A pyrometer or infrared thermometer is a device for non-contact temperature measurement. The pyrometer rests in terms of physics on the evaluation of electromagnetic radiation radiated from the object to be measured, proportional to the object temperature. The electromagnetic radiation is focused through an input optics and converted by an appropriate infrared detector into an electrical signal. There are different types of pyrometers:
Broadband pyrometers are infrared thermometers that allow temperature measurement over a broader wavelength range. Typical devices operate in the long-wavelength range between 8 and 14 μm, which makes them suitable for use in a large number of industrial applications.
Partial Radiation Pyrometer
Partial radiation pyrometers are pyrometers whose spectral sensitivity is restricted to a specific wavelength range by means of appropriate filters. Through the clever choice of the spectral ranges, atmospheric influences on the signal attenuation can be minimized as far as possible. For certain materials (e.g. glass) special narrow-band wavelength ranges are selected, which allow a measurement with a high emissivity or make a measurement generally possible by targeted selection of absorption bands in the material (thin plastic films in the μm range).
Ratio pyrometers or even 2-color pyrometers have two measuring channels for measuring the radiation intensity of two closely spaced wavelength ranges. By forming ratios of the two intensities, influencing factors on the signal attenuation such as smoke, dust or soiled optics are eliminated to a certain extent. Since a variable emissivity varies strongly in most cases with different wavelength ranges, this influence cannot be neglected or eliminated in most applications.
Advantages of Pyrometers
- Very fast measurement
- Very long, continuous measuring ranges (e.g. 250 °C – 1800 °C)
- No wear
- No influence on the measured object
- Measurement on moving objects possible
- Measurement possible at high voltages and in aggressive media
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