KANE International INF165C Infrared Thermometer

Infrared Thermometers measure the amount of thermal radiation emitted from an objects surface. To take a measurement, the object must be within the field of view of the infrared thermometer, or the reading may include objects surrounding your target. This target size is determined in the distance to spot ratio stated on the instruments specifications. At a ratio of 10:1, a distance from your target of ten feet will give you a circle with one foot diameter. At 20:1 ratio gives the same one foot target now at 20 feet, so you can see that higher is better, but typically more expensive due to the cost of the optics involved.

The other common question is regarding emissivity. In simple terms emissivity is a percentage of energy emitted from a surface compared to the energy emitted from a black body source. If a surface emits one half (1/2 or 0.5) the amount of energy at a given temperature & wavelength as a black body, it is said to have an emissivity of 0.5.

Surfaces closest to the black body level would be flat black, & those farthest from it would be mirror or chrome surfaces. With a set emissivity level some surfaces may measure lower than actual, because their surface is emitting less thermal radiation at a given temperature. Although you may have a fixed emissivity of 0.95, most items measured will provide a reasonably accurate result. Having a fully adjustable emissivity will give you the ability to fine tune your instrument to a specific application.