Automatic Adiabatic Calorimeter Shield Control

An automatic adiabatic calorimeter shield control has been built and operated successfully for approximately 700 hours. It has been used with an existent low temperature (10 to 300°K) intermittently heated calorimeter in runs of up to 100 hours duration. Each control unit consists essentially of a difference thermocouple, high sensitivity taut suspension galvanometer, a set of four photomultiplier tubes, a relay servo mechanism, a reversible ac motor and gear train and two ON-OFF control relays. The observed behavior of the control and the internal consistency of the data obtained during its use indicate that the precision with which it controls the shield temperature is comparable with that obtainable from a trained human operator.