Pyrometer Emissivity Correction Calculator
An infrared thermometer set to the wrong emissivity reads the wrong temperature. Correct a reading from the instrument setting to the true target emissivity, for single wavelength pyrometers.
- 1/T = 1/Tm + (λ ÷ c₂) × ln(εtrue ÷ εset), c₂ = 14,388 µm·K
- T = 813.9 °C
Emissivity Correction (Wien)
Temperatures in kelvin, λ in µm and c₂ = 14,388 µm·K. Valid for single wavelength (narrow band) pyrometers where λT is below about 3000 µm·K.
Worked example
A 1 µm pyrometer set to ε = 0.95 reads 800 °C on steel with true ε = 0.8. The corrected temperature is about 814 °C.
Frequently Asked Questions
What is emissivity?
The ratio of radiation emitted by a surface to that of a perfect black body at the same temperature, from 0 to 1.
Why does a low emissivity surface read low?
It emits less radiation than the instrument expects for its temperature, so the instrument underestimates the temperature.
How can I find the true emissivity?
Compare with a contact thermocouple at a known temperature and adjust the emissivity until the readings agree, or paint a spot with high emissivity paint.
Learn more on the blog
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