Automatic Calorimetry in the 3–30 K Range. The Specific Heat of Copper

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Abstract
Automatic data acquisition is by means of a slightly modified version of a hard-wired system described previously (Martin and Snowdon, 1970) combined with an on-line minicomputer which controls the calorimeter heating rate and computes temperature and specific heat. The new cryostat, calorimeter assembly, and adiabatic shield control are briefly described. Experiments to verify the accuracy of germanium thermometry with the automatic ac bridge are detailed. Operation of the system is illustrated by results on pure copper which show a standard deviation of 0.3% (mostly due to temperature scale defects rather than inherent lack of precision) and agree well with the Copper Reference Equation below 20 K but above this temperature agree more closely with the results of Cetas, Tilford, and Swenson [Phys. Rev. 174, 835 (1968)].