Industrial Process Control

Industrial Process Control

There are many industrial applications where contact based temperature measurements are not suitable or desired, for example because contact measurement is slow, the object is hard to access or the contact probe could influence the measured object. In these cases, non-contact temperature measurements are the method of choice. They are used in many industrial applications such as control of manufacturing processes of very hot or fast moving objects as in glass and metal fabrication, and also in the food and pharmaceutical industry where special sanitary requirements are imposed.


There are a lot of advantages to non-contact temperature measurement like:

 

  • Measurement of moving or vibrating objects
  • Fast measurement speed of multiple values per second
  • Measurement in explosive, corrosive, high voltage or hot environments
  • No physical or chemical influence on the measured object
  • Long lifetime and low maintenance of the measuring system

 

In industrial temperature measurement applications the emissivity of the object plays an essential role. The emissivity of the human body is close to 0.98 and therefore close to 1 it can be neglected for non-contact human body temperature measurements. If the emissivity is significantly smaller than unity (e.g., 0.9) it has to be considered carefully. This is especially the case for metals or glass which are typical examples for materials whose temperatures are to be measured contactless during manufacturing processes. Additionally the emissivity not only depends on the material, but also on the temperature and oxidation state and processing method of the material. Remote measurement of temperature in industrial applications often starts with detailed knowledge of target emissivity under the precise conditions of the intended measurement.

A key factor for precise industrial measurements is the choice of the right filter in front of the infrared thermopile sensor. To reduce the dependency of varying atmospheric transmittance between sensor and target, a high quality optical filter for the range of 8-14 µm should be included usually. This wavelength range is also known as the far IR atmospheric window, where almost no absorption occurs. Therefore the radiation emitted by the object of interest will be received by the sensors almost unchanged, independent of the ambient conditions like ambient temperature or humidity.

The Heimann F8-14 standard filter has sharp edges at 8 and 14 µm and therefore provides the ideal suited filter for precise and high quality industrial measurements with low distance dependency.

Other applications for industrial process control include temperature observations for welding and welding reworks, friction welding, exhaust temperature monitoring as well as permanently installed or hand-held pyrometers.


Most commonly used sensor series for industrial remote temperature measurements are:

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