It is common knowledge that all bodies, depending on their temperature, emit electromagnetic waves, i.e. radiation. Energy is transported along with this radiation, ultimately permitting non-contact measurement of the body's temperature with the help of the radiation.
The radiated energy and its characteristic wavelengths primarily depend on the temperature of the radiating body.
Ideally, a measurement object will take on all the energy (absorption) and convert it into its own heat radiation (emission). In such cases it is referred to as a “black body radiator”. Such behavior virtually never occurs in nature; rather, additional reflection and transmission of the radiation at or through a body occurs.
However, in order to nevertheless obtain reliable measurements with infrared measurement systems in practice, it is necessary to identify this emission, reflection and transmission behavior (also see 1.4) accurately or to eliminate this influence by suitable means.
This can be achieved with the aid of reference measurements using contact thermometers or by deliberately modifying the measuring area to make it suitable for infrared measuring technology, e.g. by applying lacquer coatings, adhesive and glue, plastic coatings or paper stickers.
Whether and how these measures are to be performed depends ultimately on the measurement object and the measurement environment. Classifying applications according to the appearance of the measurement objects and their surface helps when assessing this.
