Message Board Thread - "Emissivity issue"

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Emissivity issue Prabhu 2/8/2005
Hello all,

I have been facing an issue regarding emissivity.
I have two Al plates with a small gap in between. The plates are heated to around 300 C. When I point my IR sensor at the plate surface and measure the temperature, it corresponds to the respective thermocouple reading. But at the gap ( air) it shows significantly higher reading compared to the thermo couple at the gap.
I was wondering if I could do some formula to correct this reading assuming the emissivity of the air is 1.0 (??)

Thanking you all,

Re:Emissivity issue electricpete 2/8/2005
That is called the cavity effect. If the cavity is deep and temperature on inside of cavity is uniform, it acts very close to emissivity 1.0.

If also the you knew that the the actual temperature were uniform from inside/between plates to outside of plates due to high thermal conductivity and steady state conditions, then you should apply emissivity correction to the outside cooler portions to make them read same as the inside... although perhaps cooling is better on outside in which case this would not be completely correct.

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