Evaluation of SRD1000 Superconductive Reference Devices

Recently, a superconductive reference device, SRD1000, with ten reference materials has been developed to enable simplified in situ calibration of interpolating thermometers. We report on the evaluation of SRD1000 prototypes at various laboratories. The devices were built and tested by HDL and KOL, calibrated at NMi-VSL and then distributed to other partners where they were re-calibrated against the local realisations of the PLTS-2000 or laboratory scales. As a result, we obtained data on the superconductive transition temperatures, widths and shapes for four different devices. Reproducibility, sharpness of the transitions, supercooling and sensitivity to magnetic fields are evaluated. This leads to estimates of the uncertainty in determination of the transition midpoint and temperature.