An Automatic Data Acquisition System for Calorimetry: The Specific Heat of α-Al2O3 between 300 and 470 K

The data acquisition system, using a commercially available automatic ac bridge, digital voltmeter, and transistorized digital logic modules, is suitable for both discrete and continuous heating calorimetry. The output, via a Teletype, is a printed record and punched paper tape. The total cost of parts was less than $25 000. The computer program to handle the output is described. As an illustration of the operation of the system the results of measurements in the range 300–470 K on the calorimetric standard sample α-Al2O3 are given. The measurements, having a precision of ±0.1%, were made in an improved form of the calorimeter described by Martin and Snowdon [Can. J. Phys. 44, 1449 (1966)]. Agreement with the latest National Bureau of Standards results (Ditmars and Douglas) is around 0.1% when they are corrected to the same temperature scale. The effect of heater lead resistance on the results has been experimentally determined.