Emissivity; Definition - optris PI 200 Operator's Manual

Emissivity

8 Emissivity

8.1 Definition

The intensity of infrared radiation, which is emitted by each body, depends on the temperature as well as on
the radiation features of the surface material of the measuring object. The emissivity (ε – Epsilon) is used as
a material constant factor to describe the ability of the body to emit infrared energy. It can range between 0
and 100 %. A "blackbody" is the ideal radiation source with an emissivity of 1.0 whereas a mirror shows an
emissivity of 0.1.
Figure 47: Composition of IR radiation
I IR radiation
ε
Emission
ρ
Reflection
τ
Transmission
79-
ε + ρ+ τ = 1