STATISTICAL HYPOTHESES TESTING FOR PHASE TRANSITION IDENTIFICATION IN CRYOGENIC THERMOMETRY
Work partially funded under EU SofTools_MetroNet Contract N. G6RT-CT-2001-05061.
The identification of the phase transition is required in thermometry in order to reproduce the International Temperature Scale of 1990 (ITS-90) defining fixed points.
This paper proposes the use of statistical hypotheses testing methodologies for phase transition identification by simply monitoring the temperature behaviour. Only the pure structural change model is taken into consideration, that is the model in which the components of the parameter vector are allowed to change all together.
A statistical test for a single known change point is briefly presented in the paper. The procedure is extended to the more interesting application of the detection of a single unknown change point. A sliding window algorithm is proposed for the on-line detection of a possible change point.
The method has been applied to identify the triple points of the four gases realizing the cryogenic range of the ITS-90. The pure structural change model has proved to be an innovative tool for a reproducible and reliable phase transition identification.
