In this diploma work, the working principle of resistance temperature detectors and thermistors (NTCR and PTCR) is described. Their table data for resistance-versus-temperature dependence are given and analysed as well as the use of certain sensors. In chapter 2.1. the emphasis is placed on the resistance thermometers, also called resistance temperature detectors. Afterwards, there is also a description of the Pt-25 probe, which was used as a reference during calibration. The chapter 2.3. focuses on the sensors with a negative temperature coefficient, while also describing calibrated NTCRs and their characteristics. Determination of two approximation curves is described: a three parameter one (AC1) and a two parameter one (AC2) which are compared with the three-parameter Steinhart-Hart equation by using table data of NTCRs and calculating unknown parameters by the least-square method. Temperature is therefore approximated using determined parameters and the difference from the reference temperature is calculated. The main part of this diploma work is displayed in section 3. First there is an explanation of the set-up (measuring procedure with measuring equipment), after which a calculation based on data from chapter 2.1.2. and 2.3.4. follows. Finally, the results of calibration of these resistors from previous years are compared with the new results. It has been shown that the measurement uncertainty can be at the level of 10 mK or even better for narrower temperature range.