Development of a high temperature standard platinum resistance thermometer equipped with a platinum disk guard electrode

A new model of a high temperature platinum resistance thermometer, which has guard electrodes that eliminate the effects of leakage current flowing through the insulators at high temperatures, was constructed and evaluated. The effectiveness of the guard electrode was evaluated and confirmed by measuring the immersion characteristics at the copper freezing point. In this paper, we report the results obtained from another prototype HTSPRT, where the guard electrode structure is a button-like disk. Measurement of the freezing point of copper using this prototype HTSPRT is shown.