Abstract: A temperature controlling system for investigating thermal transformation having a program-controller operated furnace the temperature of which is changed with a predetermined speed, and into which a sample and a reference substance containing elements with identical thermal parameters are placed. The sample and the reference substance containing elements are coupled with temperature sensing elements detecting their temperature and both elements are connected to a temperature comparing unit forming the difference of the two temperatures. The output of the temperature comparing unit is coupled through a differentiating network, limit switches and an actuating unit with a quasi-static temperature input of the program controller.