RayTek MI Miniature Infrared Sensor - Manual (Page 19)

Basics
MI 11
4 Basics
4.1 Measurement of Infrared Temperature
All surfaces emit infrared radiation The intensity of this infrared
radiation changes according to the temperature of the object.
Depending on the material and surface properties, the emitted
radiation lies in a wavelength spectrum of approximately 1 to 20 μm.
The intensity of the infrared radiation (”heat radiation”) is dependent
on the material. For many substances this material‐dependent
constant is known. This constant is referred to as the ”emissivity
value”.
Infrared thermometers are optical‐electronic sensors. These sensors
are sensitive to the emitted radiation. Infrared thermometers are
made up of a lens, a spectral filter, a sensor, and an electronic signal
processing unit. The task of the spectral filter is to select the
wavelength spectrum of interest. The sensor converts the infrared
radiation into an electrical signal. The signal processing electronics
analyze the electrical signals and convert it into a temperature
measurement. As the intensity of the emitted infrared radiation is
dependent on the material, the required emissivity can be selected on
the sensor.
The biggest advantage of the infrared thermometer is its ability to
measure temperature without touching an object. Consequently,
surface temperatures of moving or hard to reach objects can easily be
measured.