Primary thermometry from 2.5 K to 140 K applying dielectric-constant gas thermometry

Recent thermodynamic temperature measurements at PTB with dielectric-constant gas thermometry were performed up to 140 K. Particular care was taken to check for possible systematic sources of errors by repeating experiments applying two new measuring capacitors and both helium and neon as working gases. The development of a new method for determining the effective compressibility of the new capacitors as a function of temperature has decreased the uncertainty significantly. The combination of the recently obtained results with former values of thermodynamic temperature, corrected using new thermodynamic input data, has yielded a consistent dataset in the range from 2.5 K to 38 K as well as at 84 K, 120 K, 130 K, and 140 K. This dataset is in good agreement with the newest results of acoustic gas thermometry, which has quite different sources of uncertainty compared with dielectric-constant gas thermometry.