A simple inexpensive instrument for flash heating metal filaments has been designed which is being used in studying sorption phenomena at very low pressures and in measuring heat capacities and total emissivities of metals. The instrument permits selecting both absolute heating rates and their time dependence; in particular, filament temperatures increasing linearly with time can be obtained. Furthermore, the heating circuit allows the attainment of a preselected maximum filament temperature without appreciable over‐shooting. This paper describes the concept and design of the device; detailed experimental results are being reported elsewhere.