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Metrology and Measurement Systems

The Journal of Committee on Metrology and Scientific Instrumentation of Polish Academy of Sciences

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Influence of Size of Source Effect on Accuracy of LWIR Radiation Thermometers

David Cywiak
  • Corresponding author
  • Centro Nacional de Metrología, Km 4.5 Carretera a los Cues, 76246 Municipio el Marqués Qro, Mexico
  • Email:
/ Daniel Cárdenas-García
  • Centro Nacional de Metrología, Km 4.5 Carretera a los Cues, 76246 Municipio el Marqués Qro, Mexico
  • Email:
/ Hugo Rodriguez-Arteaga
  • Centro Nacional de Metrología, Km 4.5 Carretera a los Cues, 76246 Municipio el Marqués Qro, Mexico
  • Email:
Published Online: 2016-12-13 | DOI: https://doi.org/10.1515/mms-2016-0050


Determining the size of source effect of a radiation thermometer is not an easy task and manufacturers of these thermometers usually do not indicate the deviation to the measured temperature due to this effect. It is one of the main uncertainty components when measuring with a radiation thermometer and it may lead to erroneous estimation of the actual temperature of the measured target. We present an empiric model to estimate the magnitude of deviation of the measured temperature with a long-wavelength infrared radiation thermometer due to the size of source effect. The deviation is calculated as a function of the field of view of the thermometer and the diameter of the radiating source. For thermometers whose field of view size at 90% power is approximately equal to the diameter of the radiating source, it was found that this effect may lead to deviations of the measured temperature of up to 6% at 200ºC and up to 14% at 500ºC. Calculations of the temperature deviation with the proposed model are performed as a function of temperature and as a function of the first order component of electrical signal.

Keywords: size of source effect; radiation thermometer; temperature; field of view


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About the article

Received: 2016-01-20

Accepted: 2016-06-27

Published Online: 2016-12-13

Published in Print: 2016-12-01

Citation Information: Metrology and Measurement Systems, ISSN (Online) 2300-1941, DOI: https://doi.org/10.1515/mms-2016-0050. Export Citation

© Polish Academy of Sciences. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. (CC BY-NC-ND 4.0)

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