Single wavelength infrared thermometers filtered in the short wavelength region of 2.0 to 2.5 microns offer good performance when measuring low emissivity materials at low temperatures.

For example, a large Midwestern automotive component supplier had been sandblasting an aluminum part before painting. The sandblasting was done specifically to increase the emissivity value in an attempt to improve the performance of a long-wavelength infrared thermometer. The sensor was used to confirm that the part had reached the proper pre-heat temperature of about 220°F (104°C). By changing from a long-wavelength sensor to a short-wavelength sensor, the measurement accuracy for the sandblasted part improved from +/- 20°F (+- 11°C) to +/- 3°F (+- 1.7°C). In addition, parts that had not been sandblasted could be measured with an accuracy of +/- 6°F (+- 3.3°C). Eliminating the sandblasting step lowered the aluminum part emissivity from 0.35 to 0.10, and resulted in an estimated cost savings of about $1 million per year.

The accuracy improvement associated with the shorter wavelength sensor is shown in the figure below. The shorter wavelength sensor shows an improvement in measurement from about 18°F (10°C) to about 5°F (2.8°C) when measuring a 220°F (104°C) target with a 10% variation in emissivity. This alone does not explain the total improvement in accuracy achieved by the component supplier. The short wavelength measurement also benefits from the fact that most metals have a higher emissivity value at the shorter wavelength. Therefore, considering these two benefits the shorter wavelength sensor offers as much as ten times more accurate readings than is a long wavelength sensor.