Venta en línea de instrumentos de prueba y medida

The emissivity of a material (often written e), is the ratio of the energy which it radiates by a black body wich radiate at the same temperature. It is thus a measurement of the capacity of a body to absorb and re-emit radiated energy.
Emissivity depends on several factors: the temperature, direction radiation, and its wavelength.

Emissivities depend on the wavelength to which one takes measurement. You defer to the instructions to know the wavelengths to which your apparatus operates.

Caution: the following values depend on the current nature of material and the conditions of measurements.

Tables of emissivity - metals:



Tables of emissivity - not metals:



You can determine an unknown emissivity according to one of the following methods:
1. Using a thermocouple or another adapted method, determine the current temperature of material. Then measure the temperature of the object and regulate emissivity until the correct temperature is reached. You then determined the exact emissivity of measured material.
2. To measure temperatures relatively very high (until 260°C), place on the target an enough large plastic label to cover the spot of measurement. Then measure its temperature while having regulated emissivity on 0,95. Measure the temperature of a near zone located on the object and modify emissivity until obtaining the same temperature. You then determined the exact emissivity of measured material.
3. If that is possible, apply to a part of the object to measure a black painting matte posting an emissivity higher than 0,98.  Then measure the temperature of the zone thus painted while having regulated emissivity on 0,98. Measure the temperature of a near surface located on the object and modify emissivity until obtaining the same temperature. You then determined the exact emissivity of measured material.