Significance of Fluctuations in Sky Radiant Emittance for Infrared Thermometry

Idso, Sherwood B.; Jackson, Ray D.

Significance of Fluctuations in Sky Radiant Emittance for Infrared Thermometry

1968

Idso, Sherwood B. | Jackson, Ray D.

A theoretical analysis of clear sky radiant emittance in the 600 to 11300 cm-1 waveband showed that this energy flux should be fairly constant over a diurnal period, contrary to some recently reported measurements. New experiments revealed this to be true and indicated that the source of error in the earlier work was due to equipment malfunction. The errors in radiometrically determined surface temperatures caused by neglecting the small variations which do occur were determined to be less than the limits of accuracy of present-day infrared thermometers in many applications of infrared thermometry to soil and plant research. A nomogram predicted the temperature error to be expected from neglect of clear sky radiant emittance variations for surfaces with temperatures between O and 60 C and infrared emittances between 1.00 and 0.90.

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