J. Koken’s research while affiliated with Eindhoven University of Technology and other places

A method is described of stabilizing the temperature of a heated wire under changing conditions of cooling and evaporation. It depends on controlling the resistance of the wire by the use of a power supply having a special current-voltage characteristic. The characteristic has been obtained by a slight change in a normal commercial apparatus. The great advantage of the control is its simplicity. Application of a thermocouple or optical measurement of the temperature of the heated wire is not necessary. Measurements on a tungsten wire at 1100°C showed the temperature to change less than 10°C in spite of a 800% variation in the energy input. Working at constant voltage causes the temperature to change more than 200°C by this input variation. The method can be applied to electrical furnaces, degassing of metals, electromotors, hot filament ionization of gases, etc. Variations in cooling rate require a different voltage-current characteristic of the power source than does evaporation or aging of the wire.