Temperature Control for Frequency Standards

A brief summary of the factors influencing the stability of temperature-control assemblies, in which control is obtained by adding heat and without the use of circulating mechanisms, is given. These factors include the degree of insulation; rate of application and method of distribution of heat; sensitivity, regularity of operation, and position of thermostat; degree of "ripple" attenuation; and the operating temperature. Examples of three types of control units regulating to within approximately ± 0.5 deg., ± 0.1 deg., and ± 0.01 deg. C, respectively, at 50 deg. C are given, with heating rates and details of construction. Diagrams and photographs are included.