Model for a class of temperature control systems

A temperature control system is described consisting of a small metallic oven enclosed with insulation material, a power transistor for the heating element, an operational amplifier, and a thermistor for the temperature sensor. Industry has only recently begun to use the power transistor itself as the sole source of heat instead of a conventional resistive heater network which spreads the heat over a wide area. This arrangement is attractive because it eliminates the heater winding (relatively expensive and unreliable), but it does have different thermal properties from those provided by the conventional method. The objective of the research is to approximate the thermal transfer function that exists between the power transistor and the thermistor based on experimental data. The results provide information on relatively small heat control systems in which the controller active element is the heating element itself