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Radiative temperature measurements:

Radiative temperature measurements The sensor for thermal radiation need not be in contact with the surface to be measured , making this method attractive for a wide variety of applications . A distinct advantage to measuring temperature by detecting thermal radiation . The basic operation of a radiation thermometer is predicated upon some knowledge of the radiation characteristics of the surface whose temperature is being measured, relative to the calibration of the thermometer .

Slide 2:

Radiation refers to the emission of electromagnetic waves from the surface of an object. This radiation has characteristics of both waves and particles , which leads to a description of the radiation as being composed of photons . The photons generally travel in straight lines from points of emission to another surface, where they are absorbed, reflected, or transmitted . The thermal radiation emitted from an object is related to its temperature and has wavelengths ranging from approximately 107 to 103 m . It is necessary to understand two key aspects of radiative heat transfer in relation to temperature measurements.

Slide 3:

First, the radiation emitted by an object is proportional to the fourth power of its temperature . In the ideal case, this may be expressed as: Where Eb is the flux of energy radiating from an ideal surface, or the blackbody emissive power. The emissive power of a body is the energy emitted per unit area and per unit time.

Slide 4:

Second, the emissive power is a direct measure of the total radiation emitted by an ob ject . However, energy is emitted by an ideal radiator over a range of wavelengths, and at any given temperature the distribution of the energy emitted as a function of wavelength is unique.

Planck distribution of blackbody emissive power as a function of wavelength.:

Planck distribution of blackbody emissive power as a function of wavelength.