engleski

Tin-Filled Multi-Entrance Fixed Point

In this paper, the advantages, design possibilities, performance of the Multi-Entrance Fixed Point (MEFP) concept are described. The purpose of MEFP is to replace equalizing blocks in any temperature-controlled zone with phase transition of matter during melting or freezing. The phase transition in such a calibration is not intended to be the temperature standard itself, but only provides for spatial thermal homogeneity and temporal stability during comparison calibration. Knowing that some of the main uncertainty components in the uncertainty budget of the comparison calibrated thermometer are the radial and axial gradients in the isothermal zone and knowing that comparisons comprise by far the majority of all calibrations, the improvement of speed and quality of calibration is of significant importance. The tin-filled MEFP with multiple entrance tubes, designed in the Laboratory for Process Measurements allows for simultaneous calibration of several thermometers against a standard thermometer. MEFP prototypes filled with other materials and with other design characteristics are pending production. This concept allows the use of modest purity materials to fill the cell, since a standard thermometer is used as the calibration reference. During this investigation, thermometers were calibrated against a standard in the same furnace, using both the standard equalizing block and the MEFP. The measurement results indicate that the use of MEFP decreases the uncertainty contributions from temperature gradients and the stability of the bath by an order of magnitude, compared to the standard equalizing block.

Comparison calibration; equalizing block; Multi-Entrance Fixed Point

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