High-purity platinum wire is produced for use in both Standard Platinum Resistance Thermometers (SPRTs) and type S and type R thermocouples. The resistance ratio W(T90) and thermoelectric characteristics of the wire are a function of chemical purity and physical strain, and the characteristics of a given specimen can be compared to those of Standard Reference Material (SRM) 1967. A commonly reported resistance ratio which is highly sensitive (i.e. most readily observable) to impurity and strain is the so-called residual resistance ratio X_RR or R(273.15 K)/R(4.2 K). We present data in terms of X_RR and W(T90) from well-annealed Pt samples of the original SRM 1967, its contemporary substitute SRM 1967a, and a collection of NIST capsule-type SPRTs. We analyze the correlations in our resistance ratio data and compare our contemporary data with historical data from the literature.
Conference Dates: August 22-25, 2011
Conference Location: National Harbor, MD
Conference Title: National Conference of Standards Laboratories International 2011
Pub Type: Conferences
Residual Resistance Ratio, platinum, high-purity, temperature, resistance thermometry, ITS-90, resistivity