The emissivity of a measurement object describes the degree of heat radiation emitted by this object in comparison to an ideal heat radiator, the so-called „black body“.
The ratio of the radiation intensity emitted by a body to the radiation intensity of a black body of the same temperature is called the emissivity of the body. The emissivity can assume values between 0 (no radiation) and 1 (100% radiation).
However, the values in the tables are not absolute values, as the emissivity of a material is influenced by various factors. These include:
- Temperature of the measuring object
- Wavelength in µm at which the measurement is taken
- Geometry of the surface (flat, concave, convex)
- Surface finish (polished, rough, oxidized, sandblasted)
- Transmittance (e.g. for thin plastic films)
- Spectral range of the measurement
- Measurement angle
The following table is used to determine the correct emissivity for your measurement object and to set it in the novasens infrared temperature measuring device or pyrometer:
Non-metals
| Refractory and building material |
Value |
| Red brick, raw |
0,75 – 0,9 |
| Fireclay |
0,75 |
| Asbestos |
0,95 |
| Concrete |
0,7 |
| Marble |
0,9 |
| Silicon carbide |
0,85 |
| Plaster |
0,9 |
| Aluminium, fine grain (Alumina) |
0,25 |
| Clay/Alumina coarse grained |
0,45 |
| Silicon, fine grained |
0,4 |
| Silicon, coarse grained |
0,55 |
| Zirconium silicate up to 500°C |
0,85 |
| Zirconium silicate up to 850°C |
0,6 |
| Quartz, rough |
0,9 |
| Mineral Carbon, graphite |
0,75 |
| Black carbon |
0,95 |
| Glass |
0,95 |
Metals
Iron and Steel
|
Value |
| Cast iron polished |
0,2 |
| Cast iron, turned up to 100°C |
0,45 |
| Cast iron, turned up to 1000°C |
0,6 – 0,7 |
| Steel plate, matt |
0,6 |
| Soft steel |
0,3 – 0,5 |
| Sheet steel, oxidized |
0,9 |
| Sheet iron, rusty |
0,7 – 0,85 |
| Cast iron (crude), rusty |
0,95 |
| Crude block iron |
0,9 |
| Cast iron, molten |
0,3 |
| Soft steel, molten |
0,3 – 0,4 |
| Stainless steel, polished |
0,1 |
| Stainless steel, various |
0,2 – 0,6 |
| Aluminium |
Value |
| Aluminium, polished |
0,1 |
| Aluminium, heavy oxidized |
0,25 |
| Aluminium oxide at 260°C |
0,6 |
| Aluminium oxide at 800°C |
0,3 |
| Aluminium alloy, various |
0,1 – 0,25 |
| Brass |
Value |
| Brass, polished |
0,1 |
| Messing, crude surface |
0,2 |
| Brass, oxidized |
0,6 |
| Copper |
Wert |
| Copper, polished |
|
| Copper sheet, oxidized |
0,8 |
| Copper, molten |
0,15 |
| Lead |
Wert |
| Common lead |
0,1 |
| Lead, oxidized 25°C |
0,3 |
| Lead, oxidized, at 200°C |
0,6 |
| Nickel and alloys |
Wert |
| Nickel, high grade |
0,1 |
| Nickel sheet, oxidized |
0,4 – 0,5 |
| Nichrom |
0,7 |
| Nichrom, oxidized |
0,95 |
Miscellaneous metals
|
Value |
| Zinc, oxidized |
0,1 |
| Galvanized iron |
0,3 |
| Tinned steel |
0,1 |
| Gold, polished |
0,1 |
| Silber, polished |
0,1 |
| Chrom, polished |
0,1 |
| Various materials |
Value |
| Enamel (all colours) |
0,9 |
| Coat of oil paint (all colours) |
0,95 |
| Lacquer |
0,9 |
| Matt black coating |
0,95 – 0,98 |
| Aluminium lacquer |
0,5 |
| Water |
0,98 |
| Rubber (smooth) |
0,9 |
| Rubber, crude (coarse) |
0,98 |
| Plastics, misc. (sturdy) |
0,8 – 0,95 |
| Plastic coating (0,05mm thick) |
0,5 – 0,95 |
| Polyethylene coating (0,03mm thick) |
0,2 – 0,3 |
| Paper and cardboard |
0,9 |
| Silicon polish (0,03mm thick) |
0,7 |
