Omega Engineering OS524, OS530HR, OS531, OS53X-CF, OS533, OS532 manual Calculating Temperature, λ m = T

Appendix: How Infrared Thermometry Works A

Wien’s Displacement Law describes the exact mathematical relationship between the temperature of a blackbody and the wavelength of the maximum intensity radiation.

λm = 2.898

T

where λm = wavelength measured in microns T = temperature in Kelvin

Calculating Temperature

The net thermal power radiated by an object has been shown to depend on its emissivity, its temperature and that of the ambient temperature around the object. A very useful equation known today as the Stefan-Boltzmann Law has been shown both theoretically and empirically to describe the relationship.

I = thermal power in watts/meter2

ε= Emissivity

σ= 5.6703 x 10-8watts/meter2 x K4 (Stefan’s constant) T = temperature of object in Kelvin

Ta = temperature of ambient surroundings in Kelvin

The infrared thermometer uses this equation directly in calculating the temperature of an object. The incident power is measured by the infrared detector. The emissivity of the object is determined by the user. The ambient temperature is measured by a sensor inside the thermometer. With all quantities known, the thermometer uses the Stefan-Bolzmann Law to calculate and output the temperature of the object.

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