An Interlaboratory Comparison of Relative Humidity and Temperature Probes Using Diverse Generation Techniques

Abstract

An interlaboratory comparison using relative-humidity (RH) and temperature probes at three national measurement institutes and two accredited laboratories has been carried out. The work had three purposes: firstly, to establish the instruments’ level of reproducibility and suitability for use as transfer standards within their specified range of operation; secondly, to show the agreement of a method of RH generation utilizing certified non-saturated salt RH standards when compared with a method of RH calibration using a chilled-mirror reference and platinum-resistance thermometers; and finally, from the results obtained it is possible to establish the equivalence between the participating laboratories, to the level of uncertainty achievable with the transfer standards used. A total of six RH probes were tested in two groups. The instruments of the first group were calibrated in the range from 10 %rh to 90 %rh at a temperature of 23 °C. The second group of instruments was measured in the same RH range, but at the temperatures of 5 °C, 23 °C, and 50 °C. The objective of the tests on the second group of instruments was to determine the effect of a wider operating temperature range on performance. This article presents and discusses the results of the comparison in the context of an international collaboration that provides confidence in the measurements performed by the participants within their respective accredited scopes and the ILAC or the CIPM mutual recognition arrangements.