AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-5-1861-2012 Technical Note: Calibration device for the krypton hygrometer KH20 Foken T. 1 3 Falke H. 2 University of Bayreuth, Department of Micrometeorology, Bayreuth, Germany Gesellschaft für Akustik und Fahrzeugmesswesen mbH, Zwickau, Germany Member of Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany 01 08 2012 5 8 1861 1867 Copyright: © 2012 T. Foken 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/articles/5/1861/2012/amt-5-1861-2012.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/5/1861/2012/amt-5-1861-2012.pdf

A calibration device for krypton hygrometers (KH20, Campbell Scientific, Inc.) with variable path length is presented. This unit allows for in-situ calibrations of the krypton hygrometer, which is typically not very stable over time, during measuring campaigns. It was constructed mainly for application at high altitudes and low temperatures, where further improvements are needed to the IR-hygrometers which are normally used. The changing path length requires that a changing concentration of the absorber be simulated. Because oxygen absorbs more strongly than water vapour, the calibration is made against oxygen and transferred to water vapour. The design of the calibration instrument is made as one unit containing a stepper motor system, PC and humidity sensor. For the calibration, it is necessary to install the krypton hygrometer on this unit.

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