Basics; Measurement Of Infrared Temperature; Emissivity Of Target Object - RayTek Raynger Series 3i Plus Operating Instructions Manual

Basics

4 Basics

4.1 Measurement of Infrared Temperature

All objects emit an amount of infrared radiation according to their surface temperature. The intensity
of the 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. It is referred to as "emissivity value"
(see section 10.2 Typical Emissivity Values, page 56.
Infrared thermometers are optical-electronic sensors. These sensors are able to detect "radiation of
heat." 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
analyzes the electrical signal and converts 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.

4.2 Emissivity of Target Object

Determine the emissivity of the target object as described in section 10.1 Determination of Emissivity,
page 56. If emissivity is low, measured results could be falsified by interfering infrared radiation from
background objects (e.g., heating systems, flames, fireclay bricks, etc., close beside or behind the target
object). This type of problem can occur when measuring reflecting surfaces and very thin materials
such as plastic films and glass.
This measuring 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.
16 3i Plus
info@Raytek-Direct.com 1.888.475.5235
Rev. A1 Jan 2015