Black radiator

A body that is hit by radiation and absorbes it all, is called a black radiator.
This body has no losses due to reflection or transmission and emits the maximum possible energy in all directions equally.
For a defined waveband, the emitted radiation depends only on the temperature of the black radiator.
In reality one can not find a body that can emit 100% of a radiation.
The best possible reproduction is achieved with a cavity with matte black walls all having the same temperature.
A beam falling through a hole into the cavity is reflected and absorbed several times at the inner wall.
The radiation coming out of the hole corresponds to the temperature of the body.
This effect is used, e.g. in the calibration of IR measuring instruments.

Black radiator in Injection Molding

Infrared: Schematic structure of a black radiator

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This glossary of plastic industry is provided by PLEXPERT Canada Inc.


The radiation detected by a thermal camera in a non-contact temperature measurement consists of the reflection, the transmission and the emission of infrared radiation emanating from objects in the field of view of the camera. The emissivity is a dimensionless measure that indicates the ratio of the emitted radiation of the measurement object in relation to the incident radiation.

Emissivity depends on the material, the surface texture and, in some cases, the temperature of a body. In general, the higher the emissivity of a body, the easier the temperature can be measured with a IR-camera.

The following relationship applies: Emissivity + Reflection + Transmission = 1

Emissivity in Injection Molding

Infrared: Emissivity of different materials (Concret = 0,95, Wood = 0,90, Plastic = 0,97)

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This glossary of plastic industry is provided by PLEXPERT Canada Inc.

Infrared camera

The thermal radiation of objects is found behind the visible red spectrum of light.

This range is called the infrared wavelength range.

Infrared cameras are used to make the temperatures of the “thermal radiation” (wavelength between 1µm and 20µm) visible.

The camera consists of a lens, a spectral filter, the detector (sensor) and appropriate electronics for amplification, linearization and corresponding signal processing.
Infrared cameras are used in many areas, because they allow the measurement of difficult to access or moving objects with short measurement and response times.
During the measurement there is no influence on the object to be measured.

In the field of plastics technology, infrared cameras are used, for example, for testing and monitoring the injection molding process.

Infrared camera in Plastic Industry
Infrared camera in Plastic Industry

Infrared camera for use in manufacturing

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This glossary of plastic industry is provided by PLEXPERT Canada Inc.