Development of single helix type SPRT

New three different types of standard platinum resistance thermometers are developed to cover the whole temperature range of the International Temperature Scale of 1990. For high temperature use a sapphire based thermometer is fabricated to reduce electrical insulation errors and for middle temperatures a single helix type thermometer filling with argon in the sheath is developed to decrease the oxidization errors of platinum sensing wire. For low temperature range a new metal sheath thermometer with a hermetical seal is designed. The basic characteristics of these thermometers are studied and some comparison results with conventional designed thermometers are reported.