2
GENERAL
2.1
Measuring temperatures using Infrared Radiation Thermometers
Above a temperature of absolute zero, which is approx. - 273 °C or 0 K, all bodies
emit electromagnetic radiation, the wavelength and density of which depend on the
temperature. Up to a temperature of approx. 600 °C, the wavelength of the radiation
can be found exclusively within the infrared range (thermal radiation). It is only at
higher temperatures where part of this radiation is emitted in the form of visible light.
The radiation emitted by the body (radiation density) also depends on the surface of
the individual body. At a fixed temperature, the maximum radiation density is emitted
by a "blackbody" source of radiation. All real bodies only emit a fraction of this radia-
tion density at the same temperature. The ratio of this fractional part to the maximum
radiation density is called the emissivity
ε. Naturally, the emissivity is always < 1. It
depends on the nature of the surface of the material, on the material itself and on the
wavelength. If the emissivity is known, the temperature of the object can be deter-
mined by measuring the infrared radiation emitted by the very object.
Devices used to measure this kind of radiation are called Infrared Radiation Ther-
mometers.
As the measurement is effected without the Infrared Radiation Thermometer being in
contact with the object, no distortion of the temperature field due to heat dissipation
need to be feared, as is the case, e.g., with probe-type thermometers.
The Infrared Radiation Thermometer is a measuring transducer, which receives the
infrared radiation emitted by the measuring object itself and transforms it into a
standardized output signal.
All optic and electronic components are located in a small housing of a solid con-
struction, which is made from die-cast metal so that the installation of a Infrared Ra-
diation Thermometer is possible even in narrow spaces.
By selecting a number of various lenses and detectors, it is possible to generously
modify the measuring field, if the measuring distance is given.
For the application of the Infrared Radiation Thermometer under high ambient tem-
perature, water-cooling, air purge fittings and vacuum tight lenses can be delivered
as accessories.
2-1
95582717
GENERAL
KT19 II
04/02/14e
HEITRONICS Infrarot Messtechnik GmbH
