This work is aimed to design a continuous temperature controller in a closed gauging fixture space. On the top of the fixture, there is a hole where a thermally modified wood sample is fitted in. Consequently, the heat transfer is examined on the sample. Ceramic resistance heaters are the heaters used. The programmable logic controller with the additional modules is used for the continuous control. The temperature sensing is carried out by the means of the platinum resistance sensor.The work is divided into three parts. The first part presents the theoretical analysis of the programmable logic controller and its additional modules structure. Also the most common temperature sensors are mentioned in this part. The second practical part presents the design and construction of the triac regulator of the a.c. power. Additionally, the overall connection of the particular programmable logic controller with the triac regulator of the power, power supply and temperature sensors is depicted here. The third part presents the identification of the transmission function characteristics and coefficient calculation of the controller by means of Naslin Method. In this part, we also consider and practically carry out the operating programme of the programmable logic controller which, by means of PWM pulses, controls the triac regulator. The regulator subsequently controls the power of the ceramic heaters. The conclusions of the particular calculated and experimental measurements are imaged in the graphs. The most adequate values for the controller are chosen from the conclusions.