Operation
Manual
5
Raytek
CM
4 Basics
4.1 Measurement of Infrared Temperature
Everything emits an amount of infrared radiation according to its 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 the ”emissivity value”,
see 10.2 Typical Emissivity
Values
on page 19.
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 parameter. The connected electronics generate electrical
signals for further analysis. 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 in the absence of contact.
Consequently, surface temperatures of moving or hard to reach objects can easily be measured.
4.2 Sight
To assure the target is bigger than the spot size, the distance between the sensor and the target should
be nearer for a smaller target. Refer to the diagram below.
Figure 2: Proper Sensor Placement
4.3 Ambient Temperature
The sensing head should work under ambient operating range in Technical Data.
4.4 Atmospheric Quality
In order to prevent damage to the lens and erroneous readings, the lens should always be protected from dust,
smoke, fumes, and other contaminants. For this purpose an air purge collar is available. You should only use oil free,
clean “instrument“ air.
Best Good
Incorrect
Target greater
than spot size
Target equal
to spot size
Target smaller
than spot size
Background
Sensor
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