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An Attempt to Simplify the Determination or the Size-of-Source Effect in Radiation Thermometers

  • H. Rodríguez-ArteagaEmail author
  • D. Cárdenas-García
TEMPMEKO 2016
  • 94 Downloads
Part of the following topical collections:
  1. TEMPMEKO 2016: Selected Papers of the 13th International Symposium on Temperature, Humidity, Moisture and Thermal Measurements in Industry and Science

Abstract

The knowledge of \(\sigma _{d}\), the parameter that measures the size-of-source effect of a radiation thermometer, as a function of the diameter d of a radiation source is mandatory to estimate the appropriate corrections to temperature values measured when aiming to radiation sources of different sizes. To obtain \(\sigma _{d}\) as a function of d is a complicated task because there is no universally recognized mathematical function that relates them. The direct method to evaluate \(\sigma _{d}\) usually requires a radiation source of appropriate size and a set of many diaphragms with increasing diameter. How good is the approximation to \(\sigma _{d}\) estimated in this way depends on the number of diaphragms used. To reduce the time and cost to evaluate \(\sigma _{d}\), it is desirable to have methods that provide good approximations with a reduced number of diaphragms. In this paper, we present a method to obtain an approximation to \(\sigma _{d}\) as a function of d with a limited number of diaphragms. When using this method, deviations of less than \(1\;{^{\circ }}\hbox {C}\) are obtained when measuring radiance temperatures of \(500\;{^{\circ }}\hbox {C}\), between the measured temperatures and those calculated from values of \(\sigma _{d}\). We also propose a simple equation to interpolate approximated values of \(\sigma _{d}\) for those diameters between those used in its evaluation, but a limitation is that \(\sigma _{d}\) must be bigger than 0.98.

Keywords

Radiation thermometer Size-of-source effect calculation Size-of-source effect function 

Nomenclature

Q

Quotient between of the diaphragm’s diameters used to quantify the size-of-source effect and the exponential function of parameter \(\sigma _{d}\).

d

Diameter of each diaphragm’s aperture.

\(\sigma _{d}\)

A parameter that denotes the size-of-source effect for a given diaphragm’s diameter d, equal to 1 when the thermometer is irradiated from a hemispherical source that produces a maximum signal in its detector or a fraction of 1 when the diaphragm’s diameter is not big enough to produce such a signal.

S(T)

Calculated values of detector’s signal of a radiation thermometer, as function of measured temperatures, in arbitrary units.

T

Measured or calculated temperatures, in K.

References

  1. 1.
    P. Bloembergen, Metrologia 46, 534–543 (2009)ADSCrossRefGoogle Scholar
  2. 2.
    I. Pušnik, G. Grgić, J. Drnovšek, Meas. Sci. Technol. 17, 1330–1336 (2006)ADSCrossRefGoogle Scholar
  3. 3.
    P. Saunders, Temperature: Meas. Sci. Technol. 20, 025104 (2009)Google Scholar
  4. 4.
    H. Preston-Thomas, Metrologia 27, 3–10 (1990)ADSCrossRefGoogle Scholar
  5. 5.
    R.E. Bedford et al, Techniques for approximating the international temperature scale of 1990, BIPM, (1997) reprinting from 1990 first edition, 104–106Google Scholar
  6. 6.
    P. Saunders et al., Int. J. Thermophys. 29, 1066–1083 (2008)ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2017

Authors and Affiliations

  1. 1.Thermometry DivisionCentro Nacional de MetrologíaEl MarquésMexico

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