Abstract
Platinum resistance thermometers (PRTs) are widely used in precise temperature measurements in scientific and industrial applications. The majority of the sensors used are Pt100 sensors under the JIS (Japan Industrial Standard). For more precise temperature measurements at the 0.01°C level, the thermometer should be calibrated by means of comparison measurements using a traceable standard thermometer with small uncertainties. This paper discusses the comparison method and its uncertainty for evaluating a thermometer that has similar characteristics with standard PRTs for the temperature range of 0°C∼30°C. We built a comparison bath, and evaluated that the uncertainty of the comparison measurement is as good as 0.43mK (k=2). Furthermore, as a demonstration of the comparison measurement using this equipment and method, we evaluated a small sized PRT of 1.2mm diameter and 10mm length, which fulfills the requirement for W (29.7646°C) of a standard PRT in ITS-90. The comparison results demonstrated the usefulness of the method as well as the usefulness of the evaluated PRT. This development enables quantitative evaluation of the characteristics of individual thermometers, and will provide useful data for the evaluation of uncertainties in temperature measurements.
