A HIGHLY SIMPLIFIED THERMIONIC CONTROL OF TEMPERATURE

Three recent articles (1, 2, 3) describe methods of heat control which seem unnecessarily complicated in view of the present technical development of control tubes in the radio industry. Those methods, just mentioned, use mechanical relays and have wiring schemes which, although not complicated to those acquainted with radio, are nevertheless too difficult for many people to construct. One of the simplest and most effective schemes involving the use of thyratron tubes and no mechanical relays was described by Schwenk and Noble (4) in 1937. The scheme here described is a further simplification and adaptation of thyratron methods. Recently two well-controlled incubators were needed and were obtained by converting two old ovens that had long been around the laboratory unused. These ovens had been controlled by the usual mechanical thermostat and allowed a temperature variation of ? 2? C. The conversion of the ovens to valuable incubators was done as follows ?1 A five-volt transformer