PROCESS FOR MANUFACTURING PLATINUM RESISTANCE THERMOMETER

摘要

To provide a process for manufacturing a platinum resistance thermometer being stable with a less resistance value variation over service temperature range through clarification of a quantitative mechanism of resistance value variation with respect to the oxidation/reduction of platinum resistance wire. [MEANS FOR SOLVING PROBLEMS] The process comprises the step (S1) of enclosing a purge gas containing an inert gas and oxygen in a protection tube provided with a thermosensitive part of platinum resistance wire; the step (S2) of raising the internal temperature of the protection tube to a temperature region in which the platinum is in reduced form at a partial pressure of oxygen in the purge gas as determined from platinum oxide formation free energy; the step (S3) of replacing the purge gas with an inert gas wherein oxygen is 1 kPa or below; and the step (S4) of sealing the protection tube under the replaced condition.