Fluke Ti20 User Manual download pdf (Page 65)

Appendices

Typical Emissivity Values C

C-5

Table C-2. Emissivity Values for Non-Metals (cont)

Material Emissivity

1.0 µm 1.6 µm 8 to 14 µm

Limestone n.r. 0.4-0.98

Paint (non-Al.) — 0.9-0.95 0.9-0.95

Paper (any color) n.r. 0.95 0.95

Plastic (opaque, over 20 mils) n.r. 0.95 0.95

Rubber n.r. 0.9 0.95

Sand n.r. 0.9 0.9

Snow n.r. — 0.9

Soil n.r. — 0.9-0.98

Water n.r. — 0.93

Wood, Natural n.r. 0.9-0.95

To optimize surface temperature measurement accuracy consider the following:

• Determine the object emissivity for the spectral range of the instrument to be

used for the measurement.

• Avoid reflections by shielding object from surrounding high temperature sources.

• For higher temperature objects use shorter wavelength instruments, whenever

possible.

• For semi-transparent materials such as plastic film and glass, assure that the

background is uniform and lower in temperature than the object.

• Hold instrument perpendicular to surface whenever emissivity is less than 0.9. In

all cases, do not exceed angles more than 30 degrees from incidence.

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Fluke Ti20 User Manual Page 65