Estudio e implementación del punto triple del mercurio en la calibración de instrumentos que miden la magnitud temperatura

Abstract

The purpose of the present research was to study the Mercury triple point (TP-Hg) defined in the International Temperature Scale of 1990 (ITS-90) for the Standard Platinum Resistance Thermometers calibration. The definition and development of this triple point are used to stablish a primary standard of temperature in the National Metrology Laboratory of Ecuador. In addition, it allows improving calibration and measurement capabilities of the laboratory to future declaration and registration in the key comparison database of the International Bureau of Weights and Measures (BIPM). The Hg TP was measured in two different methods, such as, freezing and melting. Each phenomenon was reproduced with an ISOTECH Mercury cell of 99.99999% purity, a high stability maintenance bath, a Quartz-Sheath SPRT, and a high uniformity and accuracy thermometric bridge. Furthermore, the group of listed equipment has traceability with the National Institute of Standards and Technology (NIST-EEUU). The data repeatability and reproducibility of the research measurements was calculated with the ANOVA accuracy method from the standard ISO 5725-2. The physic model was stablished. This model considers suppositions about the measuring and relevant physical variables. The model was represented according to a mathematical language where the countable uncertainty forces are determined. Also, the freedom degrees were chosen to stablish a level of trust that let obtain the expanded uncertainty associated with this measurement.