Calorimetry automation in the 0.4–3 K range: Use of the NBS superconductive fixed point device and the specific heat of copper

Operation of an automatic data acquisition system, with an on-line minicomputer, in the 0.4–3 K temperature range is described and illustrated by results obtained on pure copper. The temperature scale was set up using both 3He vapor pressure thermometry and the NBS superconductive fixed point device. On the basis of specific heat measurements on pure Cu and Cu alloys, it appears that the temperatures assigned by the NBS to the superconducting transition temperatures of cadmium and zinc are too close. The required adjustment is within their assigned uncertainty limits.