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Comparison of psychrometer calibrations - Pre-study

Project Description

In this project, a comparison is carried out between the participating national measurement institutes in the field of humidity.
The aim of the comparison is to:

  • Investigate the equivalence between the psychrometer calibrations performed by the participating laboratories.
  • Gather practical calibration data and further information relevant for review of relative humidity CMCs.
  • Gain practical experience for a similar but larger future comparison.

The method of comparison is calibration of a psychrometer in the range:

10%RH to 95%RH in the temperature range: 15 °C to 70 °C.

The 9 points to be measured are:
15 °C: 20%RH, 50%RH, 95%RH
45 °C: 10%RH, 50%RH, 95%RH
70 °C: 10%RH, 50%RH, 95%RH

Final Report 2011-03-22

Methods to realize a comparison of psychrometer calibrations were studied in this project.  DANIAmet-DELTA benefitting its solid experience in psychrometry developed a Pt100-based psychrometer to be used as the transfer standard. Handling of the wick was found to be a major factor affecting the quality of the results.

As a final stage, a full comparison between the laboratories was carried out to study the equivalence of the psychrometer calibrations performed by the participating laboratories. As a summary of obtained results, degrees of equivalence divided by the associated expanded uncertainties (k=2) are given in the following table. The results were reported in details in Tempmeko & ISHM 2010 Conference [A. B. Kentved, M. Heinonen, D. Hudoklin, Practical study of psychrometer calibrations, submitted to  Int. J. Thermophys.]   

Thermometry (T)
Anders Kentved, FORCE Technology (Denmark)
Coordinating Institute
FORCE (Denmark)


Reg. No.
Collaboration Type
Final Report