RayTek 54301 - page 89

Appendix

Thefollowingtableprovidesabriefreferenceguidefordetermining

emissivityandcanbeusedwhenoneoftheabovemethodsisnot

practical.Emissivityvaluesshowninthetableareonlyapproximate,

sinceseveralparametersmayaffecttheemissivityofamaterial.

Theseincludethefollowing:

1.Temperature

2.Angleofmeasurement

3.Geometry(plane,concave,convex)

4.Thickness

5.Surfacequality(polished,rough,oxidized,sandblasted)

6.Spectralrangeofmeasurement

7.Transmission(e.g.thinfilmsplastics)



Tooptimizesurfacetemperaturemeasurements,considerthe

followingguidelines:

• Determinetheobjectemissivityusingtheinstrumentwhichis

alsotobeusedforthemeasurements.

• Avoidreflectionsbyshieldingtheobjectfromsurrounding

temperaturesources.

• Forhighertemperatureobjectsuseinstrumentswiththe

shortestwavelengthpossible.

• Fortranslucentmaterialssuchasplasticfoilsorglass,assure

thatthebackgroundisuniformandlowerintemperaturethan

theobject.

• Mountinstrumentperpendiculartosurfaceifpossible.Inall

cases,donot



exceedanglesmorethan30°fromincidence.