Evaluación de la incertidumbre de medición espectrómetro de chispa para implementación norma ISO 17025: estudio de repetibilidad y reproducibilidad.

Abstract

ISO 17025 standard details requirements that testing and calibration laboratories must meet to ensure its competence, two of these requirements are the evaluation of the measurement uncertain and the assuring of quality of results. In the present project the evaluation of the measurement uncertain of the spark spectrometer in the foundry laboratory at Escuela Polytechnical Nacional was carried out by measuring the concentration of aluminum, silicon, magnesium and iron through a statistical study of repeatability and reproducibility combined with a process of identification and quantification of sources of measurement uncertain, as well as, the estimation of the combined uncertain and the expanded uncertain by a coverage factor k to obtain a confidence of 95%. In parallel, an interlaboratory study was carried out between the foundry laboratory and the extractive metallurgy laboratory at the Escuela Polytechnical Nacional. The measurements obtained in both laboratories for the same elements mentioned above were compared using a t-test of two populations for related samples with a significance of 5%. For the project, aluminum samples were prepared with ASTM E1251-17a and ASTM E716-16 standards, material was obtained from an extruded aluminum shaft available in the foundry laboratory warehouse, cut by a horizontal band saw and finally machined on a parallel lathe.