Acoustic measurement of the triple point of neon T _Ne and thermodynamic calibration of a transfer standard for accurate cryogenic thermometry

Abstract We used absolute primary acoustic gas thermometry (AGT) to calibrate a Pt–Co resistance thermometer on the thermodynamic temperature scale by measuring speed of sound in helium at T * chosen be near triple point neon, Ne . Prior present AGT, was with neon triple-point cell as part an interlaboratory comparison. Taken together, results comparison and AGT redetermined = (24.555 15 ± 0.000 24) K. This new value is consistent other recent determinations obtained various methods. After completing calibration, we link ratios measured single-pressure refractive-index (SPRIGT) different laboratory. (Gao et al 2020 Metrologia 57 065006) Now, *-linked SPRIGT system can thermometers range 5 K ⩽ without using international ITS-90. At most temperatures this range, uncertainties are smaller than those ITS-90 systems National Metrology Institutes thermometers.