A Simple Microcomputer-controlled Calorimeter: the Heat Capacity of Copper, Invar and RbNiCl3 in the Range 2?20 K

Abstract

A simple inexpensive microcomputer has been used to control an adiabatic pulse-type calorimeter. The data acquisition control system incorporates a Rockwell AIM65 microcomputer to control all aspects of the thermometry and the injection of the heat pulse into the sample. Details of the hardware and software requirements are discussed, including the interface of the system with a host computer that uses the UNIX operating system. The performance of the apparatus was evaluated by measuring the heat capacity of 1965 Calorimetry Conference copper between 2 and 20 K. The results show a total r.m.s. deviation of less than 0·4 % and agree well with the copper reference equation (r.m.s. deviation 0·4 %). Measurements are also presented of the heat capacity of Invar (Nilo 36) and RbNiCI3 over the same temperature range. In the case of RbNiCh the heat capacity anomaly associated with the paramagnetic-anti ferromagnetic transition is observed at 11·1 K.