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MP Series
Users Manual, Rev. 1.0, Apr 2021
3 Basics
3.1 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 signal 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.
3.2 Emissivity of Target Object
To determine the emissivity of the target object, see section 9.3
is low, measured results could be falsified by interfering infrared radiation from background objects (such as
heating systems, flames, fireclay bricks, etc. located close beside or behind the target object). This type of problem
can occur when measuring reflective surfaces and very thin materials, such as plastic film and glass.
This measurement error can be reduced to a minimum, if particular care is taken during installation and the sensing
head is shielded from these reflecting radiation sources.
24
Typical Emissivity
Values, page 62. If emissivity
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