Pyrometer Behavior

are the wires reversed?

Yes, it does have that designation on the face of the dial and I have the compatible thermocouple. Your explanation makes perfect sense and is exactly what I have observed.

I will relocate the pyrometer to a spot that does not permit it to gain heat from the oven.

Thanks for your input.

BTW, at first I did have the wires reversed, even though they were connected in accordance with the terminal ID's, which resulted in your described response.

The USA color coding for thermocouples is, shall we say, different?

Red is negative, the other colored wire (Type K is yellow) is positive. If you're an automotive guy, it probably seems backwards.

Thanks, I guess some mechanical things must remain counterintuitive.

At the risk of sounding gauche, was a female involved in that choice somehow?

Doogleass -- A thermocouple consists of two specially selected wires of different metal alloys that will produce a potential difference beween the two based on the particular alloy combination and the temperature difference between the hot junction and the cold junction. The hot junction is at the end of the thermocouple where you are measuring temperature. The cold junction is back in the meter where the sensing and recording circuitry is.

Now if the meter circuitry containing the cold junction heats up from being too close to the furnace then the temperature difference is going to be less. Hence the lower temperature reading. Note that substantial temperature rise in the meter can cause a host of other inaccuracies in the device since it was designed to work at normal ambient temperatures. So the meter may not have seen an actual 800 degree temperature rise. (which would likely be pretty rough on the wire insulation.) Hopefully you didn't actually hurt it.

Ed Weldon