Evaluation of self-heating effect in platinum resistance thermometers

The electrical resistance of Platinum (Pt) metal wire is used as thermometric property because of its high sensitivity to temperature with a positive temperature coefficient. Self-heating is a well-known effect in resistance thermometry occurred due to Joule heating in the sensing element. The importance of self-heating correction in temperature measurement and its value for different types of platinum resistance thermometers (PRTs) were investigated and evaluated in this work. We studied the factors affecting the self-heating correction of PRT such as, the amount of current flow, resistance of Pt wire, construction of PRT, thermal contact medium and operating temperature. The heat dissipation is influenced by construction of PRT as it depends on thermal conductivity of gas filled in sheath, sheath material, and method of winding of Pt wire on electric insulator. The paper provides a detailed interpretation of factors influencing the self-heating correction value of PRTs.