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Updated: Aug 7, 2026

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere
Published on: April 30, 2018
High-accuracy determination of water vapor refractivity by length interferometry
René Schödel1, Alexander Walkov, Ahmed Abou-Zeid
1Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany. rene.schodel@ptb.de
Abstract:
Humidity is the most problematic parameter for the accurate determination of the refractive index of air. Besides the fact that the humidity measurement can be limiting, the existing empirical equations for the refractive index of moist air are either restricted to 20 degrees C or are based on insufficient knowledge of the refractivity of water vapor. To overcome this problem, a new kind of measurement method for the refractivity of water vapor is suggested that is based on the accurate measurement of the absolute length of a step length by interferometry under vacuum conditions and subsequent measurements at different well-defined absolute water vapor pressures.
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