The Cluster of Excellence “CENTRE FOR TACTILE INTERNET WITH HUMAN-IN-THE-LOOP (CeTI)” [1] deals with developments and inventions concerning smart devices used in many fields, e.g. medicine and skill learning. For the integration or electrical interconnection of smart components, electrically conductive materials are often integrated into the clothing. To maintain the flexible, textile character of such smart textiles, polymer-based yarns with a metallized coating are mostly used for this purpose. In order to be able to use these yarns both in everyday life situations and in personal protective equipment with high safety requirements, it is necessary to specifically characterize and evaluate the long-term stability of the materials used. Knowledge of the electrical properties under the influence of temperature and moisture is particularly important for clothing worn close to the body, since the stress on the materials due to body and skin temperatures and user perspiration is particularly high here. At present, it is only partly possible to characterize the electrical stability of textile conductors under different application-related climatic conditions using standardized test methods. For this reason, this paper presents a newly developed measurement and test method that makes it possible to evaluate the electrical properties of yarns under defined temperature and humidity influences over a specified period of time. On the basis of different tests, the results of which are also discussed here, the measurement accuracy and repeatability of the method can be proven.