optris PI 200 Operator's Manual page 80

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80
Figure 48: Spectral emissivity of several materials: 1 Enamel, 2 Plaster, 3 Concrete, 4 Chamotte
If the emissivity chosen is too high, the infrared thermometer may display a temperature value which is much
lower than the real temperature – assuming the measuring object is warmer than its surroundings. A low
emissivity (reflective surfaces) carries the risk of inaccurate measuring results by interfering infrared radiation
emitted by background objects (flames, heating systems, chamottes). To minimize measuring errors in such
cases, the handling should be performed very carefully and the unit should be protected against reflecting
radiation sources.