica, the mineral that shears into thin flat sheets. Its a redish brown in its natural state. How they manage to wrap mica on these thin wires is a mystery to me.

I was hoping for a way to determine the upper limit temperature for these things. My understanding is that type J alloy is limited to around 1700F and type K to 2100+F. Perhaps this is because either (a) the curve of voltage generated drops off at the extreems, or (b) the alloys themselves are liable to melt or oxidise..

Maybe i need a primer on thermocouples in general.

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