Determination of the uncertainty source in calibration of standard platinum thermometers at fixed points using collective standard

The objective of this paper is to present new method for determination of the uncertainty source (uncertainty as a result of impurities) in calibration of standard platinum thermometers at fixed points using collective standard, The main reason for using collective standard for determination of this uncertainty source Is impracticability of any other classical method for determination of this source. Usually, this source is determined on the basis of the chemical analysis of the material prior to the actual assembly of the fixed point cell. It is possible that in the assembly process and especially during the usage of the cell, some impurities pollute the fixed point material, so the uncertainty source, based on the chemical analysis can be underestimate of the real uncertainty contribution.